Unusual Clunk on Pedal Start

[purpurite]

Recently picked up a winter bike that is a full Shimano 105 setup, and I have overhauled the whole bike to near perfect condition. I threaded in pedals to take a test ride this morning, and was surprised to hear a strange heavy, hollow thunk coming from the bottom of the bike, on initial pedal force. It doesn't happen every time, but every so often on pedal start. It's not a sound I have ever heard on a bike before.

I pulled the cassette off of the rear hub and cleaned everything and reassembled, and tightened the cassette properly, and the sound still exists. My next step is to disassemble the bottom bracket and see if there is anything unusual there. It's a TruVativ GXP BB, and I know they aren't favorites of many, so it might be something failing there.

When I got the bike, it was visually not maintained, covered top to bottom in mud, grime and a little rust on a few steel parts. I know that there are things that I will uncover as I go, but this one is confounding me. I can't tell exactly where the sound is radiating from, so I'm throwing darts with my eyes closed trying to guess what the sound could be.

Anyone have a similar experience or have any ideas? No other sounds or red flags anywhere except the front of the first pedal stroke.


Guesses?

[prototoast]

My guess is the one of the bottom bracket cups needs to be tightened a little bit.

[purpurite]

My guess is the one of the bottom bracket cups needs to be tightened a little bit.

That was my guess. The cassette was the easier of the two fixes... tomorrow morning the BB comes apart to be cleaned and re-assembled. I hope everything is still in working order and it's just a simple torque to fix.

[ultraman6970]

Lose headset?

[scoobydrew]

Subscribing to this thread to see what suggestions others have and what the solution ends up being.

I'm experiencing something similar on one of my bikes. The pedal feel and sound is similar to the clunk when setting a quicklink via the pedal method.

[oldpotatoe]

Recently picked up a winter bike that is a full Shimano 105 setup, and I have overhauled the whole bike to near perfect condition. I threaded in pedals to take a test ride this morning, and was surprised to hear a strange heavy, hollow thunk coming from the bottom of the bike, on initial pedal force. It doesn't happen every time, but every so often on pedal start. It's not a sound I have ever heard on a bike before.

I pulled the cassette off of the rear hub and cleaned everything and reassembled, and tightened the cassette properly, and the sound still exists. My next step is to disassemble the bottom bracket and see if there is anything unusual there. It's a TruVativ GXP BB, and I know they aren't favorites of many, so it might be something failing there.

When I got the bike, it was visually not maintained, covered top to bottom in mud, grime and a little rust on a few steel parts. I know that there are things that I will uncover as I go, but this one is confounding me. I can't tell exactly where the sound is radiating from, so I'm throwing darts with my eyes closed trying to guess what the sound could be.

Anyone have a similar experience or have any ideas? No other sounds or red flags anywhere except the front of the first pedal stroke.


Guesses?

What rear wheel, hub? Mavic by chance?

[purpurite]

No, Ritchey Aero Comp hubs, Shimano cassette.

[Veloo]

Never experienced but curious to find out root cause.

[purpurite]

Ok, so that was... something.

Spent a good part of the morning pulling the cranks (easy) then trying to remove what appeared to be a slightly boogered up GXP bottom bracket. The drive side came off fairly easily and without any issue. Then the fun started.

My Park GXP bottom bracket tool didn't fit the non-drive cup. At all. I tried to clean up the chewed spline lugs with a small jewelers file, and nothing worked. Cleaned up the exterior of the drive cup with a small flat file and it still didn't fit. Finally ran a digital caliper across the diameter and FFS, the non-drive side up was 45.10mm while the drive side cup was 44.10mm in diameter across the flats. Am I losing my mind? Is this a thing? I've built a handful of GXP bottom ends, including my two other bikes, and I have never seen a BB cup size discrepancy from left to tight side.

Then it got good.

I cleaned up the cup all around with a file and Dremel, because at this point all hope is lost and I'm replacing this POS ASAP. I got it to a point where the Park BB socket would uncomfortably be persuaded on. No looking back now. Soak in Kroil, heat up the BB shell, pull out the breaker bar and go to work.

Twisted my 1/2" to 3/8" drive adapter in half. No joke.

Pull out a 3/8" torque wrench, which I wanted to avoid, and give it one more shot to loosen it up before going completely medieval on it. Force, force, force, force, force, SNAP—it came loose. And in the process, my body mass and all of my force came down mouth-first on the top tube. I thought I put my teeth through my lip. Once I started seeing normal colors again and stopped swearing (and feeling for my lower teeth), I got the rest of the drive cup out.

This damn thing is 1mm larger than the other side. This is insane. I think it's TruVativ, so scratch that brand off of any future purchase list.

BB is cleaned and open, and I won't be able to continue troubleshooting on this until the new BB comes in next week. But I got to thinking while I was wrestling with the BB.

What if a single pawl inside the rear hub is seized or broken? That's kinda what it feels like when the klunk happens. Like it's one spot inside the rear hub. The sound seems to be that hollow cassette sound, only deeper, heavier and louder—but only once in a while.

Anyone know if the Ritchey Aero Comp hub is rebuildable?





I need a beer.

[purpurite]

Photos for fun...

[purpurite]

My guess is the one of the bottom bracket cups needs to be tightened a little bit.

Hahaha, yeah, no.

[jtbadge]

I've had this exact thing happen with a pawl that was binding. Cleaned grease out, replaced with chain lube. All good now!

[purpurite]

I've had this exact thing happen with a pawl that was binding. Cleaned grease out, replaced with chain lube. All good now!

Ooooohhhh, you might be on to something.

Bears v Packers coming up in 20, so I'm taking a break now. Need to give my hands and wrists and lower lip a little time to heal up.

[charliedid]

Fun

I'd have put a pipe wrench on it if I knew the BB was toast. If you have not tried one I think the Wheels Manufacturing GXP BB is a really solid value.

As an old GF used to say 'split my lip, bog'd my trip'

PS I hate working on bikes :-)

[charliedid]

And yeah, pull that hub apart and take a look see.

[Veloo]

WOW!
Glad you're (fairly) OK.
Can't believe you snapped the adapter.

[m_sasso]

What brand of tool was that, who made that 1/2" to 3/8" drive adapter? :eek:

[purpurite]

What brand of tool was that, who made that 1/2" to 3/8" drive adapter? :eek:

Great question. I usually only buy Craftsman sockets, but I have a feeling I bought this to adapt my manual needle torque wrench for BBs, and I think it was MasterForce from Menards. No markings, I'm betting on Masterforce.

[purpurite]

Fun

I'd have put a pipe wrench on it if I knew the BB was toast.

I tried. I don't have a big enough pipe wrench, so I used what I had. I'm 150 pounds soaking wet, so I use mechanical leverage when at all possible. I may have used too much this time. :eek:

[tomato coupe]

Bears v Packers coming up in 20, so I'm taking a break now.

Is this their 200th game?

[Veloo]

Is that a house brand?
Like our Canadian Tire Mastercraft? Or Home Depot Husky?

Great question. I usually only buy Craftsman sockets, but I have a feeling I bought this to adapt my manual needle torque wrench for BBs, and I think it was MasterForce from Menards. No markings, I'm betting on Masterforce.

[purpurite]

Yup. Who knows who makes it? I normally don't buy cheap tools for this reason.

[purpurite]

Is this their 200th game?

Yup. I'm not optimistic with this one.

[NickJ]

This anecdote might be helpful. I picked up a brand new TCR this fall. Of course I expected some weird noises for the first 50-100 miles as it broke in. The rear hub was ridiculously quiet, very stealth. But I had a very odd clunk during power down - very similar to what you describe.

I’m out for a ride around mile 40 of ownership, we stop for coffee, then upon returning to the ride: all of a sudden I own the loudest bike in the history of bikes. You can hear me and my rear hub coming from half a mile away. Something clicked and the hub started to work. AND the clunk disappeared too.

Your issue could be as simple as: A. Give it some time. B. Pull the hub ratchet cover and see what’s what.

[purpurite]

The rear hub was ridiculously quiet, very stealth. But I had a very odd clunk during power down - very similar to what you describe.

Your issue could be as simple as: A. Give it some time. B. Pull the hub ratchet cover and see what’s what.

Yeah, the hub is strangely super quiet, but it's a fairly old bike build. I pulled the cassette and yanked the axle out, and it doesn't have cartridge bearings in the freehub, which I wasn't expecting. Ball bearings everywhere. In order to get the freehub body off, though, I need a 12mm allen key, which I don't have (who does?). So, progress is stalled for a couple of days.

I tend to now think it's a pawl not engaging in certain spots, if not at all. I'll find out more once I get the freehub body off, but I think I'm getting closer.

[charliedid]

I tried. I don't have a big enough pipe wrench, so I used what I had. I'm 150 pounds soaking wet, so I use mechanical leverage when at all possible. I may have used too much this time. :eek:

Amen

[oldpotatoe]

Yeah, the hub is strangely super quiet, but it's a fairly old bike build. I pulled the cassette and yanked the axle out, and it doesn't have cartridge bearings in the freehub, which I wasn't expecting. Ball bearings everywhere. In order to get the freehub body off, though, I need a 12mm allen key, which I don't have (who does?). So, progress is stalled for a couple of days.

I tend to now think it's a pawl not engaging in certain spots, if not at all. I'll find out more once I get the freehub body off, but I think I'm getting closer.

Menard's does..Comes off similarly to a shimano BIG allen in there, lefty-loosey. Been a while, not sure it's a 'unit' like shimano or has pawls on outside.
BUT if able to see..clean with tooth brush, oil 'em, don't use grease..

[purpurite]

op, or anyone else, have you ever seen GXP bottom bracket cups that were different ODs? One was very much 44mm and the other was definitely 45mm and was not something I have encountered before. I looked for specific 45mm cup tools last night and I couldn't find any. Product defect or operator error?

It could be why it was so painful to remove—it may have been "installed" with a lot of red Loctite instead of proper torque. Looking back at the photo of the two cups, the threads are pretty different looking between the two. It's possible someone may have glued that thing in there because of a lack of proper tools.

[Elefantino]

I'm going to go with a sticky pawl.

[TiminVA]

Similar sound happened to me back in the summer. Obviously hubs and bottom bracket were the first things I checked, but it ended up being one arm of the crankset spider was cracked. This was an Ultegra 6800 with around 20,000 miles on it.

[purpurite]

Comes off similarly to a shimano BIG allen in there, lefty-loosey.


The allen runs through the hub and into the base of the freehub... lefty-loosey, correct? Even with a beaker bar it won't budge. This thing is unbelievable.

[BobbyJones]

Side note for anyone else reading this far.

I went through something similar as the OP. Couldn't find the "Clunk". Swapped pedals, replaced BB, swapped wheels... ran down the list of every part of the bike where two "things" joined.

It ended up being a Co2 cart in a saddle bag thunking against the post.

Sounds silly, but it was just one of those noises. No one wishes a damaged part on anyone else, but glad the OP found it.

[charliedid]

The allen runs through the hub and into the base of the freehub... lefty-loosey, correct? Even with a beaker bar it won't budge. This thing is unbelievable.

Can you set the wrench in a vice and turn the wheel?

[purpurite]

So here's the conclusion of the story (so far). I'm still waiting on a new BB to come in—they shipped it UPS Mail Innovations without letting me know, so I might see it sometime in January if I'm lucky.

12mm hex key was acquired today (holy crap, that's a big hex key). I wrestled with the internal nut for about an hour. Broke the vise base off of my bench (I needed a new vise anyway), bent a 2' breaker bar tube, tried heat, Kroil, lefty-loosey, righty-loosey, you name it. It wouldn't budge. Finally, it cracked loose and I was able to get it off. I don't even recall what direction it took to loosen it. What the hell were they doing when they put these things together?

So I hosed out the inside of the hub and freehub with brake cleaner, then set up a shallow cup with mineral spirits to soak everything. Ran brake cleaner through it again, and sure enough—the freehub spun clean with a ratchet sound and everything! I made a micro oiler of 50% mineral spirits and Phil's Tenacious oil, and then soaked the internals of the freehub. I like a little thinner oil in something like this so it can creep everywhere.

I put the axle, cone washers and bearings back in with some thick Phil's grease and adjusted the cones on the new steel axle so play was perfect. Put the cassette back together, then got the wheel back in the rear dropouts. The wheel spins perfectly with the cassette just sitting still, and in reverse, the beautiful sound of a hub's pawl clicks.

I'm 99.9% sure the hub was the problem and the pawls were sticky and not engaging properly. This should fix the problem completely, but I'll know for sure when I (someday) get the bottom bracket installed and the drivetrain all back together.

For now, I'm calling it a victory. Put my knee on its throat and made it cry uncle. Loser. And I only went through 3 Band-Aids, 2 beers and had to buy a new hollow axle, a new bottom bracket, 3 new tools and now a new small bench vise.



Thanks for all of the help, guys. This was one of those fights that I refuse to lose. I think it's better now that it was when it was new, so I'm happy. I'll let you know how it goes when it's all back together and I can test ride it, but I'm confident it's over.

[charliedid]

So here's the conclusion of the story (so far). I'm still waiting on a new BB to come in—they shipped it UPS Mail Innovations without letting me know, so I might see it sometime in January if I'm lucky.

12mm hex key was acquired today (holy crap, that's a big hex key). I wrestled with the internal nut for about an hour. Broke the vise base off of my bench (I needed a new vise anyway), bent a 2' breaker bar tube, tried heat, Kroil, lefty-loosey, righty-loosey, you name it. It wouldn't budge. Finally, it cracked loose and I was able to get it off. I don't even recall what direction it took to loosen it. What the hell were they doing when they put these things together?

So I hosed out the inside of the hub and freehub with brake cleaner, then set up a shallow cup with mineral spirits to soak everything. Ran brake cleaner through it again, and sure enough—the freehub spun clean with a ratchet sound and everything! I made a micro oiler of 50% mineral spirits and Phil's Tenacious oil, and then soaked the internals of the freehub. I like a little thinner oil in something like this so it can creep everywhere.

I put the axle, cone washers and bearings back in with some thick Phil's grease and adjusted the cones on the new steel axle so play was perfect. Put the cassette back together, then got the wheel back in the rear dropouts. The wheel spins perfectly with the cassette just sitting still, and in reverse, the beautiful sound of a hub's pawl clicks.

I'm 99.9% sure the hub was the problem and the pawls were sticky and not engaging properly. This should fix the problem completely, but I'll know for sure when I (someday) get the bottom bracket installed and the drivetrain all back together.

For now, I'm calling it a victory. Put my knee on its throat and made it cry uncle. Looser. And I only went through 3 Band-Aids, 2 beers and had to buy a new hollow axle, a new bottom bracket, 3 new tools and now a new small bench vise.



Thanks for all of the help, guys. This was one of those fights that I refuse to lose. I think it's better now that it was when it was new, so I'm happy. I'll let you know how it goes when it's all back together and I can test ride it, but I'm confident it's over.

Bravo!

[purpurite]

Just to follow up on everything on this one, first of all, I want to issue a retraction and apologize to Menards for blaming the Masterforce adapter—it was a Husky product from Home Depot, so stay away from that junk.

Second, got the new BB finally (don't EVER allow something you order to be shipped via UPS Parcel Select, unless you don't care when it arrives). Installed it this evening with grease and my trusty beam torque wrench. Nice and smooth, easy peasy. Got it all tightened up and I needed to adjust the high and low a bit on the FD, but everything shifts perfectly and there are no funky noises or skips in the drivetrain.

I believe the issue was the gummed up internals in the rear hub causing one of the pawls to stick disengaged, which would explain why it didn't happen on every pedal rotation or every engagement. Once it was cleaned out and lubed, it works perfectly.

Thanks to everyone who participated in this thread, it was rather entertaining trying to figure out what the issue was—scabs and bloodletting aside.




Doug

[djdj]

Great story. Thanks for sharing. :beer:

[commonguy001]

Great story. Thanks for sharing. :beer:

Agreed!
Good read this morning and a positive outcome. Glad the bike is finally sorted.

Having ridden bikes that have a “slip” just every once in a while when you start pedaling- I’ll be checking the hub next time without a doubt.