THEORETICALLY, a 18x7.5+43 should sit about 1.35mm IN from where a 18x8+48 would sit. . . . is this mathmatical hypothisis something I can trust, or do different wheel brands and sizes work kinda like shoes where everyone has their own basic sizes and standards? (i.e. Nike's size 12.5 is Rebock's 10.5)

I believe I've posted in here before, but now I need to get back into it.

I really wish I could just have a set of wheels with different offsets handy to slap on the car and see what works.

I may drop the car about an inch later on with coilovers, but right now it's on stock suspension. I'd like to run a 215, which is what I was running in the front before with the 8.0 wide rim. Is 205 pretty much the only option?

How much can I expect the rim to stick out from the fender, realistically? I know what it should be theoretically, as stated above, but somehow things aren't stacking up right.

Also, is there a change with 2 pc wheels in lip depth in relation to offset? I was looking at a chart and I noticed that a rim of the same width with a +50 offset had a smaller lip than a +43. I was told that the lips are generally the same, they just take more material off the inside pad/mounting surface to create the diferent offsets.

The reason I ask is because if the center hub is the same on all the wheels of a specific type, then offset wouldn't make any difference for brake clearance would it?

 

[QUOTE=Mountain-man,Dec 5 2008, 02:44 PM]THEORETICALLY, a 18x7.5+43 should sit about 1.35mm IN from where a 18x8+48 would sit.

 

Thanks for the explination. The tire thing is new to me and did clear some things up.

So, if I understand this correctly, you are saying that a 18X8+48 with a 215 tire would yeild the same tire clearance as a 18x7.5+43 with a 205 tire? So given that, the center lines of the two wheels are, as you stated, 5mm different, therefore if I placed a 215 tire on the 7.5+43, the tire would stick out 2.5mm further than they did with the 8.0+48 wheel . . . correct?

A screen shot of my own visual thing I threw togeather. Hopefully it's legible. I've had it for a while, but just added the tire specs. Sidewall profile is a non-issue so I didn't bother getting that to scale.

 

Yep! The calculation that is happening there is that you are taking your tire width difference of 10 mm, dividing that by 2 since half of that width exists on either side of center (remember offset is measured from wheel centerline) and subtracting the difference in offset. The result is zero.

You almost got it, but not quite. If all you're changing is the offset, the tire moves that exact amount. Remember, the offset is measured from wheel center. AND, the tire is always centered on the wheel (duh.) So if you compare any given tire width between two wheels (your example being the 215) then the tire will move in or out by exactly the difference in offset of the two wheels.

[snip]

Ah yes, the good ol' AutoCAD to the rescue. Been there done that. But your model is a little off. I think the reason is that you need to keep the tire centered on the wheel.

 

[QUOTE=spa-zz,Dec 6 2008, 07:11 AM][snip]

 

I did not have a chance to go through the entire thread, but I did read the main posts. I couldn't however find what size center bore would be needed for wheels for the s2k. any help would be appreciated and sore because its likely been covered.

 

70.1 mm front and 64.1 mm rear.

 

Thank you very much kind sir.

Any chance in getting the center bore changed on a wheel if its to small?

 

Maybe. I don't know if it's safe to do so.

 

A good tool shop should be able to bore it out concentrically to tight specs, but you'll be paying big $$ for the setup time.

If it only needs to be opened a few thousanths of an inch, I think you'd be fine. If you're talking more than a mm, then I'd say no. But I suppose it would depend on the wheel too. Some have more material than others.