Mixing tire sizes, bad idea?

I am now 1 tire down on both my summer and winter wheel/tire sets. I have access to some parts from previous vehicles to try and fix this.

Summer is 205/55/16, winter is 205/60/15, and I have a used set of 205/65/15 in storage. My idea is to replace the flat snow with one of the taller tires and run that on the back(FWD) for the summer.

Using general measurements, the summer tire is 24.9" diameter, 837 rev/mile, the taller tires are 25.5" diameter, 817 rev/mile. That should be a 2.5% difference.

On the back of a fwd car, in theory it should work fine. My only real hang up is the ABS. Would that difference on one corner be enough to mess with the anti-lock or cause any other issues?

Could you run both of the larger tires on the back? I have no idea what the effect of just one would be.

I have mixed and matched all sorts of tire widths and diameters and sidewalls on FWDs and found that they pretty much all do exactly what you'd expect them to do as far as traction/handling.

I will say from my experiments that i am a big believer in running a staggered tire setup on FWDs.

As far as ABS, you can find that out pretty quickly. Hard to say what variance any given car will tolerate.

I'd do both rears just so I wouldn't have to think twice about it later.

The "other" tire is on a wheel with a different bolt pattern, so I would be going to a shop for a mount and balance. Doing a matching set would require 3 total M/B, as I would be pulling a good snow tire off one rim and re-installing it in the fall. The cost of 2 additional mountings puts me into buy a used tire in the proper size price range, or nearly buy the cheapest new tire to use for a year.

As long as its not all wheel drive, go ahead, although there is a possibility of setting an ABS code at higher speeds. I had mismatched front and rear on a car once, and it set a code once the speed difference got up to 10kph. I think that was with 55's vs 65's.

Go to a junkyard for a tire of the same size? Probably not more than $40 and probably less if they don't have a match for it.

I am weird like this but I have done this more than once to get through a "situation" or two.

My rule of thumb: Make sure that the drive axle has two matching tires on it, and make sure that the stickier tires are in the rear. Unless of course you're trying to get more rotation on a FWD car. As long as the drive axle has matching sizes, you're probably ok

I would only do it if I was strapped for cash. The handling and the ride should be noticeably funky with 1 different sized tire.

If you're paying enough for mount and balance to approach the cost of a used tire in the 'correct' size, i would just buy a used tire.

I agree with Vigo (which seems to happen a lot)

It will jack more weight on the opposite corner front wheel.

OK, not much, but.

I suspect the ABS is probably OK, or else you probably wouldn't find ABS-equipped cars being supplied with donut spares.

That said, I wouldn't do it as anything other than a temporary measure. Mismatched tires are just a bad idea, IMHO.