problems with rubbing need help...

[beatinfirebird]

i have a 94 firebird. it is a v6 and comes with the 215/60/16. recently i put some 18s on it and the tire size is 245/40/18. i went to the tire size calculator and put both sizes in and my 18s with tires are about an inch smaller the the 16s.but when i hit a bump the backs it the lip on the quater panel. what can i do to stop this? is it possible the shocks are bad or is there anything i can do to fix this?

[RDS]

what size wheel and offset do you have?

[beatinfirebird]

im not sure on either i bought them used from a buddy. the tires are 245/40/18 does that help on the width and how would i find out the offset?

[RDS]

It might give you the wheel size and the offset on the inside of the wheels. check that out and we should know.

[mrr23]

from our email conversation

well not only is tire height important when upsizing wheels, but rim offset is just as important. sounds like the wheels stick out further than what stock offset wheels were at.

215/60-16 = 26.1 tall
245/40-18 = 25.7 tall

less than 1/2" shorter. and you have to remember that difference is divided in half. meaning the radius, measurement from center of circle to outside (center of wheel to tire) is only 1/4" shorter, if you were to measure from fender lip to tire.

now, what can we do to stop this.

1. new rear springs. they are old and sagging.
2. shocks. they are old and not dampening the movement enough.
3. putting spring spacers in side the springs. this will keep the springs from compressing as much.
4. rolling the fender lip. taking the inside of the lip and bending it upward.

i would go with 1 and 2 first.

[beatinfirebird]

now if i have to roll the rear lip how far should i do it and whats the best way to do it and whats the best tool to use? about how many inche at top should i roll it in?

[mrr23]

you are only talking about 1/2" at most without damaging or cracking the paint.

[beatinfirebird]

i got some air shocks today u think that will fix it? how far should i roll the fender and what tool should i use if this dont fix it?

[mrr23]

well, the air shocks will definately help. keep them inflated to at least 100 psi and you should be good to go.

[beatinfirebird]

i put about 25 pounds in it and it dont rub at all. i had two people in he back last night and air them to about 35 and they didnt hit at all. i checked the rim size and it was 18x8 but i didnt see anything with offset on it.