Assuming that ABS is the limiting factor in stopping distance, what is the benefit of brake upgrades that are require 17" rims? Does the 12.5 kit that fits under 16" rims just reduce the possibility of fade or does it pretty much eliminate it completely? If it does eliminate it completely, why bother going to bigger kits?
Brake questions?
- Thread starter NJSHO
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SHO Continental
Moderator
12.5s fit under slicers. Even with the 12.5s pads still matter.. I watched a set of gen2s one with 13" cobra brakes the other with 11.6s with Carbotech pads do a brake test.. they were dead even, and then the 3rd time they did that I almost rear ended them because my brakes were faded and the SHO behind me almost hit me because my brake lights weren't hooked up 
The brakes were still very new.
The bigger kits are easy to install and get parts for as opposed to the 12.5 whcih needs some modofications and custom rotors. It is good for less totational mass.
The bigger brakes will allow you to stop sooner, my ABS hasnt kicked in yet. They will reduce fade as well.
The bigger kits are easy to install and get parts for as opposed to the 12.5 whcih needs some modofications and custom rotors. It is good for less totational mass.
The bigger brakes will allow you to stop sooner, my ABS hasnt kicked in yet. They will reduce fade as well.
SinisterSHO
Rust free
It really depends on what you are doing.
FWIW, the 13" brakes and the 12.5" brakes are probably going to be very close in performance. The biggest reason you upgrade to a larger rotor is for more surface area, and the brakes will be able to cool faster. However, your pads will make the biggest difference. The better pad, the less fade your going to get. Granted in a daily commute, you're not going to have to really worry about fade. On track is where you want your brakes to perform well.
Larger rotors give you more area which will cool faster, and help against fade. But I dont think that half inch is going to make a huge difference.
FWIW, the 13" brakes and the 12.5" brakes are probably going to be very close in performance. The biggest reason you upgrade to a larger rotor is for more surface area, and the brakes will be able to cool faster. However, your pads will make the biggest difference. The better pad, the less fade your going to get. Granted in a daily commute, you're not going to have to really worry about fade. On track is where you want your brakes to perform well.
Larger rotors give you more area which will cool faster, and help against fade. But I dont think that half inch is going to make a huge difference.
jedhead
New Member
Pads and tires can influence braking performance greatly too. Here is a good article that should help answer your questions:NJSHO said:
http://www.shotimes.com/brakes/survey/brakes1.html
I went with the 12.5" brakes because I was able to pick up a used set for $400. I was able to have Todd make a custom set of 2 piece rotors for me thanks to SHOpaz who had all the specs and had Todd create a set for him. The main advantages with the 12.5" setup over the stock brakes are:
1. PBR Calipers use a larger brake pad increasing the area of the friction surface to act on the rotors.
2. PBR calipers have two pistons pushing on the pad increasing the amount of pressure that can be applied pads pushing on the rotors.
3. Lower rotating mass help the car stop and accelerate better.
4. Lower unsprung mass helps the handling because there is less momentum the suspension has to deal with when the tires are moving up and down.
I think the best setup for street use is the 98 SHO brake upgrade with some high performance pads like CarboTech, Hawk, PFCM and others.
Bob
Shoaz
Studly dood
A few thoughts:
1. The 12.5" Baer kit DOES NOT fit under the slicers. It will fit under many (maybe most) 16" aftermarket rims, but not under slicers. The 12.2" kit _barely_ fits under slicers, and then only with a spacer. Many people find 16" rims favorable for road course use since they do provide some handling and tuning advantages. Usually the motivation for getting bigger rims is to fit bigger brakes underneath them, but, as mentioned, there's not going to be much performance difference between the 12.5" and 13" systems for these cars. I opted for the 12.5" because it was close enough to the biggest system and still allowed the use of 16" rims.
2. Bigger brakes (i.e., larger diameter rotors) provide more braking torque for the same clamping force. The larger rotor can absorb a bit more heat, but that doesn't really help much. Directional vanes and larger area do help ventilation and radiative cooling.
3. The 2-piston PBR calipers provide better brake modulation. Once you get used to multi-piston calipers, single-piston calipers seem crude in comparison, especially in brake release. Since these calipers are aluminum they're also lighter and dissipate heat more easily than the stock iron calipers.
4. ABS is not a limiting factor in braking performance. If you're doing things right, the ABS should never (or at least seldom) kick in. Threshold braking will always result in shorter stopping distances than if the ABS is pulsing the brakes. If the ABS is kicking in during braking, especially in the front, that's a signal that you're applying the brakes too quickly (rather than squeezing them on) or too hard. Race rubber helps alleviate this as well since the tires won't be as apt to slide. If the tires are sliding easily bigger brakes won't help; it's good to try to match the tire and brake effectiveness so that you don't have too much brake for the tire or vice-versa.
5. The only way to completely eliminate fade at the track is to keep your foot off the brake. Plenty of people have melted down every possible brake kit for the SHO because it's not hard to do. The SHO is a fairly heavy car capable of some pretty decent straight-line speeds, so it's not hard to cook the brakes on a road course, especially if the course layout is ******* brakes. I've got 12.5" Baers, TCE two-piece rotors, Porterfield R-4 pads, 3" ventilation ducts, and Castrol SRF brake fluid, and if I over use those dudes I can still melt 'em down in a hurry, especially at AMP (which is ******* brakes). The mod that had the biggest effect on brake management for me was the ducts.
6. The point of going to bigger brakes is to a) shorten stopping distances, especially with race rubber, b) increase the heat tolerance of the system (i.e., have something that can handle more heat before failing...not immune from failure, just an increased failure threshold).
7. Pads make a huge difference, too. There are lots of tradeoffs, though, especially between grip and rotor wear.
When I first started tracking the SHO with the stock brakes I learned very quickly that I had to leave a fair amount of room between me and the Porsches/BMWs when entering a corner or I was going to leave a big imprint in their rear bumper. I was lucky to learn this without actually hitting anybody. Once I got the Baers on with track pads I could brake with those guys easily for a few laps, then I had to back off. Once I got the ducts and the SRF in I could brake with them (even outbrake them sometimes) consistently throughout a session, as along as I'm reasonably careful to manage them.
Good brakes make a big difference. It took me a long time and a lot of patience and development to get a system that works well and consistently for me. Technique matters and other folks have worse/less problems that I've had. Lance still uses the 96 brakes with the stock calipers and does really well with them (but his car is reasonably light, too).
Jedhead - I'm glad to see that you and the other folks that are getting Todd's two piece rotors for the 12.5" kits are benefitting from that work. You're all most welcome...Todd makes good stuff.
1. The 12.5" Baer kit DOES NOT fit under the slicers. It will fit under many (maybe most) 16" aftermarket rims, but not under slicers. The 12.2" kit _barely_ fits under slicers, and then only with a spacer. Many people find 16" rims favorable for road course use since they do provide some handling and tuning advantages. Usually the motivation for getting bigger rims is to fit bigger brakes underneath them, but, as mentioned, there's not going to be much performance difference between the 12.5" and 13" systems for these cars. I opted for the 12.5" because it was close enough to the biggest system and still allowed the use of 16" rims.
2. Bigger brakes (i.e., larger diameter rotors) provide more braking torque for the same clamping force. The larger rotor can absorb a bit more heat, but that doesn't really help much. Directional vanes and larger area do help ventilation and radiative cooling.
3. The 2-piston PBR calipers provide better brake modulation. Once you get used to multi-piston calipers, single-piston calipers seem crude in comparison, especially in brake release. Since these calipers are aluminum they're also lighter and dissipate heat more easily than the stock iron calipers.
4. ABS is not a limiting factor in braking performance. If you're doing things right, the ABS should never (or at least seldom) kick in. Threshold braking will always result in shorter stopping distances than if the ABS is pulsing the brakes. If the ABS is kicking in during braking, especially in the front, that's a signal that you're applying the brakes too quickly (rather than squeezing them on) or too hard. Race rubber helps alleviate this as well since the tires won't be as apt to slide. If the tires are sliding easily bigger brakes won't help; it's good to try to match the tire and brake effectiveness so that you don't have too much brake for the tire or vice-versa.
5. The only way to completely eliminate fade at the track is to keep your foot off the brake. Plenty of people have melted down every possible brake kit for the SHO because it's not hard to do. The SHO is a fairly heavy car capable of some pretty decent straight-line speeds, so it's not hard to cook the brakes on a road course, especially if the course layout is ******* brakes. I've got 12.5" Baers, TCE two-piece rotors, Porterfield R-4 pads, 3" ventilation ducts, and Castrol SRF brake fluid, and if I over use those dudes I can still melt 'em down in a hurry, especially at AMP (which is ******* brakes). The mod that had the biggest effect on brake management for me was the ducts.
6. The point of going to bigger brakes is to a) shorten stopping distances, especially with race rubber, b) increase the heat tolerance of the system (i.e., have something that can handle more heat before failing...not immune from failure, just an increased failure threshold).
7. Pads make a huge difference, too. There are lots of tradeoffs, though, especially between grip and rotor wear.
When I first started tracking the SHO with the stock brakes I learned very quickly that I had to leave a fair amount of room between me and the Porsches/BMWs when entering a corner or I was going to leave a big imprint in their rear bumper. I was lucky to learn this without actually hitting anybody. Once I got the Baers on with track pads I could brake with those guys easily for a few laps, then I had to back off. Once I got the ducts and the SRF in I could brake with them (even outbrake them sometimes) consistently throughout a session, as along as I'm reasonably careful to manage them.
Good brakes make a big difference. It took me a long time and a lot of patience and development to get a system that works well and consistently for me. Technique matters and other folks have worse/less problems that I've had. Lance still uses the 96 brakes with the stock calipers and does really well with them (but his car is reasonably light, too).
Jedhead - I'm glad to see that you and the other folks that are getting Todd's two piece rotors for the 12.5" kits are benefitting from that work. You're all most welcome...Todd makes good stuff.
SinisterSHO
Rust free
You mentioned fluid Eric, besides a higher temp rating, what are the advantages of a different fluid? Or is it that fresh fluid is going to work better than old fluid?
Shoaz
Studly dood
Fresh fluid definitely works better than old fluid, and even with fresh fluid different types have different boiling points. If you have trouble with boiling brake fluid (which I did frequently), then addressing cooling as well as increasing the boiling point will both help. Most brake fluids high boiling point is only valid before the fluid gets a chance to absorb any water, which is why it needs to be fresh.
There are lots of good treatments on the web regarding brake fluids, including the following:
http://www.shotimes.com/php-bin/modules.php?op=modload&name=News&file=article&mode=thread&order=0&thold=0&sid=59
http://www.stoptech.com/tech_info/wp_brakefluid_1a.shtml
The Stoptech site data is a bit more recent. Stoptech's white papers are, in general, excellent IMHO. You can see them all at:
http://www.stoptech.com/tech_info/tech_white_papers.shtml
There are lots of good treatments on the web regarding brake fluids, including the following:
http://www.shotimes.com/php-bin/modules.php?op=modload&name=News&file=article&mode=thread&order=0&thold=0&sid=59
http://www.stoptech.com/tech_info/wp_brakefluid_1a.shtml
The Stoptech site data is a bit more recent. Stoptech's white papers are, in general, excellent IMHO. You can see them all at:
http://www.stoptech.com/tech_info/tech_white_papers.shtml
Gotta step in a minute Bob and help you out,
Larger pad area does not change the torque or 'power' of the brakes. It's location can have some minor effect but larger for the most part only means longer life.
Piston qty does not effect the 'power' or clamping of the rotor. Piston AREA does. i.e a ten *** caliper with one inch pistons can produce less toque than a either a four *** FSL or the stock iron one. Multi pistons simply apply more even pressure to the pad plate. Think no banana.
Changes to brake performance come from:
Rotor OD
Pad Cf
More piston area
Each has its own pros and cons.
Larger pad area does not change the torque or 'power' of the brakes. It's location can have some minor effect but larger for the most part only means longer life.
Piston qty does not effect the 'power' or clamping of the rotor. Piston AREA does. i.e a ten *** caliper with one inch pistons can produce less toque than a either a four *** FSL or the stock iron one. Multi pistons simply apply more even pressure to the pad plate. Think no banana.
Changes to brake performance come from:
Rotor OD
Pad Cf
More piston area
Each has its own pros and cons.
jedhead
New Member
Todd,
Thanks for the help and corrections.
Bob
Thanks for the help and corrections.
Bob
SinisterSHO
Rust free
I was just thinking about that. How does the Wilwood FSL compare to the PBR Cobra caliper, as well as the stock. And just for comparison, how about the BSL6?Todd TCE said:
SinisterSHO
Rust free
Sorry, piston area.
SolidState
No Mo SHO
this is a good thread. It should be stickied to the top.
Shoaz
Studly dood
Most of the PBR calipers use two 38mm pistons (some are 40mm, but they're rare). I'm not sure what units Todd is using for the area comparisons (sq in?) but it could be calculated pretty easily.
SinisterSHO
Rust free
So [i'm a little drunk] a stock caliper made of aluminum could give you the best performace?
Yes you are.
No, it would only be a lighter version of a singl ***. The efficiency of the single piston is called into question for feel, responsiveness, and pressure point on the pad plate. And on a larger rotor would tend to over bias the front of the car quite a lot.
All just talk, there isn't one anyhow. Go back and get another beer.
No, it would only be a lighter version of a singl ***. The efficiency of the single piston is called into question for feel, responsiveness, and pressure point on the pad plate. And on a larger rotor would tend to over bias the front of the car quite a lot.
All just talk, there isn't one anyhow. Go back and get another beer.
jedhead
New Member
Here is a couple of pictures of my brake set up with slicers. I don't have any spacers and the slicers fit. I did notice that the previous owner of the calipers modified (ground off) the calipers. The slicers look like they are stuffed with rotors and no much room is left. I like the stuffed look.
Slicers with TCE/Baer 12.5" brakes. I just grabbed a slicer from the yard so its covered with mud.
My Calipers. You can see where they were modified.
Bob
Slicers with TCE/Baer 12.5" brakes. I just grabbed a slicer from the yard so its covered with mud.
My Calipers. You can see where they were modified.
Bob
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