Wheel sizing

[Bobsyouruncl]

 

6.5" (+34mm to +60mm offset, +55) *for 2.5i only

7.0" (+37mm to +57mm offset, +55)

7.5" (+40mm to +54mm offset, +55)

8.0" (+43mm to +51mm offset, +53)

8.5" (+45mm to +48mm offset, +45) *will need to roll the fenders if tires are wider than 255

9.0" (+43mm to +45mm offset, +43) *will need to roll the fenders if tires are wider than 255

9.5" (+38mm to +40mm offset, +38) *will need to roll the fenders if tires are wider than 255

I read this in the wheel fitment thread and had some questions. I'm trying to get an 18" wheel that can run 225's or maybe 235's better than my stock spec b wheels at 7" wide. I don't want to mod fenders and the car is lowered an inch or so. I'm wondering what offsets with a 225/40 or 235/40 or 45 would work. 

I'm confused as to why he lists the offset range of an 8" wide wheel from 43 - 51 but then highlights 53 as the closest to stock range, and you recommended it as the standard upgrade when it falls outside the listed range? 

[tehspud]

It was said in the paragraph above those sizes, the highlighted offset is the closest to the stock scrub radius. https://en.m.wikipedia.org/wiki/Scrub_radius

I’m guessing the range is just what is/was commercially available  

 

[BoozeRS05]

18x8 +48 with 225/40/18 would look and fit great. Or size down to a 17x8 +48 and 225/45/17.. 18” for better appearance, and 17” for better performance. Neither should require fender work or additional camber to fit.

Weight will make a dramatic difference too, under 20lbs wheel weight ideally.

[Bobsyouruncl]

Thanks for the info. 

Looks like an 18x8 wheel with 48 offset will push the scrub radius towards the positive a 1/4". Are there any benefits or drawbacks to that? I'm assuming it's impossible to avoid if going wider. 

Also I'm wondering what the differences between an 225, 235, and 245 tire size would be? Is there a point of diminishing returns? I plan on running some Michelin PS4 's for summer daily and possibly some autocross and maybe one day track driving. 

[Bobsyouruncl]

Anyone have any input? 

[BoozeRS05]

You stated that you didn’t want to mod the fenders and you’re lowered.

The option for upgrading which I provided is mild, and would look and fit great. If you want to go beyond that you’re more than welcome.

I personally run a 17x8 +48 with a 235/45/17 and a 3mm spacer in the rear. I’m lowered with stock fenders. My wheel’s weigh 15.5lbs, and I run a 17” wheel bc my roads suck plus I like the performance aspect of a smaller diameter wheel. I’ll likely size down to a 225/45/17 tire next bc my fronts rub with aggressive loading. I’ve tried probably 2 dozen different wheel and tire setups over 12 years with my wagon. 

[Bobsyouruncl]

I'm just curious, what are the performance gains with a smaller diameter wheel? Is it just wheel weight? 

I'm pretty ignorant when it comes to tires suspension and their relationship to performance so i was more wondering, from a performance perspective, what is the give and take going from a 225 to 235 tire? Is wider always better if you can get away with it? And is less sidewall better or worse and what other factors play into that? 

[BoozeRS05]

There’s a good bit of info on these questions just from doing basic searches online. In the long run you’ll want to understand these things for yourself and pick a setup that suits your preferences.

If you want to get your feet on the ground you have a basic idea of what will fit and function very well.

[Bobsyouruncl]

I havent been able to find many wheel options at 18x8 48. I'm wondering if anyone has a resource or knows of any that could point me in the right direction? 

[Infosecdad]

Rota Gravels (Legacy STi style clone) are common at that size.

https://www.fastwrx.com/products/rota-gravel-18x8-48-5x100

[Bobsyouruncl]

Thanks for that, I did see those as one of the only options. 

[Bobsyouruncl]

On 2/28/2024 at 7:42 AM, BoozeRS05 said:

There’s a good bit of info on these questions just from doing basic searches online. In the long run you’ll want to understand these things for yourself and pick a setup that suits your preferences.

If you want to get your feet on the ground you have a basic idea of what will fit and function very well.

Booze, have you run a +45? 

I'm considering an 18x8 +45 with 235/40/18. Wondering how much different that is to a +48? 

Like I said I've only found one +48 that I remotely like and they are heavy and I don't love the color. 

[BoozeRS05]

I’m at a +45 in the rear with my 3mm spacer, which doesn’t rub on a 235/45/17 and I’m pretty low. It rubs in the front though, just a little, without the spacer.. I’d like to say you’ll be fine with a +45 offset and that tire.

It’s a real PITA finding the best fit and maxing out tire size. I’ve run a 18x8.5 +48 and 225/40/18 in the past without issue. I also had a 17x9 +45 RPF1 with a 235/40/17 and it fit without rubbing except slightly on the inside fender liner. I also had a 18x8.5 +40 with a 235/40/18 and it rubbed a lot even with a decent bit of camber.

A little bit of camber will help make the fronts fit of it only needs a little tweaking, assuming you have a good performance alignment shop nearby.

[Bobsyouruncl]

Well based on that it seems like it would most likely be ok. Thanks for that. 

[Bobsyouruncl]

Does the spacer effectively decrease the offset? If I'm thinking about this right? 

[BoozeRS05]

Yep, I have a 3mm spacer in the rear only so it’s effectively +45.