lateral chain movement
 

My C. Itoh has been having an issue lately with the pedals feeling kind of sluggish, a sort of grinding feeling. At first I thought it might be in need of a good cleaning and lubing (which it is) but I've also noticed a significant amount lateral movement with each complete rotation of the crank arm. On the downstroke with my left crank arm, the chain moves so far to the left that it slides against the front derailleur, and when I pedal down with my right foot, the chain gets back to somewhere in the center of the derailleur where it isn't touching anything. I know the hub wobbles quite a bit but I think that is normal (?). Could the problem be arising from the wheel simply being out of true?

The chainrings are moving sideways top and bottom because the entire crank assembly is rocking in the frame.

The cause is almost surely a loose bottom bracket, or failed bearing there. BBs vary and I have no idea what kind you have, and whether you need an adjustment or replacement, but you can do an eyeball check or look up the specs, and/or search for information and tutorials related to loose bottom bracket on the internet.

Sure the problem could be only one issue and that issue could be an out of true chainwheel. There are simple tests to try to figure this out. One is to grab one crank arm at it's pedal end and try to rock it in and out against the frame. I find it easiest to rotate the arm so it nearly lines up with the frame's chainstay. Placing one's fingers between the frame and the arm and the other hand squeezes the arm against the frame while the fingers try to pry the arm back. If the BB bearings or the arm's attachment to the BB are the problem you'll feel slop. By removing the chain from the rings then spinng the crank you can watch the rings as they rotate past the ft der cage. Do they run past without any side to side run out? Remember that if the arms are loose on the spindle or if the BB is sloppy these will cause run out.


For an experienced wrench these steps take less then one minute. From these two steps a lot of info can be had. Andy.

Hub wobbling is not normal. [Touring?!?]

The crank arm seems pretty sturdy. Rotating the pedal backwards with the chain on I can still see the chain moving laterally the same amount with each rotation, even without the force of me pedaling with my full weight. With the chain off, the chainrings are apparently oriented at a slant, so that the teeth move toward and away from the center of the derailleur cage as they turn forward or backward. It seems obvious that the crank itself isn't loose or shifting, but that the bracket (or at least the chain rings) is crooked in relation to the frame. Which I wish were not the case since I'd rather just have to adjust something myself than have to go to the shop and get a piece replaced, but cest la vie I reckon

It seems frightening to me as well but I've noticed on several of my friends' hubs as well. I've been spending some time hanging out with friends here and there helping each other figure out how to fix stuff on each others' bikes, and basically anytime I've tried to put a back wheel back onto my or any of my friends' bikes, I've noticed the hub wobbling. I remember looking through old threads to see if there were anything already posted about it on here, and the consensus seemed to be that hubs wobble because there are so many components and there is a slight margin of error in how each of them fits together, so there is naturally some degree of wobble. But I can just as easily believe that hub wobble is something that shouldn't be happening :o

Are you talking about the cogs having some "orbital wobble" or that the axle/bearings/hubshell is sloppy?


This is a big difference. The terms you use in your posts are not what are commonly used, hence our confusion. This is one reason why good and many photos can help shorten the translation from your terms and our experiences.


What I tried to explain in my first post was the difference between the BB/bearings being sloppy/loose and the chainrings being out of true. Both can have similar initial looks but have vastly different solutions.


Now you're talking about rear hubs. I'll try to help more but after a few replies and continued inability to really understand your questions it can be a challenge for us too. Andy.

I was just replying about a separate issue. I think that the chainrings are out of true. Nothing seems loose on the bottom bracket but the way the chainrings line up with the front derailleur still seems to change as they rotate, which causes the chain to move laterally when its on either of them.

The hub on the rear wheel also wobbles but that is a separate issue which I don't actually think is significant enough to be causing the lateral chain movement.

Sorry for the confusion. I can take pics in the morning.

Had a similar problem a while back after I had an 'off'. The chainrings were not running in a true plane and the chain would rub the inner derailleur cage every revolution. I straightened the chainrings, only for the problem to still be there, albeit less noticeable. Turned out to be a slightly bent crank spider.

Not saying this is your exact problem, but worth a look.

I'm expecting that it probably is a bent spindle and/or chainring... I actually believe the problem could've started when my chain popped off while mounting and trying to go immediately into a climb w traffic behind me (I work delivering food and the store I deliver for is on one of the steepest hills in New Brunswick). It popped off in the middle of such a momentous downstroke that I toppled straight over, humorously if not perilously.

I thought I had bent my derailleur cage in the fall because that's when I first noticed the chain rubbing it, but it has slowly become more apparent that the problem is probably elsewhere. I kind of thought it had developed over time from simply lightly bumping my chainrings/a crank arm occasionally when I lifting my bike over a curb, but what you are saying makes me think that MOST of the damage was probably done in that fall :/ I'll take it to the shop ASAP I suppose. But honestly this is more motivation to just throw money down on a safer bike for the winter, rather than putting more money into this one right away ^_^

thanks for the info everyone