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  1. #1
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    What diameter hole do I need in the rim for a Schrader valve?

    I'm new in the area I'm in now. I got a bike that has presta valves, but the cheapest on Amazon are the Schrader tubes. I have a slight preference for them anyway, so I want to drill out the rims a bit to allow this. I'm in a slightly rural area and Amazon beats the only bike shop around.

    I'm hoping that it's a standard bit size like about 5/16 inch. I realize I will need to be careful to smooth the edges of the hole after drilling. Are there any problems with doing this?
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    A 5/16 inch bit will work fine for drilling out the hole. I actually just got done converting a mountain bike rim from presta. The one thing to be careful of is rim width. If this is a narrow rim like found on road bikes, making the hole larger could potentially reduce the strength of the rim at that point.

  3. #3
    rebmeM roineS JanMM's Avatar
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    In the past, I used a hand reamer to enlarge presta holes to just big enough for schrader.
    I prefer presta now.
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  4. #4
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    A quick search on Amazon showed they do carry Presta valve bike tubes at a variety of prices, including very reasonable. I wouldn't compromise my rim to save a few cents on my tubes.

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    Quote Originally Posted by HillRider View Post
    A quick search on Amazon showed they do carry Presta valve bike tubes at a variety of prices, including very reasonable. I wouldn't compromise my rim to save a few cents on my tubes.
    Especially if it's an aluminum rim. Aluminum and its alloys does not handle stress very well, and any small imperfections in the edges of a home-drilled hole will become stress risers.

    All to save what? $1? At most?

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    There are plenty of reputable online retailers beside Amazon. A little digging should turn up plenty of good deals on Presta valve tubes. I echo the above comments recommending against drilling your rims.

  7. #7
    Senior Member Shimagnolo's Avatar
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    I don't see any issue with enlarging the valve hole unless the existing hole is already right up against the rim walls. I've done it on a few rims without any ill effects and have never seen a rim fail at the valve hole. OTOH, I've seen lots of rims fail at the brake tracks, spoke holes, or as a result of impacts on the rim edge. The valve hole area doesn't seem to be highly stressed.

  9. #9
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    +1, no reason not to enlarge the valve hole for Shrader valves if that's what you prefer. The only limitation is rim width. It's not a matter of strength, but the need for the clearance for the wider valve between the beads of the mounted tire.

    If you have fairly narrow rims, make a valve sandwich between the tire beads, and compare to the inside rim width. You want at least 1/16" clearance so the valve doesn't bind and can seat properly, 1/8" in better.
    Last edited by FBinNY; 12-02-11 at 11:22 PM.
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  10. #10
    biked well well biked's Avatar
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    21/64"

  11. #11
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    Quote Originally Posted by fleisc66 View Post
    A 5/16 inch bit will work fine for drilling out the hole.
    Thank you, and that's a size I do have.

    Quote Originally Posted by Shimagnolo View Post
    Great link. I just checked and getting 10 tubes costs a total of $23 including California tax and insurance. I was expecting a large shipping charge but there wasn't any. (I'm stuck in California for a bit.)

    Presta and Schrader cost the same in the size I want, but I'll probably get Schrader anyway. I'll think about it and maybe go through to check out on the weekend.

    I did ask a manager at a bike shop a few months ago and he said there was no problem drilling out the holes as long as they were kept smooth. But it was nice to hear a couple more people with some experience say that too.

    So altogether quite a lot of helpful comments. Thank you.
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    biked well well biked's Avatar
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    Quote Originally Posted by Closed Office View Post
    Thank you, and that's a size I do have.


    The correct size is 21/64." A 5/16" will work if you wallow it out a bit, but if you just drill the hole without doing that the hole will be too small.

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    Quote Originally Posted by well biked View Post
    21/64"
    I probably don't have that size in my drill bits but it sounds more precise. I sometimes make a hole a bit bigger by putting the drill in at a bit of an angle and then rotating it. If it seems tight at all, that's what I'll probably do for the extra 64th.

    Thank you too.
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    biked well well biked's Avatar
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    Quote Originally Posted by Closed Office View Post
    I sometimes make a hole a bit bigger by putting the drill in at a bit of an angle and then rotating it.
    That's exactly what I mean when I say you have to wallow the hole out a bit with the 5/16" bit. That's what we call it where I come from, anyway.

  15. #15
    Senior Member Shimagnolo's Avatar
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    Quote Originally Posted by Closed Office View Post
    I probably don't have that size in my drill bits but it sounds more precise. I sometimes make a hole a bit bigger by putting the drill in at a bit of an angle and then rotating it. If it seems tight at all, that's what I'll probably do for the extra 64th.

    Thank you too.
    Go to the local hardware and look/ask for a "Tapered Reamer".

  16. #16
    SE Wis dedhed's Avatar
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    Quote Originally Posted by Shimagnolo View Post
    Go to the local hardware and look/ask for a "Tapered Reamer".
    That'll pretty much negate any savings on tubes!
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