alanpikku

I was running 245 in the rear before with no issues. I'm currently making 370 whp on a turbo kit. With my 245's, I was able to hit 140 mph in a very stable manner. Acceleration stayed straight and true. Last week, I upgraded to 255's in the rear, and that's when the issues started happening. After the rear tire install, I noticed the rear end drifting the faster i went. I could not get pass 100 mph without the car getting too scary. I got an alignment the next day, and have since put 200 miles on these tires. Although not as bad, it still drifts left and right when I get on the gas during 60+ mph speeds. Do you guys still think my alignment is out of wack? Or are the 255's messing with my suspension geometry some how? Btw, the 245 and 255 are the same brand tire. Hankook K110.

Froth.

You're likely feeling the Mold-Release agent on the tire causing it to be slipping around. When the tire is made a fairly severe release agent is used so the mold doesn't stick to the tire(heat + pressure = Rubber sticks to things). The drawback is that the Mold release does impregnate the rubber slightly and leaves a shiny almost greasy surface to the tire. Depending on manufacturer they could be worse, or better...but generally after 500 miles the Mold release has worn off.

-Froth

alanpikku

I guess that means I have 300 miles to go. Thanks.

sillyboybmxer

or you can just go do some donuts
actually though,...^ he is correct, although i feel like mine were greasy for like 700 miles

alanpikku

I would love to, but I don't want to have a blown diff.

CaptainMike

Make absolutely sure your tire pressures are totally even left to right.

alanpikku

I just checked it and it's fine. My car is very twitchy and still likes to float around at higher speeds. It's getting annoying!

CaptainMike

Do you know what your alignment numbers are? Too little toe might cause instability. Release compound and tread squirm could also be contributing.

Duke Togo

Really quick but when you change the tire size with the same width rim it's possible the sidewall height and contact patch are different - also tires arent the same in all sizes it's possible that the different size is causing tramling as well or your old tires may have been stiff from heat cycling and low tread depth would have reduced tread squirm.

Here's a quick graphic that should show a difference in contact patch and sidewall height based on sizing.

alanpikku

I have no idea the numbers.