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Old 05-25-08, 09:33 PM   #1
trueno92
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tires/tyres 20" and smaller, perfectly round?

I have been trying to figure out if bike tires are perfectly round and true? for those 700c I can definately see that being a yes, but with folder/recumbant tires, they can take pretty high pressure, yet they don't have the percision of their full size cousins..

Recently purchased shwalbe marathons and for some reason, there is a slight bulge and I suppose a bit of a shift in the tread. could this be something to do with the tube thats inside the tire?

I read briefly about people using windex or talc to mount the tire etc, would that help something like this?
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Old 05-25-08, 10:22 PM   #2
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Sounds like the bead is not seated well in the rim.

Let all the air out, and work the bead out of the rim (it may fall out when you let the air out, sometimes with rubbery snapping sounds)
Spray some windex on the bead, Then inflate a bit, just enough to get the shape of the tire, and spin the wheel. If the tire wobbles relative to the wheel, grab the tire and work it around. Don't look at any color stripes on the tire, these are rarely perfect, look at the ribbing near the bead.. If it dives, pull the tire out, if it jumps, push the tire in.
The bead should be eager to find it's way back into the groove, it's usually not too hard. Sometimes cheaper, or higher PSI tires like your Schwalbes, are tricky and take some fiddling around.
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Old 05-26-08, 05:29 AM   #3
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It is probably just the bead not sitting into the rim correctly. Sometimes the tube can get caught in between the tire and the rim, causing a bulge. However, there is a very small chance that the tire itself is bad. On a very rare occasion, even in a bundle of 50 brand new tires, we would get a new tire that had a wobble in the tread that was from the manufacturing process and had to be returned.
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Old 05-26-08, 08:25 AM   #4
trueno92
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It appears to be seated on the rim, from looking at the bead guide that is right over the rim. Its even, but would appear to be a lump in the tire. I don't think the tube could twist inside the tire? I almost want to remount it, but I had to inflate it to 160psi just to get the bead to sit evenly when I first installed it and want to avoid that if I could.
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Old 05-26-08, 09:18 AM   #5
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I haven't observed any general quality differences between 700c, 26" or 406 tires.
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Old 05-26-08, 06:30 PM   #6
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160 psi may have damaged the cords.
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Old 05-26-08, 08:55 PM   #7
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Quote:
Originally Posted by eldenh View Post
160 psi may have damaged the cords.
didn't Sheldon have a tire mounting mantra to the tune of "more pressure!"?

(I don't think the act of pumping would damage the chords but could get the tire to seat properly)

uncorrected typo: chords I'm not sure the BANG that happens when the tire finally seats would be a chord, but I thought the typo was novel enough to leave in

ramble, ramble...
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Old 05-26-08, 09:41 PM   #8
trueno92
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btw I don't hear an audiable "pop" or anything like that when the bead seats. I just notice the tire is round and correctly on the rim.

Tried to remount today and there is a slight bulge on the sidewall about 3 inches to the left of the stem.

Should I hear anything to tell me that the bead is seated correctly?
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Old 05-26-08, 10:57 PM   #9
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Quote:
Originally Posted by trueno92 View Post
btw I don't hear an audiable "pop" ...
Should I hear anything to tell me that the bead is seated correctly?
The "poping" sound is with car tires with a lip to slid over and seal a tubless tire.

I've replaced many tire's on many bikes, but never had to wait for poping noises or use 160psi to seat tires.

Make sure your tube is instaled properly and do not use the painted line as a guide.

If the tire is bulging, maybe you should inspect it inside out, and don't use 160 PSI to seat the bike tire anymore
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Old 06-02-08, 12:26 PM   #10
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thanks for the headsup, i'll move the tire around to make sure it is free from the tube and use some soapy water as lube on the bead, when i reinstall. i'll stay away from 160psi!
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