Drivetrain overhaul

Drivetrain Drivechain Drivetrain

I'd done pretty well on the fitness side continuing to ride the 'Shift through the winter, but the muddy/sandy conditions had really taken their toll on the drivetrain. There were also some rattly annoyances I wanted to sort out, primarily the complete loss of all (!) the bolts securing the rear mudguard in place.

To get rid of this goop I took the whole rear derailler, rear cassette sprockets and chainwheels apart and soaked them in white spirit. Once clean it became obvious that the derailler's jockey wheels had become extremely worn. In fact, "worn" is an understatement - they had totally changed shape to resemble ninja stars. Moreover I was very puzzled how they'd ever fitted onto the spindle - the axle hole on one of them was far too big. It was only after searching around for ages looking for a missing bushing that I realised that over a million revolutions it'd just worn that way.

The extremely worn jockey wheels, compared to some new equivalents (top). Not only are they a totally different shape...

Though they'd had a few years abuse, I was still a bit shocked so little of the wheels were left (on the plus side, shifting was still pretty much ok, so it just shows what margins of tolerance there were). Nevertheless I thought it'd be a fun challenge to try to get hold of some improved wheels that might wear a bit slower, particularly around the bearing, which in the cheap ones was a metal-on-plastic "Flintstone" wheel - i.e. one with no bearing at all. No wonder it wore down!

Wilma!!! The wheel without a bushing had worn so much around the axle that it had a far bigger hole in it than it needed, and would wobble any-which-way. Surely I could do better than a bearing design from the stone-age?

My ideal wheel here would be as indestructible and maintenance-free as possible. Most higher quality wheels use sealed ceramic bearings - which are better, but also more temperamental and can apparently fail completely, i.e. the wheel will stop going around. My top jockey wheel already had a "bushing" bearing - a cylindrical collar made of metal that was a bit rough, but much less worn.

My solution was to spend £5 more and buy replacement wheels intended for a much fancier derailler. It's difficult to get the spec of these, but I had it on good authority that they contained ceramic bushings. Now quite rare, these used to be the quality solution for this sort of wheel.The wheels are for a 10-speed but fit perfectly in my derailler.

An unusual ceramic-on-ceramic bushing on the jockey wheel. These are pretty much indestructible and barely need lubricating. They're not even very expensive, but are a bit hard to find.

The chain was pretty worn and I figured a new one was in order, but gratifyingly my remixed cassette (made of sprockets taken from other cassettes during Covid parts shortage) was still performing and lasted really well. As a bonus it's now easy to take the sprockets apart and clean them really thoroughly.

I was taking a long, hard look at my chainrings and cranks. They were a very basic set I'd had since I first built the bike, and while I'd switched out the worn middle ring a few years ago, were really very worn. They were also extremely heavy - a quick investigate with a magnet indicated the whole thing, including the big ring and cranks, was made of steel. The big ring alone weighed the best part of a kilo!

Weight is not high up my priority list by any means, but for basic-quality rings that seemed a bit ridiculous. What I really wanted were Middleburn Hardcoat rings - these used to be manufactured up in Cumbria and had a reputation for extreme wear-resistance. Unfortunately Middleburn shut down a few years back when the owner retired(it was not a big concern) - and obtaining them new is very difficult. So when I saw a really nice complete set on ebay which was actually square-taper ... even though it was £150, I couldn't resist.

Barely used Middleburn cranks. All three rings have the distinctive dull-copper "Hardcoat" - which combined with the odd spider - is very unusual

Compared to my old cranks, which look very rubbed and worn in comparison

Of course this meant moving my pedals off my old cranks. Once I'd actually managed to get them off, I noticed that one pedal body was actually in the process of completely unscrewing itself from the spindle! I've seen this happen very slowly over time before - it tends to lead to metal fatigue and eventually the snapping of the pedal cage, something which is very inconvenient if it happens far from home (have you ever tried riding 10 miles using only one pedal? I have. Not keen to repeat...).

Just slowly working its way loose from the body of the pedal. Eventually this will fail in the middle of nowhere, leading to an un-pedalable bike...

Slowly working the screws back in - some force required. This won't last forever, but there'll be much less movement (and hence metal fatigue) on each stroke now

Fortunately catching it in time tends to preserve the pedal for a while longer. I've nonetheless gone a bought some replacements (as well as replacement UN-55 square-taper bottom bracket - after I learnt Shimano have discontinued them!).

Definitely the nicest crank and chainrings I've ever owned

The big ring is quite a bit larger - 46 teeth up from 42. Importantly, though, the smallest is the same (22) meaning I keep my very low gear.

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