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

chitown_riv98 wrote:

Must be nice baller

Dude, we are modding a 20 year old buick...

If we were 'ballers' you think we would be working on this platform??                                            actually, probably, yes. LS9 swapped, tho. That will happen on my 2nd gen 8 Riv. Just give me 10 more years..

no previous post edit 'cause thread bump

Size:18x8
Offset:42mm
Backspacing:6.22"
Bolt Pattern:5-115
Rec. Tire Size:245/45-18
Weight:19.0 lbs.

or

Size:17x8
Offset:40mm
Backspacing:6.10"
Bolt Pattern:5-115
Rec. Tire Size:225/55-17
Weight:17.7 lbs.


17"s - cheaper tires, better MPG, lil bit lighter

18"s - more grip area ~9%

I am 20% racer 80% DDer. Leaning towards the 17s and 225 tires. Any reasons you guys can think of to go for the 18s? Bout $300 difference between the 2 setups.

If it helps, my wheels are 17's and i did 235/50/17. That little bit more width from the back looks so much better.

I lied. My 17's are 17x7.5 with 40mm offset. 5.82 backspace. They are almost flush with the top of the fender. 245/45's fit perfect. I know I can fit 255/45's on them no problem.

Charlie, you will NOT gain traction going from a 225 to a 225, even if it is a 17" wheel. You need to go 235 or wider. You will not be happy with the results of another set of 225's. Just sayin.....

What Abaddon said. Even if you went to a 235 you might not feel the difference. 245+ Or bust.

Z-type wrote:

If it helps, my wheels are 17's and i did 235/50/17. That little bit more width from the back looks so much better.

Thanks. I didnt see 235 tires listed for the 17s but I will keep looking. Do you know the width of the wheel, offset, and backspacing?

Abaddon wrote:

I lied. My 17's are 17x7.5 with 40mm offset. 5.82 backspace. They are almost flush with the top of the fender. 245/45's fit perfect. I know I can fit 255/45's on them no problem. Charlie, you will NOT gain traction going from a 225 to a 225, even if it is a 17" wheel. You need to go 235 or wider. You will not be happy with the results of another set of 225's. Just sayin.....

Roger that. Do I need to be concerned with rub factor with 235+ tires and ~40mm offset?

charlieRobinson wrote:

Roger that. Do I need to be concerned with rub factor with 235+ tires and ~40mm offset?

Not as far as I can tell. I have zero rubbing, and room for more tire with what I have now. Obviously, going crazy on the offset is going to cause issues. Too much, and you'll put the tire right against the strut.

EDIT: You could even just go with a 235/55/R16 like what's on my Camaro...quite a bit wider that the Riv tires.

245/50/17 tire
with
Size:17x8
Offset:40mm
Backspacing:6.10"
Bolt Pattern:5-115
Rec. Tire Size:225/55-17
Weight:17.7 lbs.

with the eibach springs, you dont think I will have any rub issues with this setup?
Stock offset is 32mm? is 40mm ok?

leaning towards these right now just want to make sure they will fit well

The problem I have with that wheel is the backspacing. At 6.1", it's putting you .3" closer to the strut than my wheels. At a 1/2" wider, they're going to also stick out another .2" farther.

They will probably fit just fine. I'm able to get a finger between the tire and the strut. My finger is over .5" thick (I just measured with a Micrometer )

You have to think of this as well...Even though the tire/wheel will fit nicely, and be closer to the strut, you don't want to be too close. Under hard cornering, if the space is too tight, you'll end up rubbing the strut when the tire flexes. IF you're too close to it...

http://www.willtheyfit.com/index.php?width=225&aspect=60&diameter=16&wheelwidth=7&offset=55&width2=245&aspect2=50&diameter2=17&wheelwidth2=8&offset2=40#content

Just use that site. It puts everything into a nice little diagram for you.

Nice link! Thank you!

I have the non-polished stockers. Are they 6.5" wide? Anyone know?

Here's what I came up with. Thanks for filling it out, Matt.

According to a quick search our stock size is 16x7 with a 35mm offset. Can't confirm, but I can tell you that an 18x7 225/45/18 with a 55mm offset fits just fine.

This might help you figure things out:

https://rivperformance.editboard.com/t1080p180-faq-big-wheels-question-will-they-fit#156494

I realize the offset info is missing, so if you learn anything from this, please post.

Sorry I'm a little late Charlie - my wheels are 17 x 7.5, 45mm offset and 6.02" backspacing according to TireRack. As for the tires, I just forced the issue when I ordered them. They fit fine, they're just not the recommended size.

AA wrote:

This might help you figure things out:
https://rivperformance.editboard.com/t1080p180-faq-big-wheels-question-will-they-fit#156494
I realize the offset info is missing, so if you learn anything from this, please post.

I have been looking online for the missing details but have yet to find them. Thank you for bringing that link back to the foreground.

Z-type wrote:

Sorry I'm a little late Charlie - my wheels are 17 x 7.5, 45mm offset and 6.02" backspacing according to TireRack. As for the tires, I just forced the issue when I ordered them. They fit fine, they're just not the recommended size.

Not late at all!~ Thank you for this info. And you experience no rubbing or ill effects with this configuration?

I am looking at a 42mm offset 17x8 with similar backspacing. If it works for yours I am almost confident it will work for mine.

Oh I can't see you having any problems with that setup. 235/245 width tires look awesome on these cars because of how far in the bumper curves down. And like Scott's wheels, if you get the right tires the edges will be almost flush with your fenders, and that changes the entire look of the car.

This is only an opinion, but I like 17's on these cars too - I think the 18's leave too little sidewall in most cases if you get a tire the stock height. Make sure whatever wheels you get have centering rings for the hubs if necessary!

Abaddon wrote:

The problem I have with that wheel is the backspacing. At 6.1", it's putting you .3" closer to the strut than my wheels. At a 1/2" wider, they're going to also stick out another .2" farther.

They will probably fit just fine. I'm able to get a finger between the tire and the strut. My finger is over .5" thick (I just measured with a Micrometer )

You have to think of this as well...Even though the tire/wheel will fit nicely, and be closer to the strut, you don't want to be too close. Under hard cornering, if the space is too tight, you'll end up rubbing the strut when the tire flexes. IF you're too close to it...

are wheel spacers too sketchy  to be a solution?

charlieRobinson wrote:

are wheel spacers too sketchy     to be a solution?

You'll probably be fine. Z-type has about the same backspacing, little different offset though.

Spacers are not what you want if you can help it....unless you want to mount some 14" gold wires with whitewalls

Abaddon wrote:

charlieRobinson wrote:

are wheel spacers too sketchy     to be a solution?

You'll probably be fine. Z-type has about the same backspacing, little different offset though.
Spacers are not what you want if you can help it....unless you want to mount some 14" gold wires with whitewalls

Ok. Thank you.

I am looking at 18" wheels now because the 245/45/18 tire options seem more plentiful and cheaper than the 245/50/17

Z-Type wrote:

I think the 18's leave too little sidewall in most cases if you get a tire the stock height.

A 45 profile 245 18" tire is almost exactly the same rolling dia as a stock 16 R60 225 tire. I don't mind the look of low profile, but it does change the ride significantly, and will put more wear on your suspension - freshen things up for insurance.

I was really tempted to run a 50 profile on my 18" wheels, but wasn't sure if there might be interference issues when steering, strut rub, etc. The main reason is the wheel openings on Rivieras are pretty large compared to more current cars. A 50 profile would help fill the gap, and would give a more compliant ride. The salesman at Tire Discounters convinced me to go with 45 profile, as it was a more common size they knew would fit.

Charlie wrote:

are wheel spacers too sketchy nervous to be a solution?

I used to think so, and assumed it put more load on the hub bearings, but I have no real evidence that's true. I think a lot of cars are rolling on them with no problems.

Spacers can work as long as you buy some quality parts. If you can avoid it, definitely try to. There are a lot of people who run them and never have an issue though.

AA, with your tires and wheels mounted, do you think you could have went up to a 50? Will you when you need a new set?

I want a lil more meat on the wheels too which is why I would like to run a 245/50/17, but all the tires I am seeing in that size are $$$. The 45/18s tires are cheaper. Even tho the 18" wheels are more expensive than the 17"s the total package with tires is cheaper and will be cheaper to maintain in the future, I suppose.

It's a tough call. I need to get under there and see how close the 45 profile tires are to struts and fender liners. Right now I've got a lot going on, so can't say when that will happen.

Man... those 18s sure look good

17s lookn good tooo

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?