Brucey wrote:…..my chum's supercommuter bike is just about due for another chain and freewheel, so other parts are being changed as required too. On the shortlist are
- stainless steel track nuts (the old ones were very rusty but otherwise OK)
- change from a 44T aluminium chainring to a 48T steel chainring (so 48/18 becomes the 'normal' gear)
- outrigger bearing on the rear SA hub brake (the axles eventually break otherwise)
- stainless steel reaction clip for the rear brake (the old one has gone rusty)……….
Ah.... the plans of mice and men; the above was posted in sept 2019 and the track nuts were done shortly after as planned. But the reaction arm clip still isn't done
and the new chain/new freewheel/new chainring/outrigger bearing had to wait until, er,
today.
So any way you look at it, the chain/freewheel should have been utterly done in; it was the filthiest, had been on the longest, had done the most miles, had been used with a worn chainring throughout and had been the most neglected of any used to date; by time/mileage (and comparison with previous chains/freewheels) it was deemed to be 'overdue for replacement' a year ago and then did another year with just an occasional drop of lube.
I'd offered to help my chum fit the outrigger bearing and he said "you don't want to go anywhere near this bike, it is so filthy, I have not cleaned it for over a year". He spent yesterday afternoon stripping and cleaning everything and I just spent a while today helping him refit everything.
Well to say I was surprised by the result is something of an understatement. The transmission that should have been worn out more than any other on this bike basically wasn't; when measured the (freshly cleaned) chain was slightly less than 0.5% worn. The most used sprocket on the freewheel was worn more than 0.5mm (the teeth tops are usually about 3.2mm wide and these were worn to ~2.5mm) but had largely retained its shape. To put this into perspective other chains have worn so badly (in the course of a year or a year and half) that they have not only destroyed the sprockets, the chain has even started to slip, not because of hooking but because the teeth became worn at funny angles. I in no way expected the result we saw and neither did my chum; before measuring the chain we both guessed it would be well over 1% worn.
So what had made the difference? Well, the chain lube, usage, freewheel make and model had been exactly the same as the transmissions used previously on this machine, and if anything the chain had seen less frequent lube than ever before. The only real difference was the chain used. When this chain was fitted (about two and a half years ago) I remember commenting that my chum had spent a bit more than normal on the chain. I may have even commented that "it would have to last longer than normal in order to be good value for money". The chain used was a shimano CN-HG71.
CN-HG71 is currently made by KMC for shimano. I am supposing that it was when this chain was purchased too. KMC describe this chain as having 'chromized pins', and 'enhanced durability'. Shimano recommend it as being suitable for E-bikes as well as others requiring a 6/7/8s chain. On the basis of what we have seen, I would say that one of these chains is at least worth paying double for vs the chains that have been used previously on this machine. The freewheel was replaced anyway but in fact the old one would probably have worked OK with a new chain.
On the basis of the above result you would think another CN-HG71 would be an obvious choice. Well, the new chain was chosen before the wear result was known so the die was already cast and the replacement is a KMC Z7. This chain is not described by KMC has having chromized pins or enhanced durability so it is more or less back to the usual fodder, and I don't expect it to last any better than most of the other previous chains on this machine. However it won't be quite such a good experiment; the chainring size will have changed (altering the pattern of wear on the sprockets) and my chum's commute route has just (about three weeks ago) changed slightly; whilst the distance is about the same the way the roads are gritted will be different.
In other news my chum had removed the brake barrel adjusters in order to clean them properly and refit them with lots of waxoyl. I was surprised that the barrel adjusters had slipped over the deformed part of the cable that had been inside the pinch bolt. Inevitably one cable (for the front brake) didn't go back through the barrel adjuster when my chum reassembled it. I had mentioned my own recent brake cable problem and so when this happened I said 'it probably needs changing anyway". The cables were still the ones originally fitted back in 2012. When the cable was pulled out there were broken strands about 2" away from the nipple in the (aero type) brake lever, just where the cable does a small 'S' bend as it transitions from the lever to the handlebar. The damage wasn't bad but I view it as being another bullet dodged; there were no external signs that the cable was damaged, it still ran smoothly inside the housing, yet it would surely have failed sooner or later.
The outrigger bearing went on without any dramas and should greatly reduce the chances of axle breakage. That is, if it isn't cracked already I suppose. Remarkably the hub bearings (cartridge bearings in this case) are still wonderfully smooth; all that has been done to them is that when they were new I fitted an RS type seal to the outside of each standard (steel-shielded) cartridge and packed them with better quality grease. They have not been touched since then; overdue a fettle then. However time ran short during the service today and they still feel good so they were left alone. The (larger) steel chainring was fitted and this will push the wear from 'mostly on the 16T sprocket' to 'mostly on the 18T sprocket'.
So the main takeaways for me are that
1) if you want to be safe, cables should just be changed at intervals rather than left until they give obvious problems.
2) spending money on better chains is certainly not money wasted.
cheers
