Understeer

[VPRGTS]

Looking for help in solving the understeer issues (push) with Vipers.

Not that trail braking and throttle steering hasn't been fun, but it would be sure nice to get this thing to turn better.

The suspension on my car (non ACR) is bone stock, but I have removed front shims.

Adjustable front sway bar?

Bigger front tires?

Toe out / toe in?

What can be done?

 

[Frank Parise]

Here are some possibilities assuming you don't want to change your stock suspension, meaning you don't have adjustable shocks, springs, or ride heights (bummer). It would be nice if you could simply drop the front ride height or raise the rear ride height.

More toe-out can the front will improve your corner entry, although it won't help in mid-corner.

Experiment with your front tire pressures. Depending on how close to the limit you are already driving, either reducing or increasing air pressure in the front tires can help you. If you are an advanced driver, increasing air pressure may improve your cornering because it can reduce the slip angle of the tire. A beginner may benefit from dropping front tire pressures to increase the slip angle to its optimum point. Don't be afraid to use air pressures that are considerably different from front to rear. I've used as much as 5-6 PSI higher up front when all else failed and I was desperate to get the car to turn.

Increasing front camber may help, but you need to determine this by using a pyrometer and trying to keep the maximum difference in tire temps from the inside to the outside of your tire in a range of 10 or 15 degrees F.

Wider front tires and wheels can help, but this is an expensive option. It would be cheaper to put a crappy set of tires on the rear to get that end of the car losing grip before the front does. This isn't as good as getting the front end to work, but if all else fails...

 

[jrkermode]

Your 01 actually does have adjustable shocks. Have you tried adjusting them? Stiffening up the rears more than the fronts will help with understeer turning into a corner.

As Frank alluded to, you need to be more specific about where the issue lies; corner entry, middle of the turn, corner exit, high speed, low speed, etc... Your personal style of driving also plays a role.

 

[Mike H]

Not much to go on from what you provided. Would need to know tire pressures cold and hot? What tires you running? What track is is understeering on? Is it right handers or left handers?
The Viper can easily be made to induce power oversteeer. From a stock setup tire pressures are your best bet to work on as not much else is there to adjust, if proper alignment specs geared more for racing are followed.

 

[CAS]

As Frank said, toe out will help your initial turn in, but it (depending on amt of toe) will scrub speed on straights and wont help mid corner push, just provide for sharper turn in. Your stock Konis have an adjustibility function. Stiffen the rear's up (search for post on how to adjust stock shocks). If those DONT work, you might try Eibach springs in different weights for the rear.

Also, don't trailbrake. Get all your braking done BEFORE the turn, than smoothly turn in towards the apex.

Regards,
Clint

 

[jrkermode]

P.S. Northwind Engineering offers shorter spring collars, so you can alter the ride height a little bit even with the stock shocks.

 

[VPRGTS]

Tires are stock Michelin Pilot Sports.

Turn entry is not so bad. I am losing traction mid corner and I would like to be able to accelerate better coming out of the turn but I am not able to with the push the car has.

Front tire temps 130-140 across the tire and 43-44 psi front, 40-41 psi rear by the time I get back to paddock and out of the car to take measurements. I have tried everything from 30-34 psi cold /40-44 psi hot.

Front camber is -1.5, 0 toe.

How fast am I going - At Gingerman Raceway this past weekend with Viperdays, my best time was 1:35.2. Mid America (Iowa) was 1:43.6.

I was not aware my front shocks were adjustable. I will look into that.

 

[jrkermode]

Mid-corner (Steady state) understeer is easily resolved with the throttle. If you then find the car drifting too wide on exit, aim further inside the corner on turn in and drift past the apex.

I imagine there is a cone right at my apex. I then aim directly at this imaginary cone on turn in, as though I were going to center punch it. However, by the time I get there, my car has drifted enough that I end up with lots of space between my inside tires and my chosen apex. Only occasionally am I brave enough to point the car into the dirt on turn in. It usually results in a good apex, but I'm just too chicken, especially where the curbing is really tall.

Those tire temps seem low. Typically you would look for something near 170F, using a regular tire pyrometer (I have no idea what the correct, non-contact (infra red) reading would be). Perhaps they are cooling too much before you enter the pits. However, I suspect they simply aren't working hard enough. I know, I know, easy for me to say!

P.S. All 4 shocks are adjustable.

 

[KenH]

Here is a link to a past post about adjusting the shocks.

http://vca2.viperclub.org/forums/showflat.php?Cat=&Board=UBB14&Number=109636&Forum=All_Forums&Words=shock%20adjustment&Match=And&Searchpage=0&Limit=25&Old=1year&Main=109636&Search=true#Post109636

-- Ken

 

[Sonny 00 GTS ACR]

According to a seminar given by Bobby Archer at the Gingerman Viperdays last weekend, an infra red temperature reading is good for rotors and such, but not good for tire temps. The temperatures that are important are below the surface of the tread and can only be read by the probe supplied with a pyrometer. Bobby is a great resource and welcomes calls regarding setup advice. 817-877-1772.

I also had a big problem with my car pushing on Friday at Gingeman. We made some significant camber changes and reduced the angle of the wing to bring the car more in line with what the track offered. At Gingerman, trail braking and throttle steering were very helpful in allowing quicker laps but the straights wern't long enough to cool the brakes. It would take about seven laps to lose the front brakes and I'd have to back off while they cooled. It was the only track that has ever been a problem for us.

Good Luck,