Sooooo, yeah. Every revolution of the pedals, I can hear, and feel, a thud at the same position - at around the 1 o'clock position, on the right side.

Happens at the same point every time it happens - but won't always happen. It'll happen for a few minutes, then stop.

Happens regardless of the gear ratio, and still the same position, 1 o'clock.

I can't replicate the problem by pedaling backwards.

Any ideas?

Possibly loose crank to bottom bracket interface.
Possibly loose or worn pedal spindle.
I had a popping noise on every rotation that turned out to be my kneecap.

Hi,

My money is on a loose crank.

rgds, sreten.

Loose I could see, but not probably not worn, I've only been riding it a couple of months. I'll tighten it up tonight, I was worried something cracked in the bottom bracket.

Can it be tightened without removing the pedals?

If it's a new bike take it back to the dealer and tell them to fix it. You may need a special tool.

Try removing the crank arms and adjusting the bottom bracket if old skool. It is generally best to remove crank arms and then reassemble using a torque wrench. Also check your sprocket bolts as one of them may be loose.

Put the right hand pedal at about "2 O'clock" with a little pressure on the pedal, wiggle sideways and note if you feel anything loose. If so, isolate if it's the pedal, the crank attaching to the bottom bracket axle, or the axle itself. Then repeat with the left pedal.

Report back, with pictures if possible to help identify the specifc model/type of parts you have.

I would but I got it from crappy tire - retail chain, they likely won't do jack, and if they do try and fix it, it'll likely end up worse than I brought it in, I don't mind shelling out for a tool, I'll likely need it again in the future anyway.

I was hoping to avoid getting too deep into the bottom bracket - as in, removing anything other than the crank arms at most, but looks like it'll be unavoidable.

thanks for your advice everyone!

Had this happen to me two weeks ago. Every rotation of crank would result in a thunk around the 1 o'clock position. Turned out to be a loose bottom bracket.

I thought it was crank arm as the crankset was recently replaced but was BB

"One o'clock position on the right side." Do you have a kickstand?

Hah.

There are actually three possibilities, with the last listed being quite likely.

1. Right (or possibly left) crank loose on the spindle - requires 15mm socket or 8mm allen wrench to tighten, and critical to do as soon as possible - otherwise you will be buying a new crank arm. Best to tighten both even if having no problems.
2. Right pedal loose on the crank - requires long, thin strong 15mm (pedal) wrench to fix. Again good idea to check for tightness, especially on dept. store bike.
3. Loose BB cup, especially drive side - requires crank arm extractor and BB tool to fix.

lol. if that were the case, it'd be happening when I pedal backwards as well

Ok it's definitely the BB that's loose, and it seems to be a little looser now, unless it's just my imagination because I'm more aware of the issue.

Cranks are tight, so I can definitely rule that out.

Measuring the wobble against the front derailleur to the gears it'll wiggle about 2-3mm.

I'm guessing I need to remove both cranks to tighten the cups? I think I'll have to take it into the shop at this point, is it expensive?

Here's a link to the bike, better picture than i could take on my own, but I don't know if there's any obvious info on the make/mfg. Had a quick look at some of the repair sites, doesn't seem too complicated, if I have the right tools.

https://www.canadiantire.ca/AST/brows....jsp?locale=en

I'm really out of touch with current bikes, but given a dept. store bike I would indeed recommend removal of both crank arms, whether a conventional or cartridge style BB. First loosen the non-drive side cup, then make sure the drive side is tight. Finally tighten (to proper torque) the NDS if a cartridge or adjust the cup/lockring if a conventional.

You should be able to tighten the cup on the BB without removing the cranks.

Just loosen the lockring with some pump pliers and use a spanner or some needle nose pliers to turn the adjustable cup about 1/8" at a time until it seems snug on the bearings w/o restricting the spin. Also, if the bike is real cheap, you could have busted the bearing cage, but that's pretty unlikely