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Wheel with a high spot
Last Post 08/25/2014 04:06 PM by Mike Kingery. 4 Replies.
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Ride On

Posts:450

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08/24/2014 06:33 AM
I've got a tubular wheel that I let my brother borrow. We mounted it in his frame. The wheel wouldn't spin freely. It was fine side to side, no brake pad hit. The tire would just hit in a spot on the underneath side of his brake mounting. There is a high spot, a hump. We put it back on my bike and no problem but you could see the high bump. If you just look at the wheel and tire off the bike, everything looks fine but when you spin it, you see it. I never notice it when I ride it. Should I mark the spot, pull the tire off, check for excess glue or just ignore it and tell by bro he is out of luck and he should buy his own wheel. Ha ha.
pretender

Posts:41

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08/24/2014 09:53 AM
is it the tire or the rim? what kinda rim is it? if it's the rim, and it's not made of plastic, rounding the wheel is an easy task- part of any good building and/or truing exercise.
dkri

Posts:86

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08/24/2014 12:02 PM
Something to check is if the high spot occurs at the valve. Lots of tires have a bit of a high spot at the valve, because the valve doesn't sit down into the valve stem hole in the rim. If that is it, you can take a countersink or a deburr tool and slightly, gently and large the valve stem hole in the rim.

If it's a wheel that is built out of round, then pretender has it. Fairly simple thing to correct on the stand.
formerly dkri
dkri

Posts:86

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08/24/2014 04:55 PM
Also, it's fairly unusual for a carbon rim to be terminally out of round. Semantically, the difference is that in an alloy rim, you are both placing the hub in the center of the rim, and manipulating the rim itself to bring it into round. In a carbon rim, the rim ain't moving. All you are doing is placing the hub dead center in the middle of the rim. You will almost always find that a high spot is opposite a low spot (actually, you will mostly see that also with alloy rims). Move the hub away from the low spot, and toward the high spot.

A lot of cheap carbon rims are made in super crap molds. Since these molds are substandard in the first place, and ridden like rented mules, cycled too fast and not allowed to cool down between shots, the rims that come out of them can be pretty oddly shaped. I guess we are now in the realm where mom always said if you don't have anything nice to say…
formerly dkri
stinkyhelmet

Posts:82

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08/25/2014 04:06 PM
I say it is a crappy glue job. I've done it before myself.

If the high spot is not at the valve, I bet the high spot is the last section of the tire that was pulled on to the rim. The installer was concerned that the tire was not stretched enough so he was really pulling on the sections that he mounted first....resulting in "excess" tire when he got to the last section. Guys that glue their own tubbies know what I am talking about.

Along the same lines as what dkri is saying, I use a razor and trim some of the base tape that sometimes creeps up the valve stem. That excess tape will cause a high spot.
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