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Old 03-08-10, 10:50 AM   #1
chandltp
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Tires

This is probably an easy question, but I can't find an answer. How do I know what range of tires I can put on my rims? I'm running 700c x 35 right now. I was thinking of going to a 32 or 28 when I replaced them sometime this summer, but I didn't know how to know if this is possible.
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Old 03-08-10, 10:53 AM   #2
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Most likely but we'd need to know what width rims you are currently running.
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Old 03-08-10, 10:54 AM   #3
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No problem.
Why do you want to go smaller?
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Old 03-08-10, 10:59 AM   #4
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Check the Sheldon Brown website.

He has a (conservative) chart that directly addresses your question. He has lots of other bicycle "stuff" too. There's around 300 pages total.
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Old 03-08-10, 11:58 AM   #5
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Most likely but we'd need to know what width rims you are currently running.
Where does this get measured at? They are the stock rims on a Trek 7000, so I don't have any specifications.
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Old 03-08-10, 11:59 AM   #6
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No problem.
Why do you want to go smaller?
Seems like it's on the big end of the 700c tires when I was looking around at tires last year. I don't have a compelling reason, just something I was contemplating. I didn't want to contemplate too much if it wasn't possible.
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Old 03-08-10, 12:11 PM   #7
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Where does this get measured at? They are the stock rims on a Trek 7000, so I don't have any specifications.
Never mind, I found it on Sheldon's site.
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Old 03-08-10, 12:33 PM   #8
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Bicycle Quarterly tested a number of tires a few years ago and found that certain large tires, e.g. Panaracer Paselas, were faster and more comfortable than narrower tires. It's true that narrow tires feel fast because of the vibation which is transmitted to the rider, but they might not really be faster, especially on rough roads or broken pavement. During the last few years I've gone from 700x23 to 700 x28 to 650Bx 38. If my bike could fit 650x 42's I'd use them.
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Old 03-08-10, 12:48 PM   #9
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Bicycle Quarterly tested a number of tires a few years ago and found that certain large tires, e.g. Panaracer Paselas, were faster and more comfortable than narrower tires. It's true that narrow tires feel fast because of the vibation which is transmitted to the rider, but they might not really be faster, especially on rough roads or broken pavement. During the last few years I've gone from 700x23 to 700 x28 to 650Bx 38. If my bike could fit 650x 42's I'd use them.
Yeah, sure. That's why the racer types all run wide tires.
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Old 03-08-10, 01:53 PM   #10
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Bicycle Quarterly tested a number of tires a few years ago and found that certain large tires, e.g. Panaracer Paselas, were faster and more comfortable than narrower tires. It's true that narrow tires feel fast because of the vibation which is transmitted to the rider, but they might not really be faster,
AIRC, that was only considering rolling resistance in their test. If everything else (construction, pressure, etc.) is kept constant, then the wider tire will actually have a little less rolling resistance. But other factors usually aren't kept constant. Usually the wider tires are run at lower pressure for greater comfort and then the rolling resistance will increase to about the same level as a narrower tire. And most wide tires (there are exceptions) are made with heavier, less flexible construction. The constant flexing of the sidewall as the tire rotates absorbs enegy so it's best to have very supple sidewalls that bend easily - in most cases the wider tires are built with less flexible sidewalls and are therefore less efficient.

But there are two other factors besides rolling resistance - aerodynamics and weight. Both of these are clearly worse with wider tires. Air resistance is usually of most importance at racing speeds, but the added weight can also be significant if there's substantial climbing involved. So there are performance advantages for relatively narrow tires and that's why they're used for racing. The advantage is reduced at slower speeds and comfort considerations may well dictate use of wider tires for other types of cycling.
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Old 03-09-10, 03:26 PM   #11
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Yeah, sure. That's why the racer types all run wide tires.
Racer types are paid to ride their tires. Riis lost the last TT in the '97 tour because he insisted on the narrowest tire that he could run. He wouldn't have won it, but he might have improved his chance of a podium palce.
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Old 03-09-10, 03:28 PM   #12
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AIRC, that was only considering rolling resistance in their test. If everything else (construction, pressure, etc.) is kept constant, then the wider tire will actually have a little less rolling resistance. But other factors usually aren't kept constant. Usually the wider tires are run at lower pressure for greater comfort and then the rolling resistance will increase to about the same level as a narrower tire. And most wide tires (there are exceptions) are made with heavier, less flexible construction. The constant flexing of the sidewall as the tire rotates absorbs enegy so it's best to have very supple sidewalls that bend easily - in most cases the wider tires are built with less flexible sidewalls and are therefore less efficient.

But there are two other factors besides rolling resistance - aerodynamics and weight. Both of these are clearly worse with wider tires. Air resistance is usually of most importance at racing speeds, but the added weight can also be significant if there's substantial climbing involved. So there are performance advantages for relatively narrow tires and that's why they're used for racing. The advantage is reduced at slower speeds and comfort considerations may well dictate use of wider tires for other types of cycling.
Tires inflated to a 15% drop pressure have the least rolling resistance and best ride. This info was agreed on by the manufacturers.
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Old 03-09-10, 03:36 PM   #13
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Racer types are paid to ride their tires. Riis lost the last TT in the '97 tour because he insisted on the narrowest tire that he could run. He wouldn't have won it, but he might have improved his chance of a podium palce.
Do you actually believe that all bike racers are told what size tire to ride?

If Riis lost because his tires were too narrow what size did the winner ride? 35? 42?

Have you been to the TdF and seen what they ride?

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Old 03-09-10, 07:37 PM   #14
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This is my 2 cent that I posted on the touring forum when OP asked about 35 mm tires.


'Another thought-- Depending on what type of touring you are going to do, your weight, and the amount of gear you'll have; 35's might be overkill. We have done several long tours, incuding a fully loaded trip across the US on 28mm Continental Ultra Gatorskins. They are light fast and durable. I changed my wife's and my bike over to 32 mm Schwalbe Marathons this fall, and plan on taking them off before our tour this summer. Both my wife and I agree that they are significntly slower, and the difference can be felt on the hills. I'd really like to try the Conti's in 32mm, but can't find any in that size'.

We have not had any problems running 28mm on our touring rims (24mm width).
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Old 03-09-10, 07:43 PM   #15
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What do you weigh? I'd be surprised if you needed larger than a 28.
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Old 03-09-10, 08:16 PM   #16
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We have done several long tours, incuding a fully loaded trip across the US on 28mm Continental Ultra Gatorskins. They are light fast and durable. I changed my wife's and my bike over to 32 mm Schwalbe Marathons this fall, and plan on taking them off before our tour this summer. Both my wife and I agree that they are significntly slower, and the difference can be felt on the hills.
Note that the Marathons have pretty stiff sidewalls and therefore higher rolling resistance than some other tires of similar dimensions. I suspect that's much more of a factor than the greater width. I found the 28mm but stiff Armadillo tires to be much slower than some more flexible 35mm tires I have on the bike now.
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