Changed derailleur but...???

[Frimley111R]

Just changed the derailleur on my Boardman MTB but the top jockey wheel is hitting the cassette, no idea why. What am I doing wrong?...

[Davie]

Wind in that little Allen headed bolt that pushes against the derailleur hanger on the frame. That'll drop the rear mech down. There's alignment tools for most set ups but go with about 3mm clearance for starters. You'll likely need to tweak the cable tension etc afterwards again.

[frisbee]

Shimano have really detailed setup instructions for every component they make. Just Google the part number.

[Frimley111R]

Davie said:

Wind in that little Allen headed bolt that pushes against the derailleur hanger on the frame. That'll drop the rear mech down. There's alignment tools for most set ups but go with about 3mm clearance for starters. You'll likely need to tweak the cable tension etc afterwards again.

Ah got it, thank you.

Yes, it goes to the smallest cog on the cassette but misses the three largest.

[Frimley111R]

frisbee said:

Shimano have really detailed setup instructions for every component they make. Just Google the part number.

Ok thanks, nearly there. if only I was 12 years old again, when this type of thing took me 5 minutes!

[POIDH]

As above, you need to pull derailleur backwards using the 'B-tension' screw.
Download the Shimano instructions or fire up a Shimano derailleur instruction on YouTube

[Xenoous]

On a side note, is your hanger bent?

[Discendo Discimus]

Xenoous said:

On a side note, is your hanger bent?

Looks like it!

[_Hoppers]

I'd start by turning the bike the right way up before deciding what adjustments are needed.

[_Rodders_]

Fighting gravity won't be helping but the B tension screw needs adjusting.

[RicksAlfas]

A cheap bike maintenance stand is a revelation.
Mine was about £30 in an Amazon deal and it just folds up when not in use.
You will wonder how you managed without one!

[Frimley111R]

Discendo Discimus said:

Xenoous said:

On a side note, is your hanger bent?

Looks like it!

I don't know, it looks ok. If it is it is only a fraction. Gears are working ok now, I just need to adjust the derailleur to reach the largest gears.

I do have a bike stand but it is wall mounted one and I don't find it that easy to work on

[Xenoous]

Frimley111R said:

Discendo Discimus said:

Xenoous said:

On a side note, is your hanger bent?

Looks like it!

I don't know, it looks ok. If it is it is only a fraction. Gears are working ok now, I just need to adjust the derailleur to reach the largest gears.

I do have a bike stand but it is wall mounted one and I don't find it that easy to work on

Can you get a photo of the rear of the bike from the back? Mine for example (albeit a gravel bike) is completely straight and inline with all cogs

[Frimley111R]

Will do but prob tomorrow

[Frimley111R]

[croyde]

RicksAlfas said:

A cheap bike maintenance stand is a revelation.
Mine was about £30 in an Amazon deal and it just folds up when not in use.
You will wonder how you managed without one!

I'll second this. Got one from Decathlon for £30 and it really helped with renovating my ancient Giant Escape M1.

YouTube and Google AI were a great help too.

[nickfrog]

On the back of the cage there is an engraved guide as to where the chain should be when adjusting the B-screw, you'll need to shine a light towards it from the non-drive side but once you have spotted, it will make sense. You need to be on the biggest cog of course and might have to force the chain there manually if it's reluctant. Or you could adjust the screw for maximum clearance first and then shift to the big cog (it will then work) to fine tune and back it up a bit towards the engraving guide to optimise shifting.

Edited by nickfrog on Friday 11th September 08:52

[Frimley111R]

nickfrog said:

On the back of the cage there is an engraved guide as to where the chain should be when adjusting the B-screw, you'll need to shine a light towards it from the non-drive side but once you have spotted, it will make sense. You need to be on the biggest cog of course and might have to force the chain there manually if it's reluctant. Or you could adjust the screw for maximum clearance first and then shift to the big cog (it will then work) to fine tune and back it up a bit towards the engraving guide to optimise shifting.

Edited by nickfrog on Friday 11th September 08:52

Ok, thank you.

[RicksAlfas]

Might be worth swapping your cable whilst you are in there. The rear mech does look a bit out of line. Does it look better when the bike is the right way up?

[Frimley111R]

Its hard to tell. I could change the hangar but not sure if they are universal (although not looked yet). It's all working smoothly right now I just need to make the above adjustments to get to the largest cog.