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View Full Version : what could cause understeer?



k20pr
02-15-2011, 10:43 AM
hi guys the other day I was at my first track day. and the ep had to much understeer. what could I do to get rid of it? I think I had the car to low with out the extended tie rod and that could be the problem. but I really dont know.

TXEP3
02-15-2011, 10:48 AM
Too much camber in the front could cause lack of traction which means understeer, having stiffer front sway than rear would cause understeer... i'm sure there are many other possibilities, but that's what i've learned from forza =P

Zzyzx
02-15-2011, 10:56 AM
the #1 cause of understeer by far is driver error, be it coming in to the turn too hot or the improper modulation of the brake and throttle ect ect ect.

Else, what is your alignment set to? For track on street tires you should, at a minimum, be running -1.5 deg camber on the nose. -2 to -3 would be better.
you can get away with OEM spec for front toe, but rear toe should be used to fine tune the handling balance.

What are your dampers set to (assuming they are adjustible)

What anti-roll bars are you running?

spring rates?

regardless, if you've just started tracking the car your best option is to not bother trying to tune the chassis and put all your effort in to analyzing how you are driving.

k20pr
02-15-2011, 11:28 AM
I think she is set to street alignment, all other thing are stock but the only thing she haves is the raceland coilovers. the thing is that she would tear up the inside of the tire only. I dont know if the bump steer would cause that since she is set for a low ride.

27rocks
02-15-2011, 11:36 AM
Too much camber in the front could cause lack of traction which means understeer, having stiffer front sway than rear would cause understeer... i'm sure there are many other possibilities, but that's what i've learned from forza =P

I hope you don't set up your car based on a video game. Yes to much camber will generate understeer but how much is to much? Well it all really depends on your current parts you have to work with. Thicker sway in the front again YES it will cause understeer but it all really depends on the rest of the mods you have and how you set it up.

I have a 27mm front sway with a 22mm in the rear. My car is very neutral though because of the way i set it up. I also set it up to be most beneficial at higher speeds then lets say auto-x, but even there the car drives really nice. And like Zzyzx has said you have to know how to drive the car into and out of corners to minimize all the negatives about the car.

Zzyzx
02-15-2011, 11:38 AM
What is your cornering technique? Map out what you the driver were doing in each stage of the turn. Such as when are you coming off the brakes? when do you start to apply throttle? How much throttle do you apply and how? Do you "pounce" on the throttle or "squeeze" it? How about the steering inputs? are you smooth with your steering inputs while entering the turn or do you spike it?

Stolen from the nether

Your cornering sequence should look something like this.

Safe cornering requires a conscious and repeatable sequence of driver actions to properly enter and exit turns. This sequence must be smooth and flowing and requires regular practice to make it a habit. The sequence is as follows, assuming turn entry from a straight section of the course:

* Lift
While driving in a straight line and looking ahead, smoothly lift off the throttle.
* Brake
Smoothly and progressively apply the brakes in a straight line. Not all turns require use of the brakes.
* Downshift
Using heel-toe technique, downshift to the appropriate gear to maintain torque to provide for acceleration out of the turn. Not all turns require downshifting.
* Off the Brake
While looking ahead to the apex and beyond, smoothly release the brakes when you're ready to turn in.
* Quick Breath & Turn In
Take a quick breath before turning in. Practice ocular driving. Never look where you are. Always look ahead to the next point by physically turning your head. Slowly and smoothly turn the wheel to initiate the turn. Let your hands follow the eyes and use progressive steering.
* Accelerate
After initiating the turn, smoothly apply maintenance throttle, then progressively increase the throttle as you pass the apex and begin to track out to the track-out point.
* Track Out
As you pass the apex, smoothly and progressively open the steering wheel. Let the car unwind to the track-out point. This is not always needed. Your instructor will explain when and how.


Accelerate & track out are usually going to happen at the same time, as you unwind out of the turn you are progressively applying more throttle.

Passenger
02-15-2011, 11:44 AM
fwd cars cause understeer

27rocks
02-15-2011, 11:47 AM
fwd cars cause understeer

Thank you captain obvious lol

TXEP3
02-15-2011, 11:48 AM
I hope you don't set up your car based on a video game.
I haven't touched my suspension yet, but no I wasn't planning on using my forza setup as a blueprint. lol

Zzyzx
02-15-2011, 11:49 AM
fwd cars cause understeer

true, FWD does have a propensity to understeer while under throttle, but that falls under driver error again; as you the driver are trying to use more traction then the car has available.


Given years of competitive driving & subsequent tuning of the car; at this point if my car understeers or oversteers, as the case may be, it is entirely due to me having done something wrong.

Also: driver effectiveness (http://farnorthracing.com/autocross_secrets3.html)