Quick tire size question...
#1
Quick tire size question...
I'm going with new wheels on my Formula (18x8.5 40mm offset fronts and 19x9.5 45mm offset rears), and I know that going with a 35 profile tire on the fronts will be appropriate, my question is what profile for the rears?
I think being a 19" wheel they need to be a 30 profile to not throw off the speedo, but I just wanted to make sure.
I think being a 19" wheel they need to be a 30 profile to not throw off the speedo, but I just wanted to make sure.
#2
Re: Quick tire size question...
In the back, to keep the speedo correct, you need to match the stock tire. What size came on your car from the factory - 245/50-16 (25.7") or 235/55-16 (26.2")?
Diameter is a function of profile and width.
To match the diameter in the front, you would be looking at a 285/35-18 (25.9"), but that tire is too wide for an 8.5" wide wheel. You need at least a 9.5" wide wheel for the 285. For the 8.5" wide wheel you could use a 255/40-18 (26.03")
In the back you could use a 285/30-19. Some manufacturers call this a 25.8" tire, others a 26.0" tire.
Diameter is a function of profile and width.
To match the diameter in the front, you would be looking at a 285/35-18 (25.9"), but that tire is too wide for an 8.5" wide wheel. You need at least a 9.5" wide wheel for the 285. For the 8.5" wide wheel you could use a 255/40-18 (26.03")
In the back you could use a 285/30-19. Some manufacturers call this a 25.8" tire, others a 26.0" tire.
#3
Re: Quick tire size question...
Well, the car has the WS-6 factory 17 inch wheels on it, I would have to check.
I do know that on my LT1 that I have 18x9 wheels on the front and 275/35ZR18's in the front (perhaps they are the wrong size). Then on the rear 18x9.5 I have 305/35ZR18's and the speedo seems correct.
Thanks for chiming in. Sounds like a 30 profile for the rear should do it as I suspected.
I do know that on my LT1 that I have 18x9 wheels on the front and 275/35ZR18's in the front (perhaps they are the wrong size). Then on the rear 18x9.5 I have 305/35ZR18's and the speedo seems correct.
Thanks for chiming in. Sounds like a 30 profile for the rear should do it as I suspected.
#4
Re: Quick tire size question...
The WS6 coupes had 275/40-17 (25.7")
275/35-18 = 25.6". Again, minimum wheel width for that tire is 9.0". But you could get away with it on a 8.5" wide wheel. Might be a bit scrunched, but barely noticeable.
305/35-18 = 26.4". Requires a wheel at least 10.0" wide.
The speedo error between a 26.4" tire and the stock 25.7" tire would be the speedo reading 2.8% slower than actual speed, or for example 1.7MPH lower than actual speed at 60MPH.
275/35-18 = 25.6". Again, minimum wheel width for that tire is 9.0". But you could get away with it on a 8.5" wide wheel. Might be a bit scrunched, but barely noticeable.
305/35-18 = 26.4". Requires a wheel at least 10.0" wide.
The speedo error between a 26.4" tire and the stock 25.7" tire would be the speedo reading 2.8% slower than actual speed, or for example 1.7MPH lower than actual speed at 60MPH.
#5
Re: Quick tire size question...
You are correct on the size Fred (I just checked the Formula).
The Nitto 305 seems to look fine on the wheel, but I think I mispoke earlier and its actually a 10.0 wide wheel in the rear (and Nittos have been known to be more narrow than other brands).
The Nitto 305 seems to look fine on the wheel, but I think I mispoke earlier and its actually a 10.0 wide wheel in the rear (and Nittos have been known to be more narrow than other brands).
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08-23-2023 11:19 PM