altarchsa

For an '89 C4:

Front 18x8 ET42
Rear 18x9.5 ET47

What size tires would these use? Any spacers, fender rolling, etc. required?

Thanks in advance for any help you can give me in this.

DWS964

I think you will have problems with the fronts - normal is 55, some are 52ET. So that wheel will be moved out an extra 10-13mm and will likely hit something. Plus, it throws off the steering geometry by moving the tire contact patch outside the steering axis. That will cause issues with ABS performance.
The rear will fit fine, although getting a bit tight on the fender lip.
Pictures of these wheels??
Have Fun, Be Safe

altarchsa

Here they are on another member's car.

sml

We dont really need to know the diameter ... so it 9.5ET47 rear and 8ET42 front.

The best method is to use your current wheels, and you can easily work out the answer yourself .... I've outlined the process in the thread below, but basically you just measure up your current wheels and then use the online tool to determine where the new wheel would be positioned. This is easier than searching through the forums for answers and you will also know that the answer is correct.

https://rennlist.com/forums/964-foru...el-offset.html

Here is a comparison example ...
https://rennlist.com/forums/9144773-post17.html

Your current wheels would be the easiest benchmark to compare with your new proposal, but you can also use my examples below to compare.

Option 1 - use your current rear wheels eg compare an 8ET52 to 9.5ET47.
Option 2 - use my example below eg compare my 10ET40 to 9.5ET47.
Just work out where the inside & outside edges would be positioned and get out to your car and take some measurements.

For the rear, here is 10ET40 benchmark ..
https://rennlist.com/forums/964-foru...40-photos.html

For the front, here is an 8ET50 benchmark ...
http://forums.rennlist.com/rennforum...nd-photos.html

altarchsa

Thanks sml. Those are the links I searched for but couldn't find.

altarchsa

Can't 10mm spacers be used on the fronts to get them out to D90 ET? (D90 = 53, Proposed = 42 + 10mm = 52)

sml

your proposal is 8ET42.
that is 8mm further outwards than my 8ET50 example.
study my 8ET50 photos.
might be ok .. even more so with mega negative camber.
depends on ride height & spring rates also.

ClaytoVR

SML, curious why you always post that diamater isn't important? If he were trying to install 22's...8's & 9.5's what would you suggest? For fitment, the more info on sizing of wheels(all dimensions) and tires you know, the more accurate your suggestions will be. You wouldn't really want to run a 225/40/22 tire on the front, probably wont fit...

altarchsa

I'm confused. When I read your Wikipedia link, it stated that a positive ET meant that the mounting surface of the hub was outside the center line of the wheel. If the original wheel ET is a positive number, and the proposed wheel ET is a smaller but still positive ET, why wouldn't you add spacers to move it outward to match the original wheel centerline?

sml

We were discussing wheels. If we are discussing tyres, then choose the tyre to match the correct diameter. With a 22" wheel this could be difficult however.

Anyway .. this is all not rocket science with wheel offsets. Just measure your own wheels and do the calcs yourself.

We've discussed before the impact of tyres as the tyre width also have an impact ...
https://rennlist.com/forums/9140030-post5.html

Anyway, I think some people just make it too hard and adding irrelevant information (eg wheel diameter) over-complicates the analysis.

sml

ET42 is 8mm further outwards than ET50.
Use that link to do the measurements with different examples & compare.
You must be mis-understanding.

altarchsa

OK, I re-read the Wikipedia article and realize I got it backwards.

I understand the change in steering geometry if the contact patch is changed. So there's no way these wheels would be good on my car. ???

sml

from memory, I think 9.5ET47 is good.

8ET42 will be 8mm further outwards than my example which you could probably make work depending on ride height & spring rates & camber. what do you think when you look at my 8ET50 photos?