Having gotten a flat my second month with the new car and it being a bit of an ordeal to find an OEM Dunlop tire I want to get at least one spare rim and tire, in case this happens again.

It's a lot easier to find 15" than 16" OEM Fit Sport rims.

Now I realize that every expert says not to drive with mismatched tires, etc. and that a different size rim with a different tire would be worse.

However, think of the donut spare- it's a tiny rim, a different tread tire and it's way narrower than the other three tires. And it's okay to drive 50 mph on that tire, and probably that speed limitation isn't so much a handling issue as that the tire would probably fall apart faster at a higher speed.

I'm not suggesting driving 20,000 miles at 90 mph with one 15" rim, but I prefer a real spare to a donut spare... and if I had a set of four I could, if necessary, at least have the same wheels per axle.

Any great horror in doing this?

 

Bear in mind the space saver spare is only intended to get you to a safe spot or a shop. Not something you should be driving around on for days. That limitation is for a few reasons, one of them is handling.

Their is a term called roll-out used when matching tires, all sorts of goofy things happen with mismatched tires.

One of which is the difference in moments created across the axle, then there is the diminished contact patch on one corner, the difference in roll out, which is more pronounced on the drive axle.. then there is the added wear on your differential when the spare is mounted on the drive axle because it effectively simulates constant cornering and the change in wheel speed becomes yet further pronounced during actual cornering.

You really only need to worry about having the same size wheels on each axle. So 15" on the front and 16" on the rear would be acceptable, or Vice versa. but a 15" and a 16" on the same axle is a no-no and only acceptable when you are literally just limping to a safer spot or a garage.

Unless you are AWD in which case they HAVE TO be the same size at each corner or you risk binding your drivetrain and some serious head aches. But obviously USDM fit owners don't have to worry about this.

 

Thanks. I guess I was assuming that the 15" OEM and 16" OEM, since the tires are also different, might be the same radius and width, but I don't know if this is the case.

Similarly for shifting between 2010 OEM Base and Sport.

Either way, I would use the extra wheel/tire just as a full-size spare and when I got home I'd put the other, similar, wheel/tire on the other side (same axle). Glad it's okay to drive like that.

Still, my strong preference would be to own one 16" OEM rim/tire. That's what I did on my prior two cars (that's 23 years worth) and it seemed to work.

Still have one steel wheel for an '87 Integra sitting in the garage if anybody wants it.

 

Just wanted to clarify when I was using the term "moment" that is referring to the gyroscopic forces and their associated force vectors along and perpendicular to the axle.

Just by having different mass or different radii on the ends of the same axle can significantly compromise everything especially handling and braking.

 

The radius is going to be different but if you have to drive with "one clownshoe and one high-heel" put them on the back axle, match the two on the front and drive slow

 

I had the same question earlier this year when I had to replace one of my rims.

This guide really helped me understand which wheels would and would not work with my car:

Safe to Drive With Mismatched Wheels and Tires