Rear Cassette replacement advice pls

[figbat]

HNY to one and all - well I’ve finally made a start and stripped the GT - had a BB mechanical the other day etc so now just assembling the new parts - have to say although I’m in the “all the gear no idea” squad I’ve really learned a lot from your good selves and trial and error YouTube etc - 24hrs of parts submerged in “Gunk” and I can see light @ the end of the tunnel 👍

Oooh, that brake disc!! 😬

If this has been ridden recently you’ll want to look at the caliper as it looks like it has seized.

 

[HumpTdumpty]

Thanks as I said it’s amateur hour here 🙏

 

[Nigelnightmare]

I think he's taking a very sensible approach in asking a lot of questions BEFORE starting the work.
It's the best way to learn without Buggering everything up.

OP, take your time and keep asking for advice, it's never a waste of time, even if you don't use it/find another method.

 

[HumpTdumpty]

New “old” Shimano BB55 fitted sourced down in Kent quite pleased with myself (sorry) - next amateur advice question pls - re the Chainset for the triple, my BB 68 x 118 they all appear to either be 113 or 122 re chain line re Chainset - don’t really understand it all tbh - does it make any great difference the online bike retailers all say similar re there Q & A along the lines of “should work etc” but no more than that any thoughts or explanations welcome please re which way to go re purchase

Thanks

 

[Cycleops]

Your existing is 118? 122 should work. 113 might conflict with the lower chainstay.
You'll probably have to adjust the RD hi-lo and possibly the front.

 

[Ajax Bay]

The OP is saying they have a 68x118. The UN-55 is discontinued: Shimano's replacement is the BB-300.
Plenty of 118s (or 117.5s) available. Every mm less or more shifts your crankset in or out 0.5mm. Several mm less may result in the inner ring fouling the chainstay. Move the chainline out and the reach across when cross-chaining is unsatisfactory and increased Q factor.
CRC and Halfrauds both have one to fit:
https://www.chainreactioncycles.com/shimano-un300-british-thread-bottom-bracket/rp-prod198919 or
https://www.halfords.com/cycling/bi...les/halfords-bottom-bracket-68mm-475638.html?

 

[HumpTdumpty]

Your existing is 118? 122 should work. 113 might conflict with the lower chainstay.
You'll probably have to adjust the RD hi-lo and possibly the front.

Thanks I’ll give that go appreciate it as ever

 

[HumpTdumpty]

Update new (old) BB and FD fitted with a brand new Chainsett - the joys of a proper torque wrench 🤣🤣🤣- anyway with the weather outside being poor riding conditions this amateur tortoise 🐢 bike mechanic is taking it steady and slow and learning a great deal along the way - now for the brakes, chain and cassette smiling 🙂 here thanks again for all your support and advice

 

[C R]

Update new (old) BB and FD fitted with a brand new Chainsett - the joys of a proper torque wrench 🤣🤣🤣- anyway with the weather outside being poor riding conditions this amateur tortoise 🐢 bike mechanic is taking it steady and slow and learning a great deal along the way - now for the brakes, chain and cassette smiling 🙂 here thanks again for all your support and advice

From the photo it appears that the derailleur is for a much bigger chainset, and it looks like it might catch the chain when in the smallest chainring.

 

[Cycleops]

Agree with @C R . Also looks too high. Should just clear the big ring by the depth of medium screwdriver blade.

 

[C R]

Agree with @C R . Also looks too high. Should just clear the big ring by the depth of medium screwdriver blade.

The problem is that it won't be possible to lower it much further because the cage will catch the chainstay. I'm not even sure it would shift properly to the middle ring.

 

[Ajax Bay]

Agree a slight (1mm) drop of FD needed: gap when over large ring should be 0.5<1mm. OP can check, on stand with chain on small ring, when the chain starts fouling the cage ie the smaller sprockets, and ride being aware of that.

 

[HumpTdumpty]

Ok thanks all mmmmmh - so may have to get a replacement but I’ll try and lower first and “fettle it”

 

[HumpTdumpty]

Evening All after trying unsuccessfully to fit the original FD with the old BB attachment back on (no luck couldn’t get the BB to tighten) have gone and purchased this didn’t brake the bank and I have the original Acera RD on the back still - pls tell me 🙏 that this looks better and a workable fit 🤞

 

[C R]

Evening All after trying unsuccessfully to fit the original FD with the old BB attachment back on (no luck couldn’t get the BB to tighten) have gone and purchased this didn’t brake the bank and I have the original Acera RD on the back still - pls tell me 🙏 that this looks better and a workable fit 🤞

This looks good, the cage is the correct shape for the size of the chainring and it seems to clear the chainstay. The proof will be in the doing.