Could the simple solution to understeer be the right one?
07-01-2007, 03:31 PM
#16
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Originally Posted by Colm
I don't think understeer is the common gripe "right out of the box" with the RS. If anything, they are set up (Rear full stiff and front almost full soft) to oversteer from the factory.
07-26-2007, 09:36 AM
#17
Yargk,
According to the Cargrahic catalog, the RS that won the Tuner GP had the 1 inch wider front fenders with 9.5x19 on 265/30-19 and 12.0x19 on 315/30/19. I don't think I've ever seen that rear tire size before. Assuming weight distribution was not altered too much, Cargraphic widened the front track a decent amount plus added 60mm of rubber vs 20mm to the rear.
My question is Porsche widened the rear track of the RS vs the GT3 with leaving the front unaltered. Wouldn't widening the front of the RS with the wider fenders and appropriate change in front wheel offset (no change in current tire and wheel sizes for the sake of argument) have a benefit as well?
According to the Cargrahic catalog, the RS that won the Tuner GP had the 1 inch wider front fenders with 9.5x19 on 265/30-19 and 12.0x19 on 315/30/19. I don't think I've ever seen that rear tire size before. Assuming weight distribution was not altered too much, Cargraphic widened the front track a decent amount plus added 60mm of rubber vs 20mm to the rear.
My question is Porsche widened the rear track of the RS vs the GT3 with leaving the front unaltered. Wouldn't widening the front of the RS with the wider fenders and appropriate change in front wheel offset (no change in current tire and wheel sizes for the sake of argument) have a benefit as well?
07-26-2007, 10:04 AM
#18
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Originally Posted by NJ-GT
A wider wheel/tire will help the 997 GT3 to stop in shorter distances at full braking, but it won't help the understeer problem, because it happens at mid-corner and corner-exit where the front end is very light, more rubber with no extra weight won't help.
You have understeered through the early part of the corner and have applied more lock rather than less, intending to power out of the situation as you exit
You have not rotated sufficiently prior to arriving at the mid point
You have not transferred sufficient weight to the front axle
You are on the power early
There are a lot of options when it comes to dealing with this situation
increase your rotation early in the corner - if it is a right hand corner, make a small turn left to the outside of the track before smoothly turning the car in towards the apex, this will increase the turning motion and give you extra rotation, this is an alternative to trail braking and rather easier
when the car begins to understeer, unwind the steering wheel half a hand, or even a hand if you have tightened the steering wheel previously, unwi9nding the steering makes it easier for the tyres to regain grip, once they have regained grip they can start steering again
prior to losing all adhesion at the front axle, you can momentariloy transfer weight to the front tyre patchjes by momentarily tightening the steering hald a hand or so, causing the front wheeels to 'dig in', and transferring weight to the front axle and improving the turning
if you are on the power too early, you haven't entered fast enough, so enter faster, brake later and harder, increase the rotation earlier in the corner and you won't feel the need to get on the power early, so you won't experience throttle induced rearward weight transfer.
if you are still understeering at track out, you probably should have less steering angle and more throttle to move the rear end out, possibly you got this way by getting on the throttle to early having slowed too much coming into the corner.
R+C
07-26-2007, 06:54 PM
#19
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Originally Posted by Nordschleife
If you are having understeer problems at mid corner, there are several possibilities -
You have understeered through the early part of the corner and have applied more lock rather than less, intending to power out of the situation as you exit
You have not rotated sufficiently prior to arriving at the mid point
You have not transferred sufficient weight to the front axle
You are on the power early
There are a lot of options when it comes to dealing with this situation
increase your rotation early in the corner - if it is a right hand corner, make a small turn left to the outside of the track before smoothly turning the car in towards the apex, this will increase the turning motion and give you extra rotation, this is an alternative to trail braking and rather easier
when the car begins to understeer, unwind the steering wheel half a hand, or even a hand if you have tightened the steering wheel previously, unwi9nding the steering makes it easier for the tyres to regain grip, once they have regained grip they can start steering again
prior to losing all adhesion at the front axle, you can momentariloy transfer weight to the front tyre patchjes by momentarily tightening the steering hald a hand or so, causing the front wheeels to 'dig in', and transferring weight to the front axle and improving the turning
if you are on the power too early, you haven't entered fast enough, so enter faster, brake later and harder, increase the rotation earlier in the corner and you won't feel the need to get on the power early, so you won't experience throttle induced rearward weight transfer.
if you are still understeering at track out, you probably should have less steering angle and more throttle to move the rear end out, possibly you got this way by getting on the throttle to early having slowed too much coming into the corner.
R+C
You have understeered through the early part of the corner and have applied more lock rather than less, intending to power out of the situation as you exit
You have not rotated sufficiently prior to arriving at the mid point
You have not transferred sufficient weight to the front axle
You are on the power early
There are a lot of options when it comes to dealing with this situation
increase your rotation early in the corner - if it is a right hand corner, make a small turn left to the outside of the track before smoothly turning the car in towards the apex, this will increase the turning motion and give you extra rotation, this is an alternative to trail braking and rather easier
when the car begins to understeer, unwind the steering wheel half a hand, or even a hand if you have tightened the steering wheel previously, unwi9nding the steering makes it easier for the tyres to regain grip, once they have regained grip they can start steering again
prior to losing all adhesion at the front axle, you can momentariloy transfer weight to the front tyre patchjes by momentarily tightening the steering hald a hand or so, causing the front wheeels to 'dig in', and transferring weight to the front axle and improving the turning
if you are on the power too early, you haven't entered fast enough, so enter faster, brake later and harder, increase the rotation earlier in the corner and you won't feel the need to get on the power early, so you won't experience throttle induced rearward weight transfer.
if you are still understeering at track out, you probably should have less steering angle and more throttle to move the rear end out, possibly you got this way by getting on the throttle to early having slowed too much coming into the corner.
R+C
07-26-2007, 11:30 PM
#21
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Originally Posted by Nordschleife
thanks, I'm glad it makes sense to somebody else
R+C
R+C
Many experienced drivers have complained about the excessive tendency to understeer in the 997 GT3. I had the same problems with the 996 GT3, and a bunch of other cars I've driven.
The right suspension settings will make it disappear.
07-27-2007, 11:05 AM
#22
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Originally Posted by Nordschleife
Where is that rule written?
As far as understeer goes, there is more than one way of dealing with it. One option is to increase the weight on the front axle (traction being a function of weight and contact patch area), so 'brake' on the front axle only, i.e. cause the front tyres to 'bite', momentarily tranferring weight forward and increasing the capacity to function as required. Once you are able to do this, you will find that oversteer is less of a problem.
Alternately, when presented with understeer you can unwind the steering wheel to increase the amount of turning effort, this may or may not be accompanied by increased power at the rear wheels, but take care that unweights the front wheels.
What I am saying is, don't get fixated by understeer, its there to look after people. Learn to drive through it.
FYI, most race drivers prefer understeer to oversteer. Most F1 cars actually understeer.
R+C
As far as understeer goes, there is more than one way of dealing with it. One option is to increase the weight on the front axle (traction being a function of weight and contact patch area), so 'brake' on the front axle only, i.e. cause the front tyres to 'bite', momentarily tranferring weight forward and increasing the capacity to function as required. Once you are able to do this, you will find that oversteer is less of a problem.
Alternately, when presented with understeer you can unwind the steering wheel to increase the amount of turning effort, this may or may not be accompanied by increased power at the rear wheels, but take care that unweights the front wheels.
What I am saying is, don't get fixated by understeer, its there to look after people. Learn to drive through it.
FYI, most race drivers prefer understeer to oversteer. Most F1 cars actually understeer.
R+C
We all trail brake the car to promote rotation into the corner - no issue there. The problem is mid corner in big sweepers. The rear end is firmly planted but the front end washes out. The solution is to go more slowly - that isn't the objective on a track. Less throttle restores the balance but you get passed by pals driving the 996GT3 on Michelin Cups.
Based on recent experience, stickier tires change all that. Apex Late discovered that 18 in wheels from the 996 GT fit on the 997. With a set of 18 inch Cup tires, his 997GT3 went from understeer to oversteer! He corrected this by adjusting the sway bars which had been set to minimize understeer.
I'll comment further next week. I will be at the track for 3 days using my new Fikse wheels and Hoosier tires (if it is dry).
Best,
07-27-2007, 11:20 AM
#23
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Bob
have you tried 'niggling' the front to momentarily transfer weight forwards.
Otherwise how about putting on spacers and oversized tyres, if you have three days at the track, I'd take some spacers to try.
R+C
have you tried 'niggling' the front to momentarily transfer weight forwards.
Otherwise how about putting on spacers and oversized tyres, if you have three days at the track, I'd take some spacers to try.
R+C
07-27-2007, 12:54 PM
#24
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Originally Posted by Bob Rouleau
I will be at the track for 3 days using my new Fikse wheels and Hoosier tires (if it is dry).
I think you started a new arms race.
Touchette will need to bring more of those to the track soon.
07-28-2007, 10:31 AM
#25
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Andrei
I am using hoosiers because the 18 inch cups have not arrived yet. Besides, apex late will be on hoosiers as well (unfair advantage)
I am using hoosiers because the 18 inch cups have not arrived yet. Besides, apex late will be on hoosiers as well (unfair advantage)
05-22-2009, 12:56 PM
#28
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Based on a stock, corner weighted set-up with front sway bar at 3/5 and rear full stiff, I got the advice to add 2.0deg of camber at the front and add as well OEM 5mm spacers on the front wheels. Has anyone played around with spacers to neutralize understeer ?
05-23-2009, 01:08 PM
#30
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All of this makes complete sense and I agree. I suppose my question boils down to: "why did cargraphic do it if it's not the way to go?" Their car is just a highly modified GT3 RS, it should have a similar weight distribution to the street car that it started out as. Also their goal seems to only be lower lap times in the Tuner GP.