This has puzzled me (and several bike mechanics) for some time. I keep hoping that my bottom bracket will start clicking so I'll know what the problem is, but it's been about two years and I'm sure the BB would have gone by now.

Anyway, the best way to describe the problem is a "crunching" sound -- actually more of a feeling -- with every pedal revolution.

Just some random notes:

1. It's almost as if the Hyperglide chain isn't exactly aligned with the Hyperglide chain rings or cogs and the chain is just missing the teeth. The chain and cassette are brand new, by the way, but this has been going on for a long time.

2. I thought I had found the problem about a year ago in that the inside buckles of my toe clips were catching the crank with each revolution. I removed the toe clips for a while, used straight platform pedals, and the problem went away. Then it came back.

So I'm back on the bike every day now and I'm heading out on a yearly multi-day trip next month, so I want to fix this problem once and for all. More than one bike shop mechanic has told me it's not the bottom bracket, not the pedals, and not the cranks.

Any ideas?

IME, there are few "crunch" sounds that aren't indicative of something gone amiss, where a bicycle is concerned.

i'm pretty sure that if you can reproduce the symptom on demand that an LBS can fix it.

I wish I could effectively recreate the "sound" here, but it isn't even really a sound as much as it's a feeling that a bearing needs grease or something. Most mechanics only want to check the bike on a stand, and, for some reason, it doesn't happen until there is actual pressure on the pedals. The few who have actually ridden the bike either heard/felt nothing or heard/felt SOMETHING, but couldn't pinpoint it.

This is the most frustrating experience I've had in more than 40 years on bicycles.

IME, crunching sounds are a sign of a problem on the bearings. Pedal bearings perhaps? Turning the cranks on the stand might not provide the pressure on the bearings to cause it to "crunch". Try and have the pedals overhauled.

Do you feel it on other bikes? While standing? Remove/reverse the chain direction and see if that helps.

Before you said the issue is not present with platform pedals installed I would have said your chain might just be a little dry, but now I am guessing it has to be either not enough or too light of a grease inside your pedals.

Damian

if all else fails, i sometimes swap out parts just to see if something changes. occasionally it provides useful information.