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Old 11-09-2011, 06:03 AM   #376
MrZDeere
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Default Braking is pretty important...

I agree that factory breaks are pretty good and that better tires make the difference in the end. With that said however, from being on the track both completely stock and then with some upgrades, my time and the feel of the car improved with better pads and rotors. Just saying, it does help, even if just a bit.
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Old 11-09-2011, 06:47 PM   #377
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Quote:
Originally Posted by Davenow View Post
^

Your statement "ability to lock up the wheel/engage abs is irrelevant to braking performance" Is so misleading as to the point where I believe you are doing it intentionally.

OF COURSE IT IS RELEVANT TO BRAKING PERFORMANCE. How you can say it isnt, is beyond me. If you cant lock the tire, your brakes arent powerful enough. (I am talking about ability to lock it if there was no ABS, obviously we dont WANT to lock it, which is why we have ABS) What I am saying is that if your brakes are capable of bringing the tire to its adhesion limit, the point where the ABS kicks on, there is no benefit to making that brake system more powerful.

A locked up wheel, means the brake has given all it can, and has done its raw mechanical job of taking an object in motion (in this case the rotor) and stopped it from moving. If you can make the ABS kick on, your brakes are as powerful as they are ever going to get.

Here is an insanely simple example of how wrong this is... think about bicycle brakes, if you are familiar with bikes, you have rim brakes and discs, then hydraulic discs. Rim brakes lock the wheel up very easily, but in comparison to disc brakes they suck at actually slowing you down. Discs can also lock up, but they can get much closer to the point right before they lock were the most speed is being lost the fastest, thus slowing you down better. This is a simple example not involving cars but you get the idea, there is a threshold, a line were the brake looses its ability to slow you down and locks up, better brakes push that line father allowing you to slow batter and faster.

Not to mention the advantages of not having brake fad etc. I get fade just driving back and forth to work (live in the mountains), upgraded brakes would help eliminate that.

I absloutely agree with your stand points on tires, better rubber is the best thing you can do for your car, but your advice on brakes is misleading to many people on this forum.
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Old 11-09-2011, 07:56 PM   #378
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This parts needs to be more clear.

Yes of course the brakes need to be ABLE to lock up the wheel - I think that's pretty obvious.

However the ABILITY to lock up the wheel IS NOT a MEASURE of brake performance.

Brake performance would primarily be measured by the maximum amount of work they can do and/or the maximum rate at which work can be done which is power. Feel, weight, cost etc are of course other parameters.

If the wheels are locked then by definition the brakes are doing zero work and absorbing zero power as there is no motion between the rotor/pad. Any work/power is being done by the flexing/bending of the various components.Also the tire is now in dynamic friction w/ the road so stopping distance is increased pretty dramatically.

If ABS is activated - we are at least partially sliding - so again stopping distance is not minimized.

We want to measure the brakes performance at the maximum rate of deceleration without the pad/rotor going into static friction (brakes locked) and that is not the case when the wheels are locked and/or ABS is activated.




Two cars I've owned that really struggled to engage ABS/lock up the wheels were my 97 OB Wagon and 2005 OBXT.

Yes - I could stab at the brakes and make them lockup/ABS but trying to threshold brake to just below ABS'ing was difficult/barely possible.

Upgrading the factory/regular pads on both cars to a more aggresive semi-metallic compound was a reasonable fix for both. The 2005 OBXT still suffered with very poor feel though especially considering the power/weight of the vehicle.

Last edited by KNS Brakes; 11-09-2011 at 08:48 PM.
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Old 11-09-2011, 08:47 PM   #379
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Quote:
Originally Posted by Davenow View Post
A locked up wheel, means the brake has given all it can, and has done its raw mechanical job of taking an object in motion (in this case the rotor) and stopped it from moving.
This is wrong and indicates that you don't understand friction or physics.

When the wheels are locked the brake pads are not doing much if any work work and are not absorbing much power as there is no motion.. It is not the point of maximum power at all - in fact power in that condition for the brake pads and rotors is low as the tires are sliding. Any power is being absorbed by the bending and flexing of the caliper support and or knuckle etc.

This is because:

When the wheels are locked the pad/rotor interface is in static friction.

Static friction is higher than dynamic or sliding friction. So it's 'harder' for the pad to be just on the limit of ABS in dynamic (sliding) friction (or threshold braking) than it is to lock up the wheel completely (static friction).

This is because locking up the wheels means the tires are in sliding friction (less grip/power generated) rather than static friction (more grip/power generated).

Locked up brakes and sliding tires are exactly what we DON'T want and require less power than braking at the limit of the tires static friction.


Now I think it's pretty easy to understand that a brake that offers more control, durability, and endurance to operate at or near peak braking power would be worth it and my opinion is that WRX's are in OEM form pretty poor in this area considering the other capabilities of the vehicle.
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Old 11-09-2011, 08:54 PM   #380
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Quote:
Originally Posted by Davenow View Post

You flushed it, and you replaced the pads. I promise you that using a great pad, which I am sure you did (why wouldnt you? You have access to them cheap) would have not fixed the problem any better than a set of $40 pads from vatozone.






I took off nearly full thickness pads. They were painted pretty bright blue and clearly not that old but of unknown brand. They stopped very poorly and were eating the rotors.

I put on FF friction semi-metallic pads from SP Performance - about $50 at the time iirc. A modest UPGRADE that changed the performance greatly.
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Old 11-09-2011, 09:28 PM   #381
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Quote:
Originally Posted by Davenow View Post


Now, on to Subaru increasing the diameter of the rotors on the 09 WRX.

Are you really trying to make an apples to apples comparison of going from a 4 piston fixed mount caliper, to a 2 piston floating mount caliper, on a car with a completely different chassis? Do I even need to point out how stupid that is? Do you want me to let the fact that you are ignoring (intentionally?) the concept of the fixed 4 piston caliper having a HELL of a lot more clamping force than a floating 2 piston, thereby not needing the same diameter rotor?

Did you leave that out intentionally hoping the newbies wouldnt know enough to take that into consideration, or did you yourself not know enough to take that into consideration.
Lets focus here for a moment.

First - I did not say that Subaru increased the rotor diameter for 2009 - I said they increased the rotor mass. In front to be specific. Same 294 x 24 mm front rotor - but with a higher vane density and thicker friction plates. The rear rotor did increase in diameter although that may be due to the larger park brake drum (190 mm versus 170mm)

The 4 piston calipers do not have more clamping force than the 2 piston calipers on the 08+ (which are same as the 04-05 as well). I am pretty sure it's less as the pistons are smaller on the 4 pots than the 2 pot sliders. (this I will verify so as to not leave details out) When calculating clamping for a fixed caliper you take only one side i.e. 2 of the pistons and get the piston area whereas w/ 2 pot sliders you use both pistons to get area and thus force which is line pressure times area. There is some notion that a sliding caliper has some loss as a result of the caliper having to move on the slide pins but that's a second order loss. I don't have good data on the actual amount but it's small and ignored for calculations sake.

A 1 second google search

http://www.engineeringinspiration.co.uk/hyddisc.html

Hydraulic calipers come in two basic types, sliding or fixed. Fixed calipers have one or more pistons on each side of the disc which each apply an equal force to the disc. Sliding calipers have pistons on one side of the disc only and rely on Newton’s Third Law to allow an equal reaction on the back of the disc by letting the whole housing slide on one or more guide pins. Ignoring frictional effects both types will produce similar amounts of total clamp force. The benefits of fixed calipers are predominantly better efficiency and improved environmental durability. Sliding calipers on the other hand offer packaging benefits and are the only way to add an integral parking brake function.


There are some pretty evident trends here in your original post and our ongoing discussion.




Edit

The 4 pots (06/07 WRX) have 40 mm diameter pistons - the 03-05/08+ 2 pots have 43 mm diameter pistons. Assuming line pressure is constant and loss due to being a sliding caliper = zero then the fixed 2 pots generate about 15% more clamping force than the 4 pots. Care to see my calculations?

Nevermind - they are f***** SIMPLE. PI * r^^2 * 2, r = d/2, PI = (approx) 3.14

Last edited by KNS Brakes; 11-10-2011 at 12:24 AM. Reason: Fact checking
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Old 11-09-2011, 09:49 PM   #382
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Originally Posted by Davenow View Post



Know what the worst part is? There are a lot of people out there that are not informed enough to know that just because someone is a vendor, that doesnt make them know what they are talking about. Because either you are intentionally trying to make it look like you need brake upgrades worse than you do, or you actually believe it. Either way isnt good.


Im out. Ill check back on the thread in a few weeks when my head is done assploading from the stupidity ****storm this forum has become. Dont bother PMing me whining, I delete PMs on sight for the most part.
I absolutely agree that there are tons of people out there who are not informed. Why would anyone PM you based on this post?
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Old 11-09-2011, 10:19 PM   #383
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Quote:
Originally Posted by Davenow View Post
^

Im out. Ill check back on the thread in a few weeks when my head is done assploading from the stupidity ****storm this forum has become. Dont bother PMing me whining, I delete PMs on sight for the most part.


I'm glad WRXBrakes stepped in to correct some of this guys crap.
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Old 11-09-2011, 11:23 PM   #384
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I tend to not agree.. My MPS6 had far superior brakes to my WRX I dont feel as secure driving the wrx because the brakes just dont feel like it will stop in time.. I tend to give more room between cars and SLOW down way before I normally would in my MPS6 in certain circumstances.. I mean yea I agree with the O%$%$$S%$%$ cases because nothing is gonna save you probably.

But It never hurts to have better brakes I felt alot safer in my MPS6 than my wrx
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Old 11-10-2011, 12:47 AM   #385
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Originally Posted by Dat8687 View Post
I tend to not agree.. My MPS6 had far superior brakes to my WRX I dont feel as secure driving the wrx because the brakes just dont feel like it will stop in time.. I tend to give more room between cars and SLOW down way before I normally would in my MPS6 in certain circumstances.. I mean yea I agree with the O%$%$$S%$%$ cases because nothing is gonna save you probably.

But It never hurts to have better brakes I felt alot safer in my MPS6 than my wrx
When Mazda made the Speed6 (add power/weight and AWD to the 6 platform) they significantly increased the cars brake capability.

Bigger calipers, rotors, and pads in front - bigger rotors in back - and a more aggressive pad compound.

With the Speed3 - same thing. Bigger front calipers and pads (quite a bit in fact) - and a more aggressive pad compound (from Ferodo no less - not cheap for an OEM).

Most Mazda's have good brakes.

This duplicates itself in many car lines.

Lancer vs EVO

Corvette vs Z06 (C6)

Camaro vs SS

etc.

When Subaru went from the 175 HP NA 2001 RS at 3xxx pounds to the 215HP 3xxx (150 extra ponds for the GD?) they added exactly 13mm of front brake rotor and left everything else the same. Unfortunately I assume that was all they could afford to do to bring us the car we wanted for so many years. Warts and all though - I'm glad they did. The powertrain is a thing of beauty

As far as brake performance is concerned though we got a bad deal. If you debate that you are arguing w/ physics not me. Why would you do that as it makes no sense?

-Ken
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Old 11-10-2011, 01:03 AM   #386
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for the bike brake guy, disc brakes on bicycles have a much larger pad surface area than the small clamp style brakes, which allows them to brake more efficiently. also, if you are getting brake fade on the way to work because you live on mountain roads, you are probably driving too fast for conditions or riding the brakes and this is why you are getting brake fade. i have driven on east coast mountains (small) alot, used to live in ruidoso, nm (home to one of the tallest mountains in the states), and i currently reside greece where the mountains are bigger and the roads are curvier than pretty much anything on the east coast (think tail of the dragon but on every road almost), and i have never gotten brake fade driving speed limit or anywhere close to it on any of the roads in any of these places. the only time i have gotten brake fade is when i am driving like a bat out of hell and seeing how hard i can push the vehicle...basically i am only seeing brake fade when i am purposely trying to get it. for you, i bet a pad with a better temp range and some RBF600 fluid would probably make your braking system perform flawlessly on the drive to work. it really improved my brake fade issues when i would take my stage 2 wrx on some pretty hard canyon driving...

...anyways...


i am a little confused by some of wrxbrakes posts...

you keep saying about how the ability to lock up/activate abs is not a sign of brake performance, but yet you keep going back to it and using it as an example. i will say again...THE ONLY REASON THIS SUBJECT EVEN WAS BROUGHT UP WAS BECAUSE YOU BROUGHT IT UP AND CONTINUE TO BRING IT UP

he states that in his 97 and 05 ob's he had a hard time getting the tires/abs to reach their threshholds, but then he also states that having the wheels lock up or activate abs would increase stopping distance. using this same example, wouldn't that mean that your 97 and 05 ob's brakes were not bad, but actually better because it kept everything in dynamic friction not static. also, using this same thought process, wouldn't that mean that on the wrx, purely by installing stickier tires, wouldn't that decrease stopping distance. isn't all of that just saying the exact same thing davenow did just a different way....

Last edited by amalgrover; 11-10-2011 at 06:46 AM.
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Old 11-10-2011, 01:35 AM   #387
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I'll try to explain in non-engineering terms.

Lock up or ability to do so is not a MEASURE of brake performance and that's because it's not the case where the pads/rotors are working their hardest. It's not the worst case scenario for the pads/rotors. Running just under ABS engagement IS the worst case scenario and when they ARE working the hardest (and where any weakness is exposed). You can easily go PAST this by jabbing the brakes into lockup/ABS - but that is irrelevant.

In the case of the OB/OBXT - I don't know if I even tried to do that - but I know I could not smoothly brake to the threshold of the tires at all. And the tires were not special. That means the brakes were the weak link.

This is not trivial and I apologize if my explanation is less than easy to understand. The audience varies considerably.

Yes - I and you can stab the brakes and get lockup/ABS.

Try to smoothly (and quickly) get to max braking - that is what I could not do very well/at all in my OB, OBXT or for that matter my 06 WRX w/ OEM Hitachi pads.

PS
Don't anyone DARE to test what I said unless you know wtf you are doing. All i really said is that the factory brakes on MOST Subaru's aside from the STi are systematically undersized and fitted w/ soccer mom brake pads. And there are MANY ways to improve that.

Vinegar sucks - and this is a terrible sticky that only exacerbates misinformation as it goers down in usefulness.
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Old 11-10-2011, 01:39 AM   #388
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And ABS does NOT decrease stopping distance.

ABS removes the ability to lock up brakes. That is all.

Decreasing stopping distance requires more traction (easy - new tires) and the ability to manage the power that said tires create under braking.

Remember - de-acceleration = acceleration with a minus sign so no real difference.
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Old 11-10-2011, 02:07 AM   #389
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Quote:
Originally Posted by WRXBrakes View Post
And ABS does NOT decrease stopping distance.

ABS removes the ability to lock up brakes. That is all.

Decreasing stopping distance requires more traction (easy - new tires) and the ability to manage the power that said tires create under braking.

Remember - de-acceleration = acceleration with a minus sign so no real difference.
your posts are amazingly contradictory, and that is what is so confusing...it has nothing to do with the physics or engineering terms.
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Old 11-10-2011, 04:36 AM   #390
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Quote:
Originally Posted by WRXBrakes View Post
When Mazda made the Speed6 (add power/weight and AWD to the 6 platform) they significantly increased the cars brake capability.

Bigger calipers, rotors, and pads in front - bigger rotors in back - and a more aggressive pad compound.

With the Speed3 - same thing. Bigger front calipers and pads (quite a bit in fact) - and a more aggressive pad compound (from Ferodo no less - not cheap for an OEM).

Most Mazda's have good brakes.

This duplicates itself in many car lines.

Lancer vs EVO

Corvette vs Z06 (C6)

Camaro vs SS

etc.

When Subaru went from the 175 HP NA 2001 RS at 3xxx pounds to the 215HP 3xxx (150 extra ponds for the GD?) they added exactly 13mm of front brake rotor and left everything else the same. Unfortunately I assume that was all they could afford to do to bring us the car we wanted for so many years. Warts and all though - I'm glad they did. The powertrain is a thing of beauty

As far as brake performance is concerned though we got a bad deal. If you debate that you are arguing w/ physics not me. Why would you do that as it makes no sense?

-Ken
Yea my wrx brakes suck as I stated compared to my Speed6.. Im not gonna argue physics which is mand made and man is flawed... Im simply stating an obvious item
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Old 11-10-2011, 03:56 PM   #391
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Quote:
Originally Posted by amalgrover View Post
for the bike brake guy, disc brakes on bicycles have a much larger pad surface area than the small clamp style brakes, which allows them to brake more efficiently. also, if you are getting brake fade on the way to work because you live on mountain roads, you are probably driving too fast for conditions or riding the brakes and this is why you are getting brake fade. i have driven on east coast mountains (small) alot, used to live in ruidoso, nm (home to one of the tallest mountains in the states), and i currently reside greece where the mountains are bigger and the roads are curvier than pretty much anything on the east coast (think tail of the dragon but on every road almost), and i have never gotten brake fade driving speed limit or anywhere close to it on any of the roads in any of these places. the only time i have gotten brake fade is when i am driving like a bat out of hell and seeing how hard i can push the vehicle...basically i am only seeing brake fade when i am purposely trying to get it. for you, i bet a pad with a better temp range and some RBF600 fluid would probably make your braking system perform flawlessly on the drive to work. it really improved my brake fade issues when i would take my stage 2 wrx on some pretty hard canyon driving...
Rim brake pads have the same surface area if not more then a disc brake pad(mountain bikes)...

anyways...

By adding a different pad type and fluid is that not modifying your brakes? The whole point of this post is not modifying them, that the stock brakes are enough for 99.99% of normal driving conditions, which apparently is not the case...
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Old 11-10-2011, 11:30 PM   #392
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Quote:
Originally Posted by uncoiled View Post
Rim brake pads have the same surface area if not more then a disc brake pad(mountain bikes)...

anyways...

By adding a different pad type and fluid is that not modifying your brakes? The whole point of this post is not modifying them, that the stock brakes are enough for 99.99% of normal driving conditions, which apparently is not the case...
i did some research on your bike brakes (i am not much of a bicycle guy), and you are right, i was wrong, it has nothing to do with pad surface area at all. the only advantages of the disc brakes over v or cantilever brakes is consistant braking in all weather and road conditions and effort to apply the brakes. the disc brakes perform better in wet and muddy conditions where the rim brakes become inconsistant or coated with mud , and the disc brakes usually take less effort to stop the bike than v-brakes or cantilever brakes would. v-brakes and cantilever brakes also can lose consistancy if the rim gets bent, where the disc brakes are unaffected by the rim being bent. so pretty much the v and cantilever brakes vs. disc brakes don't apply in this thread whatsoever.

...and...

you didn't read what i posted. i said that i personally had never seen brake fade on mountain roads (which is what you were describing) when driving normally or even close to it, and if you are getting that problem, then that would mean you are pushing harder than normal or riding the brakes. this would put you outside of that 99% (which i have never said that the percentage was this high...just for the record), and you can either drive more like the average person or a simple pad and fluid swap would probably fix your issues. i stated multiple times in this thread that the bone stock brakes should satisfy most of the street driven subarus, and the a simple pad and fluid swap should satisfy a good portion of the ones that the stock brakes dont satisfy.


Edit: i just read your original post again, and i realized you are wrong on something. you said, "there is a threshold, a line were the brake looses its ability to slow you down and locks up, better brakes push that line father allowing you to slow batter and faster." THE TIRES ARE THE ONLY THING THAT CAN MOVE THE "LOCKING UP" THRESHOLD

Last edited by amalgrover; 11-10-2011 at 11:43 PM.
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Old 11-11-2011, 07:36 AM   #393
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Quote:
Originally Posted by WRXBrakes View Post
And ABS does NOT decrease stopping distance.

ABS removes the ability to lock up brakes. That is all.

Decreasing stopping distance requires more traction (easy - new tires) and the ability to manage the power that said tires create under braking.

Remember - de-acceleration = acceleration with a minus sign so no real difference.
It does decrease stopping distance as opposed to locking the brakes up.
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Old 11-11-2011, 11:17 AM   #394
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I just used the 99% thing since the original poster did. As far as the bike brakes just ride some rim brakes then disc brakes back to back and you will see what I mean. They do help tons in wet/muddy conditions but they stop better on dry pavement as well.
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Old 11-11-2011, 11:37 AM   #395
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I wish everyone would read this.. I didnt read every post by everyone, so I dont know if this has been pointed out, but corvettes come with just regular, "UGLY", crappy calipers as well. So, if a vette doesnt need them, chances are 99% of cars on this forum do not.
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Old 11-11-2011, 12:29 PM   #396
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Hmmm thats good reasoning, since Chevy didn't do this so you shouldn't either.
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Old 11-12-2011, 08:16 PM   #397
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ABS DOES increase stopping distance by not allowing the driver to threshold brake. If one wheel begins to break traction, the other wheels can still stop the car quicker than kicking on the ABS system. My particular ABS system makes a significant addition to the distance and I found this out when I accidentally disabled it by driving through thick snow.
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Old 11-12-2011, 08:37 PM   #398
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Quote:
Originally Posted by amalgrover View Post
THE TIRES ARE THE ONLY THING THAT CAN MOVE THE "LOCKING UP" THRESHOLD
As a first order statement, yes.

WRXBrakes....I think you are missing a point that I'm sure I've stated in this thread. If your brakes are capable of locking up the wheel, then they are also capable of threshold braking, which would be the maximum effective braking under the condition where it's being observed. Since you have to go through the point of threshold braking to get to fully locked, an easy experience to ask is "can you lock your brakes". If the brakes were incapable of asserting enough pressure to threshold brake, then the answer would be no. I would put fourth that there is virtually no modern car in existance that is incapable of applying enough stopping force to achieve threshold braking. Now, in an ABS equipped car, when tire skid is sensed, it then reduces fluid pressure, reducing stopping force. I've driven hundreds of student's cars on the track and have had no problem finding the threshold point in a lap and keeping the car there and not in abs. Perhaps there is an abs system that doesn't allow that.....but I haven't found one. I will say that I have not driven an OBS on the track that I can remember.

From a practical standpoint, in showroom stock class, you can't upgrade calipers or rotors. I spent 14 years in showroom stock before moving up. Yes, I boiled fluid. No, I didn't have trouble achieving threshold braking. Lots of different cars over the years in that class.
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Old 11-15-2011, 12:38 PM   #399
iknowphritter
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Hmmm thats good reasoning, since Chevy didn't do this so you shouldn't either.
That wasn't the point at all.. the point was corvettes are built for performance. I don't think Chevy over looks their brakes, or anything else performance wise on those cars for that matter... so if 4 pots were significantly better, why wouldn't they throw them on their vettes as well?
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Old 11-15-2011, 08:32 PM   #400
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Keep price point down? The better optioned models do have better brakes...
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