Blagave

I have read numerous threads on wheel and tire sizes and have tried to figure out the offset chart and still am confused on if the wheels I bought will fit and what tire size I can use. I plan on rolling the fenders for added clearance, would like to stay away from any rubbing.
Any help would be appreciated.

Front wheel 8 x 18 57 ET front lip 1.5"
Thinking of 235/40-18 tire

Rear wheel 10 x 18 54 ET lip 2"
Thinking of 285/35-18 tire or if possible 295/35-18

Thanks

76FJ55

I'm not certain what you are specifying with 1.5"F and 2" rear lip.
However my 85 is running 235/40-18 on 18x8 ET59 front with no fender rolling.
Rear is 265/35-18 on 18x9 ET53 rear with no rubbing and no fender rolling and stock 21mm S spacers.
I'm at the limit of tire size for my configuration.

I think you'll be good on the front, but the rear will need work. Either reduced spacers, or the fenders will need to be worked for the additional clearance.

FredR

Your car is intended to run with a rolling diameter of 25.0 inches. The front section proposed more or less meets that but the rear section does not in that it runs at 25.8 inches. That being said I currently run with that section and suspect the speedometer is probably a bit more closer to being spot on. The optimal rear size would be a 295x30x18.

On the front wheel with an 8 inch rim I suspect you could run a 245 section at ET57. Rolling the wings should ensure you have no issues. You will have no issues on the inboard side of the wheel.

All that being said I trust you understand that the front suspension is designed for wheels with ET65 to give the designed NSR [negative scrub radius]. This concerns folks like myself but many folks run with the kind of ET that your wheels have and do not complain of any issues.

Blagave

Thank you for the reply and info. The information I provided was from the seller of the wheels. The front wheel has 1.5” and think it refers the distance from outside rim to the face of wheel. The rear wheel is 2”.

Blagave

Thank you for the information. The speedo is not an issue because, I am one of those “Guys”: I am running a Z06 trans/diff and will be using gps to work the speedo. The 30 would mean smaller side wall for a bit more stiff ride?
The fronts have been the biggest concern. If I were to go to the 245 on the front, would I stay with a 35 ?
If it were your car, what would you consider?
Thanks again for the help.

FredR

Three piece wheels [like mine] are made of modular rim sections. The width of the outer section is usually smallish and the width of the inner rim is much larger. Thus my 9.5 inch front wheel has a 1.5 inch outer and a 8 inch inner section to give a total width of 9.5 inches. To get more offset the outer section has to be narrow and 1.5 inches is the smallest rim section made [as I know]. With the forged centre profile my front wheel achieves an offset of 68mm. My rear wheels use the same forged centre but have a 2 inch outer with a 8 inch inner to give a 10 inch rim with ET60. This is where the 1.5/2.0 inch bit comes from.

Thus my wheels have a more than adequate offset and are just about optimal for the space available in the wheel arch and permit use of a 265x35x18 front section- the only limitation being a slight rub on the DEVEK adjustable front sway bar at full lock that was rectified by fitting an additional spacer each side of the steering rack.

Blagave

I made a mistake. The box says 8.5 X 18 on the fronts. ET 53. PCD 130x5
rear 10 x 18 ET 65. PCD 130x5

will the fronts be ok?

FredR

A 245x35x18 gives a diameter of 24.8 inches and should be OK given the outer wall sits where my 265's on ET68 did.

A 245x40x18 gives a diameter of of 25.7 inches- a better match for your proposed rears but the increased diameter will make it a bit more marginal with respect to rub on the fender so not quite so comfortable as to whether rolling the fender would clear the rubber especially as I tend to run with more camber [now 1.3 degrees] and that also helps clearance. Thus better that someone who has run your specific combo comments on that one. At best it will be tight.

FredR

Ouch- the best you can do with that would be a 235x40 and that will be very tight to say the least.

Does your rear have a spacer fitted?

Blagave

No spacers on the rear.
Would it make more sense to run 285 in rear and the 235 in front so the tires are a bit more proportional

Blagave

Ok.....just realized the wheels were shipped to me in another manufactures box and the size on the box is not the same as what my wheels are.
What I have is 8.5 x 18 offset 56 Front wheel and 10 x 18 offset 54 Rear.
It sounds like the 8.5 width is going to limit me to a 235 tire at best on the front and the rears can fit a 295.

Thanks for everyone help, very much appreciated.

FredR

OK- that is a bit more promising. The 235 should fit comfortably.

A 245 on ET52 does not work or so was the case when I once tried my late S4 rear wheel on the front [as I remember the S4 rear wheel is ET52 and carries a 245 section] and I doubt that the extra 4mm offset you have would be sufficient. However I tried that before rolling the wing and that also gains a few mm.

Perhaps you can get the wing rolled and then find a spent 245x35 tyre, fit it and see how it looks clearance wise.

There is also a spreadsheet that Andrew Olson prepared- if you can find that it attempts to calculate what works and what does not and it is a very useful utility.

On the rears I am confident you will have no problems with a 285 section, If you run a 295 section you will not problems on the inboard side of the wheel. I suspect the outboard side will also be fine but just not as confident on that dimension. Again, you might catch something by rolling fender but the rear does not seem to be as compliant as the front.

Blagave

Fred R....really appreciate the help. I found a online tire comparison chart and I think the 235/40 and the 285/35 will work best and look proportion it to my needs.

https://tiresize.com/comparison/

Blagave

So I pulled the trigger and purchased Kankook V12 235/40-18 fronts and 285/35-18 rears. I used my 84 Euro for mock up. The rears clear with no issue. The fronts Clear on all axis’s , but think I will need to roll fenders to clear when lowering. I really appreciate the advice from 76FJ55 and especially FredR.

FredR

Based on your head on photo the front rubber looks as though it will miss the fender- remember that as the suspension compresses the radius pulls the wheel inwards relative to the fender.

As you have gone to the slightly bigger diameter option you also need to check that there is no contact between the shoulder and the rear of the wheel well components.

Nice looking wheels- are they split rim or are the "bolts" dummies for appearance? They look real enough.