Running Two Different Size Tires Okay?
 

My Fuji Saratoga has 700x35's on it for tires. The rear tire is potentially flat. I might need to replace it. I have a decent 700x38 tire I got for nothing. Is it okay to run a 700x35 in the front and a 700x38 in the back?

Yes, there's no real reason you can't have mismatched tires.

In fact there are many who'll claim an advantage to mismatched tires, though there's little agreement among them as to whether it's better to have the smaller tire up front or in back.

I rode tubulars for decades and often had mismatches as a result of tire changes. They ran both ways, depending on chance as tires flatted and were replaced, and I never felt it made any difference.

Yes. BITD BMXers would run the wider tire up front. On my tandem I run the wider tire on the rear. Andy.

Mismatched tires and wheels = no problem.

http://i189.photobucket.com/albums/z...jmmxmaseve.jpg

"Potentially flat"?

On a bike primarily ridden on the road, there might be some advantage to running a slightly wider tire on the rear. On a bike ridden off-road, it used to be SOP to run a fatter tire on the front to increase control and front traction by increasing the amount of suspension travel in the tire.

Changing from a 35mm tire to a 38mm tire will likely make little or no difference, though. It also depends on the construction of the tires.
Either way, if those are the tires you have available, they will be fine.

The old wisdom if you wanted to go fast and had unequal tires was that you put your best, fastest lightest tire in back.

But in literal answer to your question, "Running Two Different Size Tires OK?"; It depends. It depends entirely (and only) on who you are trying t0 impress.

Ben

Sometimes the stars just seem to align perfectly.

Actually,tires don't go flat,tubes do. Is the tire actually damaged in some way? If not,you can just replace the tube. Make sure to inspect the entire tire for foreign objects,inside and out. To check the inside,turn each section inside-out and see if anything pops out of the tread. Also check the rim to ensure there are no sharp spots and the rim tape to ensure it's covering the spoke holes properly. If the tire's ok,you just need to repair or replace the tube.

I am running a 700 x 25 on the front and a 700 x 38 with a more aggressive tread on the back for the winter on a fixed gear bike

Oh no! The bearings are going to wear out at different rates! LOL.

It turns out it was the tube. It was originally a Schrader valve and the previous owner put a presta valve converter on it. That caused it to blow.

Do you mean you had a presta valve tube in a rim with a larger Schrader hole? With an adapter for the larger hole? Why would that cause a failure?

If the adapter wasn't properly in place,the base of the valve could work its way into the valve opening and the tube could be cut.

It looked like the adapter was installed incorrectly and it cut the tube. I got a new schrader tube installed.

If that were true, I'd never have had that flat with tubeless 10km into a 90km stage of Crank The Shield.

I've run 23's and 25's, and can hardly tell the difference between the two.

The biggest issue I could be foresee is whether there would be any clearance issues with the larger tires.