Hey Guys. I know there are already threads about correcting understeer, but I'm curious about something. I've posted in a few places that I upgraded my rear tires to 305s while keeping the stock 235 size up front on my OZ Ultraleggeras, and my initial understeer (that our cars are known for, and strangely, loved for) has gotten noticeably worse. I have two questions:

1) Has anyone upgraded to a 245 up front on an 8.5" rim with the 305s in the rear. If so, does the sidewall look stupid? Also, will that truly counter some of my increased understeer? Do you lose noticeable turning radius with the larger tire up front as long as I stay within the same aspect ratio? (245/35/19 vs. 245/40/19)

2) If running a 245 on these rims isn't an option, do you guys recommend using a thicker anti-roll bar in the rear to return to lesser initial understeer level?

Thanks!

Ohan

 

others far more qualified than me will surely chime in but I believe that a more aggressive alignment, potentially in partnership with changes to the control arms, seems to address much of the understeer that the factory engineers in to our cars.

 

Other things equal, a 10mm increase in rear tire width should not cause the "noticeably worse" understeer you describe. If you have gone to a stickier tire, then the increased level of grip could cause more on-throttle understeer, since the car has so much rear grip anyway. Sway bar adjustments might help, can't hurt to try. I expect stiffer rear springs would offer much more, as long as you don't go beyond the damper's capacity. I recently bought a used 996 GT3, and have been impressed with how neutral the car is, compared to a 997S I had previously. I have the front bar set one hole off full soft, and the rear one hole off full stiff. But I understand the rear spring rates are considerably stiffer in the GT3, and I suspect that is a bigger factor. A problem with the 245 in front is maintaining the same relative difference in OD, front to rear. I assume you have played with tire pressure, but you could try increasing front and/or decreasing rear until you feel a difference. As already mentioned above, more front camber helps too. If you are using the OE front lower control arms, about -1.0 is about all that is usually available. I set mine at -2.2 in front, but you will need to buy the GT3 parts.

 

I would have to agree with increasing front camber to reduce understeer. I've played with toe as well, but you would want to be careful with that.

 

As ultimate understeer solution get GT3 lower control arms installed - then you`ll be able to have up to -3 degrees front camber done.

If you are running at stock alignment - re-align it to -1 camber in front (max possible what it is with stock shocks) and 0 toe and -1.5 camber in rear with 0.02 toe. It will help. If it was already done - GT3 LCA is for you.

Wider tires in front should help a bit too.

 

The absolute ultimate solution is order a GT3. I learned that last month.

 

Increasing the rear tire size should not reduce the understeer. The problem with our cars is that there is no weight to support the front grip! The best solution would be to get a stiffer rear sway bar, increase the size of the wheel & tire in the front and get more negative camber.

245 in the front may look a little beefy, but I don't see any problems with fitment...

 

I run 9" wide up front.

Wider tires and wheels in the back without doing anything to the front will increase understeer.

Jason

 

Going to a 245 tire will increase tire width but not by much...it will also increase overall tire diameter too which you do not want. Check out the tire spec on a site like Tire Rack to be sure.

You can increase front gip with a proper alignment and also learning the car characteristics and increasing your driving skill with DE's.

 

GT3 CONTROL ARMS are a must if you plan on tracking the car.

If you are not tracking, just get a aggressive alignment...

 

What kind of car did you drive before?