FAQ: Wheel & Tire, Lug, Bolt Pattern, Offset, Center Bore Info

I'm running American Racing 17x7.5 wheels. 5x115 pattern, 40mm offset, 5.79" backspace with 245/45/ZR17's. They fit perfect with no issues whatsoever. The wheel assemblies are actually further out for more of a "flush" look. Makes the car look wider.

If I were to do it again, I'd go 245/50/ZR17 though. The 45's are a bit thin in the sidewall. They handle like a mofo though.

XCELLR8 wrote:

I picked up my Riviera last week and like the car except the rims.  I have a set of rims from an old car of mine that I think will work on the Riviera.  They are a 17X8 rim with a +25 offset with a 5X115 bolt pattern.  My reading has led me to believe that the Riviera's stock rims are 16X7 with a +32 offset and the 5X115 bolt pattern.  Is this correct?  I'm thinking everything should work out as the wider rim makes the offset shorter to overcome the rim's width.  I'm wanting to run a 245/50/17 tire which is the same OD as the stock 225/60/16.  Anybody confirm my thinking?

Will those clear the brake rotors on the front? They kinda fill the stock wheels.

Albertj

XCELLR8 wrote:

I picked up my Riviera last week and like the car except the rims.  I have a set of rims from an old car of mine that I think will work on the Riviera.  They are a 17X8 rim with a +25 offset with a 5X115 bolt pattern.  My reading has led me to believe that the Riviera's stock rims are 16X7 with a +32 offset and the 5X115 bolt pattern.  Is this correct?  I'm thinking everything should work out as the wider rim makes the offset shorter to overcome the rim's width.  I'm wanting to run a 245/50/17 tire which is the same OD as the stock 225/60/16.  Anybody confirm my thinking?

If you go to www.tirerack.com and click on wheels, and input the year Riviera, you will get a selection of rims that will fit.  The offsets range between 35mm and 46mm, depending on the rim width.  I find the term offset very confusing to a lot of people.  IMO, you are way better off measuring back spacing, which is not the same.  Offset can be positive or negative, and it can be much harder to actually measure offset than back spacing.

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=101

I'm trying to use rims I already have in the garage and really don't want to buy new rims if I don't have to. Are my specs of the stock supercharged rims correct? Thanks for the feedback.

XCELLR8 wrote:

I'm trying to use rims I already have in the garage and really don't want to buy new rims if I don't have to. Are my specs of the stock supercharged rims correct? Thanks for the feedback.

I don't know. Someone has to take a wheel off and measure. Like I said, it is much easier to measure back spacing. To measure offset, you have to find the center of the rim and measure to the mounting surface. Take one of your stock rims off and measure.

To measure backspace, run a straight edge across the backside of the wheel, then measure the distance from that straight edge to the hub face.....where the wheel meets the hub.

I thought there was already a "Write Up" or 2 concerning this subject IIRC. With some very good info that would answer the OP's question without measuring the stock wheel.

But, Hey, I could be wrong. Have been many times in the past.

Good Luck with your wheel/tire mounting. Hope it all works out for you.

What Stock wheels do you have.? After you install your 17" inch wheels are you keeping the stock ones for winter use.???

There are a few calculators online that can help. Just enter the existing wheel specs and the new ones and it will tell you how much farther they'll stick out. Then just measure out to the fender to see how much farther you want to go.

Thanks for the info. I guess I'm looking for the true wheel specs of the 12 spoke painted supercharged wheels. In my reading I'm getting some mixed results.

I plan to keep the stock wheels and put them away, they are real close to flawless.

They're 16x7 with between a 50mm and 55mm offset, 70.3mm center bore, and the stud thread is 12 x 1.5.

matt270avian wrote:

They're 16x7 with between a 50mm and 55mm offset, 70.3mm center bore, and the stud thread is 12 x 1.5.

I thank you for the info. I'm just going to take a wheel off and do some measuring and comparing with the aftermarket wheels I have. I have read different factory offsets of +32, +35, and now +50 to +55. I you are correct at +50 then my rims will not work, at an offset of +25.

XCELLR8 wrote:

matt270avian wrote:

They're 16x7 with between a 50mm and 55mm offset, 70.3mm center bore, and the stud thread is 12 x 1.5.

I thank you for the info. I'm just going to take a wheel off and do some measuring and comparing with the aftermarket wheels I have.  I have read different factory offsets of +32, +35, and now +50 to +55.  I you are correct at +50 then my rims will not work, at an offset of +25.

25 should fit just fine. A common setup is jumping up to an 8" rim and running 245s. Use this website to really help you decide what you want. 18" seems to be a really good size for our cars but comfort is sacrificed, 17" looks just a hair too small IMO.

http://www.willtheyfit.com/index.php?width=225&aspect=60&diameter=16&wheelwidth=7&offset=50&width2=245&aspect2=45&diameter2=18&wheelwidth2=8&offset2=25#content

Took the Riviera's wheel off and did some measuring. The offset of the 12 spoke wheel is +51mm and they have a back spacing of 6.125", the aftermarket rims that I have are +25mm and have a back spacing of 5.625". I put one of the rims on without tires and they poke out too far for me. They might work, but I'm not going to spend $600 to $800 in tires just to find out. Thanks for all the info given.

That should only bring them out 1.5" or so. Take a tape measure to the existing rims and measure out, I'm willing to bet 1.5" would put them pretty dang close to flush.

I am in need of new tires and am thinking of getting 235's as opposed to the 225's. I have 16 inch late 90's Cadillac rims. Are there any differences/loss in performance, or will they rub against the inside fender/strut?