Spare wheel

Squidgy Black

Silly question probably, but my car has aftermarket wheels 205/50/zr17, checked the spare tire in the boot as I've a flat due to a crack in the side wall, and it's a 195/65r15.

I assume this is too much of a size difference to use until I can get the tyre replaced?

Melodeon

According to the www.willtheyfit.com tyre calculator, there's only a 2-and-a-bit mm difference in the diameter of the two.
That's utterly immaterial from the point of view of confusing the differential or messing up speed sensors or anything like that.
The car will handle differently though, so get it back onto matching tyres asap.

Squidgy Black

Melodeon wrote: »

According to the www.willtheyfit.com tyre calculator, there's only a 2-and-a-bit mm difference in the diameter of the two.
That's utterly immaterial from the point of view of confusing the differential or messing up speed sensors or anything like that.
The car will handle differently though, so get it back onto matching tyres asap.

If I can use it just for tomorrow for a short enough commute I'll be able to get it sorted Thursday first thing.

colm_mcm

As long as the car hasn't a limited slip diff, you should be fine. If it's FWD, put the spare on the back.
Different size spares are common enough, sure most cars have space savers.

2mm isn't that much of a difference though.