Negative camber tricks?
10-04-2007, 11:16 PM
#16
Racer
Thread Starter
Join Date: Oct 2005
Posts: 273
Likes: 0
Received 0 Likes
on
0 Posts
I just found the alignment printout from the last trip to the rack - only -.5 and -.7 - so there should be plenty of adjustment room left. (sorry, couldn't find the d*mn thing last night) The guy who did the work lead me to believe that the camber was maxxed out, so somethin's up.
10-05-2007, 11:16 AM
#17
Yeah, for autoX and street, you'll probably want -1 to -1.5 up front with no toe.
For full track use I'd do toe out (wears the tires a lot and squirmy at high speeds on the road) and even more negative camber.
For the backs, I left them just a little negative from stock.
For full track use I'd do toe out (wears the tires a lot and squirmy at high speeds on the road) and even more negative camber.
For the backs, I left them just a little negative from stock.
10-05-2007, 12:16 PM
#18
Race Director
Yeah, for autoX and street, you'll probably want -1 to -1.5 up front with no toe.
For full track use I'd do toe out (wears the tires a lot and squirmy at high speeds on the road) and even more negative camber.
For the backs, I left them just a little negative from stock.
For full track use I'd do toe out (wears the tires a lot and squirmy at high speeds on the road) and even more negative camber.
For the backs, I left them just a little negative from stock.
Autocrossers sometime use toe out to aid turning, but in autocross straights are very short and it is all about turns. It make more sense to give up some straight speed to ensure optimal turning. In general an autocross car should be highly unstable so that it can turn very very qucikly. A track car needs to be much more stable as in due to the high speeds the effects of weight transfer are greater and thus all that instability you want for autocross makes the very hard to mangne in the much larger more sweeping corners on big track.
On the 944 you need to have rear toe in so that under heavy braking the rear suspension does not flex to toe out. The geometry of the rear is such that this is normal. So go with 0 rear toe and under brakes the wheels toe out and the car gets very unstable. So unstable that it slows you down or you are likely to spin. A little toe in allows the rear suspension to flex out and this no toe out under braking maintain some stablilty required for maximizing entry speed.
What negative camber does for you is to lean the tire such that when the car leans in a corner the tire is more flat on the ground. Body roll incudes postitive dymanic camber and static negative is used to counter act this. This is why more camber = more grip (to a limit of course) since you have a better shaped contact patch when cornering. The raicing downside to too much camber however is in front limited braking capablity due to sub optimize tire patch shape and in the rear inside rear wheel traction limitations again due to contact patch shape. Like any thing on race car optimal is to fine the balance between those to demands.
10-05-2007, 07:09 PM
#19
Racer
Thread Starter
Join Date: Oct 2005
Posts: 273
Likes: 0
Received 0 Likes
on
0 Posts
The car is a fair weather toy and autocross car - no worries about tire wear. You're certainly right about stability (or lack thereof) in an autocross setup. I ran a fair amout of toe-out in the rear of my old Neon STS car, along with a big rear sway bar. I could drop-throttle oversteer that thing very easily - no fun on the highway, though!
10-17-2007, 07:00 PM
#20
Racer
Thread Starter
Join Date: Oct 2005
Posts: 273
Likes: 0
Received 0 Likes
on
0 Posts
Update - turns out the camber eccentrics in the front were rusted solid. Several days of soaking in PB Blaster and lots of wailing away with implements of destruction later, 3 of the 4 bolts (both lowers and the passenger side eccentric) broke loose. The driver's side eccentric snapped in two just behind the nut. Ordered all new hardware this morning, but I'll miss this weekend's autocross...d*mn!
10-19-2007, 01:09 PM
#21
Instructor
Join Date: Mar 2004
Location: Miami, FL
Posts: 119
Likes: 0
Received 0 Likes
on
0 Posts
Toe out is bad on a race track. Diabolical in the rear and not helpful in the front. The reason is any toe out or toe in makes the car slower in a straight line by introducing wheel scrub. If you want to improve turn in don't do it with toe out.
Autocrossers sometime use toe out to aid turning, but in autocross straights are very short and it is all about turns. It make more sense to give up some straight speed to ensure optimal turning. In general an autocross car should be highly unstable so that it can turn very very qucikly. A track car needs to be much more stable as in due to the high speeds the effects of weight transfer are greater and thus all that instability you want for autocross makes the very hard to mangne in the much larger more sweeping corners on big track.
On the 944 you need to have rear toe in so that under heavy braking the rear suspension does not flex to toe out. The geometry of the rear is such that this is normal. So go with 0 rear toe and under brakes the wheels toe out and the car gets very unstable. So unstable that it slows you down or you are likely to spin. A little toe in allows the rear suspension to flex out and this no toe out under braking maintain some stablilty required for maximizing entry speed.
What negative camber does for you is to lean the tire such that when the car leans in a corner the tire is more flat on the ground. Body roll incudes postitive dymanic camber and static negative is used to counter act this. This is why more camber = more grip (to a limit of course) since you have a better shaped contact patch when cornering. The raicing downside to too much camber however is in front limited braking capablity due to sub optimize tire patch shape and in the rear inside rear wheel traction limitations again due to contact patch shape. Like any thing on race car optimal is to fine the balance between those to demands.
Autocrossers sometime use toe out to aid turning, but in autocross straights are very short and it is all about turns. It make more sense to give up some straight speed to ensure optimal turning. In general an autocross car should be highly unstable so that it can turn very very qucikly. A track car needs to be much more stable as in due to the high speeds the effects of weight transfer are greater and thus all that instability you want for autocross makes the very hard to mangne in the much larger more sweeping corners on big track.
On the 944 you need to have rear toe in so that under heavy braking the rear suspension does not flex to toe out. The geometry of the rear is such that this is normal. So go with 0 rear toe and under brakes the wheels toe out and the car gets very unstable. So unstable that it slows you down or you are likely to spin. A little toe in allows the rear suspension to flex out and this no toe out under braking maintain some stablilty required for maximizing entry speed.
What negative camber does for you is to lean the tire such that when the car leans in a corner the tire is more flat on the ground. Body roll incudes postitive dymanic camber and static negative is used to counter act this. This is why more camber = more grip (to a limit of course) since you have a better shaped contact patch when cornering. The raicing downside to too much camber however is in front limited braking capablity due to sub optimize tire patch shape and in the rear inside rear wheel traction limitations again due to contact patch shape. Like any thing on race car optimal is to fine the balance between those to demands.
10-19-2007, 01:51 PM
#22
Instructor
Join Date: Nov 2004
Location: Statesville, NC
Posts: 166
Likes: 0
Received 0 Likes
on
0 Posts
Tire wear and temp will tell you if you need more camber in the rear than the front, but I would bet most track cars have a bit more (-) camber in the front. We do.
