Anyone upgraded a shimano 105 11-28 to 11-34?

UEX · 2 Jul 2021 at 11:18

Wondering how painful it would be? I have a full 105 r7000 groupset (I think apologies if wrong terminology) 52/38 and 11-28. I live in mad hilly part of Wales and am considering a wider range for the real beast hills.

I'm riding a full carbon canondale supersix with planet x carbon wheels if it matters. Rim brakes.

UTmaniac · 2 Jul 2021 at 12:05

Painful? Maybe for the wallet, but less for the heart/lungs/legs of mortals like myself.

GS cage derailleur and cassette, cost me ~£60 total before Brexit/Covid-flation, took me a couple of hours last summer to set up mainly due to lots of fun with internal routing while replacing the rear cable at the same time (only because it had frayed just before entering brifter) and having not done that sort of maintenance for a long long time.

Definitely worth it for me, moreso having put on ~5Kg since then, even though I only swapped from 11-32 to 11-34. The hills in the western South Downs aren't that long besides Bell/Stoner/Wheatham just north of Petersfield, but there's plenty of ramps that hit up to ~25%, the 11-34 gave me more climbing gear options and a slightly easier bailout for the really nasty stuff like Milland Hill; Speltham Hill; Lynch Lane; Dell Road etc. I don't race and I'm used to it from my commuters' gearing, so 2T jumps for 11-13-15 as the compromise doesn't bother me at all.

Having ridden a few hills with nasty ramps near Prestatyn in the last two years including Gwaenysgor that hits ~33%, a nice "easy" bailout gear is a godsend.

SoliD · 2 Jul 2021 at 12:06

Consider trying to find someone to swap your chainset with to a 50-34 too. PResume you mean 52-36, but usually they're a bit more in demand than 50-34 so may be able to do an easy swap.

UEX · 2 Jul 2021 at 18:15

SoliD said:
Consider trying to find someone to swap your chainset with to a 50-34 too. PResume you mean 52-36, but usually they're a bit more in demand than 50-34 so may be able to do an easy swap.

Hmmm I'd rather not do that as I specifically chose a bike with a 52-11 gear for speed. My hybrid only had a 48-13 as highest and I was spinning on the flats.

So on the shimano 105 derailleur I wouldn't be able to mount the bigger cassette im guessing

SoliD · 2 Jul 2021 at 19:57

50-11 isn't much smaller than 52-11 compared to 48-13.

#Chri5# · 5 Jul 2021 at 09:15

Which 105 rear-mech do you have?

Shimano quote the SS (short cage) at taking a 30:

https://bike.shimano.com/en-EU/product/component/shimano105-r7000/RD-R7000-SS.html

GS (Medium) goes to a 34:

https://bike.shimano.com/en-EU/product/component/shimano105-r7000/RD-R7000-GS.html

There's also the "capacity" of the mech to consider. From memory, that's the difference between the front chainrings added to the difference between the biggest & smallest cogs on the cassette. So if you fitted an 11-32 cassette, (52-38) + (32-11) = 35. The SS is quoted at 35T capacity, so ticks that box.

Shimano are known to be conservative on limits though, so if your chain length is spot on and you don't mind some messing with the limit screws, a SS mech should work with a 11-32 cassette but if you want to do it properly or go for the 34T, then a GS mech (assuming your bike came with a SS) would be on your shopping list with the cassette (and probably a new chain).