Actual Tire Widths

[93RubyZ]

As we all probably know, not all tires of the same size are actually the same size (see comparisons below of two 315/35r17 tires from Sumitomo and Goodyear -- disclaimer: these are not my photos). The topic often comes up on this forum of actual tire sizes (specifically tire widths) from different brands and models. Our cars came with wider tires than the standard Corvette which led to a wider rear body. This gives the ZR-1 a unique look and wider rear tires help preserve that look. Photos of different tires helps with providing an idea on tire width, but photos can be deceiving and what we really need are actual measurements. With that in mind, I thought I would start this thread and share measurements I've taken on tires I have had recently. Hopefully others will contribute with actual measurements on other tire brands and models.

[93RubyZ]

Here are measurements I took from BF Goodrich T/A KD 315/35r17. As you can see, these tires measure 12.75" or 12-3/4" in width. These measurements were taken with the tire mounted on a stock 11" wheel and properly inflated.

Note: in order to provide the most accurate measurement, I used a straight board and placed it over the tire and simply measured the distance from the ground to the board. Don't be concerned with the tape measure looking crooked, the photo is what is crooked.

[93RubyZ]

Here are measurements I took from the new Toyo Proxes R888 315/35r17 that replaced my BFGs. As you can see, these tires measure 12.625" or 12-5/8" in width. These measurements were taken with the tire mounted on a stock 11" wheel and properly inflated. Note that I also measured these tires before mounting using the same method and they were slightly wider (right at 12-3/4").

[93RubyZ]

For a side-by-side comparison, here is the BFG KD and Toyo R888 next to each other. Note that the BFG is mounted on a wheel and properly inflated while the Toyo is not mounted. While the Toyo appears to be about the same width in this photo (and also measured about the same when unmounted), the BFG was actually about 1/8" wider when both are mounted.

[93RubyZ]

Here is another visual comparison (no measurements -- this is not my photo) between the 315/35r17 BGF T/A KD and the Goodyear GS-D3.

[93RubyZ]

Here is another visual comparison between the BFG T/A KD 315/35r17 and the 315/35r17 Goodyear GS-C. This is my photo from years ago and I didn't' think of taking measurements back then. I recall that the BFGs seemed to be just slightly wider (by no more than 1/8" -- so really no noticeable difference).

[cbaclawski]

Originally Posted by 93RubyZ

As we all probably know, not all tires of the same size are actually the same size (see comparisons below of two 315/35r17 tires from Sumitomo and Goodyear). The topic often comes up on this forum of actual tire sizes (specifically tire widths) from different brands and models. Our cars came with wider tires than the standard Corvette which led to a wider rear body. This gives the ZR-1 a unique look and wider rear tires help preserve that look. Photos of different tires helps with providing an idea on tire width, but photos can be deceiving and what we really need are actual measurements. With that in mind, I thought I would start this thread and share measurements I've taken on tires I have had recently. Hopefully others will contribute with actual measurements on other tire brands and models.

Wow! That's a pretty substantial difference for tires that are the "same size" Did you get a chance to measure diameter or circumference? If they're anywhere near the same difference in that dimension it could actually change the final drive not insignificantly...

[93RubyZ]

Originally Posted by cbaclawski

Wow! That's a pretty substantial difference for tires that are the "same size" Did you get a chance to measure diameter or circumference? If they're anywhere near the same difference in that dimension it could actually change the final drive not insignificantly...

My apologies -- the photos in the initial post are not mine (I've edited the post to state that). I don't believe there is much difference in tire diameters, it is really the width where you see the significant differences. The photo you see is a bit of an illusion as both tires are sitting on their respective paired tire. The tire on the right (Goodyear) is wider so the tire that is standing up vertically is sitting on a higher surface and appears to be taller for that reason. These tires are likely pretty close in diameter.

[ghlkal]

FWIW ... I needed new rear tires and went with Nitto NT555G2 (315/35-17)


Here's the image of the tire _unmounted_ showing the width as 12.625" (~320 mm). Mounted and inflated to 35 psi, it was 12.5 inches (~315 mm)

[93RubyZ]

Thanks for taking the time to measure your new tires and share with the forum! I've wondered about the actual widths of Nittos as those were also under consideration for me.