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  1. #1
    Senior Member
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    Another tire pressure question

    I see you guys saying you are filling you tires to 120lbs or so (just from what I have noticed in reading) but my tires 700x28 say that the Max pressure is 80psi are these tire/rim combination wrong for my size (5'11, 240)? Bike is a 2009 Cannondale BB Disk. I went out for a ride today and it seemed like my rear tire slid a bit when turning corners going about 10 or less MPH. I filled the tires before going on the ride to the rated max.

    Thanks,
    Pat
    2009 Cannondale Bad Boy disc rider.

  2. #2
    Banned. Mr. Beanz's Avatar
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    I did a couple quick searches. Looks like your rec tire pressure is 85 for that tire. The tires I speak of are 700X25 tires rec pressur at 120. Depends on the model.

    I fyou go with Serfas Seca 700 X 28, the rec pressure is 125 psi ( I have the tire). Depends on the model. Shouldn't be a problem for you to switch out tires. Will be higher pressure, maybe a bit faster but less comfy.

    The tires you have now seem hybrid type tires (large aggressive tread). If it were me, I'd use them til they were wore , then replace just to get my money out of them.

    rec tire pressure is printed on the side of each tire. Sometimes on the label, sometimes in small raised characters on the sidewall. Go by that rec pressure.

  3. #3
    Senior Member csimons's Avatar
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    Quote Originally Posted by Pat_RI View Post
    my tires [are] 700x28 ... are these tire/rim combination wrong for my size (5'11, 240)?
    No, these are not the wrong size for your size. Any size/weight rider can use any width of tires (assuming they'll fit the bike's rim and won't be too wide for the bike's fork/frame). Wider tires are rated for lower pressures and are commonly used for a more comfortable ride. Narrower, road-style tires will allow for more speed, although they'll give a bumpier ride. Your tire size is pretty common for a hybrid bike like the Cannondale BB.

    If your tires are inflated to their recommended pressure, they probably shouldn't be skidding like that. Road tires wouldn't help, all other things being the same, though, as they are more-or-less 'slick' and provide even less traction than the city/touring tires that came with your bike.[1]

    Check out Sheldon Brown's tire pressure recommendations.[2] His table considers tire width and wheel load (body weight). If you follow Sheldon Brown's recommendations and determine that your ideal tire pressure is more than your tires are rated for (which may happen if you're a heavier rider), you may want to consider buying some higher-pressure tires.

    [1] http://www.sheldonbrown.com/tires.html#traction
    [2] http://www.sheldonbrown.com/tires.html#pressure

    Also, there's plenty of other good material at his website:

    http://www.sheldonbrown.com/
    Last edited by csimons; 08-04-10 at 11:24 PM.
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  4. #4
    Senior Member csimons's Avatar
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    Doh, I overlooked that you had provided your weight. So SB's recommendation for a 28mm-wide tire with roughly 100 pounds on each tire (the back tire will be supporting more weight than the front most of the time, so this is approximate) is 100 PSI. Since you're at 240 right now, this would be slightly higher. So you may want to look into buying 28mm tires that are rated to 110 PSI or so. I usually run my tires 20-30 pounds below SB's recommendation for comfort and have not had any problems so far, although 'snakebite' flats (pinch flats) will be more common if you run your tires low and ride on rough terrain or ride directly up onto curbs often (this type of flat is caused by the tube getting pinched between the rim and an external object).

    So in my experience, you probably should be safe at 80 PSI, although you probably should check your pressures at least once a week as all tubes leak air over time. Note that many pumps will not be accurate if you simply put the pump head onto a partially-inflated tire and begin there; usually it is necessary to drain most of the air from the tire and then pump it up again from there to get an accurate reading.
    Last edited by csimons; 08-04-10 at 11:34 PM.
    2009 Windsor Wellington

  5. #5
    Banned. Mr. Beanz's Avatar
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    Quote Originally Posted by csimons View Post
    If your tires are inflated to their recommended pressure, they probably shouldn't be skidding like that. Road tires wouldn't help, all other things being the same, though, as they are more-or-less 'slick' and provide even less traction
    Not necessarly ture. Depends on what he means by SLID (you said SKID). If alow pressure tire is mushy which most stock tirs are, it could have givenhi the feeling of sliding out form under him.

    I ride road tires and the traction is fine on 30 mph switchback mountain descents. No way is the road tire going to give you less traction at 10 mph as the OP stated. Matter of fact, there is a reason some roadtires are so expensive, good traction etc compared to inexpensive stock tires.

    This link says 60-70 psi, that's pretty soft for a tire under a 240 lb rider. I wouldnt ride it.

    http://www.rei.com/product/709112

  6. #6
    Senior Member damnpoor's Avatar
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    Wider tires require less pressure to hold the same weight. MTB tires may only be 65psi for example because they are so wide. I wouldn't worry about it.

  7. #7
    Banned. Mr. Beanz's Avatar
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    Quote Originally Posted by damnpoor View Post
    Wider tires require less pressure to hold the same weight. MTB tires may only be 65psi for example because they are so wide. I wouldn't worry about it.
    That's true but the intended use is different. 55 in my MTB tires is great but if I take them on paved turns, that can be pretty scary.

    The quick search I did, first comment was some dude concerned about the low pressure rating on the tires.

    mentioned in 2 places by the author
    http://urbanvelo.org/vittoria-randon...ed-city-tires/
    Last edited by Mr. Beanz; 08-04-10 at 11:50 PM.

  8. #8
    Senior Member
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    The tire slid out/almost fishtailed taking this corner and I was going from pavement onto a concrete bridge. I really was just asking if I should be riding a tire with greater tire pressure instead of a tire rated for 80 or so psi as the ones that came with the BB disc. I wasn't too sure if you could overfill the tires say up to 90 psi.
    2009 Cannondale Bad Boy disc rider.

  9. #9
    Banned. Mr. Beanz's Avatar
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    Quote Originally Posted by Pat_RI View Post
    The tire slid out/almost fishtailed taking this corner and I was going from pavement onto a concrete bridge. I really was just asking if I should be riding a tire with greater tire pressure instead of a tire rated for 80 or so psi as the ones that came with the BB disc. I wasn't too sure if you could overfill the tires say up to 90 psi.
    I myself would go with a higher pressure tire. But that's me as I have that muchy fishtail feeling while cornering/turning on pavement with the mtb tires, as well as the front into a fast turn. Just to mush, but again, that's me.

  10. #10
    Single-serving poster electrik's Avatar
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    Somewhat helpful..

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