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Thread: tire size

  1. #1
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    tire size

    I'm looking to get some new tires for my upcoming tour, but I have a question about tire size. I currently have a 700X35c up front, and 700X38c in back. Is the second number the width or thickness? The rear tire rubs on my rack and fender when loaded, so I'd like to get a tire that's not as tall to help with clearance.

    After researching different tire brands, I've decided that I am gonna buy a schwalbe marathon plus for the back, and something much cheaper for the front because it's easier to change flats on. Schwalbe makes them in 700x28,32,35, and 38. Which size would be the best for the rear. Should I run a different size on the front from what I'm already running as well?

    Here's some more info it helps: I ride a hybrid. I mainly ride pavement, occasional hard packed dirt/gravel, I weigh about 150, and I carry at least a gallon of water and 2 loaded panniers on my rack, and a big backpack with all my clothes and camping gear on my back.

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    Senior Member late's Avatar
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    Hi,
    the second number is how big the tire is. Since you have rubbing, drop down a size. It's best to keep both tires the same size. I prefer to keep both the same period. You might try a Marathon up front and a Marathon Plus out back.

    I'm a bit concerned about your carrying a backpack on tour. If you can. strap it on something or get front panniers.

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    I seems to be diameter, since you get both width and wheel diameter increases, so in other words the 35 of the same brand should give you a wheel with a slightly smaller diameter than the 38.

    I run the same size front and back. I would carry a folding tire of a different size for backup if it turnned out to be all that is available. But in general I feel the bike needs the big tire in the rear, and my hands and shoulders need it in the front. If you use the same tires everywhere it just makes stuff that much easier. I use the Schwalbe 38 or 37 slicks on my bike and like them. I found them on the narrow side for packed bike paths, and then ran fine on the road. For all tar, you can go as light as 28. It really depends how much of a wacking about you want to take, for an improvement in roll. I find my 700cx38 with slicks rolls great. You have to factor in air pressure, if you are running higher air pressure you will get better roll anyway. So I would rather ride a 38 hard than a 35 soft. Just more versatile since I can pull air form the 38 to get a softer ride or better float on soft trails. Don't base an idea that 35 is big enough for your comfort if you haven't been running it hard (or maybe the 35 vs the 32 in your case).

    The one change I would make without delay is to get that pack off your back and onto your bike by whatever means possible.

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    I run 700 x 32 Schwalbe Marathon Plus on my tourer. For a spare I carry the 700 x 30 folder that Schwalbe makes.

    A word of caution...the quality of these tires is such that it takes me three or four tire irons to get one on or off, two just won't do. Carry four good tire irons, just in case.

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    very useful resource on all things bicycle, sheldon brown:

    http://www.sheldonbrown.com/tire-sizing.html

    btw - Generally you go thru 1 front tire for every 2 rear tires due to weight distribution (roughly 30%/70% f/r on an unloaded bicycle). This quickly goes to 1:3 ratio if you're carrying a rear load. Something to consider if you're running different f and r tires.

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    Senior Member grolby's Avatar
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    Quote Originally Posted by late
    It's best to keep both tires the same size.
    Since when? There are plenty of reasons to have different size tires front and rear. There is nothing "best" about having equally sized or differently sized tires. Personally, I would use the larger tire in front, not in back, for better shock absorption and improved traction, but there are reasons to have the wider tire in back, also. Of course, if the tire is rubbing then its too wide! Go down a size, that'll solve the problem.

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    Senior Member halfspeed's Avatar
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    700C is designation that, at one time in France, refered to a specific tire size but now just refers to any tire with a 622mm bead seat diameter. The bead seat diameter is the primary determinant of what size rim the tire will fit.

    The "32" refers to the nominal width, in millimeters, of the tire. It is not precise. When you see "32c" or "32cc", the "c" or "cc" at the end means only that someone is either metrically challenged or doesn't understand what the number means.

    I'll second the recommendation for Sheldon Brown's site for a deeper explanation.

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    I went ahead and ordered a 700x35 marathon plus for the back, and a 700x35 marathon 2006 HS 368 for the front. With shipping, it costs me $87 for both of them so I hope they last one hell of a long time and don't get any flats.Thanks for all the info.

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