I'm a newbie to riding. I had a rear tire blowout today. It was a 25c I have a 23c will that work? That will mean that I have a 25c on the front and a 23c on the rear. What is the difference and how will riding with 2 different sizes effect my ride. TIA

Put the 23 on the front and the 25 on the rear and call it a Day.

I have no idea what a c is but i can tell you that you can go from 25mm to 23mm on the rear, no problem.

oops I did mean mm. thanks

You'll never notice a difference.

The "c" in 25c is millimeters. But millimeters kinda like the centimeters of an exercise ball. A "65cm" exercise ball is rarely gong to be inflated to 65cm (unless that owner is obsessive). Tires widths depend on inflation, age, rim width and manufacturer (and probably batch ).

25c is proper nomenclature but we don't say my tire is 2c bigger than yours.

And to the OP's question re: putting the 23c on in back - if it were me, I;d look first at the conditon of the 23 yo intend to put on. Is it new or in good shape? Yes? Put it in front. No? put it in back but be awre it needs significantly higher pressure because 1) it is in back, not front - I put 2-5 psi more in rear tires and 2) it is a smaller tire so has less air volume and therefore needs more pressure to ensure you do not bottom out and pinch flat or damage the rim or both. I use 5-7 pounds more in 23c tires than 25c.

Now, if you are racing, the old "rule" was that you always put your best, fastest rolling tire in back where it made a real difference. Those who wanted to win would put the 23 in back (assuming both tires were equal quality).

So like a lot of the cycling dilemmas, the answer is really simple, summed up as "It depends".

Ben

What? No. "C" doesn't mean millimeters in any other context.

The "C" in tire sizes stems from the 700C wheelsize designation. Over time, it detached from the rim measurement and attached itself to the tire width measurement, to look like 700x23C. A 650B tire is similarly described as 650x42B, an English 3-speed tire would be 650x35A, etc. If it's confusing, blame the French.

The "c" in 25c is a whacky shorthand reference to the "c" in "700c," which was a classic alphabetical scheme to distinguish 700c from sizes like 700b or 700d.

Descriptions like "25c" are technically ambiguous, and only manage to be coherent because other "c"-labeled sizes (like 650c) are less popular than 700c.

The "c" never meant millimeters. Nor would it make sense as shorthand if it did, since then you'd still have to reference the wheel diameter in some way so that people know what you want: "I'd like a 700c x 25c tire."

Cateye circumference chart lists 2096 mm for 700x23c tire and 2105 mm for 700x25c tire. That amounts to 9mm difference in circumference or 9/(2*pi) = 1mm difference in wheel radius. The change of the headtube angle in degrees is (180/pi) * (change of the wheel radius) / wheelbase = 60 * 1mm/1000mm = 0.1 degree. I made the computation out of curiocity So change between a 23 mm and a 25 mm tire does not matter.
Probably a good reason for putting a wider tire of the two in the rear is that the rear one is to bear more load, but that is another story.

You'll hardly notice the difference.

Ummm, how does that work??

Better when I type correctly.

Ben

Thank you.