Aaron Marga

I know it's late in the season to talk snow tires, but they say the best time to buy them is in April. However, I have my old Challenger snows lying around which were 235/55-18's. My 2017 Mustang GT comes stock with 235/50-18's. I'll confess, I'm a bit of a newb on this, but my much more mechanically inclined buddy tells me they'll fit (make sense to me dimensionally) and just throw the speedometer off ~3% (2MPH @ 60) (also makes complete sense, I see the "Tools" section above confirms this).


I more or less want to verify he's not wrong or if anyone else spins around in a GT in the winter. I will say, you're unlikely to convince me to get a beater as the money people want for their hunk of junk is ridiculous here. I have seen some other threads on this, but not much or at all on the current body style from 2015 - now. Is there any difficulties getting shops to even mount them?


I appreciate the help!

Norm Peterson

A 235/55-18 stands about an inch taller than your 235/50-18. This means you'll gain about half an inch of ground clearance (good when/if it does snow) and you'll lose about half an inch of tire to fender gap (only at the tops of the tires).

That size is recommended for wheels between 6.5" wide and 8.5" wide, which covers the wheels you have (probably 8" wide, won't be more than 8.5" wide if they're OE Ford wheels for the 235/50-18 size).

That 2 mph @ 60 estimate of speedometer error is about right, but keep in mind that that would be relative to however accurate your speedometer is on the tires you currently have (plus/minus a little fudge-factor for differences in tire wear). Mostly, I wouldn't worry about it. But since this error is in the direction of you going faster than indicated I'd avoid playing quite as freely with posted speed limits as before.


Norm