# Tire help please



## Muaythaibike (Oct 26, 2007)

my bike has 700 25 C tire size. most tires i find are 700 23 C size. can i use these? Whats the difference abd how do i know which is the best fit?


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## rdolson (Sep 2, 2003)

The 700 refers to the size rim your tires will fit on. The 25 is the section width of the tire. The larger the number (which is mm of section) the larger the tire. Larger tires can be run at lower psi for a more comfortable ride without geting the dreaded "pinch flat" which is where the tire casing and the rim "pinch" the tube and cause a flat.

Narrower tires are more "Racey" and can give you an added aero benefit along with less rotational mass at the rim. But they need to be run at higher pressures to avoid pinch flatting, unless you go tubular. (and THAT you should not even think about at this tender stage in your cycling career.)


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## Muaythaibike (Oct 26, 2007)

Thanks. For the info. But will a 700 23C tire fit on my current rim? So as long as the tire reads 700, the section width does not matter????? Just want to make sure if I buy something that it fits. Again, there are so many more options in the 700 23c size then the 700 25 C.

Thanks


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## Becky (Jun 15, 2004)

Yes, a 23c tire will fit. 

Width does come into play, but going up or down 1 size shouldn't make a difference. It's only when you make big jumps in width that you may have issues. Check out what Sheldon Brown had to say on the topic: http://sheldonbrown.com/tire-sizing.html.


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## wim (Feb 28, 2005)

Muaythaibike said:


> Thanks. For the info. But will a 700 23C tire fit on my current rim? So as long as the tire reads 700, the section width does not matter????? Just want to make sure if I buy something that it fits. Again, there are so many more options in the 700 23c size then the 700 25 C.
> 
> Thanks


"Section" could also be described as width. The "25" and "23" refers to millimeter, so a 700 x 25 tire is only 2 mm wider than a 700 x 23—a scant 1 mm per side. 

Your rims could safely accommodate tires from 700 x 20 all the way to 700 x 32, but your frame and fork limits your choice of wider tires. 700 x 25 is probably the maximum width that fits into your frame and fork. Keep in mind that these millimeter-figures are nominal, so actual widths can slightly differ from what the tire label or the seller's web site says. The only way to know for sure how wide a tire fits in your frame and fork is to experiment. Also keep in mind that a 700 x 23 tire can also be called a 23 x 622 tire, a 700 x 25 tire a 25 x 622 tire, and so on. Confusing, but that's the way it is.


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## Muaythaibike (Oct 26, 2007)

WIM,

Thank you. I want to replace my tires at some point and knowing that I can drop down to a 23 gives me many more options. 

What is the standard now a days for new road bikes. My new Trek 1600 came with 25 MM???? Also, Would I noitice a change from a 25 to a 23?


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## uzziefly (Jul 15, 2006)

There's no standard these days for road bikes. The standard is whatever the hell the bike comes stock with. Just don't exceed what your fork can accommodate and you'll be fine. 

I've been using 700 x 22 tubulars ever since I got my bike. I think I once ran different widths between the front and rear but that didn't affect anything.

So, in simple explanation, no, there'd be hardly any difference in a 25 and 23, except a 23 would probably require slightly higher pressure and be a tad faster with less rolling resistance. Even then, it's minimal. Change your tires when you really need to. Unless they keep getting punctured or something.


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## wim (Feb 28, 2005)

Muaythaibike said:


> WIM,
> 
> Thank you. I want to replace my tires at some point and knowing that I can drop down to a 23 gives me many more options.
> 
> What is the standard now a days for new road bikes. My new Trek 1600 came with 25 MM???? Also, Would I noitice a change from a 25 to a 23?


In terms of sheer numbers of tires spec'd for new road racing bikes, 700 x 23 lead the pack, followed by 700 x 25. The difference you'd feel with a 700 x 23 would come mostly from the slightly higher recommended tire pressure giving you a slightly firmer ride, and from the slightly narrower, a tad more quick-reacting footprint.

But these differences are tiny, as are the differences in "speed" between a 700 x 23 and 700 x 25 tire. I've been riding bikes seriously (unfortunately also on-and-off) for 50 years now and if you'd blindfold me, I couldn't tell the difference between a 700 x 25 and a 700 x 23 tire riding on asphalt. I'd also run into something . . .

For what it's worth: I really appreciate a slightly wider tire like a 700 x 25 or 700 x 28 when I run off the road and have to ride through dirt, gravel or grass before getting back on the asphalt. It's clear to me that a few millimeter more in tire width make such a maneuver much easier and less sketchy.

/w


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## jmkimmel (Jul 13, 2007)

Also, and this is a minor issue to the OP, but a good thing to know... going with a smaller tire will change the steering characteristics of the bike slightly by decreasing trail. Going from a 25 to a 23 on a 'normal' road bike, you decrease trail by .5mm. Like I said, not a huge difference in the tire sizes stated, but can be significant with larger changes.


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## baking3 (Jul 21, 2004)

*Sheldon Brown*

Actually, since you are just getting into the sport, read everything you can at Sheldon's site. Mr. Brown was a great resource to the cycling community who recently passed away. His site is probably the single biggest repository of bicycle-related info on the net. I learned an amazing amount of stuff from him. There are now *very* few things mechanically that I am not willing to do on my bikes.

http://sheldonbrown.com/articles.html

bak




Becky said:


> Yes, a 23c tire will fit.
> 
> Width does come into play, but going up or down 1 size shouldn't make a difference. It's only when you make big jumps in width that you may have issues. Check out what Sheldon Brown had to say on the topic: http://sheldonbrown.com/tire-sizing.html.


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## lookrider (Dec 3, 2006)

*Really good advice*



wim said:


> For what it's worth: I really appreciate a slightly wider tire like a 700 x 25 or 700 x 28 when I run off the road and have to ride through dirt, gravel or grass before getting back on the asphalt. It's clear to me that a few millimeter more in tire width make such a maneuver much easier and less sketchy./w


I'm also thinking of going up to 700 x 25 and even 700 x 28 if my bike will accomodate that. Everyone one these forums is talking about the ride quality of frames, but a wider tire with a lower pressure can have much more influence on comfort than a frame.

Stuart O'Grady won Paris-Roubaix on 700x27 tubulars so the pro's especially know that you get increased shock absorption with very little loss of with wider tires..


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## Muaythaibike (Oct 26, 2007)

You guys are F, N awesome! Thanks-

But what does "trail" mean?


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## Mel Erickson (Feb 3, 2004)

Geez guys, let's get with it. The ONLY difference you will notice between a 23 and 25 is a slightly improved ride with the 25 IF you run a lower pressure. You won't notice any difference in rolling resistance (it's very debatable and a wider tire may actually decrease rolling resistance). You won't notice a difference in handling, the contact patch is marginally wider on a 25 but it is also shorter and if you pump the tires to the same pressure it is exactly the same size, just a very slightly different shape. There will be NO effect on trail that can be detected between 23's and 25's.

You can find a better selection of tires, a wider range of colors and models and more availability with 23's. 25's are easy to come by but to get the brand and model you want you might have to buy them online because your LBS might not carry it. 25's will be a bit more comfortable if you take advantage of the lower pressures you can run.


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## wim (Feb 28, 2005)

*Minor clarification.*



Mel Erickson said:


> You won't notice any difference in rolling resistance (it's very debatable and a wider tire may actually decrease rolling resistance


Well, it's _debated_ a lot, but it's not debatable at all. According to the formula ("boiler formula") used to calculate tension in thin-walled, pressurized circular containers:

- the higher the pressure at equal volume, the higher the wall tension,
- the larger the volume at equal pressure, the higher the wall tension.

Other factors play a minor role, but this means that _at equal pressure_, the larger volume tire will flex less than the smaller volume tire. Thus, the larger tire will have lower rolling resistance. You said as much, but my point here is that this is true because of a physical law not subject to debate.


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## Kestreljr (Jan 10, 2007)

Mel Erickson said:


> (it's very debatable and a wider tire may actually decrease rolling resistance).


So are you saying that a Mountain bike slicks (around 45mm), with the same rubber compound, at the same inflation pressure, will have the same OR LESS rolling resistance as a 23mm road tire?


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## phoehn9111 (May 11, 2005)

Exactly, I don't care what scientific dogma supports the fact that wider tires generate
less rolling resistance, my instinct says it ain't so.


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## wim (Feb 28, 2005)

phoehn9111 said:


> Exactly, I don't care what scientific dogma supports the fact that wider tires generate
> less rolling resistance, my instinct says it ain't so.


It's not a dogma, it's a fact _at equal pressure_.

But your instinct isn't wrong: the reason larger tires almost always have more rolling resistance is because almost everyone runs them at lower pressures than smaller tires. The statement of fact that supports your instinct would be "at identical levels of flexion (or comfort), larger tires will always have more rolling resistance than smaller tires." Painful proof would be the 45 mm slick run at 120 psi: it would jar your fillings out on a rough road.


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