Odd Sensation While Pedaling In Certain Gears

[meteparozzi]

I've got a fairly new (3 months, 500 km) bike that has a rather annoying problem. When I'm in the 7th cog in the rear from the tire, I get a terrible popping / grinding / ticking sensation through the pedals. I never get it on the 8th or the 9th, and it seems muffled or reduced on 1-6. It's most present on the largest chainring, and only slightly less so on the middle.

The feeling gets much worse in the rain, or after I have freshly cleaned the cassette and chain, but is persistent and troublesome all the time. I'm taking it to the LBS next weekend, but I don't have much time, so I wanted to know what parts specifically I should look into.

The sensation is felt through both pedals, and I've checked the drive train for things sticking out, stinking in, rubbing, etc. There is nothing to indicate why this would happen. The chain is almost brand new, and everything is Shimano Deore, inside and out. There's no rub from the front derailler or the rear derailler. It's driving me crazy though, and I know this shouldn't be happening. I took it to the LBS once, and we took everything apart and put it back together, but to no avail. We even tried swapping a few parts, such as the 7th cog, but it didn't do any good, and I didn't have time to go full through it. The wrench told me it was ok, but when my other bikes (far cheaper I might add) ride without this, I can't be satisfied with that answer. And there are no other bike shops in town that can help, as none speak English, so I can't really get a second opinion.

The labor here is free, though, but my time is limited due to his shop hours. I'm definitely going to swap out the full cassette, and see if that helps, as it seems to be centered on that. If that doesn't work, what should I swap next?

Thanks for your suggestions in advance.

 

[artmichalek]

With only 500km, I would expect that the derailleur cables are still stretching.

 

[meteparozzi]

With only 500km, I would expect that the derailleur cables are still stretching.

Would that cause the grinding / ticking / popping feeling? Why only in those specific gears? What can I do to fix it, as I have adjusted the front and rear derailleur several times, and nothing has worked.

 

[artmichalek]

Would that cause the grinding / ticking / popping feeling? Why only in those specific gears? What can I do to fix it, as I have adjusted the front and rear derailleur several times, and nothing has worked.

If you went through the derailleur adjustment in the right order (high limit, tension, low limit), then the next thing to look at is the spacer between the 7th and 8th cogs.

 

[meteparozzi]

If you went through the derailleur adjustment in the right order (high limit, tension, low limit), then the next thing to look at is the spacer between the 7th and 8th cogs.

That was the one thing I focused on at the LBS the first time, we changed out the spacer and the cog, but it didn't do much for the problem. He said the original manufacturer had overtightened the lockring. Could that have crushed or otherwise damaged the cassette to cause this?

 

[twntbo]

I have had similar experiences over the years, but I can't give you a quick fix. I can only recommend taking it step-by-step.

During the first 500K it is not uncommon for cables to stretch and parts to loosen. I would check your chainring bolts, crank arm bolts, cable tension, pedals, etc.

I recently spent a couple of hours trying to find a creak in my bike that was driving me mad. I would have swore that it was coming from my front wheel. After checking the spokes, hubs and skewers, I moved on to the handle bars ... and finally found that one of the stem bolts just needed a little grease.

Good luck. You'll find it.

 

[meteparozzi]

Look at [...] the spacer between the 7th and 8th cogs.

I apologize, I think I misread that at first. We examined the spacer between the 6th and 7th, but not between the 7th and 8th.

I just went and took a look at the bike. The spacer you mentioned appears to be made of a different material than the others. It's quite a bit shinier than its neighbors. I will definitely make a point of swapping that when I go in.

 

[artmichalek]

he spacer you mentioned appears to be made of a different material than the others. It's quite a bit shinier than its neighbors.

I believe that spacer is actually part of the 8th cog.

 

[meteparozzi]

I went to the LBS and the wrench and I spent 3 hours disassembling and replacing one part at a time. We changed out the cassette, the rear wheel (altogether with a new cassette), the front chainring and bottom bracket, the pedals, and the chain. No matter what the sensation stayed. In some cases it got worse, in others it was slightly reduced. No matter what, though, nothing solved the problem. The only things we didn't replace were the front and rear derailleurs, as there was no rubbing from the front, and we readjusted (multiple times) the rear.

Did we give up to soon? Should we have replaced those as well? Any other ideas?

 

[gclark8]

Check the frame, rear drop-out, alignment, and also the RD frame mount, is it bent? My LBS has a jig to do this.

 

[meteparozzi]

Check the frame, rear drop-out, alignment, and also the RD frame mount, is it bent? My LBS has a jig to do this.

What should I look for on the frame and the rear drop-out? How do I check the alignment?

I know the LBS doesn't have a jig to do it, so what simple tools could I use. What would indicate a bent frame mount?

Thanks for the suggestions.

 

[gclark8]

Last year I bought a new frame and the tyre/rim was not centre in the chainstay. He checked this with two things he bolted into the drop-outs, then another that he bolted into the RD mount. These were special frame builders tools, I have not seen them anywhere else, before or since that day. You will have to ask your LBS.

 

[meteparozzi]

Last year I bought a new frame and the tyre/rim was not centre in the chainstay. He checked this with two things he bolted into the drop-outs, then another that he bolted into the RD mount. These were special frame builders tools, I have not seen them anywhere else, before or since that day. You will have to ask your LBS.

Had him check the alignment. Everything is perfectly aligned. No problems. Any other ideas as to what it could be, I'm still stumped.

Next up is replacing the rear derailler, after that every drive train part will have been changed out.