Brakes: Make Them "Touchier"? [Archive] (2024)

Kazz5

26th May 2009, 14:50

This newbie tried searching for a while and I couldn't find a direct answer. It seems most folks are putting big brake kits on that talk about the subject at all.

Anyway, I just purchased this Miata for my wife and wanted to do what I could in maintenance, etc. for it. It's a '95 with 72K on the clock. She's in very good shape compared to many I've seen. The most striking difference between it and the imports my wife and I are used to is how much more ... effort(?) if not travel(?) it takes to get the car to braking. I mentioned this to the salesman (who claimed he used to sell Miata's through their first few years when he was with a Mazda dealership - but we all know about car salesmen, eh?), and he stated that Miata brakes were not at all like most Toyota or Honda brakes where a tap would start the nose to diving.

I've not taken off the wheels to check a thing yet. The dealership's program to check their used-car trade-ins claim they looked over a whole host of things including the brakes. It seems they found a need to replace the rear pads, so goodness knows they could have monkeyed with anything.

Is there a concurrence here that Miata brakes aren't as "touchy" as other imports? What would be the things to look for in order to eliminate possibilities or improve components/tuning of the braking system to make it more like we're used to having brakes behave?

Thanks all for your input.

This is an AWESOME resource - congratulations to all!!!

tom4416

26th May 2009, 15:04

Touchy isn't the word I would use but the 1.8 liter brakes grab well and hard. However, some aftermarket pads out there are just junk and will ruin the brake feel in any car. Even putting race pads on can result in poor low speed performance as they need to get HOT to really work.

I'd start by bleeding and flushing the system, lube the caliper pins on all four wheels and examine the type and brand of pad. For everyday driving, I think the OEM is absolutely the best pad for these cars with a minimum of brake dust.

jimbonnie

26th May 2009, 15:07

I think Miata brakes are quite different than many others, though there is no way from here to tell whether your brakes are operating properly.

I would say your best bet is to find a knowledgeable member from this forum in your area who could take the car for a spin with you to test out the brakes. In lieu of that, a trusted mechanic can flush, bleed, check, and test the brakes for you.

makapaka

26th May 2009, 16:04

Ron Keil

26th May 2009, 16:38

The extra pedal travel sounds to me like the parking brake adjustment might be backed off too far. That frequently happens when an unknowledgeable maniac (oops, mechanic) replaces the rear pads. It's easy to check with just a couple of tools; hit the Garage link at the bottom of this page. Another good bet, already mentioned, is to assure the system is well bled. Again, see the Garage.

When a dealer "checks the brakes" about the only thing I can count on their doing is looking for pad and rotor wear. I wouldn't trust a dealer I don't well know as far as I can spit, and usually dribble on my beard. :wave:

EMRA's Wreckerboy

26th May 2009, 16:40

First, disregard everything your dealer is telling you, including, quite possibly, his name. If he tells you the sky is blue, go check for yourself.

Second, start with the basics. Miata brakes are not any different in principle than anybody else's brakes. So do the basic routine maintenance you would on any car. Consider a set of pads - Miatas aren't particularly sensitive to pad type in street use, but as on any car, there is a decided difference between name brand pads and "Brand X" pads. Bleed the system, adjust the parking brake (read up on that in the garage), and check the condition of the sliders in the calipers (more reading in the garage).

Then check for the symptoms you describe. If, by "effort" you mean that it requires a lot more strength to push down on the pedal and get a result, AND you've done the basic system maintenance, then further diagnosis into things like the brake booster might be indicated. If by "travel" you need to push the pedal a lot further down before you get results, the master might be an issue.

However, I suspect that once you do the basic maintenance indicated you will find you have no real problem.

<------ has a pair of '90's, both of which are on their OE master cylinders (the racecar with 250K+ miles, the other at 103K) and both of which have a rock firm pedal and impeccable brakes with not much more than routine maintenance.

Al English

26th May 2009, 17:00

The extra pedal travel sounds to me like the parking brake adjustment might be backed off too far.The only way the parking brake adjustment can effect pedal travel is when the adjustment is overly tight.

In addition to the suggestions already posted, a malfunctioning brake booster/servo can cause higher pedal effort. It's not a common problem, but it does happen.

5:04

26th May 2009, 17:36

nikkidanjo

26th May 2009, 17:43

This newbie tried searching for a while and I couldn't find a direct answer. It seems most folks are putting big brake kits on that talk about the subject at all.

Anyway, I just purchased this Miata for my wife and wanted to do what I could in maintenance, etc. for it. It's a '95 with 72K on the clock. She's in very good shape compared to many I've seen. The most striking difference between it and the imports my wife and I are used to is how much more ... effort(?) if not travel(?) it takes to get the car to braking. I mentioned this to the salesman (who claimed he used to sell Miata's through their first few years when he was with a Mazda dealership - but we all know about car salesmen, eh?), and he stated that Miata brakes were not at all like most Toyota or Honda brakes where a tap would start the nose to diving.

I've not taken off the wheels to check a thing yet. The dealership's program to check their used-car trade-ins claim they looked over a whole host of things including the brakes. It seems they found a need to replace the rear pads, so goodness knows they could have monkeyed with anything.

Is there a concurrence here that Miata brakes aren't as "touchy" as other imports? What would be the things to look for in order to eliminate possibilities or improve components/tuning of the braking system to make it more like we're used to having brakes behave?

Thanks all for your input.

This is an AWESOME resource - congratulations to all!!!

I've seen dealers say that while selling brakes that were metal on metal. Don't trust the dealer's opinion.

Don

26th May 2009, 18:22

Is there a concurrence here that Miata brakes aren't as "touchy" as other imports? What would be the things to look for in order to eliminate possibilities or improve components/tuning of the braking system to make it more like we're used to having brakes behave?It depends on what you're used to - If you're used to stabbing the brakes and getting an instant front end nosedive, that's probably never going to happen with your new Miata

Miatas have nearly a 50/50 weight distribution so the rear brakes do more of the stopping than they do on many other cars and the result is that the car stops with much less nosedive - It should stop as quickly (or probably more so) than any other Japanese import you're likely used to though . . . . 1.8 Miatas have very good brakes

If I bought a car with 72K on it which the dealer had replaced the rear pads on and I thought the brakes were at all questionable, I would probably do a proper brakejob first thing though. If he replaced the rears, likely someone else has already replaced the fronts. If you can do the work yourself, 4 new rotors and a new set of the factory pads (along with all of the stainless hardware which only comes with factory pads) would probably set you back $200 or less . . . . and then you would have 100% new 'factory brakes'

Don

Thumper 13

26th May 2009, 18:52

It depends on what you're used to - If you're used to stabbing the brakes and getting an instant front end nosedive, that's probably never going to happen with your new Miata

Miatas have nearly a 50/50 weight distribution so the rear brakes do more of the stopping than they do on many other cars and the result is that the car stops with much less nosedive - It should stop as quickly (or probably more so) than any other Japanese import you're likely used to though . . . . 1.8 Miatas have very good brakes

If I bought a car with 72K on it which the dealer had replaced the rear pads on and I thought the brakes were at all questionable, I would probably do a proper brakejob first thing though. If he replaced the rears, likely someone else has already replaced the fronts. If you can do the work yourself, 4 new rotors and a new set of the factory pads (along with all of the stainless hardware which only comes with factory pads) would probably set you back $200 or less . . . . and then you would have 100% new 'factory brakes'

Don
I humbly disagree with you. Miatas are not 50 50 bias.I have put my third set of pads up front and my rears were like new. I replaced all the pads and installed a rear proportioning valve to get more rear bias. Caution : the stock suspension allows for too much nose dive on hard braking so increasing the rear bias when you have not gotten rid of nose dive IS NOT a good thing to do. My ride is lowered 12 1/4 front and 12 3/4 rear with much stiffer springs. Therefor my car stays much flatter and can use more rear brake.

Thumper 13

26th May 2009, 19:01

JasonC SBB

26th May 2009, 21:12

gtxhawaii

26th May 2009, 21:31

If your rotors look shabby, don't have them worked on, problem metallurgy in the rotors is usually deeper than any lathe is going to cut away. New NAPA rotors cost less than some places want to clean up old rotors, and if they are good enough to race in Spec Miata races, they are certainly good enough. NAPA pads are close to Mazda factory ones, but don't wear as well, in my experience. The stock pads are clean, very easily modulated and stop the car hard enough to lock wheels anywhere. The aftermarket performance pads can be more aggressive, are almost all dirtier and few modulate as well. And many are hard on rotors. The full race pads are disturbingly ineffective in many cases till properly warmed up. NOT for street use, if so. There are lots of user reports on pads in the 'Brake' forum. Carobotech seems to be better than most on that issue?
Another issue is off brand pads, and brakes in general, that were never properly broken in. Good brakes have an even coating of pad material distributed on the rotors, so the real friction is pad material against pad material. StopTech has a nice web site with directions on breaking in pads and rotors, and some excellent technical articles on brakes in general.
And no system works well with bad hydraulics. Read the 'Garage' section on Brakes and do the maintenance. New fluid, maybe new soft lines at each wheel if the present ones have any noticeable swelling to a hand grip when the brakes are applied. If the flex lines are firm and dry, they are good to go. Slider pins NEED regular maintenance. You NEED a hex socket tool, a 12mm?? You'll usually just break an Allen wrench trying to remove the slider pins. A hanging caliper is only working one pad, and usually wearing it unevenly.
Read carefully the section on E-brakes before taking it apart or working on the rear calipers. It isn't a common design and you need to know where the piston retract/E-brake adjuster is and how it works. People ruin parts trying to force things, as the adjustment is hidden behind one of the two bolts on the back of the rear caliper. (A smaller hex wrench required.)

I Like my stockish Miata brakes, with a mix of NAPA rotors, front pads and Mazda rears, and the autocross car with normal rotors and Hawk pads is more aggressive, but similar modulation. No complaints, and I'm not having any problems when changing cars to other makes or whole different systems, new or even older. They aren't overly sensitive, I have to Want to lock wheels, but the cars Stop. And both are quiet around town or wherever when brakes are used.

Kazz5

27th May 2009, 11:06

Wow, lots of great input here. Thanks, all.

The maintenance is clearly the right place to start. I'm not a brake job man, but am willing to learn some. I'll find a qualified specialist when over my head.

With the bleed, I assume it's the right time to move up to stainless steel brake lines.

I'm intrigued with the caliper pins being a maintenance issue so I'll dive into that deeply. I'm not thrilled with the length of travel of the hand brake, so I'll look hard into that.

Bleed/flush, fill, bleed. Perhaps w/SS lines. Check caliper pins, pad mfr, pad condition front & rear, rotor condition front & rear. Look into hand brake adjustment.

That sounds like the way to get started.

Thanks, all!

Gort

27th May 2009, 12:28

I humbly disagree with you. Miatas are not 50 50 bias.I have put my third set of pads up front and my rears were like new. I replaced all the pads and installed a rear proportioning valve to get more rear bias. Caution : the stock suspension allows for too much nose dive on hard braking so increasing the rear bias when you have not gotten rid of nose dive IS NOT a good thing to do. My ride is lowered 12 1/4 front and 12 3/4 rear with much stiffer springs. Therefor my car stays much flatter and can use more rear brake.

I believe he said 50/50 weight distribution, not brake bias. Otherwise, good note on increasing rear bias without reducing front dive.

Peter

Nice91

27th May 2009, 13:49

Kazz5

27th May 2009, 17:36

Thumper 13

27th May 2009, 19:27

Ron Keil

27th May 2009, 20:06

I humbly disagree with you. Miatas are not 50 50 bias.I have put my third set of pads up front and my rears were like new. I replaced all the pads and installed a rear proportioning valve to get more rear bias. Caution : the stock suspension allows for too much nose dive on hard braking so increasing the rear bias when you have not gotten rid of nose dive IS NOT a good thing to do. My ride is lowered 12 1/4 front and 12 3/4 rear with much stiffer springs. Therefor my car stays much flatter and can use more rear brake.
Thumper, let's be a bit careful here. The F/R static weight distribution, the wheelbase and the height of the center of gravity alone will determine the brake proportioning necessary. For very easy braking there is close to zero force transfer to the front wheels and they could do just about 50% of the braking. For high-g stops there is proportionally more traction available at the front and less at the rear, so the front can do proportionally much more of the braking. The hydraulic cylinders alone will create a certain proportioning; the brake bias valve will shut off additional pressure to the rear brakes at a predetermined (or adjustable) pressure. Thus the proportion of front/rear braking force (proportional to pressure) is not directly proportional to the deceleration, as is the force transfer; it is a constant until the proportioning valve kicks in and then follows a curve, ideally reaching the exact proportioning needed right at maximum retard. Of course road traction changes from place to place and so this ratio is rarely achieved.

Even though during easy braking the forces could be carried equally between front and rear, due to the varying requirements the front brakes carry a higher proportion of the easy braking effort, on the order of 60-65%. Under extreme braking the front proportion required is closer to 75%; hence the proportioning valve. This, too, is why front pads wear more quickly than the rears even on the street.

Front-end dive, on the other hand, is just a transient phenomenon. Once the front has dived, and the rear raised (and this can be controlled to an extent by anti-dive geometry, a lesson for another post) the force transfer from rear to front has occurred and, to a high degree of agreement, is exactly the amount of transfer that would take place were there no dive at all due to very stiff springs. If the rear bias is set too high, of course, there can be momentary over-braking at this end during the pitching event, leading to rear lockup.

Enough for now. More questions? :wave:

Thumper 13

27th May 2009, 20:40

EMRA's Wreckerboy

29th May 2009, 07:45

Rear brake bias issues are common in the Spec Miata world, where we aren't allowed to install adjustable prop valves. The car, as delivered, has a ton more rear brake than desirable. The solution many use is to run a less aggressive pad in the rear, which is why you will hear of many running the "Hawk black and blue" set up, or the "Carbotech 10's and 8's".

Remember, this is on a car that gets statically balanced to a 50/50 split. Dynamically it's a whole different deal as the front brakes are doing the most work. Thus the rears are more lightly loaded and will lock easier.

Thumper 13

29th May 2009, 16:14

Rear brake bias issues are common in the Spec Miata world, where we aren't allowed to install adjustable prop valves. The car, as delivered, has a ton more rear brake than desirable. The solution many use is to run a less aggressive pad in the rear, which is why you will hear of many running the "Hawk black and blue" set up, or the "Carbotech 10's and 8's".

Remember, this is on a car that gets statically balanced to a 50/50 split. Dynamically it's a whole different deal as the front brakes are doing the most work. Thus the rears are more lightly loaded and will lock easier.

I hear what you're saying but I can not get the rears to lock up. I know my springs have got to be softer than the SPEC MIATAS I am at 450 front and 350 rear but with very little suspension travel. I am at 12 1/4 front and 12 3/4 rear and no matter how hard I try straight line, early in a turn ,or late I can not get my rears to lock up. The only thing I could try is more rear air pressure but then the oversteer comes into play

TurboEric

29th May 2009, 16:22

Back to the original poster's question, I wonder why you want the brakes to be "touchy" (i.e. overboosted). That's a trick manufacturers use to convince people the vehicle has powerful brakes, when in fact it has nothing whatsoever to do with stopping distances and can lead to applying the brakes roughly leading to premature lockup or ABS intervention. Judge your brakes on stopping distances and controllability, not how overboosted they are.

That said, also carry out the maintenance checks suggested here - can't hurt to make sure things are working as designed.

Next we can discuss throttle response and how you can fool people into thinking a car is powerful by making the tip-in throttle response exaggerated...

ZakRabbit

29th May 2009, 19:58

I have the rear valve backed out to full and still get front lock without rear lock up.

The way you've written this, provided you've got a type that you turn to adjust (Willwood, AP), your prop valve is actually preventing any pressure to the rears. As you turn it clockwise, it allows more pressure back there.

OP: Good luck! Let us know how it turns out!

Thumper 13

29th May 2009, 20:45

I have the rear valve backed out to full and still get front lock without rear lock up.

The way you've written this, provided you've got a type that you turn to adjust (Willwood, AP), your prop valve is actually preventing any pressure to the rears. As you turn it clockwise, it allows more pressure back there.

OP: Good luck! Let us know how it turns out!
So I need to run the valve stem into the body to get more pressure to the rear brakes ? In otherwords I Bassakwards. That would explain a lot. The Valve is from Summit racing but I have been told its made by the same people that make Wilwood , just the older style.

Thumper 13

30th May 2009, 07:54

OK now I'm really frustrated :mad: I turn the valve all the way in no rear lock up. I turn the valve all the way out no rear lock up. The proportioning valve is a black bodied Summitt Racing valve. Keith seemed to think it is just the older style valve. I think I will try FM's valve if that doesn't work I am putting a union on the rear and see what happens then.

Comments welcome

Yes the rear calipers are working,adjusted the park brake and it works fine. I am getting heat from the rear rotors just no lock up.

Pete Rushbrook

30th May 2009, 08:31

Thumper 13

30th May 2009, 08:36

Thumper 13

30th May 2009, 11:08

benzmx5

30th May 2009, 12:54

imports? What would be the things to look for in order to eliminate possibilities or improve components/tuning of the braking system to make it more like we're used to having brakes behave?

Thanks all for your input.

This is an AWESOME resource - congratulations to all!!!

I would do 3 things.

1 As suggessted in another response, consider upgrading to stainless braided brake lines.
When you press brake pedal some of the force you are sending to the caliper pistons is being robbed in the slight buldging of the brake lines and upgrading to stainless will reduce this brake force robbing buldge.

2 Purchase or fabricate a brake stop.
When you press brake pedal some of the force you are sending to the caliper pistons is also being delayed while it initially creates a movement of the master cylinder. Under hood video taken in Japan showed this movement and led to the creation of a mechanical stop placed at the forward position of the master cylinder to prevent this reduction in force and delay in its arrival at the caliper piston.
Pics attatched show a brake stop I fabricated from some parts I got at a hardware store. Anything pressed up against the master cylinder preventing its forward movement will work.

3 Alternate annual brake system flush using ATE Gold and ATE Blue brake fluid. The brake fluid will improve brake response and the color change will let you know when you have purged all the old brake fluid.

Ian McCloghrie

30th May 2009, 14:29

Rear brake bias issues are common in the Spec Miata world, where we aren't allowed to install adjustable prop valves. The car, as delivered, has a ton more rear brake than desirable. The solution many use is to run a less aggressive pad in the rear, which is why you will hear of many running the "Hawk black and blue" set up, or the "Carbotech 10's and 8's".

Also remember that, since optimal brake bias depends on the amount of weight transfer, changing the tires will change the bias requirements. The stickier the tires, the more weight transfer you get on braking, and the less rear bias you want.

--Ian

Al English

30th May 2009, 14:49

I would do 3 things.

1 As suggessted in another response, consider upgrading to stainless braided brake lines.
When you press brake pedal some of the force you are sending to the caliper pistons is being robbed in the slight buldging of the brake lines and upgrading to stainless will reduce this brake force robbing buldge.

2 Purchase or fabricate a brake stop.
When you press brake pedal some of the force you are sending to the caliper pistons is also being delayed while it initially creates a movement of the master cylinder. Under hood video taken in Japan showed this movement and led to the creation of a mechanical stop placed at the forward position of the master cylinder to prevent this reduction in force and delay in its arrival at the caliper piston.
Pics attatched show a brake stop I fabricated from some parts I got at a hardware store. Anything pressed up against the master cylinder preventing its forward movement will work.

3 Alternate annual brake system flush using ATE Gold and ATE Blue brake fluid. The brake fluid will improve brake response and the color change will let you know when you have purged all the old brake fluid.Everything you suggested either will, or has the potential to, reduce pedal travel. However, none of it will reduce pedal effort, and that's what the OP wants/needs. "Bulging" lines and a flexy master cylinder mounting cannot "rob" force the master sends to the calipers, they only increase pedal travel. And while bleeding/flushing the brakes is a worthwhile maintenance procedure, like the other items you listed, air in the system can increase pedal travel, but cannot reduce the "force" sent to the calipers. I happen to like ATE fluid, but "regular" brake fluid is not meaningfully different in compressibility, and transfers energy just as well as ATE does. Using ATE will not provide a "response"? improvement.

Thumper 13

30th May 2009, 15:18

Also remember that, since optimal brake bias depends on the amount of weight transfer, changing the tires will change the bias requirements. The stickier the tires, the more weight transfer you get on braking, and the less rear bias you want.

--Ian
For some reason I don't think stickier tires will have anything to do with weight transfer front to rear or vice versa unless you lock up one and not the other. Weight transfer like that is more affected by suspension rates and length of suspension travel. Now if you want to talk about cornering well that's not in question here.

benzmx5

30th May 2009, 15:48

Al English

30th May 2009, 15:50

Thumper 13

30th May 2009, 15:55

wooo

30th May 2009, 15:56

.... the location of the car's CG relative to the wheels, and the rate of deceleration, are the major determining factors in weight transfer. .....Thanks for that.

I was having trouble reconciling the other suggestions with the physical laws as we know them. :)

sdaidoji

31st May 2009, 10:27

Thumper 13

31st May 2009, 11:01

Al English

31st May 2009, 11:08

I was trying to think on this myself now. Let's see, for example, a bike applying hard only the front brakes will nose-wheelie, meaning 100% weight transfer, right?
Now back to cars, but cornering - if you have a stiff front suspension but a soft rear, the fronts could lift one wheel (as i have seem some BMW M3 doing - 100% weight transfer again) and the rear end will lift, but both wheels will still be on the ground (less than 100%).
Does this idea apply as well during braking?
See below video - i believe it did not have rear brakes at all... bear with me, the point in question in on the end of the video.
http://s190.photobucket.com/albums/z77/sdaidoji/?action=view&current=fancyminidriving1.flv
I don't fully understand your question(s)/point(s). A car doing a stoppie, wheelstand, or cornering on its two outside wheels has clearly achieved 100% weight transfer. Many cars can get close to doing one or more of the three possibilities.

About the Mini video you posted. Minis are already pretty heavy in the front. The majority of the things you can do to top lighten a Mini just make that worse. Assuming the car in the video isn't ballasted, it is extremely lightened.

wooo

31st May 2009, 11:12

Thumper 13

31st May 2009, 11:16

Al English

31st May 2009, 11:21

Mad Swede

31st May 2009, 12:01

Al English

31st May 2009, 12:18

wooo

31st May 2009, 14:15

You teach physics don't you ?Nope, and I never did.

But I did pay attention in science classes at school, way back in the old days. :)

Math, physics, chemistry, etc. are very useful because they explain so much of what we experience in the world, cars in particular. :cool:

Mad Swede

31st May 2009, 17:22

Kazz5

1st June 2009, 10:48

Back to the original poster's question, I wonder why you want the brakes to be "touchy" (i.e. overboosted). That's a trick manufacturers use to convince people the vehicle has powerful brakes, when in fact it has nothing whatsoever to do with stopping distances and can lead to applying the brakes roughly leading to premature lockup or ABS intervention. Judge your brakes on stopping distances and controllability, not how overboosted they are.

That said, also carry out the maintenance checks suggested here - can't hurt to make sure things are working as designed.

Next we can discuss throttle response and how you can fool people into thinking a car is powerful by making the tip-in throttle response exaggerated...

It's a safety check/measure. My wife moves back and forth from a "touchy" feel Camry to the Miata and I'd rather have her, and our daughter, as safe as possible in their short commutes.

I'm looking forward to diving into this next weekend, folks. Again, thanks all!

ZakRabbit

1st June 2009, 13:11

So I need to run the valve stem into the body to get more pressure to the rear brakes ? In otherwords I Bassakwards. That would explain a lot. The Valve is from Summit racing but I have been told its made by the same people that make Wilwood , just the older style.
Yep, as the knob gets closer to the "body" of the valve more pressure is allowed to the rear brakes. Did you make sure that the "in" and "out" are correct? That will also do weird things. Do you by any chance have the factory prop valve installed still? Depending on where your adjustable valve is installed, that will also do strange things.

OP: Compared to a Miata, the Camry will feel "over boosted" every time; larger car, but only about 1000lbs. heavier, larger brakes, larger rolling diameter on the wheels. Brake disc diameter and rolling tire diameter will effect the "feel" of the brakes as well.

Thumper 13

1st June 2009, 14:07

Yep, as the knob gets closer to the "body" of the valve more pressure is allowed to the rear brakes. Did you make sure that the "in" and "out" are correct? That will also do weird things. Do you by any chance have the factory prop valve installed still? Depending on where your adjustable valve is installed, that will also do strange things.

OP: Compared to a Miata, the Camry will feel "over boosted" every time; larger car, but only about 1000lbs. heavier, larger brakes, larger rolling diameter on the wheels. Brake disc diameter and rolling tire diameter will effect the "feel" of the brakes as well.
No the factory valve was the first thing removed. I have ordered the FM valve to see if there is any difference. The Summitt valve is installed in the same location the factory valve was with the union alongside for the front brakes

Ian McCloghrie

1st June 2009, 20:46

For some reason I don't think stickier tires will have anything to do with weight transfer front to rear or vice versa unless you lock up one and not the other. Weight transfer like that is more affected by suspension rates and length of suspension travel. Now if you want to talk about cornering well that's not in question here.

Absolutely it will. Weight transfer is all about the force vector being applied to the car, with more braking (made possible by stickier tires) the magnitude of the vector gets larger. Since it's still being applied off-axis, you get a larger weight transfer to the front wheels, meaning decreased traction on the rears.

--Ian

Ian McCloghrie

1st June 2009, 20:48

I was trying to think on this myself now. Let's see, for example, a bike applying hard only the front brakes will nose-wheelie, meaning 100% weight transfer, right?[/url]

Yes, it will. in fact, it will do it even if you apply the rear brakes as well as the fronts.

Granted, you won't get a "stoppie" by applying *only* the rear brake, but that's only because once the rear wheel comes off the ground it loses traction and the weight transfer goes away.

--Ian

sdaidoji

2nd June 2009, 20:05

I don't fully understand your question(s)/point(s). A car doing a stoppie, wheelstand, or cornering on its two outside wheels has clearly achieved 100% weight transfer. Many cars can get close to doing one or more of the three possibilities.

About the Mini video you posted. Minis are already pretty heavy in the front. The majority of the things you can do to top lighten a Mini just make that worse. Assuming the car in the video isn't ballasted, it is extremely lightened.
Uhnnn, it was more that during cornering, the stiffer the suspension the more weight transfer occurs, and the difference between the forces actuating in the car during cornering and braking is that cornering is the centrifugal forces, while the brakes does that during braking. So how does it differ for weight transfer between cornering and braking? Stiffer suspension will transfer more weight.
Aside from forces actuating in the car, there will of course be some differences in resitance, since the right/left sides are tied by the sway bars, while in braking there will be some diffferences in suspension stiffnes rear/front and they are not tied by a bar like side to side.
Maybe it's because of the front/rear difference? Fronts stiffer does not dive much, softer rear does extend so keep wheels on ground longer thus reducing weight transfer?
Sorry for all that, am a mechanical engineer and I got curious on that...

sdaidoji

2nd June 2009, 20:07

wooo

2nd June 2009, 20:27

....am a mechanical engineer and I got curious on that...Mr. Engineer

would you like to show us free body diagrams of a car subjected to centrifugal/centripatal force, that would allow us to calculate the "weight transfer" form inside to outside wheels. And further would demonstrate that this transfer is greater with a softer suspension.

Al English

2nd June 2009, 23:18

Stiffer suspension will transfer more weight.Per my previous post, body squat, dive, or lean can move the car's CG a little, which results in some weight transfer. Otherwise, whether a car has marshmallow soft suspension or no suspension, steady state weight transfer is the same. Body lean or dive does not absorb, dissipate, or add, any energy. Suspension stiffness can effect peak loads during transient maneuvers, but the total amount of work done(weight transferred) is the same. Consider this; if spring stiffness determined how hard the tires push on the pavement, changing springs would alter what the car weighs sitting on a scale.

It's the same concept as tightening a bolt with a long ratchet extension vs a short one. All things being equal the long one will flex/twist more , but both the long and short one ultimately transfer the same amount of force.

Does that address the question or am I missing your point?

Thumper 13

3rd June 2009, 14:05

Per my previous post, body squat, dive, or lean can move the car's CG a little, which results in some weight transfer. Otherwise, whether a car has marshmallow soft suspension or no suspension, steady state weight transfer is the same. Body lean or dive does not absorb, dissipate, or add, any energy. Suspension stiffness can effect peak loads during transient maneuvers, but the total amount of work done(weight transferred) is the same. Consider this; if spring stiffness determined how hard the tires push on the pavement, changing springs would alter what the car weighs sitting on a scale.

It's the same concept as tightening a bolt with a long ratchet extension vs a short one. All things being equal the long one will flex/twist more , but both the long and short one ultimately transfer the same amount of force.

Does that address the question or am I missing your point?
According to what you are saying here,by increasing the front springs and lowering the height of the car as well as reducing the suspension travel my car will not sit flatter therefor keeping more weight, or less travel from the rear and I will see no added benefit by increasing the pressure applied to the rear brakes ?

Al English

3rd June 2009, 14:32

According to what you are saying here,by increasing the front springs and lowering the height of the car as well as reducing the suspension travel my car will not sit flatter therefor keeping more weight, or less travel from the rear and I will see no added benefit by increasing the pressure applied to the rear brakes ?
Some of what you posted is unclear to me, but no, I didn't say that. As I pointed out at least twice in this thread, dive does move the car's CG a little, which contributes a small amount of front to rear weight transfer. the preceding factor aside, weight transfer is weight transfer, regardless of what the body/suspension are doing.

I previously mentioned that position of the GC is the primary factor. Lowering the car lowers the CG, and that reduces weight transfer.

sdaidoji

4th June 2009, 00:17

Mr. Engineer

would you like to show us free body diagrams of a car subjected to centrifugal/centripatal force, that would allow us to calculate the "weight transfer" form inside to outside wheels. And further would demonstrate that this transfer is greater with a softer suspension.
Hahaha! no, sorry, i am a production process engineer, not product development.
Just fiddle with engineering stuff.
And no, a lifted wheel (or rear end - I myself could not believe when i saw that car doing that... Seen only bikes, which brings memories of when i awas a flatland fresstyler with a bicicle).
But the concept or softer suspension = more weight transfer is not correct - a stiffer rear end will lift inside rear tire (100% weight transfer - no forces for the lift wheel). a softer rear end will still keep both wheels on the ground (less than 100% transfer).
soft suspension will roll more, not transfer more weight. :)

sdaidoji

4th June 2009, 00:29

Per my previous post, body squat, dive, or lean can move the car's CG a little, which results in some weight transfer. Otherwise, whether a car has marshmallow soft suspension or no suspension, steady state weight transfer is the same.
?
Body lean or dive does not absorb, dissipate, or add, any energy. Suspension stiffness can effect peak loads during transient maneuvers, but the total amount of work done(weight transferred) is the same. Consider this; if spring stiffness determined how hard the tires push on the pavement, changing springs would alter what the car weighs sitting on a scale.
It's the same concept as tightening a bolt with a long ratchet extension vs a short one. All things being equal the long one will flex/twist more , but both the long and short one ultimately transfer the same amount of force.

??? Sorry, it was meant as more transfer... Not more weight... (light speed transform mass in energy, that's the only thing i know of that changes mass... weight could be changed by gravity, but don't think my car will get in another planet...
And if you take acceleration (or in this case decelleration) out of the equation and consider only CG, motorcycle nose-wheeling would not happen, nor lifting rear or front wheels nor even the video posted (which does not seem to be fake... can't vouch on that tough...).
Well, thumper did say in previous post that the suspension rates and travel would be the point, which is a shorter version of what I did try to say.
Thanks anyway Al.
Sandro

sdaidoji

4th June 2009, 00:39

According to what you are saying here,by increasing the front springs and lowering the height of the car as well as reducing the suspension travel my car will not sit flatter therefor keeping more weight, or less travel from the rear and I will see no added benefit by increasing the pressure applied to the rear brakes ?
Hnnnh, no.
Considering the extreme case, wheels on the air = no braking effects for the car.
So, to keep the wheels on the ground = longer rear travel, "softer" (than front) rear suspension. Or lower rear (which will mess other car characteristics).
Then with wheels longer in the ground means more weight on them as well, which means more grip on them.

Note: that's considering you starting from an extreme case. But principles should apply? If you have some of the listed items in your setup, you might get better braking by increasing rear bias? (meaning you will be able to use more of the rear brake if your setup allows for more weight kept in the rear wheels during braking).
Well, looks like while I was writing and thinking I was able to answer my own question.
Thanks

Al English

4th June 2009, 09:51

?

???

Thanks anyway Al.
Sandro :ohno: We obviously aren't communicating, apparently I have not addressed this in a way that is understandable to you, and you are entitled to your perceptions.

ZakRabbit

4th June 2009, 12:46

According to what you are saying here,by increasing the front springs and lowering the height of the car as well as reducing the suspension travel my car will not sit flatter therefor keeping more weight, or less travel from the rear and I will see no added benefit by increasing the pressure applied to the rear brakes ?

This is correct. When you apply the brakes, the weight transfers. Unless you're talking about raising the front of your car 10" or so, you will not move the C of G enough to make a difference. If you were to remove the springs and shocks entirely, and replace them with metal rods, the same amount of weight would transfer for a given g load. When you lower your car, yes, the C of G is lowered but it's not a 1:1 ratio; there is a lot of unsprung weight that does not change. Just because you've allowed enough droop travel in your suspension that your rear tire is still touching the ground, doesn't mean that there's enough weight on there to do anything effective. You probably wouldn't even flat spot the tire.
The point being missed in this thread so far seems to be that when you add tires with more grip, you are able to brake at higher G loads which will transfer more weight to the front. Street cars turned race cars (road racing, autocross may be different) use proportioning valves to REDUCE the pressure to the rear brakes so that they don't lock up.
I know a lot of people install the prop valves then turn more bias to the rear. What they don't understand is that yeah, the car may feel better, but what you're doing is using the rear brakes to stabilize the car going into a turn, basically causing it to understeer when trail-braking. An understeering car is more stable and will give more confidence to the driver, but when racing, tends to be slower. This works to the autocrosser's advantage because it's very easy to overdrive the course and brakes set up this way may slow you down in spite of yourself.

Thumper 13

4th June 2009, 16:31

Thumper 13

7th June 2009, 09:39

Al English

7th June 2009, 11:21

With rear prop valve dialed to full open the brakes respond much better than with the stock valve. All the laws of physics and the " engineers" here are speaking based on what they have learned. I on the other hand know lots about many things except physics. I do know from REAL EXPERIENCE having lowered the ride height, increased the spring rates,adjusted the shocks,added a stiffer front sway bar and tested in a large empty mall parking lot that my car stops a lot quicker and I haven't lost any ability to drive hard into turns and come out where I want to be quicker than I could before.That sentence is way to long. English majors feel free to flame me. So for all you "text book" experts I have one response.....:p...... Real world and the written word do not always coincide. :rolleyes:Contrary to what you seem to believe, I am not a math major with no understanding of the practical. I have been a fabricator, mechanic, engine builder, and machinist. For several years I did testing and development work for an OEM. In one capacity or another I have been involved in a number of successful armature and professional racing efforts. So like you, I am basically a hands-on guy, but I also have a fairly decent understanding of the principals underlying how and why things work as they do.

Your response makes it clear that you simply don't know what you don't know. And when one believes they already know what needs to be known, there isn't much chance of anything new being learned. Some of the results you mention in this post parallel what I have posted and you apparently don't realize it. That you are unwilling to ponder, or unable to understand, the underlying principals does not diminish their importance. If my posts were not expressed well I apologize. I realize that you feel books are just a bunch of boring words and illustrations, but should you really want to understand this, books contain alternate explanations of what I posted. Hands on development, testing, and evaluation, all have value. But, successful auto designers and racers do not rely on assumption, general consensus, the anecdotal, or hillbilly engineering. An understanding of physics, and how they apply to your situation, will ultimately always put you ahead of someone who lacks that knowledge. No matter how many stick out your tongue and rolling eyes icons you post, and no matter how much you claim your perceptions trump the laws of physics, you are missing a few pieces of this puzzle.

Thumper 13

7th June 2009, 11:34

Contrary to what you seem to believe, I am not a math major with no understanding of the practical. I have been a fabricator, mechanic, engine builder, and machinist. For several years I did testing and development work for an OEM. In one capacity or another I have been involved in a number of successful armature and professional racing efforts. So like you, I am basically a hands-on guy, but I also have a fairly decent understanding of the principals underlying how and why things work as they do.

Your response makes it clear that you simply don't know what you don't know. And when one believes they already know what needs to be known, there isn't much chance of anything new being learned. Some of the results you mention in this post parallel what I have posted and you apparently don't realize it. That you are unwilling to ponder, or unable to understand, the underlying principals does not diminish their importance. If my posts were not expressed well I apologize. I realize that you feel books are just a bunch of boring words and illustrations, but should you really want to understand this, books contain alternate explanations of what I posted. Hands on development, testing, and evaluation, all have value. But, successful auto designers and racers do not rely on assumption, general consensus, the anecdotal, or hillbilly engineering. An understanding of physics, and how they apply to your situation, will ultimately always put you ahead of someone who lacks that knowledge. No matter how many stick out your tongue and rolling eyes icons you post, and no matter how much you claim your perceptions trump the laws of physics, you are missing a few pieces of this puzzle.

Hillbilly engineering............. I like that. Hey Dan,Seamus there is our new name.............. Hillbilly Engineering and Racing. Now if I can only get Seamus to get out of his kilt and into his overalls we can get a picture to post. Seamus,if you desire, just for you I'll put a Tartan Plaid design on my helmet.
We'll now be known as H.E.R motorsports :cool:

wooo

7th June 2009, 11:44

Thumper 13

7th June 2009, 11:52

When it comes to your written word I have difficulty knowing what you, and some others, are trying to say. That makes it difficult to respond. For all I can tell you might be describing things that aren't physically impossible. :confused:

I am only trying to describe the improvements I have gotten in braking as well as helping the car to handle better when I drive her hard into a turn or transition. I don't claim to understand physics and that doesn't appear to be a problem for my car either. She seems to enjoy my lack of knowledge but will to adjust and adjust her until I can push both myself and "Little Piggy" to limits in an appropriate environment. i.e not the street. A secondary benefit is thanks to Al we now have a name for our " race team ". H.E.R motorsports.I am going to get a die cut windshield banner made. Some cheap publicity when finished with the Little Piggy there will be an LS 1 / T5 03 miata next.

JasonC SBB

7th June 2009, 12:16

Proportioning MATH here:

http://forum.miata.net/vb/showthread.php?t=333680

Thumper 13

7th June 2009, 12:45

Proportioning MATH here:

http://forum.miata.net/vb/showthread.php?t=333680

I read it,still don't understand it,no surprise there however. What I do know is with the rear proportioning valve dialed to almost full I can still really drive hard and then downshift,left foot brake and right foot gas and come through a turn a lot faster than before the B.P. valve.Gets very tricky at times due to my 11 1/2 feet.Missing a shift really makes the hair stand up on the back of my neck however.

Dan_W

7th June 2009, 13:25

Fred,

Good job on hyjacking this poor guys thread ;-)

The first thing we should do is bleed the brakes to make sure you got all the air out after you swapped the valve.

As I recall from the 10 or so years ago that I bought the thing, it offered like 0-40, maybe 60% pressure reduction. When its backed all the way out (counterclockwise, look at the below links), it should be giving zero proportioning... the same as removing it all together.

Maybe the thing is no good? Seized up in some way? It has been sitting in a box for the last 6 years. You said you bought another one right?

Otherwise, maybe were looking at a more in-depth brake issue like someone else mentioned... possible different compounds on front vs rear, etc. If that doesnt solve it you may need to go with a larger piston or rotor in the rear but I'd be suprised if thats the case.

FYI, this is the valve for those that were looking for a picture. It has the summit logo etched on it but I beleive its the same valve.

http://store.summitracing.com/partdetail.asp?autofilter=1&part=DCC%2D5249088&N=700+115&autoview=sku

http://store.summitracing.com/partdetail.asp?autofilter=1&part=BAE%2D2000035&N=700+115&autoview=sku

For the sake of curiosity, does anyone know the master cyl/piston diameters for the miata? How about the rotor diameters?

Thumper 13

7th June 2009, 14:29

sdaidoji

7th June 2009, 22:49

With rear prop valve dialed to full open the brakes respond much better than with the stock valve. All the laws of physics and the " engineers" here are speaking based on what they have learned. I on the other hand know lots about many things except physics. I do know from REAL EXPERIENCE having lowered the ride height, increased the spring rates,adjusted the shocks,added a stiffer front sway bar and tested in a large empty mall parking lot that my car stops a lot quicker and I haven't lost any ability to drive hard into turns and come out where I want to be quicker than I could before.That sentence is way to long. English majors feel free to flame me. So for all you "text book" experts I have one response.....:p...... Real world and the written word do not always coincide. :rolleyes:

Don't worry, i was talking based on experience too, just looking at different ways at it.
Know what's funny? Most of the time we were saying the same thing, only different ways to express. I still laughing when i read this back. Why we were discussing so much? As an example, when you said it was a matter of suspension rates and travel, it was the exact same thing i was asking.
Unfortunately don't have a suggestion for why your prop valve is not giving the expected results. Maybe lowered rears? can't tell without seeing it...

Thumper 13

8th June 2009, 00:07

SignOfZeta

8th June 2009, 04:18

I've never found the brakes on any Japanese car to have a very good feel. They are always mushy and over boosted compared to my VWs. Same goes for the power steering. I guess people must like it that way.

Replacing pads, rotors, and maybe even the master cylinder may fix it, but unless you get really involved you're never going to have Z3 quality brake feel.

Thumper 13

8th June 2009, 07:44

I've never found the brakes on any Japanese car to have a very good feel. They are always mushy and over boosted compared to my VWs. Same goes for the power steering. I guess people must like it that way.

Replacing pads, rotors, and maybe even the master cylinder may fix it, but unless you get really involved you're never going to have Z3 quality brake feel.

You want MUSHY you should drive my daughters Saturn.

Al English

8th June 2009, 14:30

Thumper 13

8th June 2009, 17:19

If you are going to embrace that persona you may as well go all the way. Stop brushing your teeth and start dating your sister.

First you assume I have teeth to brush. As far as my sister,I love her but I think I'd date my sheep first.:D :D :D

toddkageals

11th June 2009, 06:49

To the original poster:

I have the same "problem" even after new rotors and new factory pads, cleaning/greasing the sliders, and changing/bleeding the fluid. I'm used to the brakes on my BMW 330i daily driver which are huge compared to the Miata (but they are stopping a LOT more weight). I think this is just the way the brakes on the '90 work. The thing I like about the BMW's brakes is that they seem to have much more initial bite than the Miata's (they also produce a TON of dust). The Miata has a very firm feel but needs more effort than the BMW (or just about any other car I have driven). I think this might just be the way the Miata's system is designed. Maybe the other car the sort of felt like the Miata was an old Triumph I had when I was in high school. Now....that car required a lot of pedal effort to get it to stop!

Dana R

12th June 2009, 07:19

To the original poster:

I have the same "problem" even after new rotors and new factory pads, cleaning/greasing the sliders, and changing/bleeding the fluid. I'm used to the brakes on my BMW 330i daily driver which are huge compared to the Miata (but they are stopping a LOT more weight). I think this is just the way the brakes on the '90 work. The thing I like about the BMW's brakes is that they seem to have much more initial bite than the Miata's (they also produce a TON of dust). The Miata has a very firm feel but needs more effort than the BMW (or just about any other car I have driven). I think this might just be the way the Miata's system is designed. Maybe the other car the sort of felt like the Miata was an old Triumph I had when I was in high school. Now....that car required a lot of pedal effort to get it to stop!

My other cars are all BMWs, and I agree with this assessment about the lack of initial "bite" with the Miata brakes, especially with the 1.6 cars. My Miata is a 95m edition, and it too has poor pedal feel compared to all of my BMWs. Properly adjusting the rear brakes helped a bit, but I'm wondering if some of the aftermarket pads might have more bite than the stock pads? BMW designs their rotors to wear out with the pads, and clearly the Miata rotors don't wear like the BMWs, at least with the factory pads.

Has anyone done brake pad testing for street pads?

Pete Rushbrook

12th June 2009, 07:32

Thumper 13

12th June 2009, 07:52