Crank movement after bottom bracket replacement

[Twilkes]

Went into bike shop with symptom of noise while pedalling, seemed like chain on front derailleur noise, if pedalling hard and slow enough I could even make out the rhythm of each link slipping off the metal of the derailleur edge. Sounded okay when turned by hand or light pedalling, noise came when pedalling harder, and was across half or more of the rear cogs, and not due to cross-chaining (i.e. it happened on big chainring and smaller cogs).

Bike shop checked cranks, found movement, diagnosed new bottom bracket which they replaced.

Didn't get rid of noise at all, and that evening there is noticeable play in the drive side crank/chainrings - pulling sideways at the pedal moves the top of the chainring a good 3-4mm or so. I can't detect much/any movement in the non-drive side crank.

So 1) what could cause such movement on drive side only? I'm assuming any bottom bracket movement would be detectable equally in both cranks?

And 2) How do I know they didn't just waste £65 replacing the bottom bracket when it didn't need replacing? It was maybe two years old but hardly any use, surprised if it had seen more than 100 miles. It is a Cannondale pushfit though.

Will be taking it back to the shop, just want to get an idea of what to expect them to say.

 

[Racing roadkill]

It sounds like dodgy chain ring bolts to me. Maybe they just need tightening.

 

[Levo-Lon]

If you have end float it sounds like either a spacer needed or if its like my crank set you have a adjustable crank system to remove float after setting chainline "sram"

 

[Twilkes]

Spindle loose on the crank set, how much should that set me back to replace?

Any problems getting a BB30 compatible crank set?

 

[Milkfloat]

If it has only done 100 miles, then no component should need replacing. Can you take a video to show the movement?

 

[Twilkes]

If it has only done 100 miles, then no component should need replacing. Can you take a video to show the movement?

It's in the shop so can't video it - he took the crankshaft and showed me the movement between the crankset and the axle/spindle, and that matched to what I saw when it was all on the bike. No idea if that problem has been there since the beginning.

He implied there was no way to fix the axle onto the crankset, and that replacing the whole thing was necessary.

No reason to doubt the guy I bought it from who said he hardly rode it, just around local roads a few times, but the shop are saying inside the bottom bracket was dirty and with some standing water. I've only ridden it in drizzle once for 15 minutes and one ride of 20 miles where it came back with grit on the frame (probably another 30 miles on top of that) but I'm sure it wouldn't have affected inside the bottom bracket in that short space of time.

 

[Milkfloat]

Depending on the crankset some spindles are removable. For example https://www.cannondaleexperts.com/Cannondale-BB30-Spindle-109mm-Road-KP250_p_2016.html Without knowing the crankset you have we cannot say if yours is fixed or not. I can just about understand the BB bearings being knackered but not the crankset.

 

[Twilkes]

It's an FSA Omega compact, the only one i can find on t'internet is the megaexo version, which I think is different to the BB30 version this bike would have. The guy showed me the movement and it did look like the spindle had the same pattern of slots on both ends, as if it was removable. I didn't really know what I was looking at though.

edit: so probably like this one: https://www.cannondaleexperts.com/F...034t-175mm-Crankset--Take-Off-New_p_6024.html

I'm wondering whether to take it to a different shop to a get a second opinion, I'll see what they say when the call back with a quote.

 

[Twilkes]

I've got no idea what worn bearings look like but this is what they gave me back the first time:

 

[Racing roadkill]

I've got no idea what worn bearings look like but this is what they gave me back the first time:

View attachment 493683

Bearings , clips and wave washers. They don’t look to be in bad nick, where’s the plastic shell that sits in between the bearings?

 

[Twilkes]

Bearings , clips and wave washers. They don’t look to be in bad nick, where’s the plastic shell that sits in between the bearings?

Don't know, either still on the bike or they binned it.

 

[Racing roadkill]

Don't know, either still on the bike or they binned it.

Possibly. If they were fitting a new BB, it would have a new shell, and I’d expect the old one to come back with the old bearings, seals, clips and washers though.

 

[si_c]

Don't know, either still on the bike or they binned it.

Is there one for BB30? I thought the bearings pressed directly into the shell eliminating the need for the plastic inner shell.

 

[Racing roadkill]

Is there one for BB30? I thought the bearings pressed directly into the shell eliminating the need for the plastic inner shell.

Or the last owner binned it, for weight weenie reasons? who knows.

 

[Twilkes]

Looks like this is not an isolated problem, will just have to suck it up and pay for something better, thanks for the guidance: https://bicycles.stackexchange.com/...ga-bb30-spindle-comes-out-of-drive-side-crank