I agree that downhill braking puts more stress on the system since you have forces of the car and gravity at work. But, thats not a factor at Thunderbolt which is almost flat. At Summit Main the biggest brake zone is turn 1 which is flat. VIR turn 1 is flat, the turn leading to Oaktree is up hill and the first zone at the end of the backstraight is pretty flat, maybe a slight down hill.

I think the bigger factors are: a) rate of speed, b) amount of speed that must be scrubbed off and c) recovery time before next brake use. This would explain why Shenandoah isn't too hard on brakes - despite having a high number of brake points, the speeds are pretty low. Summit Main is tougher, even though it has fewer brake points over the same distance, because the speeds are much higher. Thats my theory anyway...:-)

 

WHEW! I'm so glad this didn't turn into some East-coast/West-coast rivalry thing. Besides, we all know the Midwest has the toughest tracks of all.

Mostly I'm seconding what's been suggested about what makes a track tough on brakes. Blackhawk is particularly tough on them even though top speeds are not terribly high and you're not bleeding down huge amounts of speed - the killer is that it's such a short track and there's just never a chance to cool the brakes down even with ducts.

Anyway, just an FYI, since steelcomp mentioned 14" rotors, here are some weights taken earlier this year:

StopTech weights: (taken on 1.16.10)
- 14" 2-pc. AeroRotor: 17.5 lbs
- ST-40 Caliper (incl. braided lines): 9 lbs
- Mounting Bracket: 1 lb

For comparison, the S197's OEM GT parts are as follows:
- 12.4" rotor: 18 lbs
- Calipers (not incl. lines): 4.5 lbs

- Stoptech 1-pc. 14" AeroRotor: 23 lbs
- GT500 14" 1-pc. rotor: 25 lbs

Notice that the 2-pc 14" rotors are actually a smidge lighter than the 12.4" OEM rotors. Of course, you're still out by about 4.5 lbs going to the larger caliper (too bad it's unsprung weight, but at least it's not rotating). Also note, if you're not going to pony up the expense of the 2-pc rotors, you get hammered! And if you do go the 2-pc route, you STILL get hammered in expense (they're ungodly expensive compared to stock take-off rotors).

All told, despite the fact I'm now running the BBK w/2-pc rotors, there's still a very strong case to be made for staying stock w/upgrades.

Best,
-j

 

I think you misunderstood my comment about the 14" brakes...if the Brembo's were 13" they'd be just as effective with less weight, and yes, unsprung weight has to do with suspension, but so does suspension have to do with braking and maintaining a good tire contact patch. Try to not separate the two in your thinking. The brakes are as much a part of the suspension "system" as any other part, and tire contact patch is always the final goal.
These cars weigh 3600lbs and if driven aggressively will be hard on even the best brakes. I like to drive deep into turns so I know I'm hard on brakes. After a few laps at Buttonwillow on the stock (with all the track upgrades) brakes I knew this wasn't going cut it. One of the last times I was at Willow I had just stopped in to see some other guys run and I let one of the instructors take my car out for a few laps with the Wilwood "street" pads and after 5 laps he could tell they were getting hot. Ha ha...when he came in and pulled up I could tell they were hot too!! He said, "jump in so we can cool the brakes off a little" and we drove around the pits and talked about the car's handling (and the Viper and GT500 he chased down and passed )
One thing heavier front springs help with is nose dive.

 

So as I saved 6 pounds per wheel by going from my Steeda Ultra Lites to the Enkei's that offsets most of the increase from going to the GT500 brakes

For me the additional heat capacity with the GT500 rotors is worth it especially on a short track. In addition I have the extra weight on the front of the SC and the extra power to get the speed up between corners.

I think if you are going to a BBK then the GT500 option is the best bang for the buck. The kit is reasonable, there are a lot of different pads available for them, the rotors are relatively cheap and they hold up well.

 

You mean unsprung weight...
Did you ever do a 13" 2 pc rotor weight comparison? This goes back to my comment about 14" rotors.

 

Ish! How the heck did I manage that error? Too soon before my coffee to post. Thanks comp, I'll go back and correct the post. Which of course, makes it "too bad..., but at least..." as opposed to a simple "at least..."

Sorry, no weights on the 13" rotors. I don't have any to check. My buddy runs the Brembo 14" ones, and I have a 1-pc 14" set of Aeros I take to the track as an emergency back-up (so I had access to them).

 

Oh, and another +1 for steelcomp! The rest of your suspension is going to directly interact with your braking system. I'm currently working out a balance issue, in part brought on by some increasingly nasty nose dive (those R-comps grip like mad compared to my old street tires). So now my rear end is getting seriously squirrely on me; not fun.

Anyway, the specific point is that yes, stiffer front springs would likely help the situation, if (as I suspect) what is happening is that the rear is coming unloaded and reducing the tire contact patch to the point of making the rears damn near useless with the current compound I'm running there.

I'm scheduled to do some back to back tests next week with different rear pads, so if I find anything useful I'll post it. I have the pads, I don't have the springs, so this is the "cheap and easy" test. If it comes down to needing new springs, it will likely have to wait until next year.

Best,
-j

 

I'm interested in hearing how you make out as I'm suffering the same problem braking from 130+ mph to about 70 mph at the end of the main straight at Mosport. It is also aggravated by the braking zone starting just over the crest of a small hump and the whole car gets light.

So far my only solution is to grin and ignore it and brake later and harder after the car settles from the hump.

 

Colin what rear pads are you running? Some folks have suggested to me that both "too mild" and "too aggressive" rear pads can cause the problem I'm experiencing - which is just frustrating...thus the tests to see for myself what helps. By "aggressive" I mean mostly initial bite and then overall friction.

I'm currently running XP12s on front Stoptech brakes w/14" rotors and XP10s in the OEM rear calipers w/stock rotors. That's the common sort of "split" many folks advocate, but then I get different stories on what combination works with a larger rotor up front.

Camp 1: Larger rotors yield a longer torque arm, so the fronts are acting just a bit more aggressively than before. So going to an "even" compound front and rear yields a similar "split" as is often recommended.

Camp 2: Absent stiffer springs, the rears are just getting so unloaded that the higher initial bite compound in back is only going to lock up the rears. A pad w/less initial bite will give the rears tires a chance to work rather than snapping into lock up. So an even larger split is required (like XP12 front and XP8 in back).

Me, I'm not in either camp; I don't understand jack about what the heck is going on with my car now, I just don't like it. I'm not driving anywhere near the limit with the current set up.

When I first went on track with the Stoptech system I did have street pads in the rear (didn't get my order in on time for the rear pads). I had the Bobcat pads in. They did get loose in the back, but I was able to compensate for it with shock settings in a way I haven't with the XP10s in back. That seems to favor Camp 2's view, but that was also on a track with very different characteristics than the one I ran the XP10s. To add to the mess, there are other issues going on that I need to sort out first before I declare the current XP12/XP10 combo a failure. So the tests I spoke of are to first sort that stuff out. Then re-test the current combo, then swap back to the Bobcats and test those. If things move in a positive direction with the Bobcats, I'll likely switch to XP8s for track use. If they move negative I may order a set of XP12s and test those.

At this point, I'm so frustrated with the braking that I'm willing to shell out the money just to do the damn test. I want to drive! I can't drive if I'm second guessing my braking (call it a character flaw). I need it to be there in that "the sun will rise tomorrow" sort of way. Ironically, my old OEM fronts never gave me such angst. They were never super confidence inspiring for late braking shenanigans, but they were as consistent as the sun rising. And I even bucked convention and ran XP10s on all four corners (but never with R-comps, just damn fine summer streets: Toyo R1Rs).

Anyway, I'll keep you posted on the results.

Best,
-j

p.s. - I just realized that some of what I just said might give folks the impression I think the switch to the BBK has been all bad. It hasn't. Under most conditions they feel far better than the modified OEM set up. I'm just having a bad situation right now, but I feel confident that once things have been sorted out they'll be outstanding. I do think they'll be "super confidence inspiring" and "super consistent" at the same time.

 

Shock tuning and spring rates will help those issues...mostly spring rates in the front. Also...these cars with the ABS put a lot more braking bias on the rears. Straight line braking, brake a little earlier and a little more gently, slow in, fast out really works well with these cars.