Tire Size & Setting Up My Computer

[stpbound]

Hi all,

I was looking at my new road bike's tire size to figure out what size to input into my bike computer. The size on the tire says 700 x 23/25c. My options, according to the manual for my bike computer are 700x23 and 700x25.

Anyone know the right answer?

Thanks!
stpbound

[VeloVT]

That's actually what it says on your sidewall? Interesting... I wonder if the effective tire size for your tires depends on the PSI you're running??? Lower psi=more tire contacting ground=25 or higher psi=less tire contacting ground=23??? I've never seen anything like this before (so yeah, I don't know what I'm talking about :)!), but I would probably try to find more info on your tire specs by going to the manufacturer's website.

Maybe someone else will have a better idea though (or, well, know what they are talking about :)! ).

[jobob]

Here you go!

http://www.sheldonbrown.com/cyclecomputer_calibration.html#ccc

Scroll down to the Roll-Out Test.

[SadieKate]

stpbound, are you looking at the tire or the tube?

[Batbike]

stpbound, are you looking at the tire or the tube?

i agree with SadieKate -- sounds like you may be looking at tube versus tire. Tubes vary because they go on the inside of the tire, but tires usually come in one size -- what brand is your tire and what does it say on the sidewall?

[stpbound]

i agree with SadieKate -- sounds like you may be looking at tube versus tire. Tubes vary because they go on the inside of the tire, but tires usually come in one size -- what brand is your tire and what does it say on the sidewall?

The TIRE is the Specialized Roubaix Pro. It says 700x23/25c on the sidewall. I have not actually seen the tube yet...it's a brand new bike and luckily haven't had a flat yet!

[michelem]

Not that I have any clue what this means, but this is the info I got off of specialized.com:

The Roubaix Pro clincher is the easiest, fastest way to turn long & fast rides into long, fast, comfortable rides. In a unique construction design that merges a faster 23c wide tread with a more comfortable large-volume 25c casing, this tire offers a fast rolling, great handling tire which damps road vibration and increases riding comfort without sacrifice.


700x25c casing matched with a 23c wide dual compound 70/60 tread
DRT design for low rolling resistance and great cornering
120 TPI casing

Anyone? :confused:

[Batbike]

Not that I have any clue what this means, but this is the info I got off of specialized.com:

The Roubaix Pro clincher is the easiest, fastest way to turn long & fast rides into long, fast, comfortable rides. In a unique construction design that merges a faster 23c wide tread with a more comfortable large-volume 25c casing, this tire offers a fast rolling, great handling tire which damps road vibration and increases riding comfort without sacrifice.


700x25c casing matched with a 23c wide dual compound 70/60 tread
DRT design for low rolling resistance and great cornering
120 TPI casing

Anyone? :confused:

well .............. :confused: hmmmmmmmm :confused: :eek:

sounds like the 23c wide tread is what touches ground?; large-volume 25c casing is the inside volume of tire -- meaning it has the volume of a 25, but instead of touching ground like a 25 (more tire rolling on ground), you have a 23 coverage (less tire rolling on ground -- think racing and less rolling resistance) ... so, you get the comfort of a wider tire and the rolling resistance of a smaller tire. Now, what that means for a cycling computer -- heck darn, I don't know! :confused: :confused: :confused:

PURE GUESS: I would go with 23c because that is what is hitting ground.

since it is a new bike, would the bike shop know?!

[jobob]

Why don't you just measure the circumference yourself using the rollout method??

[Batbike]

Why don't you just measure it yourself using the rollout method??

good idea! :D