Im looking to change my rear casette to an 11-40. At present it is 11-32 with R8000 GS derailleur, my front is Ultegra R8000 50-34. What do i need to do this and how easy is it?. I'm not that mechanically minded. Thanks.

One of these I think. Haven't done it myself

https://www.wolftoothcomponents.com/col ... oadlink-dm

Pretty sure the limit on your GS derailleur is 34 teeth. You should get away with fitting a Wolf Tooth Roadlink. These can be a little hit and miss in my experience, but lots of sweating and swearing usually sees them working OK. The B screw will need adjusting. Check YouTube for some tutorials.

https://www.wiggle.co.uk/wolf-tooth-roa ... lsrc=aw.ds

Do you use the 50-11 combo much? You might have more luck swapping for a sub-compact, gravel, or MTB chainset.

ebay goats link as they are much cheaper than the Woolftooth

I dont now much about Shimano as i did it on a SRAM system but what i did was fit a MTB long cage mech and I was able to run 42 rear with a 50/34 cassette
pretty sure 46 rear wuld work as well
No idea how compatible SHimano road and mountain shifter /mechs are though but shiftmate would have a solution if not compatible

Another option would be swapping out the chainset for a GRX which would give you a 30 inner ring.

My Amazon has 50/34 chainrings and a 11-40T, 11 speed cassette. Works fine with an Ultegra RX rear mech. I can completely cross-chain. No Roadlink adapter required.

I'd try it with your existing mech. I only went for the RX as it has the clutch mechanism.

You might need a longer chain.

Gpl23 wrote: ↑Wed Jun 16, 2021 11:36 am Im looking to change my rear casette to an 11-40. At present it is 11-32 with R8000 GS derailleur, my front is Ultegra R8000 50-34. What do i need to do this and how easy is it?. I'm not that mechanically minded. Thanks.

Have you thought about just gwtting an 11-34 cassette. Added advantage is (shimano) is compatible with both 10 and 11 speed hubs by removingnthe spacer. It gives you a ratio of 1 which is a massive jump from 34/30..

Try it, you might like it, I did...

I just went with my existing set up at the rear (11-32) and stuck an MTB chainset on. My top gear is quite spinny but I don't miss the 50 tooth chainring at all. At the bottom end I've ended up going lower and lower so I started out with a 28 granny ring, went down to a 24 and am now running a 22! It's great, I spend most my time on the "big" ring (which is a 34) but I know I have super low bail out gears for off-road climbs and for riding with luggage on. I did have to faff about a bit with cable tensions to get it shifting well but it's been on for over a year now with zero issues. My shifters are GRX, rear mech GRX with a Deore chainset and SLX side pull front mech.

I'm pretty sure I have that exact setup on my road bike, with no goat link.

If it stops chucking down, I'll go and have a look...

Whilst waiting for the rain to stop, I checked the spec of the derailleur - it has a capacity of 39T, and you need 16 + 29, so it would appear that a goat link is required.

https://bike.shimano.com/en-EU/product/ ... 00-GS.html

I must have a slightly different setup

The gear ranges that Shimano publish are notoriously conservative. As above, I'm managing a 45T (50-34 and 40-11) difference without a Goatlink/Roadlink.

Ok, there was a lull in the rain, and I've popped down the shed.

R8000 GS rear mech - states 34T on the box
Fitted to my bike with an 11-40 cassette and a 50-34 chainset - NO Goat link.
B-screw dialled in pretty much all the way

Been working fine for a couple of years

YMMV

Thanks for all the advice. Im going with the 11 40 on the back option as the rest of my set up won't need upgraded.
My chain is 118 link and according to online chain length calculator it should be ok as well.
Maybe in the future i will upgrade to full grx one part at a time.

It’s worth upgrading the rear just for a clutch mechanism if you don’t have it already

Gpl23 wrote: ↑Sat Jun 19, 2021 4:25 pm Thanks for all the advice. Im going with the 11 40 on the back option as the rest of my set up won't need upgraded.
My chain is 118 link and according to online chain length calculator it should be ok as well.
Maybe in the future i will upgrade to full grx one part at a time.

Is it a new chain?
If not, there may no longer be 118 links

belugabob wrote: ↑Sun Jun 20, 2021 12:43 pm

Gpl23 wrote: ↑Sat Jun 19, 2021 4:25 pm Thanks for all the advice. Im going with the 11 40 on the back option as the rest of my set up won't need upgraded.
My chain is 118 link and according to online chain length calculator it should be ok as well.
Maybe in the future i will upgrade to full grx one part at a time.

Is it a new chain?
If not, there may no longer be 118 links

Ah yes forgot about that. New cassette new chain. Will add that to shopping list cheers.