I have a 30 sp tourer that runs Tiagra sti, a 10sp rear mtb cassette and an xt rear 9sp mech.

the rear cassette is shimano and i must say that shifing is fantastic until I select the next to lowest gear on the rear cassette.

It immediately sounds and feels as if it wants to jump out of that ratio and becomes noisy. When i view it in the work stand i can seee the mech cage moving as though the jockey wheels are unhappy with chain fit or tension.

I have put a new cassette on but the problem persists. Thinking back it seems to have always done this……the chain is not worn using my chain checker…

Can anyone

Check for bent or damaged teeth on the cassette.

Can anyone shed any light on what is going on her and help me find the problem?

I put a brand new xt cassette on yday. The problem continues in exactly the same gear…..

Do you have enough clearance between mech and cassette? May have to try a longer screw in the b adjust position, like folks using dinner plates do.

I had thought there was interference between top jockey wheel and the cassette but that doesnt seem to be the case. It also runs just fine when it goes into the largest rear sprocket. Its just the last but one that’s the problem

Have you checked the hanger alignment?

I bought a 9sp XT rear mech from my LBS which turned out to have the wrong pull ratio. So it would always skip in the way you describe. It had just been made that way. Very strange.

Replacing it (FOC) fixed the problem.

Can you post up a picture?

Hanger alignment

Is the cable attached to the mech in the right place (the correct side of the clamp?)

Is it possible that the hanger can have a effect in just one of the ratios but leave those immediately adjacent to it working fine?

Does that mean that I have to buy a glamorous hanger alignment tool from Park?

faulty shifter?

try setting it up offset by 1 click and see if the problem moves perhaps?

The big difference between the largest & second largest cog is,on the largest cog the sides of the chain has nothing to rub against.Sorry to ask the obvious ,but are you using a 10 speed chain?

There’s an X Tools alignment tool that I much prefer to the Park one (which we have at work).

I know some folk reckon to put an extra (thin) spacer between the block of gears and the last single one in order to get the shifting better. I’ve not needed to.

Lifeline is the same as the x-tools one I think. I got mine from Wiggle for 22 quid. Well worth it.

That’s an interesting thought on the spacer above… I’ve got exactly the same issue on the road bike, running Campag Veloce and it just skips from 9th to 10th when i click it… If i adjust it so i get 9th, i miss out on 2nd…. which i think i’ll need more than 9th…
But a spacer in to move 9th slightly over may work….

I havnt actually checked the chain is 10sp….im off to do that now!

What version of Tiagra? I assume the pull ratio is correct (It changed at 4600).

Otherwise, dirty cables, wobbly mech or misaligned hanger (or combination of the above).

Video!

You have tried playing with the cable tension?

That’s an interesting thought on the spacer above… I’ve got exactly the same issue on the road bike, running Campag Veloce and it just skips from 9th to 10th when i click it… If i adjust it so i get 9th, i miss out on 2nd…. which i think i’ll need more than 9th…
But a spacer in to move 9th slightly over may work…

Was having the exact same issue with 10spd Tiagra, just installed a spacer now and its solved it.

@Creg…..where are you installing the spacer? What sort of spacer is it? The cassette i have put on now is xt. This has the 3 largest sprockets mounted on an aluminium spider. Im not sure how a spacer would help.

sorry if im being dim!

Put the 3-cog block on, then the spacer, then carry on as normal. You want a 1.0mm (or thereabouts)spacer. There should still be enough thread for the lockring to engage once all the sprockets are on.

As I said, I’ve not had to do this but I know some folk have.

Surely you shouldn’t need to do put a spacer in the middle of the block?

Is the cable attached to the mech in the right place (the correct side of the clamp?)

+1

Ok…will check the cable attachment too….

I shall report back 🙂

You’d think not but remember that this is trying to get a “non-compatible” setup working; 10 speed road shifters, 10 speed MTB cassette and 9 speed MTB mech. I’m just passing on something I’ve heard.

Turns out it actually didn’t fix my issue.

It’s actually my cassette that’s wrong. I didn’t realise that they changed the shifting ratios for tiagra 4700 and it needs a specific cassette (according to crc anyway). New cassette ordered so hopefully it should fix it.

Hmm, mine came from the shop like this…i will check what series Tiagra my shifters are…

I had the same replaced the hanger; end of problem.

How can i tell what series my Tiagra shifters are? Where is it marked on the sti unit?

How can i tell what series my Tiagra shifters are?

I think the 4700 has the hidden cable routing and, although 10 speed, have the same pull ratio as 11 speed road. AFAICT you would need the tiagra rear mech or an 11 speed road mech for the 4700 shifters.

AFAIK, the older Tiagra shifters have flappy cables and the same cable pull as 10 speed.

There’s probably some sort of adaptor / alternative cable routing that would get your setup working. I’m a bit dubious that a new cassette is the answer, but I’m not an expert.

The bike is 12 months old and has hidden brake cables but the gear cables emerge from the top of the sti unit.

It was an off the shelf bike so im surprised it may havr incompatable groupset parts…