# What is a 23/25c tire?



## nramsey (Apr 25, 2009)

Hi all,

New owner of an '09 Roubaix here and have a question about the tires that came on it. They are labeled as "Specialized Roubaix Pro, 700x23/25c". What the heck is a 23/25c tire? Is it a 23 or a 25 or what? 

Thanks for the help!

Nathan


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## nramsey (Apr 25, 2009)

Maybe I answered my own question. From Specialized's site...

"Roubaix tires are the perfect match for any rider who wants ultimate performance, without the harsh ride. Comfortable large volume 25c casing and a fast-rolling 23c Dual Radius Tread (DRT) ensure a supple ride that rolls fast and corners extremely well."

So I guess it's a 23c wide tire with a bit more "volume"? Do you assume that means it's a bit taller than a normal 23c tire (same width but more volume must mean taller?)?


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## andyk (Feb 17, 2009)

Hi mate, I have the same bike... I have actually swapped the tyres out for Continental GP4000s tyres (23c)

There is a significant difference in the width... I would read the Specialized statement as a 25c case (so 25c width) with the centre tread, being that of their 23c tyres (so its a fast rolling centre, similar to the Mondo Pro I would imagine). 

Either way, a little too wide for my liking (take a look into something like the Continental GP4000s/Schwalbe Ultremo R in a 23c if you want a faster skinnier tyre)


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## PJ352 (Dec 5, 2007)

andyk said:


> Hi mate, I have the same bike... I have actually swapped the tyres out for *Continental GP4000s *tyres (23c)
> 
> There is a significant difference in the width... *I would read the Specialized statement as a 25c case (so 25c width) with the centre tread, being that of their 23c tyres (so its a fast rolling centre, similar to the Mondo Pro I would imagine). *
> 
> Either way, a little too wide for my liking (take a look into something like the Continental GP4000s/Schwalbe Ultremo R in a 23c if you want a faster skinnier tyre)


Can't do better than the Conti's, IMO. But to answer the OP's question, I agree with your assessment of the Roubaix Pros 23/25's. I would add that it's nothing more than a marketing gimmick. If you want to run 23's do so. If you want to run 25's do that! 

To the OP: It's not a taller tire, but as Andy states, wider - at the tread. I believe that if it _could_ be measured, the sidewall (width) would be 23.


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## hrstrat57 (Mar 16, 2008)

Have "em on my bike and love "em. YMMV


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## darkest_fugue (Mar 14, 2009)

i had them on my roubaix, very comfortable, i switched to the all condition pro though, the tarmac i tried came with them and i liked the feel of them more, and call me shallow but the white walls on them really went well with the rest of my bike


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## Jet Fuel (Jul 29, 2004)

I have these tires. How do I set up my computer? 23 or 25? I'm thinking 23.


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## PJ352 (Dec 5, 2007)

Jet Fuel said:


> I have these tires. How do I set up my computer? 23 or 25? I'm thinking 23.


I believe the sidewall width is 23 and the tread width is 25, so I'd go with 25.


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## tom_h (May 6, 2008)

Jet Fuel said:


> I have these tires. How do I set up my computer? 23 or 25? I'm thinking 23.


Or do an actual "roll out" / tire circumference measurement, which some cyclocomputers accept directly.

-- Inflate tires to normal pressure, Sit on bike (you want to include the effect of tire "flattening" under your weight).
-- push yourself forward for 1, or preferably 2, complete wheel revolutions. Use valve stem as a convenient "marker", eg start & finish with valve stem at 6 oclock position.
-- measure total distance traveled. 
-- divide distance by 2, if 2 wheel revs were counted. This is the tire circumference. Convert to metric, as necessary.


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## froze (Sep 15, 2002)

PJ352 said:


> Can't do better than the Conti's, IMO. But to answer the OP's question, I agree with your assessment of the Roubaix Pros 23/25's. I would add that it's nothing more than a marketing gimmick. If you want to run 23's do so. If you want to run 25's do that!
> 
> To the OP: It's not a taller tire, but as Andy states, wider - at the tread. I believe that if it _could_ be measured, the sidewall (width) would be 23.


I know, it's an old post, but I stumbled upon it, so after asking Specialized about the tire size thing I thought I would respond with what they said.

It's not a marketing gimmick. What their doing is putting a larger casing tire, a 25 in this case, so you can run lower pressure for more comfort than you could with a 23. Having that size allows the tire to have a parabolic shape to that motorcycle tires have, and allows more rubber to be in contact with the road. There also an all season tire, these will even perform on ice cold days.

I have two sets of these tires, while I'm not going to set here and tell you they're the best tire in world, but I will tell you that they are really tough against cuts, and after 1500 miles on one set I haven't had a flat and they appear to be good for another roughly 1000 miles. I also think they're more comfortable then my last tires which were Vittoria Rubino 25 tires. I don't live in mountains so there's no curves around where I live where I can push the tires but they seem on par with the Vitts. As far as rolling resistance go...well, when someone says they went from one high end tire to another and claim their new ones are fast it's simply BS, no one can tell the difference in an even 4 watt difference not alone a watt or two. So I can't tell you if the Specs are faster than the Vitts, they feel better due to riding more comfortably, but are they faster? I have no clue.

Would I buy them again? If they went on sale like they did when got my sets then sure, if not I'll find another brand on sale. I buy tires if I can get a really good sale price otherwise I don't bother, and I will avoid a brand like Hutchinson that I had a huge problem with just after 350 miles and then got no service from them, so outside of tires that gave me problems, I'm not real loyal to one brand or another. Most tire today are far superior to tires of just 15 years ago so almost any top brand will be a good tire.


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