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Testing of the Boxster calipers/A8 rotors
The testing of the Boxster calipers/A8 rotors went great. Here are my findings:
Test conditions:
The track conditions were ideal -- ~ 70 deg. F, sunny, and perfectly dry asphalt. To keep this a real world test, I kept the V8 in street form: spare, jack and tools left in trunk, new DOT 3 brake fluid, Porterfield R4S (street) pads. The car weight was exactly 4005 lbs. without passengers. The total on track weight was about 4400 lbs. with me and either one of the two of my Audi fanatic friends riding along. This represents the worst case scenario for an Audi: the heaviest Audi with an automatic transmission that doesnt provide much if any compression braking.
Portland International Raceway is an approximately 2 mile long road course consisting of a long front straight and a long back straight sections of track connected by mostly right hand turns. The course is run in the clockwise direction. See http://www.teleport.com/~autorace/pir/ for details.
On track sesssions:
The event was put on by the local chapter of Porsche Club of America. There were approximately 85 cars there. I ran with the touring group as I expected to only get up to 120 mph at the end of the front straight. This proved to be OK, but I had to pass a few cars each session or pull off and let the traffic in front of me pass so the V8 had room to run.
The first three 20 minute sessions went very well. The brake setup brought the car down from 115-120 mph at the end of the front straight and from about 90-100 on the back straight rapidly, repeatedly, and consistently. It surprised one of my friends as I didnt have to brake until about the same point he has to in his turbo coupe GT with Wilwood brake kit! I can go deeper into the pocket in my urq, but that car weighs 1000+ lbs. less and I can dial in the front to rear brake bias as well.
After each session, we drove the car into the staging area and checked the brake pads. They were holding up great with very little wear. I wasnt so lucky in the last 20 minute session. I decided to push the car harder, going further down the front straight before braking and doing a bit of trail braking (my end of straight speeds were faster as well). After a couple of laps, I could feel the brake force reduce as the fluid boiled and the pads started to leave slag on the rotors! In that one 20 minute session, I lost = the thickness of the brake pads!
I havent had a chance to take the caliper brackets off and examine them closely, but should be able to tonight. From my under car inspections, they appear to be fine. All indications are that Greg Amy did a superb job designing those brackets!
Conclusion:
The Boxster calipers/A8 rotors brake system worked great. In my opinion, it is an excellent street braking system. I pushed the braking system harder most anyone ever would (or a sane person would anyway) on the street, and the system did great. I am very satisfied with what we have done and am glad we did it!
The system could be an acceptable occasional Drivers Education (DE) track braking system if the brakes are prepared for track use (ATE superblue and some Porterfield R4 or R4E brake pads). Heck, if I hadnt INTENTIONALLY pushed the brake pads past their limit, I would not have worn them down so much.
I know that I was using the wrong brake pads for as hard as I pushed the car during the 4th session. Previous experiences with the urq using street brake pads on the race track have had much worse results (the urq could go though a set of metal master, jurid, or any OE metallic pads in ONE track day).
If I were going to consistently track the V8, Id have to agree with what Scott Justinson told me last year at Colorado Motorsports Speedway: You cant get good (track) brakes on the V8 without going to at least a 17 wheel and using a rotor the barely fits under that.
Once good 4 piston calipers are installed, the only problem that remains is heat dissipation. Thus, if you want to track a two ton plus car and be able to left foot brake, trail brake, and do it consistently all day long, you need to use a huge diameter rotor. A rotor that is twice as thick wouldnt hurt either!
Other comments:
The Dunlop D40 M2 tires (225/50/16) were near the wear bars so were the perfect cheap racing tire. I was very surprised at how well the 2 ton boat handled. The car was very easy to drive fast. There was almost no tire squeal and no surprises. The car is very balanced. Audi did an excellent job with the V8. I have done NOTHING with the suspension except replace the dead shocks with Boge Turbo Gas units (the OE shock replacement for the V8).
Let me say, however, that our urq is a much better track car than the V8. If I had been driving that, I could have run with the prepared cars and harassed some P-cars! The V8 may see track duty again on a quattro club day, but probably wont be run with the other German marques again. Those Porsches are just too light and fast!
P.S. I cant access my home e-mail address: johkar@teleport.com easily as our modem is dead. Please direct questions/comments to our business e-mail ksquaredmotorsports@eudoramail.com. It is checked at the end of the work day.
Happy Motoring!
John Karasaki
Ksquared Motorsports
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