Looking for some help with wheel/tire sizing. I currently have a 92 firebird formula with 245/50/16 stock wheels/tires with the DSE 2”drop springs. Looking to get some new wheels/tires. I’d like to do a square setup If possible. From what I have found scouring the board it seems a 275/35/18 will fit with no modification (or almost none). What I am unsure about is the wheel itself. I don’t really want to get a 4th gen wheel and run a large spacer, so aftermarket seems best. But I am having trouble determining what the correct spec would be. I believe a 18x9.5 is best and the most common backspacing is 5.25 inches with 0 offset. Is this going to work? Does anyone have a suggestion if this won’t work?
thanks.

 

With a zero offset, you'll be fine.

Width- We know a 275/40/17 with a zero offset works with no issues for almost everyone. Your combo essentially fits the same. At most, you'll have some minor scuffing, which you can fix with a very thin spacer.Typically this is more common with stock brakes. Aftermarket brakes tend to push the wheel out just enough, due to the rotor being placed on the hub. Hawk's even ships their 17x9.5 wheels with a spacer "just in case".

Diameter - Your tire/wheel diameter is basically a stock 25.6" diamter, so we know you're good there.

Offset - Assuming a zero, offset, you will be fine. -but don't be afraid of an adapter. So long as it's from a reputable company and properly installed you should have NO issues. Most of the horror stories come from not properly torquing down the lugs, OR, using adapters to push the stock wheels OUT farther, changing the geometry. The new jenky backwoods geometry causes the problem, not the adapter. In the case of our cars with 4th gen wheels, we're just using the adapter to return the wheel/suspension to proper 82-92 geometry. It's a proven part when done right.

 

Thank you very much for the information. Now I just have to find a wheel I like.

 

I’m running 1” extended ball joints with 18” C5 wagon wheels. I can’t recall, but I think that’s on 1.5” spacers with LS1 front brakes. Wheel comes close to strut and will touch the sway bar at full lock. I tried to bring the wheels in as much as possible to reduce scrub. There is barely any room at all for a bumpsteer kit unless the rod end is significantly smaller than a stock tie rod end, and I have no idea how anyone fits them without sticking the wheels out past the fender (or running 20s). Bumpsteer while driving is not at all an issue, much to my surprise. When the body rolls into a corner (autocross) I do feel the outside wheel turn farther into the turn, which does make it a touch tricky to control.

I have some data on camber gain with stock BJs and the 1” extended ball joints. I’ll have to find the excel sheet, but I think I only measured an extra .2 degrees of camber gain throughout the usable range with the 1” over the stockers.