HG30 9 spd cassette and KMC 9/73 chain compatibility


Just replaced a SRAM 11-34 9 spd cassette and unknown chain with the Shimano 9spd 11-34 Alivio HG30 and KMC 9 spd chain - only because they were beginning to get tired and it was time to change. Done 200 miles since change. Rear mech is a Deore long cage. All worked fine before I changed cassette and chain. New chain has same number of links. Changed cable inner, lubricated, cable is free and mech also free and well lubed. Whole assembly is in VGC, clean and thoroughly maintained. Not been dropped and bent since new cassette fitted. Shifters not changed. Chain mickled regularly. Cable outer not changed - so cable alignment not changed either.

Despite seemingly getting the cable tension correct (I've changed a few cassettes and chains over the years) it skips with increasing frequency in the 26-30-34 sizes. Tweaking the cable tension makes no difference. No tight links in the chain that I can see, chain joined with KMC missing link. Operation is perfect in the sizes smaller than 26t.

It's a 'bike bent so chain angle front to rear (i.e big front to small rear etc) probably not relevant and anyway the problem is the same despite whichever front ring is in use - the rings are miles away from the cassette!

With no load the mech changes sweetly, no clicking, not ghost shifts. Only when I'm riding does the problem become manifest.

I can't find anything wrong. Anyone got any ideas please?
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South Cheshire
Thanks all for the suggestions, but I don't think it was any of these, but problem appears to be sorted.

On the big sprocket the top jockey wheel was just clearing the sprocket - so B screw should be OK. I did change the section of gear cable outer at the back around the mech when I put a new cable on.

During the week, I had the bike up in the air and was able to inspect closely the alignment of the mech and the larger sprockets, and all seemed OK, and the mech seemed to be in perfect vertical alignment - so cable tension and hanger seemed OK, but I did notice that my new chain had some surface rust - it had been mickled a couple of times. So gave it its first application of Finish Line Dry Lube and worked it well in. The whole arrangement then ran a bit easier.

Rode today and virtually no problems at all.

My suspicion is that the source of the problem was the very low temperatures over the past week (like 0 degC) and the new, manufacturer's grease on the chain. In the lower sprockets the chain makes a fairly tight turn from the top jockey wheel to the cassette sprocket - as you go to higher gears that angle decreases slightly. Maybe, under very cold conditions the viscosity of the new grease between the chain plates is enough to make the chain sluggish in turning through that angle. Whatever, today, riding in about 7 degC and with a more lubricated chain, the problem was effectively non-existent.

Temperature, new grease and some additional lubrication are all that I can see have changed between the problems over the past week, and today. Furthermore, when I fitted the new cassette and chain a couple of weeks ago, the weather was less cold.

I suspect the temperature and new grease. I've some Deore trigger shifters on the way to replace the stock SRAM twist grips, so that might help even more as I'll get a more positive gear change.

Thx for the suggestions anyway.
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