Ultegra Di2 front mech failure

[fossyant]

When CFRP works right (and the fibre type / lay-up is correctly designed for the task in hand), it's bang on. If it's injection moulded chopped strand, it should be pretty strong in all directions of load.

Looking at the failure, it seems to me that there may well have been an air bubble along some of the fibres - which points to a manufacturing issue. You *really* don't want air bubbles in composite structures...

That 'failure' has written off a very expensive component though. OP needs to see what Shimano/UK Distributor says.

 

[FishFright]

Sorry. Maybe those old fashioned cable operated things aren't so bad after all .

Thats an odd kind of sorry lol

 

[fossyant]

If I'm not wrong, the electric actuator works on the chunky 'metal' back plate, so there shouldn't be much strain on the front CFRP part.

 

[JhnBssll]

The actuator drives the metal backplate, That's correct. Any force applied to the chain is transferred through the failed linkage due to the pivot positions. Upshifts put the part in tension and downshifts put it in compression

 

[Reynard]

That 'failure' has written off a very expensive component though. OP needs to see what Shimano/UK Distributor says.

Yes, of course.

But bottom line is, there shouldn't have been a catastrophic failure like that - usually such a failure would require a pretty significant impact. Therefore seeings that the component was almost new, correctly installed and well-cared-for, the only other conclusion is that it was flawed from the start.

 

[Reynard]

The actuator drives the metal backplate, That's correct. Any force applied to the chain is transferred through the failed linkage due to the pivot positions. Upshifts put the part in tension and downshifts put it in compression

And that (cyclical loading) is exactly what propagates cracks...

 

[fossyant]

Get onto Shimano/UK distributor. My experience of Shimano Mechs, is they are flawless. Had DA/Ultegra/Deore LX/XT for many years and they just work.

SRAM are the buggers for going 'too lightweight' on their MTB Mechs. My X9 is a bit 'skinny', but it works - it's not as tough as my 20 plus year old XT mech.

 

[JhnBssll]

I think it must have been flawed or damaged as you say. I've read reports of them lasting 15 to 20 thousand miles, the 200 miles this one has done should have been 1% of its life, not 100%

 

[fossyant]

Ah, new - back to shop for a new one.

 

[Pumpkin the robot]

I think it must have been flawed or damaged as you say. I've read reports of them lasting 15 to 20 thousand miles, the 200 miles this one has done should have been 1% of its life, not 100%

Mine ultegra has done 34k miles and still going strong.

 

[JhnBssll]

Quick update on this. I had confirmation today that a new Mech has been dispatched. I'm obviously pleased that they're replacing it but I'm disappointed it's taken them this long to dispatch it and also unhappy with their communication; I asked for them to send a replacement in time for this weekends ride and gave them my number to call if there was a problem. They received the failed mech on monday at 9.27am and yet it took them 4 and a half working days to send a replacement, and even then they sent it by standard royal mail with a 3 to 4 day delivery time. Most irritating.

 

[JhnBssll]

Mech arrived this morning, turns out they'd sent it tracked 48 and royal mail had surpassed themselves and delivered it in 24hrs. 5 minutes too late unfortunately as I'd already left for the ride Still, all fitted and working now so hopefully this one will last a little longer