Disappointing day at my local Firestone. Here are the 255/40/17 RS3s vs the 245/40/17 RS3s. Both are on 17x9 949 wheels. Keep in mind, the 255s are just about at the wear bars.





I will be back on 255s for the San Diego tour...

 

You'll want to stand them up and measure the tread width of the tires. Laying them flat like that measures section width and accounts for sidewall bulge (not useful in this comparison). Regardless, it looks like all the other 245/255 comparisons I did on my STU E36 M3, which worked out to about 1/2" tread width.

People choosing the 245 are doing so for gearing and weight savings, but probably compromising grip. I've never tested the weight and gearing on a momentum car such as the S2000, so there is still hope. The best way to determine if the 245 is better or worse is to A/B equally worn sets on a test course like Mineral Wells. A wear bar set versus a fresh set can throw the test either from heat cycling or overall diameter.

[EDIT] When you go to the SD Tour, you might try asking Jason Isely why he opted for the taller, heavier, pinched 265/35-18 on an 18x9 over the 255/40-17 on a 17x9 when he ran his STX RX8. Mike Simanyi is more forthcoming about his decision to go 265s on his STU M3.

 

Right, the comparison isn't as good as it would be to a set of fresh 255s. The tread widths measured ~9.75" for the 255s and ~9.25" to 9.38" for the 245s (harder to tell because they weren't worn down like the 255s).

The tread width, according to Hankook, was supposed to be wider than the 255s, which is one of the reasons I opted to get them a try.

 

so from these pics the 245's are taller then the 255s? That makes me want to call and cancel my order and switch to a order of 255's.

 

That's the part of the comparison that is deceiving. The 255s have 6 lapping days and 4 auto-x events on them, plus a few thousand miles of street driving. The 245s are fresh and as tall as they'll ever be. I don't have any fresh 255s to compare against, right now.

 

I believe you will lose roughly 1/4" from full tread to wear bars (not to mention 2-3lbs), but its been awhile since I looked at that.

 

[QUOTE=daverx7,Feb 17 2011, 05:37 PM]To me the numbers on these tires "feel funny", so I'm not sure what to trust with what is on the side of the tire (or the 255's).

 

Did you happen to weight the unmounted 245s?

 

If they are molded to 10/32" like most of the sports tires seem to be currently, then you lose 1/4" of tread from new to the wear bars. And it comes off all the way around, so if you stand the tire up and compare the heights, new vs wear bars results in a 1/2" difference in overall height.

 

well guys, you scared me into calling and changing my order. They are shipping out my 255/40s today. I don't want to make a $600 mistake. I'll let you all do the testing and if it all works out then I'll order a set. a 1/2 width is giving up 6.2% of your total contact patch. Thats alot considering they where suppose to be wider and it doesn't seem like they are much shorter at all.