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Thread: Bulge in rim

  1. #1
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    Bulge in rim

    I just rode on an old front wheel of mine for the first time in about a year, and found that when I brake, the bike jolts horribly every rotation of the wheel. The effect is jarring, noisy, and I was afraid to brake hard down hills. I took the wheel off when I got home, and found that there is a slight bulge in both sides of the rim at the seam in the rim. The spot is probably about 2cm long, and the bulge appears on both sides of the rim. I do not know if the bulge used to be there, but I never had any braking problems on the bike the wheel used to be on. Between that time and now, I have trued and tensioned the wheel, but that should not cause the rim to spread like this. The rim is a vintage Super Champion rim, probably almost 40 years old, and I have no idea how many miles are on it.

    Is there any way to fix this, short of buying a new rim? I have tried using a clamp, but could not get very much pressure on the rim this way. I can post pictures if necessary.

    Thanks for any help,

    -TC

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    is the brake track worn?

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    Somewhat, as it has been used, although I have no idea how to tell how worn it is.

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    if the brake track is severely worn and the rim is pinned construction the tire pressure could have pushed the rim walls out.

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    Any way to fix this?

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    coprolite fietsbob's Avatar
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    Wheel rebuild, new rim.

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    Well, yeah, but that's not really a fix. I was thinking more on the lines of not buying a new rim. If I managed to get a better clamp and just squeeze the rim back, would that hold, or would it just bulge out again?

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    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by Technochicken View Post
    Somewhat, as it has been used, although I have no idea how to tell how worn it is.
    Pin micrometer. You're funny. New rim.

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    Another possibility is cracking on the inner layer of the rim. Take the tire off and remove the rim tape. Look for cracks between spoke holes. bk

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    I've already done that. I have not seen any, but it is hard to tell, since the bulge is right at the seam.

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    You're already afraid to brake with that rim, and you're worried about saving it?

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    Where did you get that from?

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    "The effect is jarring, noisy, and I was afraid to brake hard down hills." --Technochicken

    I had a similar problem with a machine built front wheel. Way over tensioned causing high points wherever a spoke was and much worse at the rim's seam. Until I could get a decent set of wheels built and installed I just filed the seam as smoothly as possible to prevent the brake pad from catching. I'd temporaily use that rim now and then on new builds and eventually a spoke nipple pulled through the rim (CXP10), killing it for good.

    The 'fix' is a new rim.

    Brad

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    coprolite fietsbob's Avatar
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    OK ... terminology problem, rim is a single part , wheel is all the parts , and so given the OP's not desiring, or understanding how, to take the wheel apart , loosen all the spokes , take them out, and relace them and all that entails.
    Get a new Wheel, and rim strip , most likely, .. then put your existing inner tube and tire on that.

    A SC 58 would not distort from the wheel build like a double wall rim does.

    I have a Mavic mod 3 rim where there is a slight widespot , or bulge.
    just enough that the anodizing is worn off there first, but It.s been fine for a decade.

    FWIW there is a replica of the SC 58 made in Japan , under the Grand Bois label .

    Premium priced, but if you want to keep a collectible spec setup , that is a way to go.

    that would be hiring a hand made wheel to be built with that rim at its edge.
    Last edited by fietsbob; 08-09-10 at 09:40 AM.

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    I would rather not have to rebuild the wheel, but I would do that before I bought a completely new wheel, as I am kind of attached to the hubs on this wheelset. If this rim is on it's way out anyway, maybe I'll just borrow a few C clamps, and see what damage I can do before I shell out for a new rim.

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    coprolite fietsbob's Avatar
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    Take the tire off and take it the wheel to a bike shop, and have them assess the problem ,
    the brakes may have worn thru most of the sidewall.
    and no amount of words can do what actually seeing the problem can resolve.

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    I was thinking about that, but I get the feeling that they will just try to sell me a new wheel. There's no harm in trying I guess.

    Thanks for the help everyone.
    Last edited by Technochicken; 08-09-10 at 11:01 AM.

  18. #18
    Senior Member Chombi's Avatar
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    Quote Originally Posted by bradtx View Post
    "The effect is jarring, noisy, and I was afraid to brake hard down hills." --Technochicken

    I had a similar problem with a machine built front wheel. Way over tensioned causing high points wherever a spoke was and much worse at the rim's seam. Until I could get a decent set of wheels built and installed I just filed the seam as smoothly as possible to prevent the brake pad from catching. I'd temporaily use that rim now and then on new builds and eventually a spoke nipple pulled through the rim (CXP10), killing it for good.

    The 'fix' is a new rim.

    Brad
    Many lightweight French rims seems to have this characteristic of bulging slightly at the spoke holes. It's very common to see well used classic Mavic rims (GEL280s and GL330s tubulars) with their anodizing wearing off the braking surface, just right where the spoke nipples line up to. Not from overtensioning, but I think just a normal side effect of the rims being so lightwieght and narrow in section. Materials have their limits, specially when the minimum thicknesses are used for lightweight. The anodizing wear marks are sometimes used by riders as a sort of wear indicator on how far they are willing to trust the rims for wear.

    Chombi

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    coprolite fietsbob's Avatar
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    I think its the double ferrule pulling the inside of the double wall rim,
    and compressing it a bit.

  20. #20
    spathfinder34089 spathfinder3408's Avatar
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    If you can't straighten this rim on a truiing stand then don't waste any more time. I have spent many hours trying to save bent, bulging wheels and once they are bent, its near impossible to get them straight again. If you still want to try something before you give up on this rim, try taking both hands on opposite sides of bulge and putting knee right on bulge and try pushing it out. Its worth a try if your thinking a rim replacement anyway. you might get lucky and fix it. Good luck

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