Bicycle Mechanics - Wheel out of balance?

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dbs
02-01-09, 01:28 PM
My LBS checked the rear wheel and says it's true. I believe him. But at low speed I can feel and hear a thump or bump. It is very noticable when I spin it up in the bike stand.

Since I primarily a commuter I have slime tubes and gator skins. I realize it takes a few minutes for the slime to disperse but I noticed it yesterday 40 miles into a long ride.

While replacing tire and tube is a obvious first step I was hoping to hear if others my have had a similar issue.

Thanks.

Steev
02-01-09, 01:29 PM
Do you have the tire bead correctly seated all the way around, both sides?
jtarver
02-01-09, 01:34 PM
Maybe your slime is gooped up in there, probably trying a new tube would be a cheap way to see. If it's not that, you just have an extra tube. Maybe just take it out and put it back in, works wonders sometimes.

rm -rf
02-01-09, 01:38 PM
My wheels are heavier at the joint. On a bike stand, cranking up the back wheel makes it hop. But I don't feel it on the road at all. One time, on a freshly paved, very smooth downhill, I did feel a slight vibration. But I was going over 30 mph.

I think a low speed thump would be a tire out of round. The wheel can be true, but the tire isn't even.
Panthers007
02-01-09, 01:58 PM
I'd check it without tire/tube on. No thump = tire wasn't seated correctly. I'd also check the hub. It might be in need of an overhaul. I've even seen new hubs come with too many ball-bearings in the races - knocking the thing way out of balance. And I agree it might be the slime.
oldbobcat
02-01-09, 10:52 PM
I second Panther's recommendation, but before removing the tire and tube, just let most of the air out, press the valve stem most of the way into the hole, and make sure there is no tube caught between the tire bead and the rim. As you re-inflate, ensure that the tire bead is seated evenly around the rim on both sides.

Now if it still thumps, . . .
DannoXYZ
02-02-09, 12:17 AM
I second Panther's recommendation, but before removing the tire and tube, just let most of the air out, press the valve stem most of the way into the hole, and make sure there is no tube caught between the tire bead and the rim. As you re-inflate, ensure that the tire bead is seated evenly around the rim on both sides.

Now if it still thumps, . . .The actual process of doing this is you remove all the air. Then you pull the tyre sideways to expose a gap between the tyre and the rim-edge. No tube should be visible. Then move over a couple of inches and pull over the tyre again. Inspect ALL THE WAY around the tyre on one side, then repeat for the other side.

Most thumping problems are cause by people installing the tyre and leaving the valve-stem area for last. This then pinches the tube between the tyre and rim. Simple way to fix is to push the valve-stem deep into the tube to make sure ALL of the tube is inserted into the tyre.