Author Topic: Broken Twistshifter Bracket  (Read 359 times)

High Moors Drifter

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Broken Twistshifter Bracket
« on: August 19, 2018, 03:59:22 PM »
Just started out on a ride this afternoon and noticed the whole twistshifter was moving on the handle bars when changing gear. I stopped expecting to just tighten the screws holding the shifter in place but instead found the bracket had sheared in two. Considering my mileage on the bike is not that high and itís only ridden on metalled roads Iím quite surprised. Anyone else had this problem? Iím hoping I donít have to replace the whole shifter which will be an expensive exercise.

Id.

geocycle

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Re: Broken Twistshifter Bracket
« Reply #1 on: August 19, 2018, 04:12:40 PM »
Oh no! Never heard of that happening. Which shifter have you got?
 

Andre Jute

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Re: Broken Twistshifter Bracket
« Reply #2 on: August 20, 2018, 12:02:24 AM »
Never heard of such a thing before.

It is possible you simply got a rogue piece of metal.

However, the most likely cause is over-tightening, possibly repeated over-tightening.

See about a torque wrench, which measures tension on fasteners, at http://thorncyclesforum.co.uk/index.php?topic=13067.0

Prince of Darkness

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Re: Broken Twistshifter Bracket
« Reply #3 on: August 20, 2018, 01:40:50 PM »
I had the same thing happen. Put it down to over tightening as well. Those brackets are very lightly made and I think care needs to be taken not to over tighten. Still don't have a torque wrench, but I took more care with the new one :)
The bracket can be bought as a separate item, not too expensive.

High Moors Drifter

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Re: Broken Twistshifter Bracket
« Reply #4 on: August 20, 2018, 07:05:49 PM »
Thanks for the responses.

The shifter is the wave design itís fitted to a Mercury purchased from SJS in June 2015. Iíve not moved or adjusted the shifter hence itís not been tightened since originally fitted. After this time itís unlikely to be covered by any guarantee and Iím hoping I donít have to purchase a complete shifter at £69.99.

Iíve as yet to contact SJS to see if itís possible to just purchase the pulley enclosure.


Id

Prince of Darkness

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Re: Broken Twistshifter Bracket
« Reply #5 on: August 21, 2018, 08:38:01 AM »
Costs £15.99 from SJSC :)

Dave Whittle Thorn Workshop

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Re: Broken Twistshifter Bracket
« Reply #6 on: August 23, 2018, 09:57:30 AM »
You probably just need https://www.sjscycles.co.uk/hub-spares/rohloff-tx20-screws-clamp-for-twistshifter-light-8193/

Its intentionally weak (like a fuse) so that it shears before damaging the handlebar, it was introduced as part of the twist-shifter light concept with the advent of carbon and thin walled alloy bars.

High Moors Drifter

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Re: Broken Twistshifter Bracket
« Reply #7 on: August 25, 2018, 04:33:23 PM »
You probably just need https://www.sjscycles.co.uk/hub-spares/rohloff-tx20-screws-clamp-for-twistshifter-light-8193/

Its intentionally weak (like a fuse) so that it shears before damaging the handlebar, it was introduced as part of the twist-shifter light concept with the advent of carbon and thin walled alloy bars.

Dave.

Thanks for that, order just placed. Still a bit concerned how or what caused the failure. Quite often I ride with my hand on the twistgrip, the roads here can be very rough with broken surfaces, cattle grids and speed humps such that Iíve lost three rear lights that have shaken loose from my saddle tool bag when riding at speed, could this place extra stress on the clamp?

Regards Id.

Prince of Darkness

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Re: Broken Twistshifter Bracket
« Reply #8 on: August 25, 2018, 10:47:48 PM »
I think it is just like Dave said, it is deliberately engineered to be weak in order to prevent the risk of causing damage to lightweight carbon fibre or thin walled aluminium handlebars. Better a broken bracket than a catastrophic failure of the bar! :) If, like me, you fitted the shifter without using a torque wrench, it would be very easy to over tension the bracket. Of course, if you did use a torque wrench set to the appropriate force, then that does not apply ;)

High Moors Drifter

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Re: Broken Twistshifter Bracket
« Reply #9 on: August 26, 2018, 09:01:44 PM »
I think it is just like Dave said, it is deliberately engineered to be weak in order to prevent the risk of causing damage to lightweight carbon fibre or thin walled aluminium handlebars. Better a broken bracket than a catastrophic failure of the bar! :) If, like me, you fitted the shifter without using a torque wrench, it would be very easy to over tension the bracket. Of course, if you did use a torque wrench set to the appropriate force, then that does not apply ;)

The shifter was fitted by SJS and hasnít been touched by me since purchasing the bike. Iím sure they fitted this correctly, Iím just keen to find out if my use of the bike contributed to the failure.


Id

Danneaux

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Re: Broken Twistshifter Bracket
« Reply #10 on: August 26, 2018, 11:12:33 PM »
Quote
...Iím just keen to find out if my use of the bike contributed to the failure.
Maybe the consequence of time and vibration?

Best,

Dan.

Dave Whittle Thorn Workshop

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Re: Broken Twistshifter Bracket
« Reply #11 on: August 28, 2018, 12:04:47 PM »
Quote
Dave.

Thanks for that, order just placed. Still a bit concerned how or what caused the failure. Quite often I ride with my hand on the twistgrip, the roads here can be very rough with broken surfaces, cattle grids and speed humps such that Iíve lost three rear lights that have shaken loose from my saddle tool bag when riding at speed, could this place extra stress on the clamp?

Regards Id.

Probably the case, we generally suggest avoiding riding full time on the shifter, its not the most ergonomic shape and can lead to nerve problems.