Bike refitting in times of part shortages

After the almost failure of my drivetrain during the rather gruelling final day of my domestic tour (to Hull and Back) at the start of the year, I faced up to the Shift needing a little more maintenance that usual. No problem - I enjoy working on the bike, and even though I wasn't riding it too much it would be worth getting it into good condition.

First step was new pedals, and a new chain. Unfortunately, when I took it out for a trial I realised there was something seriously amiss - the chain skipped violently almost every other stroke, but only in my most-used gears. After enduring one of my weirdest rides (I completed a 20km loop, using only my biggest and smallest two sprockets ... try this, it's a challenge!) - during which I messed around repeatedly with the jockey wheels (I do have form in mixing these around) and derailler - it became very clear that my cassette was badly worn. Dammit!

Well, again, no worries. The cassette I've used for years are the pretty basic Shimano ("Megarange") 8 speed. They seem to be produced in the thousands, and typically could be had for the amazing price of £10 or so.

But that was before the pandemic. I now discovered that - presumably due to a combination of lack of production in Malaysia and increased demand from new cyclists - they now could not be obtained for either love nor money. The absolute best I could find was £40 - and that was if I drove 50 miles to pick one up. The "Megarange" brand itself is no longer used, and I wondered if perhaps it had been discontinued. This would be a bit of a downer, since I really love the super-low 34 tooth granny cog, but don't really have any desire to move away from 8 speed.

For fun, I had previously experimented with whether it was possible to take modern cassettes apart and rearrange the sprockets as Sheldon Brown describes. I found that, after drilling out the rivets on an old cassette, all the sprockets and spacers were freed (there is no "spider" etc). This raised an intriguing possibility - if I could obtain a different 8 speed with the right sprockets to replace my worn intermediate cogs, I could transplant the (hardly worn) large 34-tooth "megarange" sprocket I already had onto that and make myself a replacement cassette.

This is something I would never have considered when new components had been easy to obtain. But now it seemed worth a try. I bought a HG41 11-30 cassette for £20 on ebay, and practiced my rivet-drilling technique again to take apart my existing spindle.

When the new cassette arrived, I (carefully!) subjected it to the same drilling method. Then I just switched the biggest 30 tooth for the old 34 tooth, made sure the spacers were still in place, and reassembled it on the freehub body (I didn't even replace the rivets, which are apparently not needed).

Disassembling the new cassette, and removing the 30-tooth biggest sprocket (left)

Reassembly - comparing the old 34 tooth ("megarange") cog which goes in place of the new 30 tooth at the base. While invaluable on loaded climbs, it (obviously) doesn't get heavily used, so isn't badly worn like the intermediate sprockets were.

Reassembling the rest of the new cassette is as easy as sliding it onto the hub.

The smallest sprocket screws on, rather than binds onto the splines, and holds the whole assembly together. No rivets needed!

As usual, I was rather sceptical of the robustness of my handiwork. A couple of years earlier, I had performed a similar bodge with some copper washers to space out a chainwheel - amazingly I had had no trouble with it at all, and (so far) the custom cassette seems to be working well too. No more chain jumping, and shifting is smooth as silk, including onto the 34-tooth (which often has to be done in a hurry). Time will tell!

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Rachael AndersonYou are so clever! Hope no problems develop later.
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2 years ago

Scott AndersonVery impressive. Consider yourself invited along when we visit the UK this summer.
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2 years ago

Jon AylingTo Rachael AndersonThanks Rachael! I'm always a bit wary of my "fixes" - I was particularly surprised the shifting worked without any more trouble. Fingers crossed it won't decide to fail on tour when I'm away from a drill!
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2 years ago

Jon AylingTo Scott AndersonSounds good Scott! With a bit of luck we'll be installed in Cornwall when you come to the UK. Though I can't make any guarantees on my mechanical skills...
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2 years ago

Keith AdamsShimaNO have a clear philosophy of encouraging replacement rather than repair. Their tactics include phasing out perfectly good designs and replacing them with designs that are not notably better, but subtly different enough that they are incompatible with all others.

The riveted cogs are another example. Rather than making it easy to replace a couple worn ones, using the existing cassette body and retaining all the unworn cogs, they rivet the group into a single unit so that less adventurous souls will chuck the whole thing not just the worn bits.

Good on you for having the gumption to swim against their tide.
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2 years ago

Jon AylingTo Keith AdamsThanks Keith, yep I'm finding this out the hard way. I was sort of amazed it would all come apart (and go back together again) without too much trouble. They certainly don't advertise the fact!

I had another experience along those lines with replacing a chainring. I carefully bought a single ring with the right bolt diameter, only to find there were (useless!) plastic tabs preventing it sitting right on my crank. I couldn't be bothered to send it back, so following a lot of filing down (and some bodging involving some copper washers I happened to have lying around) I managed to get it fitted.

Amazingly that worked and I've had no trouble with it (touch wood) for a few years now.
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2 years ago