Left hand crank advice

[tallliman]

I was out riding today and felt something ping against my left ankle. A couple of miles later, I felt that my ankle was hitting my lh crank arm. Closer inspection showed that the central tightening bolt (that I think attaches to the other side of the spindle on 105) was very loose and the crank wobbling. I did the bolt up with my fingers and tightened the side bolts on the crank so I could get home.

I know it's difficult to say via a forum with no pics but is it likely that the crank just worked loose over time and the ping was road debris? Nothing else looks untoward.

 

[Sharky]

If it's a square taper type, I've had very occasional times when the bolt has worked loose. Once it was shortly after refitting and on checking, there was some debris left behind inside the thread, which stopped it from tightening it properly.

But it is extremely rare for them to come loose.

 

[Ajax Bay]

Make/model of chainset and BB please.

 

[tallliman]

Shimano Tiagra triple, not sure on BB

 

[C R]

Sounds like a hollow tech crank. The pinch bolts should not work themselves loose. If you rode for any significant amount of time like that get the splines checked, and the pinch bolts properly torqued.

 

[tallliman]

I had to ride for about an hour to get home but tried to stay off the power as much as I could. Probably 20mins with it loose before tightening as I said above.

Sounds like a bike shop job then.

 

[Cycleops]

For a bolt to remove like that from a square taper (if it is ST) BB and crank is very unusual. Has it had some maintenance a while ago involved crankset removal? Wherever it looks like it wasn't correctly tightened.

 

[tallliman]

For a bolt to remove like that from a square taper (if it is ST) BB and crank is very unusual. Has it had some maintenance a while ago involved crankset removal? Wherever it looks like it wasn't correctly tightened.

It had its annual service about 300miles ago (dont judge me for using the lbs!). If not at that point then probably 4000 miles ago

 

[C R]

For a bolt to remove like that from a square taper (if it is ST) BB and crank is very unusual. Has it had some maintenance a while ago involved crankset removal? Wherever it looks like it wasn't correctly tightened.

Not square taper, tiagra, so hollow tech, it looks like pinch bolts not torqued properly.

 

[Cycleops]

Sounds like a bike shop job then.

Not really, you can check and fix it yourself. Be sure to check the splines aren't damaged. If they are it means a new crank set but I doubt it's that far gone. You'll need a 5mm Allen key and a little plastic pre tensioning tool which fits in the plastic screw (may be lost) so it you don't over tighten it.
You also need to check the little black plastic spacer (9) that fits in the gap of the LH crank is still present.

I know this as I've spend this afternoon fixing one

 

[tallliman]

Thanks, I dont have the plastic tool but will see if I can order one (or just ride into town to the lbs)

 

[Cycleops]

You don't really need it, you could improvise with anything you can fit in. The whole idea is it doesn't need to be too tight.

 

[Darius_Jedburgh]

You don't really need it, you could improvise with anything you can fit in. The whole idea is it doesn't need to be too tight.
View attachment 580548

A broad screwdriver will suffice.

 

[hatler]

Or a 20p piece apparently.

 

[hatler]

Given that it's a triple I think that means that the spacer should be present. If it isn't there, then I've known that result in the crank coming off like that.