Tire Sizes for 18"

[xyeLz]

Just wondering what our tire sizes are and what will rub with 18" rims. I remember about 6 years ago when I purchased my rims I believe they were 255/45 sized tires with the 18" rims. Has anything changed?

Also curious about what size wheels we can fit. Is the offset 30 for an 01 SSEi? What about the maximum rim width. Is this 7.5"?

Thanks!

[yourgrandma]

Stock for a gxp is a 235/50 18 on a 7.5" wide wheel. We can go a lot wider though. 245/45 ought to work fine but.you need at least an 8" wheel to keep it from looking like a balloon.

I'm looking for an 8.5-9" wide wheel either in 18 or 20" diameter and I plan to run a 255 width tire.

I'll have Tp spend some time checking fitment of common offsets and widths with my wheel rite tool and post the results.

Edit: stock offset is 35mm. Depending on width anywhere from 30-40 ought to.work but you have to be picky about it if you're looking for a specific look or very wide tires. They can rub the strut and inner fenders in front.

[xyeLz]

Stock for a gxp is a 235/50 18 on a 7.5" wide wheel. We can go a lot wider though. 245/45 ought to work fine but.you need at least an 8" wheel to keep it from looking like a balloon.

I'm looking for an 8.5-9" wide wheel either in 18 or 20" diameter and I plan to run a 255 width tire.

I'll have Tp spend some time checking fitment of common offsets and widths with my wheel rite tool and post the results.

Edit: stock offset is 35mm. Depending on width anywhere from 30-40 ought to.work but you have to be picky about it if you're looking for a specific look or very wide tires. They can rub the strut and inner fenders in front.

Thanks! What do you mean we should go with an 8" wheel to keep it from looking like a balloon? Keep what from looking like a balloon? Haha sorry...

I remember there used to be a post that explained what all of this stuff meant...but I got confused by the post since I'm stupid.

[bobtaz13]

I run 255/45R18's on 18x8 rims. It is a great setup.

[xyeLz]

I just looked up my old rims. They were 18x8.5 on 255/45. What does the 8.5 actually mean? What visual impact does it have?

[yourgrandma]

What I mean is that if you run a wider tire on a given wheel, at a certain point, the sidewalls start to balloon out and it looks cheesy. I guess a lot of people wouldnt notice but I think it looks pretty bad. It also negatively impacts tire wear and handling.

So for an 8.5" wide wheel (thats the distance between the beads) a 255 width tire is the correct size. On an 8", 245 would be te better choice. For the stock 7.5" width, anything wider than 235 doesnt look right to me.

From a few minutes playing with my wheelrite, I gather a 9" wheel might fit, but I didnt check tire fitment. Odds are that with ~6.25" of backspace, 255 is about as wide as will fit in front. Not to fret, though, thats a 10" wide tread patch with most brand tires.

[xyeLz]

What I mean is that if you run a wider tire on a given wheel, at a certain point, the sidewalls start to balloon out and it looks cheesy. I guess a lot of people wouldnt notice but I think it looks pretty bad. It also negatively impacts tire wear and handling.

So for an 8.5" wide wheel (thats the distance between the beads) a 255 width tire is the correct size. On an 8", 245 would be te better choice. For the stock 7.5" width, anything wider than 235 doesnt look right to me.

From a few minutes playing with my wheelrite, I gather a 9" wheel might fit, but I didnt check tire fitment. Odds are that with ~6.25" of backspace, 255 is about as wide as will fit in front. Not to fret, though, thats a 10" wide tread patch with most brand tires.

That's logical. Makes sense to me now, haha. Thank you.

I run 255/45R18's on 18x8 rims. It is a great setup.

I thought it was great when I ran it too. Tires looked nice, rims looked nice. Didn't mess with the speedometer at all either. What offset did you use?

What offset in general should we be using for 18" rims?

[yourgrandma]

Its based on the width, not diameter.

35 or 38mm is probably where youll want to be for 8-8.5" width.

[xyeLz]

Thanks. Would 40mm work as well on an SSEi with GXP calipers?

I'm actually reading up on offset now and what it actually means... It sounds like the 38mm is referring to a POSITIVE offset. So correct me if I'm wrong - to me it sounds like a 40mm offset means the wheel will actually sit more inside the wheel well than say a 35mm offset?

[crash93ssei]

GXP wheels are 8" wide.

I run 255/45/17 on my Cutlass on an 8" wheel and the 255 width is absolutely perfect, I wouldn't run any less on it. When it comes time for new tires for my GXP wheels they will also be 255 width.

[repinS]

I'm actually reading up on offset now and what it actually means... It sounds like the 38mm is referring to a POSITIVE offset. So correct me if I'm wrong - to me it sounds like a 40mm offset means the wheel will actually sit more inside the wheel well than say a 35mm offset?

That's correct.

Here's a great resource to use to determine rim fitment and also speedometer accuracy: http://www.willtheyfit.com/

[xyeLz]

Thank you! I'm a little confused why the offset actually matters in terms of performance. It seems like it's really just aesthetic since it either mounts closer to the car or farther from the car? I guess suspension could be affected depending upon what the "optimal" distance would be, but really would there be an issue if I got a 20mm offset vs. a 40mm offset?

A lot of wheels I see are 40mm so I want to know if that's okay.

[repinS]

Generally, aesthetics aside: Too positive an offset and you will hit the strut. Too negative and you won't clear the fender, especially as the suspension compresses on bumps or heavy loads. It also puts more stress on your wheel bearings.

[xyeLz]

Thank you! Perfect explanation.

So what's a safe range for our Bonnevilles, 30-40? Or is that still pushing it?

[Ghosthawk]

I think if you stick with 35-40 with 8 or 8.5 you'll be safe. I'm running 18x8.5 +35 offset on mine with 245/45ZR-18 tires (ZR just means Z speed rated Radial tire)