Brake info/FAQ

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jamal
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Post by jamal » Wed Mar 05, 2008 8:23 am

A Lotus Exige S comes with super sticky Yokohama A048s and according to Car and Driver takes 154ft to stop from 70. In the same test, a Porsche GT3, which weighs 1200lb more, took 145ft to stop from 70, which equates to 1.1g. The GT3 had Michelin Pilot Sport Cup tires, which are road legal race tires. An Ariel Atom, which only weighs 1430lb, still took 148ft to stop on the A048s.

So we have a 3200lb car stopping in a shorter distance than a 1400lb car. Taking the back seats out of a Legacy isn't going to shorten braking distances.


Test in question

skid542
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Post by skid542 » Wed Mar 05, 2008 3:10 pm

Okay, so three different cars with two different tires, three different brake biases, three different rotor and pad selections all stop in different distances. I would expect that.

However, that example does not directly address the issue of changing only the weight of a car and leaving all other factors the same.

My last car weighed 2750lb with me in it. I know this as I drove over scales weekly. I am confident that this weight difference contributed to a shorter braking distance.

I am not trying to say that weight is the largest contributor to braking distance (because it is not), just that it is a factor with measurable effects.

It all comes down to a very simple question - with all variables held constant, does reducing the energy of the system shorten the braking distance?


I'm done.
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jamal
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Post by jamal » Wed Mar 05, 2008 11:35 pm

the point was that a 3200lb car stopped in less distance than a 1400lb car. You can't chalk that up to brake bias or pads or the calipers.

If a car stops shorter because of less weight, it's not due to the drop in kinetic energy. It's because the tires have a higher coefficient of friction at that load.

The Cf of a tire does vary with load, and generally as load increase the µ decreases. So with cheap skinny tires you might see a difference. With wide performance tires, probably not.

BXSS
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Post by BXSS » Thu May 01, 2008 2:10 pm

Alot of good info in this tread - I was trying to figure out how many 5x100 front brake set-ups Subarus came with (I came up with 7) a few weeks back.

According to folks on RS25 the new smooth 4pots from the '06 WRX work with 16x6.5 OEM rims.

I have 2 sets of JDM 4 pots (STi V3+V4) & can tell you the cast letters kept me from using my 16" forged BBS rims (14lbs each!), so the RS25 guys may be right...
I was going to take a grinder to "SUBARU" letters but found a set of 15" Enkei Rally rims that clear the big brakes (+ weigh just 12lbs each!!!).

I've seen the brakes on the Lotus & they are a joke - the fronts look like Subaru 2pot rears, but the car is light so it does not need much to get it stopped.

The GT3 has 6 piston calipers (yellows) HUGE rotors on a 1000lb heavier car so it needs this hugeness to stop the car in the same distance range.

I have to agree with SKID - comparing these 2 cars is comparing apples to oranges.
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SILINC3R
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Post by SILINC3R » Sat Nov 29, 2008 9:29 am

sorry did we go over that if you want to stop once in the shortest distance upgrade the tires and if you want to stop in the shortest distance consistently upgrade the brake system
Tony
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yazmo
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Post by yazmo » Fri Jul 17, 2009 10:04 pm

hey guy can anyone confirm this its hp+ hawk front and hps rear?
i found them here at 120 for the front and 105 for the rear is that good deal?

i think that not right! there is no front hawk pads for turbo model?
i am looking for rear rotor and pads replacement right now

Legacy777
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Re: Brake info/FAQ

Post by Legacy777 » Sat Jun 09, 2012 6:17 pm

I've unstuck this thread, but added it to sticky compilation thread.

http://bbs.legacycentral.org/viewtopic.php?f=8&t=49582
Josh

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If you need to get a hold of me please email me rather then pm

AlaskanLegacy
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Re: Brake info/FAQ

Post by AlaskanLegacy » Wed Aug 07, 2019 4:31 am

So if I read through this correctly, I could upgrade the front brakes of my 94 turbo wagon to 06-07 4 pots, and leave the oem brakes in the rear and the biased would be okay?

mike-tracy
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Re: Brake info/FAQ

Post by mike-tracy » Wed Aug 07, 2019 6:46 am

AlaskanLegacy wrote:
Wed Aug 07, 2019 4:31 am
So if I read through this correctly, I could upgrade the front brakes of my 94 turbo wagon to 06-07 4 pots, and leave the oem brakes in the rear and the biased would be okay?
Based on the brake math spreadsheet, you are moving brake torque less than 1% rearwards, I'd imagine you wouldn't even feel the difference in balance. You'll be fine.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

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