MustangDon026

On a 2008 Roush Mustang Speedster they come with 275/40/18s, no rub or anything. What would changing to a 275/35/18 do?
Looking at getting Michelin SS and they only have the 35s, not 40s
Would they be more likely to get damaged in bumps, have a rougher ride, spin more, ect?
Thanks in advance

Norm Peterson

275/35-18 is a pretty short tire and is enough smaller that you'd have to run them at slightly higher inflation pressures (guessing about 3 psi more than your 275/40's).

There's over 1/2" less sidewall when you go from 275/40 to 275/35, so the risk of getting a pinch-flat increases, especially if you let the inflation pressure run low. I doubt there's going to be much change in ride quality due to the difference in size - the change in tire mfr and model may cause a larger change here, and I'm not even going to try to guess which way. I would expect the 275/35's to be a little trickier to launch.

Have you considered either the 285/35-18 or 265/40-18 in these Michelins? I don't know how wide your wheels are, but if they're at least 9.5" wide either of those sizes would be legitimate choices. If your wheels are 9.5" wide, I don't think the maximum section width of the PSS 285/35-18 is going to be enough wider than your 275/40's to really matter unless you're almost rubbing as it is. The 265/40 will be a better diameter match and would virtually guarantee no rubbing, if you're OK with a tire having a little less sidewall bulge and a little less wheel rub protection than your 275/40's.


Norm

Cruzinaround

The OE tires for that Roush year is the Cooper Zeon RS3-S. Or The Mickey Thompson Street Comp (same tire). Superb performance tire IMO and pulls nice as a double duty Street/Track shoe.

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MustangDon026

Yeah currently the rims are 18x10. Not sure about the 285/35, they might rub up front

Also I heard those M/T don't handle curves as well as the Pilot SS. I heard they're cheaper too but they seem to be the same price for this size. Price isn't much of an issue though, just want some nice gripping DD tires mostly

Norm Peterson

Not counting any differences in the depth of molded lettering or rub strip height, the 285/35 PSS is less than 3/8" wider on a 10" wide wheel. Got 3/16" strut side clearance?

265/40's are OK'ed for wheels all the way up to 10.5" wide.


Norm

kenthicken

Pretty sure stock Roush tire in 2008 was the Cooper Zeon 2XS, since the RS3-S was not available yet.

Either way, I ran the Cooper RS3-S on my Roush, and while it was a good performance tire for the first 10,000 miles, it was an unbelievably ****ty tire shortly thereafter (with rotating every 3,000 miles). Track car, yes. A car you put some miles on, no. Your experience may vary, lol.