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Old 06-05-10, 10:44 AM   #1
YGREG
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What bigger tire sizes could be used instead of original 700x25C on the same rims?

What bigger tire sizes could be used instead of original 700x25C on the same rims? I would like to install 700x35C. Can I do it without getting new rims? Also, what letter C means in the size?

Thank you in advance,

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Old 06-05-10, 12:41 PM   #2
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Sheldon Brown site covers tire options at length. You will need to measure your rim. I have found his site to be conservative on what sizing you can use. Of course, fork and stay clearance, along with brake caliper clearance, can all come into play, so even if the rim can handle it, your bike might not.


http://sheldonbrown.com/tire-sizing.html
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Old 06-05-10, 01:03 PM   #3
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The limiting factor is likely to be with clearances in your frame, fork, and brake calipers rather than just the rim width. I've found that you can go well beyond the recommendations at Sheldon's site without having problems with a tire that's wider than shown for a given rim size. Check how much clearance you have with your current tires at the point where they come closest to touching something and that should give you a good idea of how much wider you can go.

As to the 'C', it should be associated with the 700 rather than with the 25 - so the size should be 700C x 25 (but is frequently mislabeled). At one time there were a series of different wheel sizes that all ended up with the outer diameter of the tire being about 700mm. They had different widths and the rims intended for use with narrowest width tire had the largest diameter and were designated 700A. Rims for wider tires (and therefore slightly smaller rim diameters) were labeled 700B, 700C, 700D. Eventually all but the 700C size rim were dropped and rims with that diameter (actual measurement of 622 mm) are now used for a wide variety of tire widths.
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Old 06-05-10, 03:14 PM   #4
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I've run into the brake caliper issue. I wanted to try some diamond tread tubulars as a winter tire, so I installed 32 mm cross tubulars on conventional tubular rims. Even with quick releases the calipers would not open enough to let the inflated 32's be installed. I had to deflate the tires everytime I wanted to pull off or install the wheel. These were medium reach calipers, too.
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Old 06-05-10, 05:39 PM   #5
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I run Sun MA14 rimed road wheels on my Hydrid with 700c x 40 tires without problems. Roger
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Old 06-06-10, 08:14 AM   #6
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The only real problem I could see is even if the tire fits the rim if the rim is not wide enough the proper tube for the tire would be more likely to get a pinch flat as when you pump it up it would become more of a tear drop shape rather then round or oval.
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Old 06-06-10, 08:40 AM   #7
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Originally Posted by Glennfordx4 View Post
The only real problem I could see is even if the tire fits the rim if the rim is not wide enough the proper tube for the tire would be more likely to get a pinch flat as when you pump it up it would become more of a tear drop shape rather then round or oval.
No, actually if the rim is too narrow the tire will not be as stable on turns, as it will be squeezed to a different, much higher profile than designed.
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Old 06-06-10, 08:52 AM   #8
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No, actually if the rim is too narrow the tire will not be as stable on turns, as it will be squeezed to a different, much higher profile than designed.
Agreed,which is kinda the same thing I meant, if the tube is tear drop shaped more pressure will be exerted to the top side of the tire then in between the rim section at the bead causing the tire to want to peel in a high speed corner.It's all good info.I should have posted exactly what I was thinking but I was on my first cup of coffee.
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Old 06-06-10, 11:18 AM   #9
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No, actually if the rim is too narrow the tire will not be as stable on turns, as it will be squeezed to a different, much higher profile than designed.
I remember this from when I mounted a 37mm tire on the 14mm rim of my touring bike. It was a pain to get to work, the tube just wouldn't behave. Handling was just bizarre, the bike felt like it would wash out from under me at the slightest provocation. Needless to say, that is at the extreme end of the spectrum, and that the bike feels just fine with 32mm tires on the same rims.
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Old 06-06-10, 01:42 PM   #10
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25 to 35 is no problem, as long as the tire will clear the frame and brake. There is no need to increase the working pressure north of 90 psi when dealing with 35mm tire.
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Old 06-06-10, 01:55 PM   #11
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Just as a point of reference with a fairly common rim -I have 32 mm tires on my Mavic Aksium rims. I'm not sure of the width of these rims, but I've run 23's on them. They're not the narrowest ones I have, but they're pretty typical for road rims.

The 32's installed easily, work perfectly, and actually look perfectly normal too. I'm sure I could run a 35 no problem, but dont' care for a tire quite that big.

I can run the 32's at about 60 lbs (I weigh about 165lb). Very rough road and rough pavement and no pinch flats. I might even try 50, but 60 lbs. is comfortable and fast. By the way, I use (IIRC) 19-26mm tubes in there. I tend to like smaller tubes. These, again, work just fine.

Oh, what someone else mentioned - most likely the limiting factor won't be your rims, but the frame and/or brake clearance. The bike I put the 32's on has V brakes (with road levers and Travelagent adapters), so that isn't an issue for me. There's no way I can get anything larger than a 28 (more likely a 25) on my other road bike, regardless of the rims.

Last edited by Camilo; 06-06-10 at 02:07 PM.
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Old 06-06-10, 05:53 PM   #12
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I've been running 25mm tires for the past 20 years. I've used different brands, some marked 25mm, some 23mm and some 20mm, but they all actually measured 25mm. Over that 20 year period my weight has gone from 170 pounds to 220 pounds. I'm going to try 28mm tires next. I can't see any reason yet to go to anything larger than that.
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