Is this the Shimano short or medium cage derailleur?

[Tangoup51]

For the sake of 60 quid id rather do the derailleur and chain too and not be constantly worrying about the drivetrain while im in the middle of a 100 miler in the peaks.

It's your call, but if I was you i'd save the money and time and heed faith. But have a safe ride anyway,

 

[Milkfloat]

Personally - I would try just a cassette and avoid big-big combinations. Either that or man up and stick with the 28, worse case you walk a little.

 

[Cycleops]

Where's @mickle when you want him?

Tell you what, as I'm a very helpful fair guy I'll swap you my Altus for your Ultegra. How's that? And I won't ask you for any money.

 

[Ajax Bay]

Reality is; you will get away with doing very little other than swapping your cassette.

IT may cause those issues; I already made my warning.

On review, I can see no warning in your earlier posts.

you just work your RD a bit harder than normal

Define 'working the RD a bit harder' please.
I gave no advice on whether the RD would cope (either wrap capacity or largest sprocket limit) as, first we still don't know (aiui) whether the RD is SS or GS. I agree that the best thing on that is to try it.
My suggestion was that the chain should be the correct length (for £20 expenditure (NB brought forward not 'wasted')). Whilst we all try to avoid large/large sometimes it just 'happens' - and given that the mitigation is really easy (new chain right length or insert another link or two into the old chain) that is better advice than 'suck it and see'.
So I reiterate - to @Mark1978 : buy and try the cassette. Expect to have to swap the chain too (and maybe buy it at the same time anyway). Only if you can't get it to go up onto the 32t, and only then, buy a new RD. If it works on the stand, need to check the last bit on the road/hill turning steeper.

 

[Tangoup51]

On review, I can see no warning in your earlier posts.

Define 'working the RD a bit harder' please.
I gave no advice on whether the RD would cope (either wrap capacity or largest sprocket limit) as, first we still don't know (aiui) whether the RD is SS or GS. I agree that the best thing on that is to try it.
My suggestion was that the chain should be the correct length (for £20 expenditure (NB brought forward not 'wasted')). Whilst we all try to avoid large/large sometimes it just 'happens' - and given that the mitigation is really easy (new chain right length or insert another link or two into the old chain) that is better advice than 'suck it and see'.
So I reiterate - to @Mark1978 : buy and try the cassette. Expect to have to swap the chain too (and maybe buy it at the same time anyway). Only if you can't get it to go up onto the 32t, and only then, buy a new RD. If it works on the stand, need to check the last bit on the road/hill turning steeper.

I will first ask you to review my comments more thoroughly as I said in both my messages..

"but that's no in-depth opinion."
"Swapping your RD may be necessary,"

Now, Do you know what happens to an RD when a chain is too short? Now you should understand what I mean by "Working it harder"

I agree with your reiteration, try things first before you go slamming the credit card home.

 

[arch684]

Measure the distance from the center of the top jockey wheel to the center of the bottom jockey wheel.If it's 8.5 cm then it's a gs.

 

[Ajax Bay]

Your 'warnings' were too cryptic for me to so recognise. Maybe others had more insight.

what happens to an RD when a chain is too short? Now you should understand what I mean by "Working it harder"

It breaks (cage plate most likely) or (more probably) you can't get up onto the largest sprocket (as I have said upthread). Neither event could reasonably be described as 'making the RD work harder'. In addition the latter completely stymies the OP's aim.

 

[Venod]

As an alternative you could try a 12-30 cassette, a 30 works for me with a short cage ultegra.

 

[Tangoup51]

Your 'warnings' were too cryptic for me to so recognise. Maybe others had more insight.

It breaks (cage plate most likely) or (more probably) you can't get up onto the largest sprocket (as I have said upthread). Neither event could reasonably be described as 'making the RD work harder'. In addition the latter completely stymies the OP's aim.

If you can show me the day when 1-2 chain links shorter Will BREAK a derailleur cage then I am willing to get on my knees and call you god, instead the derailleur will compensate.

The reality of my proposal of neglecting the chain altogether would put more stress on the derailleur but certainly within a withstand-able tolerance for that proclaimed amount of time of usage.
This is not rocket science, this is common sense please refrain from overthinking.

Also, having less chain links doesn't inhibit your ability to shift up into the hardest gear as much as having an inappropriate sized cage would, infact, I've been able to jump from a 28T to a 34T with a chain optimized for the 28T. (With a long caged derailleur)

 

[arch684]

As an alternative you could try a 12-30 cassette, a 30 works for me with a short cage ultegra.

I also run a 105ss with a 12/30 cassette and yes it works fine

 

[Ajax Bay]

I suggest a little experiment, @Tangoup51 . Next time you replace a chain take a couple of links out, refit it, get on a bit of a hill and with your chain on the large chainwheel, try to change into large and large. Either fail, or sink slowly to your knees and cry whatever you prefer and reach for your credit card. By the way, rocket science is straightforward, it's rocket engineering which is difficult.

 

[Dogtrousers]

Whatever you do make sure it works right cos you won't want to put the 28 back on afterwards once you have luxuriated in the joys of a 28" bottom gear.

 

[Tangoup51]

I suggest a little experiment, @Tangoup51 . Next time you replace a chain take a couple of links out, refit it, get on a bit of a hill and with your chain on the large chainwheel, try to change into large and large. Either fail, or sink slowly to your knees and cry whatever you prefer and reach for your credit card. By the way, rocket science is straightforward, it's rocket engineering which is difficult.

As I said, don't over-think things, that scenario is very unlikely to happen for anyone who is even remotely semi-competent.

Also FYI, That experiment was already concluded on the bike I had mentioned above. a chain fit for 28T working on a 34T, going large-on-large in a bike stand and all it did was stretch the derailleur out, but not enough to snap, break, or destroy it.

1-2 Links isn't enough to destroy anything, maybe damage / wear worse in the long run, but the long run is not what i'm considering here.


.. Must you overthink a common saying? ... I like your nature.

 

[Will Spin]

Probably going to be easier to buy a new bike!

 

[slowmotion]

One other question, if i switch to the medium cage and a 32, will the chain length be ok or will i need to increase it?

Use this chain length calculator. It's never let me down even though I've ridden roughshod over the official Shimano "gear rules".
http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html