[bandier]

Whew... thanks for the corrections and suggestions and quick response. What a relief.

Originally Posted by arpad_m

You're welcome, bandier. The stock offset on the 20x10 1LE fronts is +20, so you're 5mm off, but you can use 3 or 5mm spacers to adjust that back, so I don't think you'll have an issue.

I'm obviously just a guy and not a wheel/tire/suspension tester, so I can't be 100% sure, if only because my car has magnetic ride control shocks and yours has the base suspension, but I did try many combinations over the years, and the spacers will give you some leeway no matter what.



Relax, this is nowhere near as bad as you think.

Your new 285/35/20 fronts will be +0.7% (ie taller), your 305/35/20 rears are +2.5% (also taller) compared to the stock 245/40/20 overall height, so you're changing the ratio much less as you're increasing the height on both ends. As you quoted, my napkin calculation here is simply delta = rear - front using the proper sign, so your ratio change is only ~1.8%, which will be just fine.

Your mistake is in thinking these quantities are always additive, but they are actually directional, so to get the actual diff you need to subtract. If you inverted the directions between front and rear (say, taller fronts, shorter rears or vice versa), then you'd have to add their absolute values (magnitudes), but that's not what you are planning. Hope this makes sense.



The rake change is not super significant, but you would probably feel it as increased lightness in the front when pushing the car, which you don't want.

My choice for a non-1LE like yours and mine would be 275/35/20 and 315/30/20, this will work fine with zero issues, no tuning required. This is the setup I actually purchased last year when the time came to get new tires, and it's just perfect. The only problem is the limited availability of this infrequently used rear size, but as I said, everything's a tradeoff

[bandier]

LOL... in essence: individually calculate the percentage difference of the new tire front and rear tire sizes to the stock sizes, then subtract the rear percentage from the front percentage to get your total deviation. If that total is less than 3% you should be ok. If ok there then consider the changes to the vehicle rake and ensure front not higher than the rear.

I'm paraphrasing, but I think that is essentially it. Before I got Arpad's formula, Yes, I was internally spazzing out thinking I bought rims and couldn't put wider tires on my car.

Originally Posted by Cellet

Did you get the explanation?

[arpad_m]

Originally Posted by bandier

I'm paraphrasing, but I think that is essentially it. Before I got Arpad's formula, Yes, I was internally spazzing out thinking I bought rims and couldn't put wider tires on my car.

Haha, I know the feeling and the cold sweat

GM designed a healthy tolerance margin into these algorithms. My only wish is all this stuff (ECM, TCM, cluster, infotainment etc) were open source, but that's a pipe dream...

Once you have the new tires mounted, let us know what you went with and how it all worked out.

[Edward Paul]

What did you end up with?
The more I try to see what's needed the more I get confused.
2022 LT1 and the rim company suggested two sizes front and rear.
F 275/40/20 or 285/30/20 and R 315/35/20 or 305/30/20.

[bandier]

I know the feeling. Ha ha, dont mean to laugh... It did suck. I recently installed 285/35R20 in front and 305/35R20 in rear. They are working out fantastically. Arpad has posts on this tread and is a wealth of knowledge and experience in helping me comfortably come to this tire sizing decision. It was not his top pick but did reassure me it would work without computer issues. Some say going with the 35 sidewall over a 30 allows a mushiness in the response of the tire. I suppose its possible but I have not noticed. I was trying to avoid teeth rattling when that occasional pothole pops up.

Originally Posted by Edward Paul

What did you end up with?
The more I try to see what's needed the more I get confused.
2022 LT1 and the rim company suggested two sizes front and rear.
F 275/40/20 or 285/30/20 and R 315/35/20 or 305/30/20.

[Edward Paul]

Thank You.
There are just so many options now days I'm expecting the gluten free ones too.
I don't know why they narrowed down the tire sizes to two.
I'm thinking 285/30/20 & 305/30/20.

[Msquared]

I think this all got pretty complicated, and I'm not sure the OP ever did quite grasp the actual explanation. What matters is the difference in between the front and rear diameters of the tires on the car. How they relate to the OE set is not relevant. At least on an SS 1LE, the car comes with rear tires that are 1.5% taller than the fronts. Obviously that's not a problem. The threshold seems to be that if the rears are more than 3% taller than the fronts, it starts to cause problems. I have gone as far a 2.7% taller rear without any problems. In a nutshell, just reread the first sentence of arpad's post #8. It's really all you need to know.

Given that, the OP's suggested sizes of 285/35/20 and 305/35/20 would not cause problems with the TCS/ABS, even for an LT1 Camaro. However, those are quite tall and I would advise against them for both handling and potential rubbing issues. The stock SS 1LE and ZL1 tire sizes of 285/30/20 and 305/30/20 would be much better on 20x10 and 20x11 wheels. You could vary either width by 10mm and be okay: one or the other, or both 10mm narrower or 10mm wider, but not both in opposite directions. I would NOT go with 275/40 fronts or 315/35 rears!

[bandier]

Yes Msquared, I did grasp the actual explanation regarding the difference between the front and rear diameters as the primary concern. Although, I'm sure you could be correct that the 30 series tire may perform better than the 35s. Since the calculations confirmed the 35s would work, I opted to try them out. So far so good... They seem to be handling very nicely and I do not have rubbing issues unless turning full lock to of one the directions. I agree Arpads input is essential when calculating different tire size options.

Originally Posted by Msquared

I think this all got pretty complicated, and I'm not sure the OP ever did quite grasp the actual explanation. What matters is the difference in between the front and rear diameters of the tires on the car. How they relate to the OE set is not relevant. At least on an SS 1LE, the car comes with rear tires that are 1.5% taller than the fronts. Obviously that's not a problem. The threshold seems to be that if the rears are more than 3% taller than the fronts, it starts to cause problems. I have gone as far a 2.7% taller rear without any problems. In a nutshell, just reread the first sentence of arpad's post #8. It's really all you need to know.

Given that, the OP's suggested sizes of 285/35/20 and 305/35/20 would not cause problems with the TCS/ABS, even for an LT1 Camaro. However, those are quite tall and I would advise against them for both handling and potential rubbing issues. The stock SS 1LE and ZL1 tire sizes of 285/30/20 and 305/30/20 would be much better on 20x10 and 20x11 wheels. You could vary either width by 10mm and be okay: one or the other, or both 10mm narrower or 10mm wider, but not both in opposite directions. I would NOT go with 275/40 fronts or 315/35 rears!