back spacing...offsets...keeping the centerline

[Baldwin]

Ok...the 2nd VX I bought...aka: Jr...has such a severe chrome peel that it still leaks so I'm getting new rims. But after reading all the posts and pics, I'm still confused on backspacing and offset. The tires on the rims are way too big and the front bumper was cut. Hate that...and everyone that looked at the Jr. pointed that out immediately. So I'm gonna reduce the 285/60/18 with 265/50/20's...with new rim that's 20x8.5.

The wheel shop says I need the +15 offsett and not the +35. But OEM is +38. Why wouldn't I want the +35? Won't the +15 stick out? Does the backspacing change when you change wheel widths? When the tire is turned all the way to the right/left, won't the outter part of the tire hit the inner part of the fender? It did when they tried to put a 0 offset first. I'm thinking +15 is still not enough and it should be +35. I want the centerlines to be the same.

[89Vette]

There's nothing wrong with moving your centerline outboard. It's called a wider wheelbase and Pontiac made it their advertising campaign!

Seriously, a wider stance can be shown to be more stable...though we're not talking much. The +15 offset is what I'd pick too. It's what I bought...and can be seen in this thread. Notice LDub's tires will be exactly the same as yours. (I'm referring to his first pic in the linked thread).

Mine are bigger in diameter --- since they're 285's.

I can see where 285/60's would be too big -- unless you're willing to do some moderate trimming. I had to do a bit -- with smaller 285/50's. But, mine is undetectable. (Unless you compared to a stock, unmodified bumper).

265/50's for sure would be small enough to fit w/o any trimming. Even with the extra negative (outboard) offset. IIRC, they'll be about 1.5" smaller in diameter than my tires. And, I did NOT have to remove that much material.

You'll be fine with 15mm offset...and it's what I'd pick. Unless you really like the inset wheel look. 38mm will also work. So really, it's a matter of personal taste on how you like the wheels positioned (flush or inset).

Look how my 15mm 20x9's look! Your's will even be a hair further inset...


Then, look at Dub's to get a good idea how they'll fill out the wheel well.

[89Vette]

Dupe post.

[Baldwin]

thanks. will see if today. will have to order the new bumper soon.

[Triathlete]

I have a front cladding in the for sale section if you are interested...uncut and unmolested

[tom4bren]

I'm guessing that you really don't want me to chime in on this discussion

[Maddawg]

Ok...the 2nd VX I bought...aka: Jr...has such a severe chrome peel that it still leaks so I'm getting new rims. But after reading all the posts and pics, I'm still confused on backspacing and offset. The tires on the rims are way too big and the front bumper was cut. Hate that...and everyone that looked at the Jr. pointed that out immediately. So I'm gonna reduce the 285/60/18 with 265/50/20's...with new rim that's 20x8.5.

The wheel shop says I need the +15 offsett and not the +35. But OEM is +38. Why wouldn't I want the +35? Won't the +15 stick out? Does the backspacing change when you change wheel widths? When the tire is turned all the way to the right/left, won't the outter part of the tire hit the inner part of the fender? It did when they tried to put a 0 offset first. I'm thinking +15 is still not enough and it should be +35. I want the centerlines to be the same.

If you kept the same offset as the stock wheels (+38mm) and increased the wheel to 8.5" (an inch wider than stock) your wheel will stick out one half inch further than it does now (the wheel will also stick out one half inch further inside. Just remember that the more the offset approachs zero, the further out the tire will move. Moving out increases the steering radius and will cause interference problems with the fender. Go figure...1 mm=.03937 inch. The difference between 38mm and 15mm = 23mm. So, 23mm x .03937 = .906, almost an inch (further out) on top of the half inch of the wider wheel.