why do some front wheel drive cars lift a back wheel when cornering hard?

what does it show? in terms of suspension set up? springs too hard or soft? too little anti roll or too much?

my fiesta was lifting about 6" at the weekend on track, have been told its good to lift but only just off the ground, how do you control it?
thanks jim

 

i think it's the stiffnes of the chasis, mostly happens with shorter cars and if the shocks are short.

say you have a standard escort mk4 with normal shocks if you jack it up it goes up a long way before the wheel gets of the floor
but if you put some uprated shocks on there there will be less travel than the standard one's so the wheel will come of the floor at half the hight it would of with the standard one's thats the way i see it hope this helps

 

To do with weight transfer over thre front wheels, and not a lot of weight on the rear.
The shell is stiff enough to do this on a lot of fwd cars, going hard into a corner the outer front wheel is loaded up and the suspension compreses, as ther eis not a lot of weight in the rear of the car it does not compress as much, so remains higher relaitive speaking, the actual tilt of the car does the rest.
tabetha

 

FWD cars are prone to understeer, so to counter this and make them go fast round corners, the rear antiroll bar is often beefy and the outbound schock travel is limited. This helps the steering but only up to the point when the inside wheel lifts off. Then any further body roll at the front will again only reduce steering as the front tires get to a bad angle.

 

so a stiffer anti roll bar would help reduce the lift and keep the understeer down?

 

Front or rear?
If it's lifting too much, then a front ARB might improve the steering. In general a stiff front ARB won't really help steering.
Lifting the roll center at the front and using dampers with limited outward travel might help.

 

on the rear am going to fit a second anti roll bar, i have doubled the spring rates on the back think this might help keep the front end from understeering a little more?

 

Kind of but its incorrect thinking..

Rear ARB's promote oversteer which counteracts the front end understeer it wont stop it

Oversteer from the rear can be corrected with adjustable geometery.

Sticking two ARB's on the rear wont make much if any difference.

 

And its not just back wheels.

My old Mk4 used to do it at the front too



Picture circa 1991 cornering very hard on a damp track, but with no oversteer or understeer and staying fairly level.
I dont run any ARB's front or rear

 

what do you suggest then? it's a mk3 rs1800 fiesta, it's running 325lb front springs and 450lb rears

 

driving lessons lol

 

Hard to say without seeing a video.

You could be turning in too sharp causing the rear to lift too high etc.

Softening off the back will help initially though