Tag: grease

#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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November 16th – A hazardous time of year, and not just just from the black ice on frosty mornings. Many hazards lurk in the damp autumn waiting to steal the wheels from beneath the incautious cyclist – one of the worst is leaf mulch. Fallen leaves, ground into a pulp by feet and wheels turn to a soapy, slippery grease that makes steering and braking a hazard.Combine this on busy roads with road grime, oil and spilled diesel and you have a real recipe for an accident.

The only answer is to be vigilant, beware of the front brake and take it easy.

July 4th – Cycling in the rain presents its own hazards and challenges, but is especially hazardous in the rain following a dry, hot spell.

When roads are dry, the surface, which is gently abrasive, grinds residue from tyres and collects dust and detritus, plant matter and spilled oil, fuel and other gunk from vehicles. This is all mixed and blended by traffic action into a sort of instant-grease mix, just waiting for the atmosphere to add water.

When the rains come, the first surface waters and traffic action mingle with the powder to form a soapy, slippery fluid that actively foams and reduces traction. Cornering in this goop on narrow tires can be like cornering on ice, and wheel spin and braking skids are the signs that one needs to be careful.

Most car drivers would never notice it. But anyone on two wheels dreads the sight of the white froth on a road surface, just waiting to steel your wheels from under you.

Take care folks.

November 5th – In Shenstone, a timely reminder of the season. The roads were thick with leaf pulp, caused by the action of traffic on fallen leaves. It looks muddy, but it’s also soapy and greasy. Hitting this goop on road tyres can be a sobering experience as it’s apt to steal your wheels from under you; the balsam and sap mix to form a lubricant that remains, even after the debris is removed, so take care anywhere where there are overhanging trees – from up on the Chase, to residential suburbia.