Tire question
08-29-2018, 08:00 PM
#1
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Join Date: May 2001
Location: Granville, NY, United States
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Tire question
I posted awhile back about wheels and tires. Now looking for tires only question. I've got 20x9 fronts and 20x10 rears. What is the best size tire for both. Got the stockers on now. Think I need wider both front and rear, and a little lower profile in the rear. Any ideas? Thanks
08-30-2018, 12:06 AM
#2
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Location: Okemos, MI
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Re: Tire question
Those aren’t super popular sizes around here. A 9” wide wheel is normally paired with a 275-width tire, and that works well for 17-18” wheel diameters. With a 20” diameter, the loss in sidewall is going to reduce significantly the range of widths that will be okay. 9” is only 229mm, so you might need to go as low as 235-245 for it to fit. I think you need to go to TireRack and start looking at tires, and look to see what the recommended wheel widths are. Don’t use anything that is outside the recommendations. IMO, the tire should always be wider than the wheel.
For the 10” (254mm) wheel, we’d normally think of something in the 285-305 range, but again you might need to go smaller because of the loss of profile height.
Stock tires are 25.6” overall diameter. If you want stock-ish stance and an accurate speedo without recalibration, stick with something close to that. If you go higher, that gives you more sidewall, which gives you more width flexibility, but you’ll have to recalibrate (or tolerate an inaccurate speedo), and you’ll give up some acceleration too.
For the 10” (254mm) wheel, we’d normally think of something in the 285-305 range, but again you might need to go smaller because of the loss of profile height.
Stock tires are 25.6” overall diameter. If you want stock-ish stance and an accurate speedo without recalibration, stick with something close to that. If you go higher, that gives you more sidewall, which gives you more width flexibility, but you’ll have to recalibrate (or tolerate an inaccurate speedo), and you’ll give up some acceleration too.
Last edited by JakeRobb; 08-30-2018 at 12:09 AM.
08-30-2018, 09:09 AM
#7
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Re: Tire question
I was the one who gave you the previous info:
https://www.camaroz28.com/forums/201...-tires-886761/
Did you end up with the wheel/tire combo shown for the SS, aftermarket option #2?
Probably would have been a good idea to follow up on that thread, since by not responding, I was left with the impression you may never have read it, or if you did, never did anything with the info. A simple reply of “OK” lets the people who tried to help you know they didn't waste their time.
Once you confirm what you ended up with is what was shown in the reference chart, we can help you find new tire sizes.
https://www.camaroz28.com/forums/201...-tires-886761/
Did you end up with the wheel/tire combo shown for the SS, aftermarket option #2?
Probably would have been a good idea to follow up on that thread, since by not responding, I was left with the impression you may never have read it, or if you did, never did anything with the info. A simple reply of “OK” lets the people who tried to help you know they didn't waste their time.
Once you confirm what you ended up with is what was shown in the reference chart, we can help you find new tire sizes.
08-30-2018, 04:19 PM
#8
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Join Date: May 2001
Location: Granville, NY, United States
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Re: Tire question
I so appreciate that. But that chart only shows stock tire sizes. I’m looking for advise on optional sizes. Thinking 275/30 on 9 inch fronts and 305/30 on 10 inch rear. Is that good. Just looking for guidance. Anyone have any advise???
08-30-2018, 04:57 PM
#9
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Location: Hell was full so they sent me to NJ
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Re: Tire question
You need to keep the outside diameter of the tires the same as stock. If you go to a smaller diameter, you lose a bit of ground clearance, and the gap between the top edge of the tire and the fender lip increases - tires look too small. With the rear tires, if you do not match the stock tires, the speedometer and odometer will read incorrectly, or you will have to have the PCM programmed with the new tire size.
From the chart, your stock front tire is a 245/45-20. That tire is 28.7" diameter. A 275/40-20 would have the same 28.7" diameter. And it will fit correctly on wheels ranging from 9" to 11" wide. If you used a 275/30-20, the diameter would only be 26.5". Not going to look good. Just move the stock rear tires to the front wheels.
From the chart, your stock rear tire is a 275/40-17, which is 28.7" diameter as noted above. A 305/30-20 would be 27.2" diameter, throwing the speedometer/odometer off by more than 5%, plus would not match the front tire. Your choices would be:
- a 305/35-20 at 28.4" diameter. That tire will fit correctly on a wheel 10"-12" wide. The smaller diameter would cause the speedometer to read about 1% higher than actual speed, no big deal.
- a 315/35-20 at 28.7" diameter, same as the stock tire. No speedo error. But, that size tire is generally recommended for wheel widths of 10.5"-12.5". Probably not a big problem with a 10" wheel, but not within spec. Check various tire manufacturers. Not all manufacturers have the same wheel width recommendations.
And something I can't help you with - whether either of those tire sizes are going to rub on the inner fenders. If you look at "aftermarket option #3" in the chart, it does show a 265 tire in the front, and a 315 in the rear (although those are for 22" wheels.
From the chart, your stock front tire is a 245/45-20. That tire is 28.7" diameter. A 275/40-20 would have the same 28.7" diameter. And it will fit correctly on wheels ranging from 9" to 11" wide. If you used a 275/30-20, the diameter would only be 26.5". Not going to look good. Just move the stock rear tires to the front wheels.
From the chart, your stock rear tire is a 275/40-17, which is 28.7" diameter as noted above. A 305/30-20 would be 27.2" diameter, throwing the speedometer/odometer off by more than 5%, plus would not match the front tire. Your choices would be:
- a 305/35-20 at 28.4" diameter. That tire will fit correctly on a wheel 10"-12" wide. The smaller diameter would cause the speedometer to read about 1% higher than actual speed, no big deal.
- a 315/35-20 at 28.7" diameter, same as the stock tire. No speedo error. But, that size tire is generally recommended for wheel widths of 10.5"-12.5". Probably not a big problem with a 10" wheel, but not within spec. Check various tire manufacturers. Not all manufacturers have the same wheel width recommendations.
And something I can't help you with - whether either of those tire sizes are going to rub on the inner fenders. If you look at "aftermarket option #3" in the chart, it does show a 265 tire in the front, and a 315 in the rear (although those are for 22" wheels.
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