Bicycle Mechanics - Uneven wheel...or something

I had my back tyre replaced yesterday because it had a hole in it and was causing the tube to blow out. Now when I ride it, every time the wheel goes around, there a particular spot where it feels like i'm going over a dip. So when I'm riding fast, it's all bumpy and stuff. I've checked the spot and there doesn't seem to be anything obviously different about it. Any ideas on what it could possibly be? Do I need a new rim?
Thanks
-Luke

You either have a "flat spot" in your rim, or a bead-seating issue with your tire. Look very carefully to see if the rim's radius changes slightly at one point. Spin it in the bike fast, and look at one point to watch as the rim travels through your view. If it goes in towards the hub, it's a flat spot. If not, you might try deflating your tire, and wiggling it left and right all the way around. Make sure no tube is coming between the bead and the rim sidewall.

Um, what's a bead...? I think that might be it. Also in regards to re-inflating the tyre, is there anything really wrong with doing it at a service station? people have told me it isn't good for the tube, but i can't really get 60-70psi from a hand pump...

What he means mate, is that when you pumped the tyre up, it didn't seat evenly around the rim. Often there's a tiny line along the side of the tyre which you should see running either parallel with the rim.

That's my bet anyway.

Like waterrockets said spin the wheel and watch it - you might even see the point where it's uneven. In any case, let some air out, wriggle the tyre with your hand to allow it to sift into a more natural position and pump it up again.

The service station issue dates back to the days when service stations had really good compressors. A bike tube only holds a small amout of air and it was common for people who weren't watching to pop the tube. Great fun for spectators, a tad annoying for the bod with the bike. Buy yourself a decent floor pump (from a bike shop, I've yet to buy one from an auto shop that's worked for long) - I have no trouble putting 110psi in my tyres but yeah, the hand pumps you carry on the bike can be good incentives for using a compressor and the only reason I don't use my compressor at home is that I can pump the tyres of two bikes up by hand before the compressor has finished building up pressure, but, back when I had four bikes and a handful of footballs to pump up ...

Richard

Sheldon Brown's explanation of bead (http://www.sheldonbrown.com/gloss_ba-n.html#bead)

It's a tad brief but if you follow the links to other terms you'll soon find yourself learning more about tyres than you ever wanted to know.

Richard

(and for the spelling nazis out there, it's you lot that are spelling 'tyre' wrong :D )

I've seen this problem with an older touring bike. The bike had very wide rims, but the owner had tried to put 25mm tires on the bike. The tires were too narrow for the rim, so they didn't seat correctly, leading to a slight "bulge" in a portion of the tire.

What kind of wheel and tire? If your tire is too narrow for the rim, well, get a properly sized tire. If the tire just isn't seated correctly, do as others have said and let the air out and reseat it on the rim.

lucas, you might have a twist in the tube. Deflate the tire, have a good look at the tube and bead. Sometimes the tube might be a little too big and get a wrinkle in it, which causes a lump in the tire.

...but i can't really get 60-70psi from a hand pump...

Get a floor pump; even a moderately priced one will give you 150 psi.

Get a floor pump; even a moderately priced one will give you 150 psi.



We have two of these in the house. They easily pump to 110+ PSI, will do Schraeder or Presta, and have a pressure gauge built-in. However, be GENTLE with them when you pump. They feel like they'd break in a day if you were to go "crazy-man" on them. Ours have lasted a long time, but we baby them when we use them. A bargain at $13.

http://www.nashbar.com/profile.cfm?category=106&subcategory=1075&brand=&sku=7625

We have two of these in the house. They easily pump to 110+ PSI, will do Schraeder or Presta, and have a pressure gauge built-in. However, be GENTLE with them when you pump. They feel like they'd break in a day if you were to go "crazy-man" on them. Ours have lasted a long time, but we baby them when we use them. A bargain at $13.

http://www.nashbar.com/profile.cfm?category=106&subcategory=1075&brand=&sku=7625

Or you can buy one that doesn't feel like it'll break and use that.

Or you can buy one that doesn't feel like it'll break and use that.

Kind of true, but not entirely. Unfortunately the seals in expensive pumps ($40+) don't seem to last any longer than in the cheap ones. Here's some *indirect* evidence. The pumps are sorted by price. If more expensive pumps are better, you'd expect to see lots of long bars at the top and shorter ones at the bottom. I don't see that trend:

http://www.mtbr.com/reviews/pump/index_byprice.shtml


Here it is sorted by rating. Most of the top-rated pump retail for under $30, which means you can probably find them online for $20 or so.

http://www.mtbr.com/reviews/pump/index_byrating.shtml


Anyway, most of the pumps that are specifically meant for bicycles will do the job. Stay away from anything from the auto parts store. Those things don't usually pump more than 60 or 80 PSI.