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Old 05-18-07, 02:41 PM   #1
txaud
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Flat spot on road tire

Hello. I have pretty new (~200 miles) conti tires on my road bike. I have discovered a flat spot on the front and back tires that produce a fairly bumpy ride. My LBS has tried to remedy this problem with new rim tape and powdering the tubes with no success. Is this suggestive of just bad tires? Any suggestions to help smooth out the ride are really appreciated. Thanks!
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Old 05-18-07, 02:44 PM   #2
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My tires have flat spots as well, both my Panaracer Nifty Swifties and IRC Duro Metros. I've tried all the tricks, but the flat spots remain. Not sure if they actually affect the ride though..
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Old 05-18-07, 03:00 PM   #3
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have you ever had this rim straightened before?
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Old 05-18-07, 03:02 PM   #4
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Look at the sides of the tires for the "bead line" a raised ridge of rubber that is on almost all tires. It should be a short distance from the edge of the rim by an equal amount all around. A flat spot will occur when the bead is seated too deeply in the rim, and the bead line will dive down toward the rim at that spot. It will be more likely if you mount a narrow tire on a wider rim. To correct it, deflate the tires till soft and use either talc or a slippery all purpose cleaner (409, Fantastic, etc) on the inside of the rim at the flat spot. Slowly inflate the tire, trying to work the tire out with your thumbs (some shops have a tire seating tool for this). If still flat, Make sure all other areas on the tire are OK (not too far out from the rim) and then carefully overinflate the tire till the flat area pops out. I have routinely overinflated by 20lbs or more to get a flat area to pop out.
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Old 05-18-07, 06:35 PM   #5
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Where is the flat spot relative to the valve stem?

Sometimes the thicker rubber at the base of the valve stem keeps the tire bead in that area from seating all of the way down on the rim. The result is a flat spot exactly opposite the valve stem. The solution is to partially deflate the tire, push the valve stem into the rim, and reinflate the tire.
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Old 05-19-07, 07:51 AM   #6
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Thanks for the ideas. The rim has never been worked on and the LBS checked to see if it was true...no problem with that. They also tried the talc but I think that I will try it again giving extra attention to the area of the flat spot.

I'll update on the results. Thanks again for your advice!!
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Old 05-19-07, 08:01 AM   #7
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----- noob alert ------

may I ask what is a "flat spot"?
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Old 05-19-07, 10:00 AM   #8
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Originally Posted by mito2008
----- noob alert ------

may I ask what is a "flat spot"?
It means that the tire isn't perfectly round in circumference.
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Old 05-19-07, 04:04 PM   #9
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Quote:
Originally Posted by Retro Grouch
It means that the tire isn't perfectly round in circumference.
Yup.. if you spin the wheel and watch it from the side, you'll see a 'dip' when the flat spot goes past you.
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Old 05-20-07, 05:51 AM   #10
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True about the valve stem, major cause of blowouts. Just push the stem into the tire, push the tire down, pull stem back out and inflate.
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Old 05-20-07, 05:57 AM   #11
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Quote:
Originally Posted by cny-bikeman
True about the valve stem, major cause of blowouts. Just push the stem into the tire, push the tire down, pull stem back out and inflate.
As long as you have enough valve stem for your pump to grab onto, you don't have to pull the valve stem out. Air pressure will push it out. Too much pulling and tugging on the valve stem, especially if you are using ultralite tubes, can be a bad thing.
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Old 05-20-07, 02:45 PM   #12
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Well, I did say pull, not yank!
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Old 05-20-07, 04:59 PM   #13
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Well, I did say pull, not yank!
I understand. You know that and I know that but what about the thousands of my other fans who are reading this?
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Old 05-20-07, 05:23 PM   #14
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This is happening on my Schwinn World. I bought the tires and new tubes early last week and put them on. The tires are IRC 90s and were about $17 apiece. I got to ride it yesterday on an errand, and the bumping caused the rear tire to work itself out of alignment twice on the ride. It's bad enough that the chain shakes.

I'll probably just take it to the shop tomorrow, drop it off, and see what they can do. This whole business is getting expensive.

Is it just me, or do bike tires suck these days? I don't recall this happening in the past, especially with the tires that came from the Schwinn dealer where I bought the bike.
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Old 05-20-07, 07:00 PM   #15
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To the OP: If the flat spot is occurring because the tire bead is sitting too low inside the rim, then the recommendation is to inflate above the maximum pressure to try to pop the bead up to the right channel. You can tell by looking at the sidewall: if it's narrower where the flat spot is then the bead is sitting deeper in the rim than it should be. Or the sidewall may have lines on it parallel to the rim and if they dip closer to the rim at the flat spot it's the same problem
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Old 05-21-07, 02:15 PM   #16
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It turns out to be that the bead is sitting too far in the rim. Thanks for your suggestions...I am grateful to have a board such as this for advice! I am looking forward to a much smoother ride once I get this fixed.
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Old 05-27-07, 09:02 PM   #17
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The beads on my tires popped into place. Turns out both wheels have a bit of rim-hop that even the bike shop can't fix. Safe to ride, but a bit annoying. I'll spring for new wheels sooner or later.
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