chas0039

I want to use a 700x23 on the front and a 700x25 on the rear. Is there any safety or other issue I should be aware of?

Thanks

MrCjolsen

Nope. None at all.

HillRider

None whatsoever.

Bob Dopolina 

Check out the Continental Attack/Force combination.

chas0039

Thanks guys. I kind of figured that was the case, but it never hurts to check with the pros.

Al1943

I'm not real happy with mine, not because of the mixed sizes but because of the way they ride and handle. They seem to have a hard rubber compound and feel a bit unstable. I use them on my time trial aero wheels but don't like them for hard cornering.

Bob Dopolina 

These tires are designed for racing and aggressive cornering. The black ones will have the new "Black Chili" compound. Go to the Conti site and check it out. I'm not sure where you feeling of instability comes from. (your mother I know mine does) Are you talking about traction or do you feel flex in the sidewalls?

Al1943

I don't have the newer "Black Chili" compound. I think the tires are OK, they just don't seem to have near the grip that my Michelin Pro2 Race tires have. They feel harder and seem to chatter more on rough pavement. Maybe they would feel better with less air pressure but I bought them for time trials and like to run 120 psi in time trials.

operator

Your bike will instantly explode the second the tires hit pavement.

wroomwroomoops

I've built up a ****bike (you have nice bikes, bikes, beaters and ****bikes, and this is it) to test a chain tensioner and to maybe keep it to run around in the parks around my home. I had two spare tires (both used, but still "alive") that I could throw onto it: one semi-slick and the other a knobby XC/DH. I decided to put the knobby tire in the back and the semislick in the front. Is that the correct idea, what do you guys think? It should have good grip and cornering in gravel, and I didn't want to use new tires, just these two used ones (it's a ****bike), so my only choice is knobby in front/semislick in the back or knobby in back/semislick in the front.

Bob Dopolina 

I'd put the knobby on the front. You can handle the rear wheel sliding out a bit but if the front goes...OUCH!

wroomwroomoops

You are right, but I was hoping the grips on the side of the semislick would keep it from sliding - I guess it would only slide while cornering, and the thread on the semislick is supposed to prevent just that, on loose?

rmfnla

This doesn't really apply to a road bike unless you will be riding in dirt or wet.

Slick tires give the best traction on dry roads; treads and knobs are there to make people feel more secure.

You have more weight on the rear tire (which is why you get more flats back there) so the additional air cushion of the larger tire will do the most good there. Again, this applies to a road bike on the road.

Riding in the dirt requires a larger contact patch up front for better traction on turns; in that case the larger tire goes up front (not that 2mm would make that much difference in this case).

Bob Dopolina 

I think the OP was talking about riding on mixed surfaces, road, dirt paths, gravel etc. In that case I'd stick with the knobs on the front. I do agree that a slick tire gives better traction on the road and if it were a strictly road application, I'd put the slick on the front..

wroomwroomoops

It's not slick, it's a semi-slick. As I said:
which was an answer to:

Al1943

The OP was talking about mixing a 700 X 23c road tire with a 700 X 25c road tire. Nothing to do with slicks or knobbys.

wroomwroomoops

Sorry, it's all my fault...

Bob Dopolina 

AHA! The Finn hijacked the thread!

As a reply about the semi-slick/knobby combo, I think it would come down to what KIND of knobs were on each tire. In the end, I'd go with whichever tire looks like it will give the best cornering on mixed surfaces and loose stuff like gravel. THAT tire, I'd put on the front.