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  1. #1
    Fat & Single
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    Road tyres on wide CX wheels

    I have a set of XC carbon rims, they are 21mm inside diameter. It looks like the narrowest tyres I should be using are 32c ?

    Is there any lightish 32c road tyres that I could fit to these rather than running trekking/commuter tyres ?

    They have a 70psi max rating so that's where I am a bit stuck or I could try something like the Hutchinson Secteur 28's.

  2. #2
    Cranky Old Bastard
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    I bought a set of Easton 29er wheels for my cross bike that I use mostly on the road.
    The rims are 19mm internal and 24mm external width and I mounted 25mm road tires with tubes. They work great. The tires measure 25.1mm wide on those rims.

    I was disappointed that the aluminum rims are only rated for around 70psi but I'm running 85/90 with no problem. The wheels were setup for tubeless and intended for off-road tires and I think that's why they listed such low pressure. I have disc brakes, BTW, so rim wear won't be a factor.
    Naturally, I will watch the rims for any problems.

    I think 28s may work for you but won't advise you to go higher than rated pressure, especially with carbon rims and rim brakes.
    "When you know absolutely nothing, anyone who knows 1% more than nothing sounds like an expert."

  3. #3
    Fat & Single
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    Cheers Randy, mine are disc wheels too but its the pressure that's the worry with carbon rims, I don't want them blowing out on me !

    Good to hear you have 25c on 19mm, if I thought I could get away with running the max 70psi on 28's I would go that way.

  4. #4
    Cranky Old Bastard
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    Quote Originally Posted by ozzybmx View Post
    Good to hear you have 25c on 19mm, if I thought I could get away with running the max 70psi on 28's I would go that way.
    One advantage of wider rims is that they're not as likely to pinch flat, but if you're heavy I can't say that 70psi is enough for 28mm tires. I'd try it, but I weigh 170 and ride on mostly smooth roads.

    I'd email the rim manufacturer and describe what you're wanting to do.

    I'm taking chances running my pressures higher than rated but I don't expect a problem with the quality rims. Only time will tell.

    Cheers!
    "When you know absolutely nothing, anyone who knows 1% more than nothing sounds like an expert."

  5. #5
    Fat & Single
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    Im pushing 200lb and will be just over it when ready-to-ride. Might send the manufacturer an email.

    My ENVE 29er wheels have a sliding scale on pressure/tyre width.... 23c/120psi, 28c/100psi, 33c/80psi and so on, the china-carbons just state 70psi max.

  6. #6
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    Quote Originally Posted by ozzybmx View Post
    My ENVE 29er wheels have a sliding scale on pressure/tyre width.... 23c/120psi, 28c/100psi, 33c/80psi and so on
    I wonder if this has anything to do with the leverage the tire exerts on the rim bead while cornering. A bigger tire might exert more force.

  7. #7
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    Don't hold me to it but I believe the force on the rim is proportional to the surface area of the inside of the tire multiplied by pressure.

    So a 33c tyre at 50psi is putting way less pressure on the rim than a 2.4" (~60mm) Racing Ralph mtb tyre at 50psi.

  8. #8
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    I have a Felt F75X with Felt CXr4 wheels (22mm ID/24 OD) and I run 25c tire up front (Specialized Armadillo) and 28c in rear (Specialized Nimbus). I just finished century ride yesterday with no issues. I run 28c tubes F/R and I am 165 lbs and use 65-70 psi of pressure. Feels like riding on clouds, I love it.

    Specialized makes these Armadillo tires up to 28c and the Nimbus up to 38c. Both are super stiff wire bead tires that can really take abuse. They have good rolling resistance.
    Last edited by tazunemono; 08-05-2013 at 06:54 AM.

  9. #9
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    Quote Originally Posted by ozzybmx View Post
    Don't hold me to it but I believe the force on the rim is proportional to the surface area of the inside of the tire multiplied by pressure.
    Aha. Pounds per square inch. Makes sense to me.

  10. #10
    Fat & Single
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    Light-bicycle (carbon rim manufacturer) says max 70psi with any tyre... I tried to explain about the physics of it, he changed his mind to "maybe" and tried to sell me some road rims.

    Tazunemono, will have a look at those tyres, sounds like a 28c will fit fine, will adjust the pressure accordingly, a few psi over isn't going to matter.

  11. #11
    CX'er
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    conti grand prixs can be pretty wide, I have 28c. I wouldn't worry about the width as much as the pressure, the new trend is wider rims like HED beligium or velicity A23 with internal widths close to 20mm and they're supposed to be great for 23mm tires, though I prefer 25mm on them, but I'm heavy-ish (220).

    70 psi should be fine for tires that wide, I run around 80/70 with the 28mm grand prix tires when running my cross bike on road tires.

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