Dreaming60’s

I'm having a real hard time getting my head wrapped around this and would appreciate some help.

So, reading posts on this forum and talking to a couple C1 owners, I've learned that a 225x60x17 wheel with 4.50 backspace will fit an unmodified C1 (1962 in this case) corvette without rubbing problems in the rear. Finding the right 17" wheel with 4.50 BS is proving impossible. Most come with 4.00 BS, which might be solved with a 1/2" spacer....if I understand BS correctly.

Then I thought maybe more wheel would look better on my car, so to keep the tire height the same I would have to change the aspect ratio to 55 instead of 60. Most likely go with 225x55x18, but the wheels I find in this size are showing offsets as well as BS.

So, am I thinking correctly that a 6mm positive offset moves the centerline of the wheel forward 6mm or about 1/4" and adds to the BS? I found some correctly sized wheels that will fit my car, but they have 4.25 BS as well as the 6mm positive offset. So does this mean I actually wind up with a 4.00 BS wheel or a 4.50 BS wheel with this combination of BS and Offset?

Thx,

Butch

AZDoug

A 1/2" spacer added to wheel with 4.5" BS would be the same as a wheel with no spacer and 4.0" BS. Off set is sort of another way of saying backspace, but it doesn't account for wheel width, where BS does. A 7" wheel with 4.5" BS will fit under your rear fenders, a 4" BS wheel could cause fender lip interference.

Google backspace vs offset.

Doug

Dreaming60’s

Thanks Doug.

I found this website that explains it pretty clearly. If I understand it, positive offset and larger BS both move the wheel inward. So, if the wheel I want comes with 4.25 BS, plus has 6mm or 1/4" offset, it totals just under 4.50 actual BS and this wheel should fit. If this is wrong thinking, someone please sing out, as this will be a very expensive mistake/ for me.

https://www.autoanything.com/wheels-...el-backspacing


Butch

AZDoug

No, BS and offset are closely related but, it isn't additive. You can have 6MM offset on a 5" wide wheel, or a 12" wide wheel. It just means 6MM of the wheel is further inboard. One will obviously fit on your car, the other won't.

Off set refers to offset from center line, with no account for wheel width, BS accounts for wheel width, at least on the back side. A 7" wheel with 4.5" BS has 4.5" inboard,and 2.5" outboard. An 8" wheel with 4.5" BS has 4.5" inboard, 3.5" outboard. One would have about 36MM offset, the 8" wheel, only 12 MM offset.
Doug

Dreaming60’s

Doug,

My deleted post must have come just after yours hit the forum. I learned this same thing you mention by going to another website. Not easy finding these wheels with 4.50 BS and correct hub diameter.

Can you tell me again what you used on your car, as it looks great and I'll just stick with 17" wheels. I know you did a lot of research before you found your solution.

Thanks,

Butch

3JsVette

I don't know what the budget is but all the billet wheel companies (Billet Specialties, Budnik, Team III, to name a few) and American Racing will build you a set of wheels to your specs. It will certainly be more pricey but you get exactly what you want with the correct back space and hub bore.

AZDoug

Factoid found some 4.5" BS wheel from US Mag, or someplace. I woudl have bought some of those if i knew about them.
Ask him.
Doug