Pedal fell off AGAIN!

[figbat]

We could do with some more images of the OP situation - the BB with cranks removed, the driveside, a wider view etc. For whatever reason the shaft is not through the frame enough. Reasons for this could be that the shaft is shorter than expected, there are spacers on the driveside (either on the shaft itself or between the BB bearing and the frame) or it simply hasn't been seated fully. My understanding is that Hollowtech II is a consistent size regarding the cranks themselves, with any differences in frames and BBs handled by spacers. Given that the frame in question here uses a 68mm BB (the narrowest option covered by H-II) there appears to be no obvious reason why the shaft would be too short - if anything it could come out too long if not spaced correctly.

And back to a previous discussion on the pre-load cap. The tightening torque is embossed on the tool (IIRC 0.7 - 1.3Nm so let's say ~1Nm). The tool is 4cm across, so a radius of 2cm, or 0.02m. To achieve a torque of 1Nm would require a force of 50N, so equivalent to a 5kg weight applied tangentially to the rim of the tool. Unfortunately having given a torque value I can't see a way of applying the torque accurately to the tool, which is why I was led to believe the tool was designed to be unable to overtorque the cap when tightened by an average hand.

 

[Willam]

We could do with some more images of the OP situation - the BB with cranks removed, the driveside, a wider view etc. For whatever reason the shaft is not through the frame enough. Reasons for this could be that the shaft is shorter than expected, there are spacers on the driveside (either on the shaft itself or between the BB bearing and the frame) or it simply hasn't been seated fully. My understanding is that Hollowtech II is a consistent size regarding the cranks themselves, with any differences in frames and BBs handled by spacers. Given that the frame in question here uses a 68mm BB (the narrowest option covered by H-II) there appears to be no obvious reason why the shaft would be too short - if anything it could come out too long if not spaced correctly.

And back to a previous discussion on the pre-load cap. The tightening torque is embossed on the tool (IIRC 0.7 - 1.3Nm so let's say ~1Nm). The tool is 4cm across, so a radius of 2cm, or 0.02m. To achieve a torque of 1Nm would require a force of 50N, so equivalent to a 5kg weight applied tangentially to the rim of the tool. Unfortunately having given a torque value I can't see a way of applying the torque accurately to the tool, which is why I was led to believe the tool was designed to be unable to overtorque the cap when tightened by an average hand.

Loads of pics, the pedal has stayed on, tho I still don’t trust it, the distance from the bb cups is a total of around 92mm maybe 1mm less but no more than 92mm.

 

[Cycleops]

92mm. That’s what I’ve got with the spacers on my road/gravel Spech.
Amount of splines showing looks about right.
Fingers crossed eh 👍.

 

[Willam]

92mm. That’s what I’ve got with the spacers on my road/gravel Spech.
Amount of splines showing looks about right.
Fingers crossed eh 👍.

The thing I can’t work out, if you look at inside the crank, only half of it has splines , the other half is smooth, taking into account the splined not being used when the crank is in place, at most there are only around 50% of the available splines used to hold the crank on? Seems a bad design to me, wouldn’t using all the splines be better?

 

[si_c]

There are spacers fitted between the cups and the frame by the looks of it, 5mm worth. Might be worth removing.

 

[Cycleops]

The only possible answers for the ‘missing’ splines are that they have somehow become ‘lost’ or the cranks are not genuine Shimano. Are you sure they are Shimano?
Mine have splines right across.
As si_c says there does look to be some material on the cups but can’t see if this extends beyond the cup ends.

 

[Willam]

There are spacers fitted between the cups and the frame by the looks of it, 5mm worth. Might be worth removing.

I see why it looks like there is a spacer there but it’s the design of the crank, might be the reason for the gap…here is a better picture I don’t see a spacer here.

 

[Willam]

The only possible answers for the ‘missing’ splines are that they have somehow become ‘lost’ or the cranks are not genuine Shimano. Are you sure they are Shimano?
Mine have splines right across.
As si_c says there does look to be some material on the cups but can’t see if this extends beyond the cup ends.

As sure as I can be, Probikekit was the shop. I’ve seen pictures online with the same half smooth and half splindles in the crank arm online.

 

[Willam]

The only possible answers for the ‘missing’ splines are that they have somehow become ‘lost’ or the cranks are not genuine Shimano. Are you sure they are Shimano?
Mine have splines right across.
As si_c says there does look to be some material on the cups but can’t see if this extends beyond the cup ends.

Here is picture from a known online shop with the same half/half crank arm.
https://www.sjscycles.co.uk/cranks/shimano-duraace-fc7900-left-hand-crank-arm-silver-175mm/

 

[Cycleops]

I think it just might be one of those insoluble mysteries.
The only solution I can think of is that Shimano might have changed the design of the cranks at some point. Both mine have splines running it's length of the crank interface so perhaps thats the later incarnation when they discovered cranks were working loose. Who knows, but that's the best idea I can offer. Perhaps others can give some input.

 

[faster]

I think it just might be one of those insoluble mysteries.
The only solution I can think of is that Shimano might have changed the design of the cranks at some point. Both mine have splines running it's length of the crank interface so perhaps thats the later incarnation when they discovered cranks were working loose. Who knows, but that's the best idea I can offer. Perhaps others can give some input.

All of mine are also only half splined.

I don't think the design has ever been changed. If it had, we'd have seen posts about incompatibility between new & old spline designs (particularly relating to crank arm based power meters) . I've never noticed such a post.

If yours really are splined all the way @Cycleops , the only explanation I can think of is that your cranks are counterfeit.

 

[FishFright]

As sure as I can be, Probikekit was the shop. I’ve seen pictures online with the same half smooth and half splindles in the crank arm online.

I've bought a few things from them , there office is pretty close to my home .

 

[Willam]

The funny (ish) think is that every time this thread pops up on my unread list I imagine that the pedal has dropped off AGAIN

Guess what…it dropped off again!

 

[Dogtrousers]

Guess what…it dropped off again!

I told you that Blu-Tack wouldn't hold

 

[Willam]

Waiting on a torque wrench, if the bolts are torqued correctly then I can at least rule that out, I’ve emailed Whyte to see if they have a replacement recommendation, if any one would like to recommend a road 1x ten speed crankset that would be good, around 40 teeth hollowtech.