[TNfirstgen]

I’m needing some advice concerning varying from stock sized tires. I have a 2021 LT1 with the stock 245/40R20 (27.7”) tires. I’m looking to switch to the MRR 1le replica wheels and run the factory 1le tire sizes, 285/30R20 (26.7”) and 305/30R20 (27.2”). Will this change in tire size cause any issue with the traction control or any other systems in the car? I’m worried the 1” overall drop in front tire size may make the unhappy, wether that be traction control or something else I’m maybe not thinking of. It seems the SS cars are fine doing this setup, but im concerned that LT1 may be different since it has 245/40s all around. Will this setup work fine without the car throwing any lights or warnings? What about the speedometer, will it be a great deal off?

[WhiteMale]

One might assume they're OE sizes and would be OK but I'd be interested to hear other inputs as the basic advice is staying in a window from OE sizes that came on the car. I dont' remember if it's 1" up or down in diameter that can cause traction/stabilitrak issues.

[TNfirstgen]

Originally Posted by WhiteMale

One might assume they're OE sizes and would be OK but I'd be interested to hear other inputs as the basic advice is staying in a window from OE sizes that came on the car. I dont' remember if it's 1" up or down in diameter that can cause traction/stabilitrak issues.

I’ll be very disappointed if going to a factory size of another car won’t work. I’ve seen several people do the change, but not got the clarification i need to go ahead and order everything. I considered going to a 275/35R20 front since it’s nearly the same size as what i have now, but then the front will be bigger than the rear and I’m sure that would not make the Stabilitrak happy.

[Scargoes]

the overall OD of the replacement tires doesn't matter. The car won't be able to tell if you are running 25" tires or 27" tires. What matters is the size difference between the front and the rear. That ratio is what will set off a warning or cause undesired effects with stability control/traction control.

I'm not sure what tires you were thinking of running, but if they made a 295/30 that would bring the ratio down but still fit on the width rim without and serious stretching or pinching of the tire.

[TNfirstgen]

Originally Posted by Scargoes

the overall OD of the replacement tires doesn't matter. The car won't be able to tell if you are running 25" tires or 27" tires. What matters is the size difference between the front and the rear. That ratio is what will set off a warning or cause undesired effects with stability control/traction control.

I'm not sure what tires you were thinking of running, but if they made a 295/30 that would bring the ratio down but still fit on the width rim without and serious stretching or pinching of the tire.

Thanks for that info. I’m leaning towards continental extreme contact sports. Not sure if they make a 295 with that AR, but I’ll certainly check. If that’s the case, and a 1le doesn’t have TC issues, I’d assume I’d be fine then, right? I would assume the 1le would have any special considerations, unless the tire size programming for the speedometer also would make TC not have issues.

[TNfirstgen]

Another thing I have a question about is if i do decide to run a 275/35r20 front tire to help eliminate wheel gap, will that have ill effects if i run the 305 rear due to the smaller rear tire than front?

[arpad_m]

Originally Posted by TNfirstgen

Another thing I have a question about is if i do decide to run a 275/35r20 front tire to help eliminate wheel gap, will that have ill effects if i run the 305 rear due to the smaller rear tire than front?

You will have no problems, the difference is small enough and your new fronts will be a bit shorter than stock as well. I'd do 315/30/20 or even 325/30/20 in the rear, though.

[TNfirstgen]

Originally Posted by arpad_m

You will have no problems, the difference is small enough and your new fronts will be a bit shorter than stock as well. I'd do 315/30/20 or even 325/30/20 in the rear, though.

I may consider that in the future if i make more power, but i really don’t want to have to worry with the harness relocation and such just yet.

[Aaron07]

Originally Posted by TNfirstgen

Another thing I have a question about is if i do decide to run a 275/35r20 front tire to help eliminate wheel gap, will that have ill effects if i run the 305 rear due to the smaller rear tire than front?

It would seem that you would want to keep the OD as close to stock as possible for speedometer reasons, at least I am. I too have MRR 1LE wheels on the way with the Conti Extreme Contact Sport tires in 1LE sizes, 285/30 FR, 305/30 rear. (I am a regular SS) There are tire calculators online where you can compare your stock size to different sizes and see the mathematical differences. IMO keep close to your stock OD. EDIT: I am also lowered 1'' so I don't have the wheel gap concern that you do. If I was in your shoes that would also definitely be a concern of mine.

[TNfirstgen]

Originally Posted by Aaron07

It would seem that you would want to keep the OD as close to stock as possible for speedometer reasons, at least I am. I too have MRR 1LE wheels on the way with the Conti Extreme Contact Sport tires in 1LE sizes, 285/30 FR, 305/30 rear. (I am a regular SS) There are tire calculators online where you can compare your stock size to different sizes and see the mathematical differences. IMO keep close to your stock OD. EDIT: I am also lowered 1'' so I don't have the wheel gap concern that you do. If I was in your shoes that would also definitely be a concern of mine.

One thing that i found out is that SS and LT1s, although have different rear tire widths, have nearly the same OD (.1” shorter rears on SS). So with that fact, i believe it would be no different for me to run the 1le sizes. I will lower the car eventually, hopefully it doesn’t look too goofy for now if i go with the 285. Where did you order your wheels from? I’m going to use wheelfire i believe. Somehow they don't charge tax, so they are nearly $300 cheaper than everyone else.

[Baddawg53]

I switch my SS to 1le sizes and supercar 3's with no issues, then I put NT01's on and the car really doesn't like it. I have to run with all the nannies off with this setup. I'm assuming I'll have the same deal when I go 18 inch square setup.

[TNfirstgen]

Originally Posted by Baddawg53

I switch my SS to 1le sizes and supercar 3's with no issues, then I put NT01's on and the car really doesn't like it. I have to run with all the nannies off with this setup. I'm assuming I'll have the same deal when I go 18 inch square setup.

Same size tires with the Nittos? I’ve heard tire sizes change from brand to brand, but if that’s the case the difference in front to back OD of the 1le sizes must be right on the limit.

[Aaron07]

Originally Posted by TNfirstgen

One thing that i found out is that SS and LT1s, although have different rear tire widths, have nearly the same OD (.1” shorter rears on SS). So with that fact, i believe it would be no different for me to run the 1le sizes. I will lower the car eventually, hopefully it doesn’t look too goofy for now if i go with the 285. Where did you order your wheels from? I’m going to use wheelfire i believe. Somehow they don't charge tax, so they are nearly $300 cheaper than everyone else.

I recommend AFE power lowering springs when you do lower.. I bought a complete wheel and tire package that includes the tires, wheels, lug nuts, new tpms, wheel weights, mounted and balanced from CarID.