Wheel Alignment
 

I just changed the chainring on my bike, for the first time. I've got sugino rd cranks. The rear wheel seems like it's aligned, but if I press my finger on the sidewall of the rim slightly whlile I spin the wheel, I can feel slight variations in pressure agains my finger, so I'm sure the alignment isn't "perfect." Also, I never really checked my bike before (and I didn't set it up), but now I see that the chain is tighter at some crank positions than others. At some points it almost seems tight, and at some points almost loose. Is this all normal? Is there any special way to make sure everything is aligned as good as possible? Also, is the variation in the chain tightness possibly related to the bottom bracket or the cranks? I understand that better cranks, for example, are made to closer tolerances. Maybe the chain ring also?

I guess also the slight wheel variation could be the wheel itself of course. But the fact that the chain is tighter in spots makes me think maybe its the axle alignment in the drop outs. By the way, this is a Surly Steamroller.

that's normal.. chainrings arent perfect. as long as your chain isnt going from grinding tight, to almost bouncing off, you're alright.

yeah if it really bothers you, check the chainring bolts. It's not something i'd be terribly concerned about.

Get your wheel trued if that's bothering you.

I had a similar problem with the crank. You're never going to get it perfect because most chainrings aren't perfectly round. However, the chainring might be slightly off-center of the crank spider. It probably just needs minor adjustment. I loosened by chainring bolts slightly (so they were loose, but still a wee wee bit of friction on the chainring movement on the spider), made sure the chain had no slack, then gently spun the crank a couple of times until the major stiff parts went away, then retightened the chainring bolts. The pressure of the chain had centered mine. I'm sure that's not the proper way to do it, but it worked for me.

i had a similar issue with the variable tightness, so just to be sure i re-packed my bottom bracket (with the tightness came squeaking) and discovered that one of the BB cups had worn unevenly and was causing my crank to shift at the axle.

what rugen said. I had a problem like that which turned out to be a mis-stamped (surley) cog, so the wheel was true, the crank was centered, but the chain was still loose enough to pop off, or so tight the cranks would barely turn. If it still persists, take the rear wheel and spin it, and watch the cog... if it hops up and down, that's bad news. replace cog before riding on.

Make sure to check your hubs as well.

You can test for this by taking the chain off. If the tight spot is still there with the chain disengaged, I would think the bb is your culprit.

maybe you could try this?

http://sheldonbrown.com/fixed.html#tension

I've got no first hand experience doing this but it might help

It sounds to me like your problems are (1) a wheel that needs truing and (2) completely normal variations in chain tension. (1) is easy to fix or to have fixed, and (2) is not really a concern if your chainline is straight.

By the way, how much chain slack should there be?

I used to like a tight chain for trackstanding but someone on these boards converted me to slack---it's much better for your drivetrain. I would try and rotate the ring so that the chain is tightest in the trackstand position, and then set tension for just the tiniest bit of up and down movement (over a span of, say, 1/2") in the cranks when the wheel ish't moving. If the chain "pings" when you trackstand youve done this right.

I tightened up the chain a bit, using the Sheldon Brown method of "walking" the axle back. That seems to work pretty well. At the tightest, I've got maybe 1/16" without really pulling up too hard. At the loosest, it's about a 1/4" or so. I think this is a little tighter than what I had when I got it. I guess it will also loosen up slightly over a little time.

That sounds great, could be a bit tight but as long as you have slack all the way through the rotation it's a matter of taste really. The idea is for the chain not to be under any tension at all (beyond what its weight creates) when the bike is at rest with the cranks in the tightest position.

Rode it this morning and no problems; and very quiet.