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FordGT40
FordGT40 New Reader
3/11/14 3:29 p.m.

Okay, I did a little testing over the weekend and maybe my brakes are not as bad as I remembered them to be from my last track day. I took the car out to an isolated area with a nice long straight road with little traffic and did a few 60-0 tests. This was a very unscientific test but at least it should give me something to go by. I have a 3.73 rear end in my car and have got the speedometer gear that is supposed to correct things but when my speedo reads 60 I'm actually doing about 56 or 57 MPH. With that said, my average distance from 60 to 0 was an unofficial 144'. I have ordered a set of 13" rotors with 2 piston calipers from Summit racing. I'll re-do the test after I change them and see what happens.

pres589
pres589 UltraDork
3/11/14 4:52 p.m.

144 feet is not impressive. Your speedo sounds about right for a factory setup. You will probably need new flex hoses to get "Cobra" calipers to work on your car.

z31maniac
z31maniac UltimaDork
3/11/14 5:15 p.m.

Bigger brakes won't make you stop faster. Braking is mostly a function of your tire compound.

Bigger brakes are bigger heat sinks so they won't fade on track, and of course a larger rotor ends up with more torque because of leverage, but with added weight.

FordGT40
FordGT40 New Reader
3/12/14 8:05 a.m.

I realize it's not an impressive number but when I looked at the distance marked out on a road it just looked a lot shorter than I thought it would be. Hopefully on a track day I won't be doing any 60-0 stops anyway, if I am I have more serious problems I guess. The kit I bought has new braided lines and my tires are Nitto NT555's - hopefully the new brakes will work better for me and if they don't at least they will look better.

dean1484
dean1484 GRM+ Memberand PowerDork
3/12/14 8:59 a.m.

My 94 has the PBR swap and I have been chasing brake balance in it. As in I don't have much of any rear brake. I have changed the steel lines, the soft lines, the proportioning valve (to a 98GT one) new rear calipers and the master and it has made no difference. I am at a loss as to why I don't have any rear brakes with the PBR calipers from the later GT in my 94.

I am seriously wondering if the lines on the master are backwards. I have not tried swapping that around that yet. This summer I have to dig in to this again but if anyone had any suggestions it would be hugely helpful. I may actually swap back to the stock calipers. I got the car with the PBRs on it so I have never tried it with the stock calipers up front but driving the car the way it is in any kind of snow or even wet roads leads to front wheel lock up really easily.

wvumtnbkr
wvumtnbkr GRM+ Memberand Dork
3/18/14 1:35 p.m.

Dean: It sounds like your master cylinder is not sized properly for the different front caliper volume. All of your volume is going to the front and there isnt much left to engage the rear pads.

GT40: As stated previously, tires have WAY more to do with stopping distances than brake rotors or calipers. I would even say Pads have more to do with that than rotors or calipers.

When you did this test, did you get into ABS? What was the spread on the tests? (For example, 130 the shortest 170 the longest?) If you didn't get into ABS, were you right at the edge of threshold braking each time? If you did get into ABS, the test is kind of invalid. In other words, there were other factors involved that had nothing to do with braking performance.

If you don't have ABS, can you lock up the tires? Can you lock them up after 10 hard stops? That is the only indication that you need larger brakes.

All of the above is IMHO!

Good Luck!

Rob R.

FordGT40
FordGT40 New Reader
3/19/14 1:25 p.m.

wvumtnbkr: Thanks for the input, my test was just a 3 stop test for my own benefit. All of the stops were within 10-15 feet of each other. VERY unscientific I know but at least as good as the butt dyno I figure. I tried to get just to the edge of my ABS and there were no lock ups. I've got the new brakes installed now and am in the break-in process. If nothing else they look a lot better! [URL=http://s1261.photobucket.com/user/randyholbrook/media/Brakes/003.jpg.html][/URL] [URL=http://s1261.photobucket.com/user/randyholbrook/media/Brakes/004.jpg.html][/URL] [URL=http://s1261.photobucket.com/user/randyholbrook/media/Brakes/005.jpg.html][/URL] [URL=http://s1261.photobucket.com/user/randyholbrook/media/Brakes/002.jpg.html][/URL] [URL=http://s1261.photobucket.com/user/randyholbrook/media/Brakes/007.jpg.html][/URL]

wvumtnbkr
wvumtnbkr GRM+ Memberand Dork
3/20/14 9:21 a.m.

Remind me what the intended use of this car is?

If it is going to see track days and you are already concerned with brake issues, I would be changing out those new rotors for solid blanks.

Drilled rotors = show. They crack!

Sorry for being a Debbie Downer. I have been down this road before.

Rob R.

FordGT40
FordGT40 New Reader
3/20/14 10:41 a.m.

Rob, my use for this car is for weekend driving, cruise-ins, maybe an occasional autocross and 2-3 track days per year. Just yesterday I found an article on the Tire Rack website that said exactly what you are saying about cracking. I did a lot of internet research on this but apparently not quite enough. The Tire Rack article did say that IF you use them on a track day to keep a very close watch on them and replace them at the first sign of cracking. I'm new at all of this, having done only 4 track days total and I'm old so I probably drive the car at around 8/10ths on the track. Do you think they would be okay for this use or should I get some solid ones to change out for track events? Thanks for the advice.

Apexcarver
Apexcarver PowerDork
3/20/14 10:47 a.m.

Get solids for track events. Even then, if you really use your brakes, you should be watching for cracks.

Read this, http://corner-carvers.com/forums/showthread.php?t=3144&highlight=rotor+crack

Be sure to do cooldown laps to prevent uneven cooling.

wvumtnbkr
wvumtnbkr GRM+ Memberand Dork
3/20/14 10:49 a.m.

Run em. Just keep an eye on them!

I have witnessed a rotor explode on a CTS-V that was drilled.

That car had 500 hp and slicks. I am pretty sure they were pushing the braking system a lot harder than we are!

Keep an eye on them and when it is time to replace the rotors, just go with blanks.

Rob R.

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