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  1. #31
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    I get rim slip less often on the rear wheel because the weight on the wheel presses the tire and tube tighter against the rim. My front wheel needs adjusting more often due to less weight on it. Regardless of what some may say it is caused from the quick acceleration caused from the engaging of the engine to propel the bicycle. (you are essentially going from a human powered bicycle to a horse powered bicycle) Obviously human legs do not cause this to happen. I have seen superglue posts and double-sided tape posts as solutions. I haven't had a reason to take my tire off to try those solutions yet. (fingers crossed) Below I've included a pic (left front wheel) of my valve stem (over-compensated) to the opposite direction of the second pic of the unfavorable position. I inflated the tube to 30psi when the first pic was taken. The second pic was taken 21 miles later.

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  2. #32
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    This is a common issue for the rear tyre in a motorised application, but from my experience (some 30,000 kilometers of experience) it doesn't compromise reliability.

    My motorised bike has a sick bike parts shift kit with a 9 tooth jackshaft sprocket and a 48 tooth chainwheel sprocket driving a tetra chainwheel setup with a 24 tooth low gear.
    The rear cassette is a modified Shimano 29'er; retaining it's 36 tooth sprocket.

    This combination generates enormous pulling power, enabling me to climb an 18% gradient with 80 kilos being hauled behind the bike in a multi combination trailer setup.

    Because i value comfort over speed, my rear tyre pressue is 24 PSI.
    The worst the valve stem will bend to is 45 degrees through torque slippage.
    The tyre will wear out before the valve stem shows any significant damage, in fact i have replaced 4 rear tyres before needing to replace the tube from valve stem damage, of which the distance equated to be around 10,000 kilometers.

    That said, i use thorn proof inner tubes.
    In short, don't worry about the angulation of the inner tube valve stem, at least with thorn proof tubes.

    If you send me a PM, i'll send a link showing my setup. Once you see the weight and the required torque needed to be put through the system, you'll no longer have any concern for a valve stem that sits on a bit of an angle.

    Cheers
    Fabian
    Last edited by Fabian; 04-19-2012 at 03:51 PM.

  3. #33
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    Well, after 127 miles at 35psi I had to deflate and readjust the tire/tube on the rim which is way better then the 21 miles I had with 30psi. I inflated my tire to 40psi this time. I'll update my findings when it is time to readjust. Judging by the difference in the first two tests I should get around 313 miles out of them. I'm sure they are deflating slightly as time goes by which is when more slippage is occuring. Regardless, I don't mind readjusting them especially if it is every 300 plus miles or there abouts.
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  4. #34
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    Alright, it is time to readjust. I didn't get quite as many miles as I expected but more than my previous amount. (205 miles when inflated to 40psi) I can live with that. Some suggested applying soda along the outer bead of the tire, letting it dry and then re-inflating. I wonder if I used elmer's glue or rubber cement if that would keep it from slipping. Regardless, I don't mind readjusting them even if it is only after 200 miles or thereabouts.
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  5. #35
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    The forces you exert on the tires (i.e. torque and load variation) are most likely causing them to move on the rim taking the tube along for the ride. Common in the offroad motorcycling, where rim locks are used to prevent this. Avoiding low tire pressure and making sure the bead of the tire has a nice clean grip surface on rim is important as well as making sure bead is seated fully.

  6. #36
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    I don't understand why a person should be worried about this situation. In the early days i used to have some apprehension about it but now the valve stem sits on a 45 degree angle and stays that way, never giving any trouble, though i use thorn proof tubes.

  7. #37
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    Quote Originally Posted by Fabian View Post
    I don't understand why a person should be worried about this situation. In the early days i used to have some apprehension about it but now the valve stem sits on a 45 degree angle and stays that way, never giving any trouble, though i use thorn proof tubes.
    Well...

    Quote Originally Posted by The_Aleman View Post
    In one year, I had 6 or 7 cut valve stems between F&R. I tried 26x3.0 tubes and it made the problem worse.
    One time my bike made it 5 miles before the valve stem tore off. I had to do the walk of shame 3 miles home.

  8. #38
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    Interesting because i'm using thorn-proof tubes and running 26 x 2.125 tyres at 25 psi for comfort and get around 10,000 kilometers (replacing 4 tyres) per tube, before the valve stem gets cut up to the point where i replace the tube.

    Haven't had a valve stem tear out yet.

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