Bicycle Mechanics - New crank, sealed BB, new grinding sensatin

I recently replaced crank with a slightly bent outer CR, with an entire crankset (four bolt chainrings are getting hard to find cheap). Anyway, I actually have two problems.

I went from 175mm to 170mm, 44/32/22 to 42/32/22, Sugino 350x to Shimano STX (the budget choice).

I took it out for a test ride and, for the first time, felt a kind of grinding sensation in both crankarms. It wasn't like a sand-type of grinding, but a feel like I was grinding something bigger (like a bearing). It's kind of slight, but still noticeable. I havea sealed BB, but I think it's compatible with the new crankset. Am I just experiencing new sansations because the outer CR has fewer teeth and/or the cankarms are shorter or is my BB going out? I didn't feel this sensation at all until I put the new crankset on. Literally overnight.

Also... When I went from 44 to 42 on the outer CR, the diameter dropped a bit and now the chain is situated right at a bulge in the derailleur, has less clearance and basically grinds a bit (not what I'm feeling in the crankarms) on either side. I can't adjust it to sit perfectly, so...

What should I do? Return the new crankset and put the old one on? D I need a new BB, etc, etc, etc

TIA.

First two things that came to mind here:

1) You're using an old chain on new rings. How much mileage/age is on your old chain?

2) The teeth of the derailleur may be rubbing on the edges of the front derailleur's inner or outer plates in the middle or big rings. Have a really close look while rotating the cranks.
If this is what's happening, the derailleur will need to be raised enough to provide clearance.


The issue you mentioned about the bulge... the cage can be re-shaped and widened a bit using a pair of pliers and a deft touch. It's common practice :) but the first thing to do is to readjust the front derailleur's indexing. Start here, perhaps: http://www.parktool.com/repair_help/howfix_frontderailleur.shtml

New chain (sorry. Forgot to mention that)

The chainring teeth are not rubbing against the derailleur. There's no sound to associate with this sensation. Only the feel. And I only feel it when I'm having to apply moderate to heavy force to pedal. At higher speeds, when I'm just kind of spinning, I don't feel it. Also the sensation is equal in both crankarms, that's why I think the BB. Chainring teeth rubbing would be stronger in the right crankarm.

But the odd thing is the literally overnight-ness of this...

Make sure your bottom bracket shells are clean and greased. check to make sure the actual bottom bracket is tight and not loose.

I'm almost inclined to say the answer is simply "STX." Give it some break-in time and see what happens, I guess. Is the 42T going to be enough high gear for your purposes? I commute on my mountain bike and I'd wrap that out in a hurry going downhill towards downtown, but for off-roading it's probably not going to be an issue.

Originally posted by CarlJStoneham
New chain (sorry. Forgot to mention that)

The chainring teeth are not rubbing against the derailleur. There's no sound to associate with this sensation. Only the feel. And I only feel it when I'm having to apply moderate to heavy force to pedal. At higher speeds, when I'm just kind of spinning, I don't feel it. Also the sensation is equal in both crankarms, that's why I think the BB. Chainring teeth rubbing would be stronger in the right crankarm.

But the odd thing is the literally overnight-ness of this...

I feel exactly the same sensation, and also not sure what it is , yet. It started after rebuilding the bottom bracket...

I suspect the bearings...

Here is the article dealing with the issue.

Grinding Noise Coming From the Bottom Bracket. (http://www.parktool.com/repair_help/FAQgrind.shtml)

Originally posted by Inoplanetyanin
I feel ecactly the same sensation, and also not sure what it is , yet. It started after rebuilding the bottom bracket...

I suspect the bearings... Perhaps your bearing retainers are oriented backwards, assuming your bottom bracket uses retainers in the first place. The ring-shaped face of the retainer goes into the cup, with its "fingers" reaching out at you as you look into the cup.

To MechBGon.

Yeah, I think 42 may not be enough. I may just go back to the 44 and deal with the slight warp in the outer ring until I can track down a reasonably priced 44/32/22.

As for breaking it in, I had kind of wondered that myself. I'm gonna put the 44 crankset back on and see how it feels. it goes back to being smooth, I'll know it was just the new crankset.

Thanks for all the posts everyone. As of now, the 42 goes back to Nashbar... :)

You can often straighten chainrings and even crank spiders with a deft touch and a mallet, by the way :) Commonly done.