Hello to the infallible STW hive mind. I recently put a 32t 8 speed mech on my Spesh Allez (SORA 8 speed from the factory) in preparation for some more hilly riding I have planned (the bike is only a double and I have old and useless legs – please don’t tell my to MTFU as I may cry).

I did some research and it seemed 8 spd MTB stuff should be compatible with 8 spd road stuff – or so I thought.

I bought a cheap SRAM chain and 32t cassette and it worked pretty well, except even with the B screw reversed there was a bit of interference with the big sprocket and the jockey wheel. Rideable, but “not quite right”.

So – with my birthday coming up I put in a casual request to my dear family for a cheap 8 spd MTB rear mech to finish the job, and joy of joys if a package didn’t arrive yesterday containing a Shimano Acera mech.

Put it on last night and the pull ratio doesn’t seem right – it doesn’t traverse the full cassette so middle gears aren’t properly engaqed and top cog missed entirely.

What have I done wrong? Bad research? Or incorrectly fitted?

Off to make a cup of tea and await sage-like advice…

I know its stating the obvious but have you got the limit screws set right and the tension on the cable?.

I think it should work? The only thing I can think of is the cable can either go inside or outside the clamping bolt on the mech, I think this has something to do with the pull ratio and mixing/matching 8/9/10 speed bits.

Edric 64: I am certainly capable of doing something stupid like forgetting limit screw, but on this occasion I don’t think I have made an obvious mistake.

Nespoonpas: that sounds worth a look. I shall venture to the shed. Wish me luck…

Another obvious question – is it a shimano shifter? If so, it sounds like limit screws

There’s a good bit of interoperability with 7/8/9 spd stuff, so in principle, it should be fine.

Assuming chain length is ok, I’d say to double check the limit screws, tho’ they are normally fine out of the factory … but, if I’m reading the problem correctly, you have got a long-cage rear mech haven’t you? A mid/short cage won’t go as far as a 32 (hmm, actually, is there a mid/short Acera option anyway, or are they all long-cage? (Shimano tech-site here I come 🙄 )).

If it helps 😉 … I run an 11-32 8spd Shimano CS-HG50 cassette on the back of my road bike (on my lovely early 1990’s Dura-Ace 7400 hubs). The shifting is via a set of 9spd Dura-Ace SL7700 bar-end shifters on friction, and a rapid rise XT 9spd M770 (long cage) rear mech, and an XT cable set. No idea what the chain is, probably a Sram PG991, but either way, it all works fantastically well.

Thanks chaps for all the genuinely helpful comment. I was suitably encouraged to go check everything afresh and backed off limit screws and started again. I had got the indexing wrong (cable tension) so one shift never got actioned. All now working properly. Just need to go and find a hill.

Three cheers for the hive mind. Hip hip…

The only thing I can think of is the cable can either go inside or outside the clamping bolt on the mech, I think this has something to do with the pull ratio and mixing/matching 8/9/10 speed bits.

Cable & which side it goes round clamping bolt differs between rapid rise & non rapid rise mechs & yes right royally F’s up changing if you get it wrong 😳