Anyone here with experience with the V710s, specifically in the 215/40/17 and 245/40/17 sizes?

According to Kumho's published specs, these two sizes have the same section width and overall diameter(9.1" and 24.1" respectively). I originally assumed that the 215s were the older "round shoulder" design, and thus wider than standard 215s... and the 245s were the square shoulders, and thus narrower. But apparently they are both from square shoulder molds.

So, are the 215/40/17s really 9.1" wide? And would a 8" wide wheel be preferable, as Kumho recommends? Im interested as Im trying to decide what tire to run for NASA TT, and there is a 7 point difference between these two tires... but supposedly no size difference

 

No, they don't. The section width and diameter for those two sizes are different on the Kumho website, as follows:

Section width 215/40-17: 9.1"
Section width 245/40-17: 9.8"
Overall diameter 215/40-17: 24.1"
Overall diameter 245/40-17: 24.7"
Approved wheel widths 215/40-17: 7.0-8.5"
Approved wheel widths 245/40-17: 8.0-9.5"

I'm guessing you're pulling your numbers from the Tire Rack website, which appears to show erroneous specs for the 245/40-17 size (i.e. copying the specs for 215/40-17).

Apparently, yes. Remember, that's the section width, not the tread width. I believe the section width is measured in the middle of the sidewall, when the tire is mounted on the size rim specified.

Kumho does not recommend that particular wheel width; as the specs note, they approve the 215/40-17 for any width from 17x7 to 17x8.5. The 17x8 width is the measuring width, i.e. the rim width that they use when coming up with the other measurements shown in the specs, such as the section width.

 

Wow... I couldve sworn I checked kumhousa.com and found the same results as Tire rack. But you're right, I was looking at the Tire Rack specs yesterday when I made this thread.

And let me rephrase the last part. Wouldn't one want to use the same wheel as the manufacturer uses for their specs? In this case, 17x8"? I realize the tire is approved on the given range stated by Kumho, but I was always under the impression that the wheel the manufacturer uses is probably what the consumer wants to go with as well...

 

Didnt they just go from round to more square shoulders in certain sizes? There was an article in the last grm.

 

Yes, I believe so. Only certain sizes feature the square shoulder.

 

A 17x8 is most likely going to be a bit narrow for a 245 race tire. I ran the 245-40-17 on my 17x9s in my old BMW and they were pretty close to perfectly square. They will certainly fit on a 17x8 but if you had the option to go to an 8.5 I dont think it would be a bad idea.

 

Sorry, I guess I should have been more clear.

My intention was actually to run the 215/40/17, not the 245. I was looking at the 245 for comparison sake, as I have been trying to decide which tire to run. Kumho specs their section width as 9.1" on a 17x8" wheel for the 215/40/17. While 9.1" is wider than most other 215s available(based on the data I can find).... a 8" wheel seems a little wide for a 215 tire. But then again, they are race tires.