[Mr645]

The crank on my bike is an Oval 700 series and I have no issues with it, except now for the third time the round threaded insert that keeps the crank arm on keep coming loose.
My LBS where I also bought the bike tells me it should not happen. 1 times, ok perhaps loose from the factory, but three times? They are suggesting I bring the bike in and they replace the crank assembly under warranty.
Any other ideas on why this happens?

 

[Jwiffle]

Possibly it wasn't tight enough when initially installed, and with some use the crank arm or spindle got a little worn so now the arm comes off easily. If it's not worn, maybe a little thread locker will do the trick. Otherwise, just get it warrantied at your shop like they suggest. Because it really shouldn't keep coming loose.

 

[Mr645]

I took it over to my LBS today and they suggested two things. First, a little locktite and second, while marked 1nm torque, I can go much tighter on it, try double that and if it comes loose again we could consider replacing the whole crank, but careful examination did not show any wear or any reason why this has happened 3 times.

 

[RaptorTC]

I had a heck of a time with my Oval 730 crankset that came on my CX bike. The bolt worked its way loose and I had no choice but to ride it home like that. After that it kept coming loose and in time widened the splines on the crank arm to the point where there was tons of play in it despite being tight. I ended up scoring a Sram Rival crankset on eBay for $40 and now all is well.

 

[Roland44]

I had a heck of a time with my Oval 730 crankset that came on my CX bike. The bolt worked its way loose and I had no choice but to ride it home like that. After that it kept coming loose and in time widened the splines on the crank arm to the point where there was tons of play in it despite being tight. I ended up scoring a Sram Rival crankset on eBay for $40 and now all is well.

Nice deal you got there. I should be searching eBay more often I guess. I am glad everything works fine now!

 

[junior1210]

The crank on my bike is an Oval 700 series and I have no issues with it, except now for the third time the round threaded insert that keeps the crank arm on keep coming loose.
My LBS where I also bought the bike tells me it should not happen. 1 times, ok perhaps loose from the factory, but three times? They are suggesting I bring the bike in and they replace the crank assembly under warranty.
Any other ideas on why this happens?

I've had similar problems with FSA cranks with external BB. Loc-Tite 242 on the threads and 261 (if I remember right) on the splines has worked well to keep everything tight.

 

[looigi]

1 nm? I'm not familiar with this crankset specifically. Is this the retaining bolt that's coming loose or is it a ring that the head of the bolt bears against when loosened to self-extract the crank arm?

 

[JCavilia]

Since the shop is offering to replace it on warranty, why are you fussing about it further? It seems to be defective, and it's probably been damaged by the repeated loosening. Just get a new one and be done with it. If the new one mucks up, then maybe make a replacement decision; but at the moment you're being offered a no-cost fix. Why not take it?