more understeer with aftermarket tires?
 

can a car's balance be affected by changing tire compound? this year i ditched the stock tires and replaced them with yokohama advan neova ad08 of the same size as the stock. i've done a couple of track days on them and i noticed, apart from the increased traction and mechanical grip, is that it seems the handling dynamics of the car changed. last year the car basically had a bit of understeer, but can easily kick the tail out with a bit of throttle. I even spun out a few times while exiting corners. This year on the new tires it seems the car understeers almost as much as a fwd car. The front tires would be squealing throughout the turn. Giving it a bit of throttle doesn't seem to break the rear loose. It's as if the rear tires have much more grip than the front. I haven't messed with the suspension at all, so that shouldn't have an effect. Can different tires really cause more understeer or is it just my imagination??????? :icon14:

Maybe the grips of AD-08 is not as good as the RE050.??

Absolutely tires will change many aspects of your cars handling. From the compound, to the tread pattern and everything in between. If you are going to be tracking your car you have to pick your tires very carefully.

If the grip increased as you said, the understeer you report would not be unusual. Consider: If on your old tires you were losing grip front and rear, then applying throttle could swing the rear around a bit as your report. Now since the grip threshold is higher, when you notice the understeer, the rears still have some grip and it is harder to kick the back around. It may not be the case that the ratio of front to rear grip has changed, rather you are noticing the understeer while the rears still have some grip.

With these new tires you may have to change your entry a bit. You could enter a little slower and the increased grip would allow you to throttle up earlier on corner exit. Or you could come in hotter and try and recreate the situation where your rears are loose enough to kick it around a bit.

In any event what's important are your lap times -- understeer or not how do your lap times compare to those with the stock tires?

Yes, tires do have a big effect on a car. Different sizing front to rear on our cars is a big contributor. The tire contributes a huge amount to the overall damping of the suspension, which effects tire loading and therefore traction. Try lowering your front tire pressure, which will increase loading on the front tire, and typically helps understeer. You could also try an alignment adjustment, add some -camber to the front.