On a 2wd, you could run a wagon/ tractor wheel
Or a tiny wheelbarrow wheel as a spare for a short distance. The size really doesn't matter. 

-craig

On Oct 4, 2013, at 8:22 PM, Dave Mcneely <mcneely4@COX.NET> wrote:

> I'm not brilliant or especially knowledgeable, but the donut spares that come on new cars are quite a bit smaller than the full sized tires and wheels for the car.  Mine says to run it at not over 50 mph and not for more than 50 miles.  Fortunately, I've never had to use it at all.  You might be ok.  But, for me, for the camper, I have five identical tires and wheels.  mcneely
> 
> ---- Alain Thibault <alainthibault@TELUS.NET> wrote:
>> Hi
>> I am running 215-60-16 and carrying a stock tire 14''as a spare. Could I still be able to use it for a small distance should a flat tire occurs?
>> 
>> Sent from my iPhone
> 
> --
> David McNeely