I'm looking to upgrade to Budniks on my 1989 Iroc-Z. The car is lowered with Koni shocks and aftermarket springs. Can i fit 18 x 10 in the rear and 18x 9 in front without modifications?

 

There are tons of threads on this subject, and I believe even a link to an offset calculator in the tools section. But I squeeze 19x10's. They should bolt right on but you may run into some trouble with the bump stops in the rear

 

As mentioned, don't be afraid to search. LOTS of info on this subject. ....but for normal thirdgens without crazy custom work, stock length rear, and normal wheel offsets, I like to say that a 9.5" wide wheel with a 275 is the "UN" official biggest you can go without mods. Now I know for a fact guys have gone bigger without mods, but not everyone has. Some guys won't touch a certain mod unless it's direct bolt in, some jump in with two feet and are more than happy to figure it out. Depends who you are, LOL! I'm going 295 out back. Might fit, but I'm prepared for some minor work to make it fit. We'll see. If you want a guarantee....stick with 9.5"/275mm.

 

I'm leaning towards 10". Thanks for the feedback

 

With a reasonable installed offset, 10" will fit the rear without issue. 9.5" on the rear, installed with an approximate offset of zero, clears by about 1.5". So it wouldn't be difficult to calculate a nice fit for 10" wheels in the rear, and plenty of 3rdgens have them. The front, however, will likely require more careful calculations to fit 10" wheels, but it's certainly been done too.

Having 9.5" wheels all around, myself, it's my opinion that 9" is the ideal width for 3rdgens, particularly in front. The new 17" reproduction GTA and IROC wheels are all 9". I doubt that was a random guess.

So a staggered combo of 9" in front and 10" in back would fit easily and look good.

But staggered combos are not rotation-friendly, as I'm sure you know. Granted, most 3rdgens nowadays are probably not daily drivers and probably aren't driven enough that rotating the tires is likely to ever be necessary, or at least, not needed as often as whatever "normal" is considered to be. But if being able to rotate them simply is important to you, then using one size for all four wheels (and tires) would be the easiest to work with AND look good too.

 

I just spoke with Budnik and he said 18 x 10 in rear with a 5.5 back space and 18x 9 in front with a 5 back space should fit. What do you think about that?