BrandonH

It's been a long winter, and last night found me reviewing last years' race tapes. At Summit Point, I chased another G car around for the last 4-5 laps at pretty close proximity. Never got by, but got to critique his line etc in detail.

What I noticed this time that I missed before, was a frequent puff of tire smoke from the inside (Rt) rear tire in turn 6. Turn 6 is a medium low speed right hander linked immediately following RH T5, the slowest corner on the track.

So what is causing the smoke? Sometimes it was a pretty big puff. I guess it must be wheelspin, but does this suggest the absence or presence of a limited slip diff? ie is it more likely caused by wheelspin because the inside unweighted wheel is spinning, or by friction because a semi locked wheel is dragging? Or something else I'm not thinking about. I felt like I was faster in this corner and would like to better understand if this was a variable. (I have an LSD)
B

JCP911S

Brandon. I would bet it is from brake lock up. I freqently trail brake right into the apex at that turn, so the right rear tire is really unloaded... I often get a chirp there.

RedlineMan

Hey;

I'm betting on FRONT right tire lock. A 911 usually will not lighten its rear wheels that much, but the front certainly likes to take some time off and three wheel the car, eh?.

By the way, here's the same turn as your avitar, with the tire smoke I just described!

JCP911S

Could be... I'm usually not looking out of my back window right there (at least not intentionally), but just at that point, braking load is transferring weight forward, and turning is transferring weight to the left, so the right rear is the odd corner out in terms of loading plus I usually have my inside front on the curbing, so its getting alot of vertical load from that. Without an adjustable proportioning valve (not legal) I can get alot of rear lockup on my car under hard braking if I am not careful. If I could, I'd actually back the rear braking off a tad.

BrandonH

Interesting. I'll have to watch the tape more closely. Your photo illustrates why front lockup would look like rear lockup.

JCP, just figured out who you are (one of the guys in the _front_ half of the G pack) Thanks for the comment.

RedL: Yes of course that's the corner in the avatar. Main difference is that your car is correctly placed on the track. I can only plead heat of battle, but I'm obviously shortchanging myself ~10feet of run entering the worlds longest, uphill straightaway...
B

JCP911S

Brandon, thanks for the compliment "back of the front half of the pack" is alot nicer sounding than "middle of the pack"

buckdr1

Just guessing, not sure of the year of your car. Perhaps your LS(depending on type) needs new clutches? Sticking brake piston/s, does your car has any bias for front/rear adjustment? Sounds like your loosing time though, and probably gonna panic anyone behind you.
Good hunting
Bill

BrandonH

All sounds bad except the part about panicing anyone behind. I once bought a Momo steering wheel with two little side mounted built in horn buttons. The salesman cackled evilly that he had _His_ connected to the brake light switch.
B

DGaunt

Brandon, Is that Mosport in the pic?

RedlineMan

Dave;

5B to be exact, Old Bean!