Tag: rear

#365daysofbiking Ring of no confidence

Thursday, October 15th 2020 – An interesting one here for the Bob Big Book of Mechanical Failures.

A bike I look after has an 11 speed rear sprocket cassette – Shimano CS M7000 XTR. Like all hyperglide Shimano cassettes 11 speed and below, it fits on the free hub splined body by sliding on to an asymmetrical groove pattern to ensure all components are correctly aligned synchronously for smooth gear changes. The whole lot is held on by a fine threaded, normally tightening lockring, driven with a special tool.

Unlike lower range cassettes, which are generally 2 or 3 piece, this arrangement turns out to be discrete sprockets for all but the largest three, and appropriate spacers which you stack on the free hub before applying the lockring. The lockring should actually tighten by precession and has grooves and a crinkle washer to stop it coming loose.

So why did this factory assembled cassette locking undo itself, allowing the ring and smallest few sprockets to tumble off the free hub and grind against the inside of the frame? I think personally because it wasn’t tightened enough in the factory.

The ring looked bad at first, until I realised that the silver ribbon was not swarf but the remnants of a foil table on the ring.

Cleaned and popped back together, all worked well. But in all my years, I’ve never seen that happen before.

Check your bikes folks. This could have been nasty.

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#365daysofbiking Cubic

January 13th – I’ve been given a new rear light to try out, a Bontrager Flare RT. it’s a funny little black cube, about an inch square. It’s eye-burningly bright, with multiple modes, an ambient light sensor, and a shocking degree of intelligence and connected features.

It’s got bluetooth and ant+ wireless communications, so it links to my bike computer and a nifty app lets me control the light, change it’s pattern and have it detect deceleration and work like a brake light too.

The instructions are bizarre and opaque. It’s not got great battery life, but it does recharge via USB. But it’s certainly bright and very, very red.

I not sure what problem it’s trying to solve, but it’s a fun, impressive thing for sure. And it’s actually pretty cheap for the huge amount of tech it’s bristling with.

I’ll report back when I’ve got a feel for it’s quirks.

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July 16th – In the bike shed at Telford, something that worries and irritates me.

So many companies sell seat post mounting rear lights and reflectors, which seem like a good idea.

Until the rider wears a jacket that overhangs the saddle. Or uses a carrier.

I’m surprised this issue never, ever seems to have been addressed.