Bicycle Mechanics - Is that normal?

Hello, how's it going everyone? nice to find a online community where everyone has a passion to cycling.

Anyway, I have a problem with my bicycle tyres these days, last year, I bought a Felt 600, great bike, but I was using it for urban riding rather than mountain biking, so I bought a pair of continental sports contact.

Though I returned them the next day... the problem, somehow was about uneven shape of the tyre, but not significant. Let's say you flip your bike around, then spin your wheels, by looking at them horizontally, looking at their side, you would notice it's spinning perfectly, then suddenly a lump here and there... I rolled it in my house's flat floor, and you could feel a slight bump, I i would assume in high speeds, great chatter will occur.

Today, I went to the local bike shop to buy another pair of road tyres, a pair of Serfas Barista, and a pair of matching tubes. But there was still this problem... and even worse than the Continentals I had before... the Conti's had one visible hump during a free wheel spin. But these Serfas' had multiple humps and lumps, though not significant. but the worse thing was looking at the tyres spinning at a vertical angle, you could see the tyre wobbling...

I can tell you I used the correct tubes, both road tyres I bought were new and in good condition, and I pumped them up to their maximum capacity, then I discovered the things...

so can anyway tell me why this is happening to the tyres? is it the tyre installation process? I follow the instructions, but would it be when I install the tubes? like as if the tube would change shapes inside?!? I thought when tubes expand, they'd correct them selves inside, though i did pump the tubes up slightly until it appeared as a circle shape, then insert them inside the tyres...

The strange thing was, I put the stock gravel tyres back on my bike, and i tried to see if it would have similar problems on the two road tyres i installed, and amazingly, no problem! a perfect circulating circle...

Can anyway help me find the solution

Thank you

I'm no expert, but I have noticed this with "folding" tires, i.e., tires that don't have a wire bead, but are sold folded up and rubber-banded. Where the folds were sometimes there is a slight lump in the tire profile.

Just to make sure, deflate your tires some, and squeeze the sides to confirm that they are seated really well in the rim. Then pump them up again, this may help with the lumps some.

bk

thank for the reply, yeah, as you've mentioned it, I did squeez the sides and flat'n the tyre completly, hoping to correct any problems within.

but still like that...

dose my problem happen to any one of you?

maybe dust the inside of the tire and the outside of the tube with baby powder, talcum powder, etc. Possibly the tube is not laying completely flat inside the tire and and twists or irregularities are causing the lumping issue. I have noticed irregularities in tires before, but never enough to be perceptible when riding.

I have a problem with my bicycle tyres ... continental sports contact.

the problem, somehow was about uneven shape of the tyre, but not significant. Let's say you flip your bike around, then spin your wheels, by looking at them horizontally, looking at their side, you would notice it's spinning perfectly, then suddenly a lump here and there... I rolled it in my house's flat floor, and you could feel a slight bump, I i would assume in high speeds, great chatter will occur.

Today, I went to the local bike shop to buy another pair of road tyres, a pair of Serfas Barista, and a pair of matching tubes. But there was still this problem... and even worse than the Continentals I had before... the Conti's had one visible hump during a free wheel spin. But these Serfas' had multiple humps and lumps, though not significant. but the worse thing was looking at the tyres spinning at a vertical angle, you could see the tyre wobbling...

so can anyway tell me why this is happening to the tyres? is it the tyre installation process? I follow the instructions, but would it be when I install the tubes? like as if the tube would change shapes inside?!? I thought when tubes expand, they'd correct them selves inside, though i did pump the tubes up slightly until it appeared as a circle shape, then insert them inside the tyres...


This is an issue with "seating" the tyre, at least in the case of the Continental. Serfas is a low-end brand and they may well be defective.

See: http://sheldonbrown.com/flats.html#seating. Continental tyres are known for being a tight fit, and often require considerable overpressure to get them to seat properly the first time.

Please, if you're going to ask a question on one of the Newsgroups or email lists that I frequent, don't ask me by private email at the same time. It's really a bummer to go to the trouble of composing a private answer, then to have the question re-asked in public and either have to ignore it or rephrase it to make it more general in application.

If you use the list first, and don't get a useful answer, then, feel free to approach me privately.

Sheldon "Round Is Good" Brown

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thanks Sheldon and others for the help

the problem seems to be gone now, but Sheldon, can you further explain the lumps that caused by the tyre valve? i didn't really get it and there dose seem to be some problems in that area.

oh by the way Sheldon, I didn't know you are a member on this forum, so I asked the members here, plue you, and I was looking through your website.