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  1. #1
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    tire pressure of MTB rims with Slick tires

    I've noticed from the archives that many people have put slick tires on their mountain bikes for road touring, but nobody seems to have addressed the critical area of tire pressure.
    My rims, mavic x517s, are "rated" (they are not real clear here) in their web site as suited for pressures from 30 to 60 PSI. Thinner slick tires are usually intended to be inflated to about 80 to 100 PSI. In researching my rims prior to purchasing the bike they came with someone said he put slick tires on and it split the rims after a relatively short time, and was denied warrany replacement because he used the higher pressure tires.
    Going to a 700 rim (ie, road bike intended for higher pressures) is out because the brakes would not align. Does anyone know if 26" rims exist that are actually rated for the higher pressures, or are people using lower tire pressures, or are people just tempting fate and hoping everthing works out. Admittedly, the rim on my bike is purposely built light for xc racing and perhaps a heavier rim would be stronger.
    Any feedback would be greatly appreceiated.

  2. #2
    Super Biker Mtn Mike's Avatar
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    Mavic lists max pressure specs based on tire width for their rims. I couldn't find the 517, but the717 XC disc and all their other rims have pretty similar pressure specifications. The specs are listed at the bottom of that page.

    edit:
    After looking that chart over, I realized that I had been running my 517s with too high psi (65psi with 2.0 tires! ). Along with a worn braking surface, perhaps that's why they cracked!
    Last edited by Mtn Mike; 01-17-05 at 08:34 AM.

  3. #3
    Get the stick. darkmother's Avatar
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    The rim rating is strongly dependent on what tire diameter you mount on the rim. For example, with a 2.1" mtb tire at 60 psi, the stress on the brake serface may very well be too high, especially as the brake surface wears down. With 1.25" slicks on the other hand, I doubt you will have any difficulty running within the rated tire pressure range-certainly more than 60 psi. FWIW, I have run 100 psi in 1.4" slicks on light MTB rims with no problems in the past.

  4. #4
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    650c rims are the same size as 26" rims. You usually find them on Triathlon/time trial bikes, and they're designed for high pressure tires.

  5. #5
    Super Biker Mtn Mike's Avatar
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    To end some of the confusion here, I copied this chart from Mavics website. Indeed, running a 1.0 tire should be safe on your rim.

    TIRE SIZE MAXIMUM PRESSURE
    inches bars psi
    1.00 7.70 113.00
    1.20 7.00 103.00
    1.50 6.00 88.00
    1.75 5.20 76.00
    1.90 4.80 69.00
    1.95 4.50 66.00
    2.00 4.30 63.00
    2.10 4.00 59.00
    2.20 3.70 55.00
    2.30 3.30 49.00

  6. #6
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    True, I ran 26 x 1.0 at 100psi with no problems for a long time, 26 x 1.25 at 90psi too. The biggest problem I had was getting 1.0 as this was before the internet(was widely used for buying) and my LBS had limitations on minimum ordering.
    Another problem was Conti making 26 x 1.0 with weak sidewalls. If you kept them high you risked a blow out from a hummingbird wing tapping your tire on the side, if you kept them low a pebble would slap your rim if you rode over it

  7. #7
    Senior Member d2create's Avatar
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    i'm running my 1.5" Armadillo Nimbus at 80psi.
    2008 Rivendell A. Homer Hilsen
    Pics and Specs Here!

    2010 Specialized Rockhopper 29er

  8. #8
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    Wow, great responses. I certainly appreciate all the help.

  9. #9
    I drink your MILKSHAKE Raiyn's Avatar
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    Quote Originally Posted by d2create
    i'm running my 1.5" Armadillo Nimbus at 80psi.
    Ditto

  10. #10
    Just riding andygates's Avatar
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    Ratings schmatings. I'm running 26x1's at 100psi on my 618's, even with half the braking surface worn away by roadgrit. On a healthy rim the tyre will blow off before it'll damage the rim.

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