Road Cassette on an MTB/Trecking bike - trouble indexing

[point5clue]

This is sort of ebike related as its on an ebike, but feel free to send me off to a general bike maintenance forum....

When I converted my Dawes Sonoran last year I changed the 11-34 8 speed cassette for a 11-30 figuring that I wouldn't need the lower gears. After a few hundred miles of riding I realise that I spend almost all my time in top few gears which are the same between the two, so have just upgraded yet again to a 12-23.

I can't seem to get it indexed right - I thought all cassettes were basically interchangeable, but does anyone have any experience or tips? It is ok in the lower gears, but just where I expect to be in the smaller cogs it is unreliable shifting up or down!

Would the chain make any difference ? I use cheapo Clarks 7-8 Speed Anti-Rust Chain -


old (indexes perfectly) - Shimano Acera ECSHG418130 Speed Cassette - Silver, 11-30 Teeth
new(trouble at 12-13-14-15 range) - Shimano Sora HG50 8 Speed Cassette - Silver, 12-23 Teeth

 

[tommie]

New cassette = new chain

or have you changed the chain as well?

Also i`d take a link or two out of the chain as you`ve went from 30t to 23t

 

[Deleted member 4366]

The chain shouldn't make a difference. Undo the shifter cable, reset the high end-stop and start again from there.

 

[point5clue]

Yes, Chain is less than 50 miles old - I did my best with it today, and will see how I manage on my commute tomorrow morning.

Funny, it will be dark and freezing, but I look forward to the journey to work now in a way I didn't last year when I was driving.

 

[point5clue]

Finally had a chance to put it on the stand today and adjust properly rather than just stoping on the road, twiddling the barrel and setting off agin.

I just will not shift down cleanly in the higher gears. Adjusting the derailleur in any more means it rattles on the cog. I can however push down two (its a piano shifter) which shifts only one, but rattles, then instantly click up which settles nicely into the desired gear.

Shifting down from 4-3-2-1 is clean, and shifting up is clean all the way. At least this way around I have the option of pushing through two gear in one motion with the piano shifter - long push click is easier than click click push (have I lost you ?)

I'm wondering if the MTB derailleur is just not suitable for such a different type of cassette ?

 

[Deleted member 4366]

Something is sticking - either the cable or the derailleur. You need to put some 3-in-one oil in the right place.

 

[JPGiant]

Check the B screw adjustment is correct - the guide (top) wheel in the derailleur maybe catching the cassette sprocket teeth in some gears.
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