[orange blaze]

I have found some nice black wheels here in Canada. 20x8.5" and 20x11". Rims look like they will fit fine from my observation. I would like 245x45 tires up front and 305x35 in the rear. Reason for this is to fill up the wheel well so I don't have to lower it. I have motorsport tech custom adapters in front that pushes the wheel out 8mm. The rear 11" wheels have a 45mm offset. I was also thinking of 255x40 tires front and 295x35 rear. I need to know by Monday because of the sale on these wheels and tires. I don't have a picture of the wheels but they are a Fast FC04 gloss black if you want to google it. They are a flow and form wheel so nice and light. Any help would be much appreciated and pics if you have.

[Markoz28]

305/35/20 is going to be too tall. I would do a 305/30/20 or a 315/30/20. With 45mm offset you may not need a spacer with 305/30/20 but I would get a 3-5mm spacer for the 315/30/20.

As far as the fronts go, I have no idea.

[arpad_m]

IMO you can make your original plan work, just move the Motorsport Tech spacers to the rear instead of the front to get rid of the unwanted -10mm scrub radius difference. You didn't mention the offset for the front wheels, I assumed it's the same as OEM.

Now on to the caveats:

- if you stick with this setup of 245/45/20 front, 305/35/20 rear, note that the speedometer will read incorrectly unless you modify your tune, but everything should work, you are only changing the front/rear height ratio by 0.7% and you will not invert the car's rake

- make sure you relocate the main body harness on the driver side, and you might need to heat up the wheel well liner and reshape (push back) one of its ridges to avoid rubbing completely. You'll see which one I'm talking about.

See below what I did to verify, using tiresize.com and wheel-size.com (in the rear I assumed the 8mm spacer you mentioned, which effectively modifies the +45 wheel offset to +37). Also, there are guys here who run 305/35/20 in the rear without issues (I have a 285/35/20 front, 315/30/20 rear setup myself).

[orange blaze]

Thanks for all that info.I need the custom adapters up front as the wheels i have on now had a 35 mm offset and so i needed 10mm to get back to stock and then another 8mm to push it out a little more. That way i thought if i ever wanted to put 245/45 tires it would clear the spring perch. For the rear the ZL1 has 20x11 43mm offset so i was hoping that my new wheels with 45mm offset would still work or if i had to i could add a 2mm spacer. I know there are some owners here that use 305/35/20 in the rear with an 11" wheel. I will have a closer look at reply and see what i come up with. Thanks for your help.

[arpad_m]

Originally Posted by orange blaze

Thanks for all that info.I need the custom adapters up front as the wheels i have on now had a 35 mm offset and so i needed 10mm to get back to stock and then another 8mm to push it out a little more. That way i thought if i ever wanted to put 245/45 tires it would clear the spring perch. For the rear the ZL1 has 20x11 43mm offset so i was hoping that my new wheels with 45mm offset would still work or if i had to i could add a 2mm spacer. I know there are some owners here that use 305/35/20 in the rear with an 11" wheel. I will have a closer look at reply and see what i come up with. Thanks for your help.

Makes sense. I'm just a guy and not a mechanic, my experience with different setups is very limited, but this should work. I'd get 3 and 5mm spacers for the rear just in case.

Oh, and one more thing, if you use a wheel adapter/large spacer, the stock wheel studs will be too short with not enough thread engagement, the maximum spacer size is 5mm, you will need longer studs if you want to go beyond that. See how many threads remain with a 5mm spacer below.

[orange blaze]

Thanks. My adapters are not spacers so they come with there own studs.