Body Roll and Traction Problems

[Thee 240sx Owner]

Ok now I posted this before in the General section and I got much info on it but it wasn't entirely what I was looking for. I have my car(89 240sx) that i had regular tires on it before... Stock ones that where Kuhmos 195/70/R15 on all four.. Now my bought a set for the back that were 215/70/R15 and ever since then I noticed that I get alot of body roll. I use to be able to take turns really good. Now it seems that it wants to slip alot... ie i was getting off an exit ramp keeping up with my friend and we were doing bout 70 on it and before with my old tires I could take it with no problem... but with the new tires I notice that my back end felt like coming up from under me... I had to slow down to bout 50 to take the turn. Any clue on why it would be like that... Also bout the traction problem... In the rain I noticed that turns are also like that... Even if I take a moderate turn at 15Mph it seems to want to slide around alot... Now I have a 120lb System setup in the back and i'm just wondering if maybe thats throwing my weight ratio off or something.. I would have thought that would give my better traction being that its more weight on the tires but I guess it doesn't... If you could shed some light on this it will be greatly appreciated...

-Jack

[Grant@tirerack]

If these are on the stock rims, it may be a case of bigger is not always better. You have a couple of things going here with the tire/rim sizes. The sidewall height is almost 1.5" taller than stock and you are adding a wider contact patch with the same width rim. The tire contact patch grips better but on that narrow of a rim with that tall of a sidewall, the sidewall does not maintain its shape and will flex a lot more. You either need to get into a wider rim or a shorter sidewall tire. This all assumes you are running with the stock rim. There is no benefit in running a wider tire out back with the same width rim. They fill out the wheel wells better but that's about it. :rolleyes

[Thee 240sx Owner]

LoL They are on stock rims... so if i got wider rims that would solve a lil bit of my problems with handling wise??

[SmithSR]

Not necessarily solve them....but it may be an improvement. I think there is an issue with different available grip limits between two different sized tires. Grant hit the nail on the head about the tire flexing more. You've basically lengthened the distance from the wheel hub to the ground. Any time you lengthen a "lever", that lever becomes more prone to flex. Make sense? As you travel around an off ramp, the taller tires will tend to flex more and be less stable than a matching set of four. The four identical units will act in more of a predictable manner.

-Phil

[Grant@tirerack]

If you get wider rims there would not be as much sidewall flex and that would help. On the next set go with a lower sidewall profile.

[Thee 240sx Owner]

Ok.. I just figured since they were on stock rims.. i didn't want to get low pro or anything like that although i know they would handle alot better for the whole side wall reason.. thanks alot for your time Grant and Phil