[FlukeSS]

Is it ok to have a slightly larger overall diameter front wheel/tire over the back if the difference is less than 1%?

26.73 front 26.67 rear

[laynlo15]

Yes, but why so short? Both are about an inch shorter then stock.

[Roostie]

Those tires are very close. You would have bigger differences than that just from different amounts of tire wear on the front and rear tires.

[FlukeSS]

Originally Posted by laynlo15

Yes, but why so short? Both are about an inch shorter then stock.

325 rears and 285 front

[enzia35]

They're pretty close to the stock diameter on the zl1 1le, so they should work.

[ember1205]

Originally Posted by FlukeSS

Is it ok to have a slightly larger overall diameter front wheel/tire over the back if the difference is less than 1%?

26.73 front 26.67 rear

Originally Posted by FlukeSS

325 rears and 285 front

Diameter is determined by the ratio of width (what you call out in your second post) to sidewall height. Going wider with the same ratio yields a taller diameter. Keeping the width the same while dropping the ratio yields a shorter height overall.

Is there not a width/ratio setup to achieve the diameter you want/need?

Also - most tire manufacturers will offer a Revolutions Per Mile rating which helps you ensure that your speedo and odo remain accurate.

[FlukeSS]

Originally Posted by ember1205

Diameter is determined by the ratio of width (what you call out in your second post) to sidewall height. Going wider with the same ratio yields a taller diameter. Keeping the width the same while dropping the ratio yields a shorter height overall.

Is there not a width/ratio setup to achieve the diameter you want/need?

Also - most tire manufacturers will offer a Revolutions Per Mile rating which helps you ensure that your speedo and odo remain accurate.

Well my car is a 2SS non 1LE. I'm assuming I don't have the wheel well clearance the ZL1 has. Which is why I was trying to stay with the 27.8 or smaller diameter.

I was just brain storming if I can do a 19" rear wheel with 325/30R20's keep my front 20" wheel with 285/30R20's. I wasn't sure if the front tire being slightly larger in diameter would affect things adversely.

[ember1205]

Originally Posted by FlukeSS

Well my car is a 2SS non 1LE. I'm assuming I don't have the wheel well clearance the ZL1 has. Which is why I was trying to stay with the 27.8 or smaller diameter.

I was just brain storming if I can do a 19" rear wheel with 325/30R20's keep my front 20" wheel with 285/30R20's. I wasn't sure if the front tire being slightly larger in diameter would affect things adversely.

Have you already swapped the fronts? Stock should be 245/40-20.

I do know that the front fenders, at a minimum, attach to the car slightly differently and that's why you can't mount the ZL1 skirts to a non-ZL1 car. This could be how they achieve a bit more width on the stock tires (285/30-20) for a ZL1 compared to the 2SS (245/40-20).

The ZL1 stock would have a wheel diameter of 26.73" while the 2SS would be 27.72". The 2SS wheels would actually be taller, but the ZL1 is definitely wider. Again... the fender and its mounting orientation likely have at least something to do with the difference.

Do you already have ZL1 "size" tires on the front?

[cdrptrks]

Originally Posted by FlukeSS

Well my car is a 2SS non 1LE. I'm assuming I don't have the wheel well clearance the ZL1 has. Which is why I was trying to stay with the 27.8 or smaller diameter.

I was just brain storming if I can do a 19" rear wheel with 325/30R20's keep my front 20" wheel with 285/30R20's. I wasn't sure if the front tire being slightly larger in diameter would affect things adversely.

You should be fine with that rear tire size from a clearance perspective. I believe rear clearance is the same on SS and ZL1. I don't think running 20s up front and 19s in the back is common but it probably wouldn't cause a problem for driving on the street IMO. I have run ZL1 1LE wheels with the stock Supercar 3R tires on track on my SS 1LE without any clearance issues and so have others on here. The speedometer does display a few percent lower than the actual speed with that setup; you can change the revs per mile value with a tune to fix it but that voids your warranty. I would recommend buying the ZL1addons rock guards for rear tires that large and the wiring harness relocation mod behind the driver's rear fender liner to be safe. There are some good YouTube videos that help to show it better but here's the instructions thread with a picture:
https://www.camaro6.com/forums/showthread.php?t=485975

I would not recommend 305/30/20 fronts for frequent driving on the street. They poke even with the strut mod and -2.8° of front camber (since SS front fenders are narrower than ZL1 1LE fenders) and the rock guards are not enough to stop pebbles from being thrown at the sides of the car. The SS 1LE comes with 285/30/20 Goodyear Supercar 3 tires stock and they are fine to run frequently on the street but rock guards are a good idea and side skirts might help too.

For reference:
https://www.camaro6.com/forums/showthread.php?t=502166
https://www.camaro6.com/forums/showthread.php?t=526353

[wnta1ss]

If it's that close then it should not bother stabilitrack. It's when the rears get noticeably shorter than the fronts that stabilitrack freaked out on my SS. The tire circumferences for the wheel sensors are now available in HPT for those who tune. Stock tune values for 3 different factory tire combinations:

2017 SS with 245/40-20 and 275/35-20 tires
Non-driven tire circumference=2164mm
Driven tire circumference=2150mm
VSS tire revs per mile=748.34

2017 SS/1LE with 285/30-20 and 305/30-20 tires
Non-driven tire circumference=2123mm
Driven tire circumference=2150mm
VSS tire revs per mile=748.34

2018 ZL1/1LE with 305/30-19 and 325/30-19 tires
Non-driven tire circumference=2061mm
Driven tire circumference=2100mm
VSS tire revs per mile=766.05

[FlukeSS]

Originally Posted by ember1205

Have you already swapped the fronts? Stock should be 245/40-20.

I do know that the front fenders, at a minimum, attach to the car slightly differently and that's why you can't mount the ZL1 skirts to a non-ZL1 car. This could be how they achieve a bit more width on the stock tires (285/30-20) for a ZL1 compared to the 2SS (245/40-20).

The ZL1 stock would have a wheel diameter of 26.73" while the 2SS would be 27.72". The 2SS wheels would actually be taller, but the ZL1 is definitely wider. Again... the fender and its mounting orientation likely have at least something to do with the difference.

Do you already have ZL1 "size" tires on the front?

Currently: Front 20x10 ET20 275/30R20 Rear 20x11 ET43 305/30R20

Looking to do: Front 20x10 ET20 285/30R20 Rear 19x12 ET41 325/30R20