Shimano Medium Cage Derailleur Capacity

[bondirob]

What's the absolute maximum size cassette I can use with a Shimano medium cage gs derailleur?
I do know that with the short cage the maximum spec is a 28t cassette but in reality it will work fine with a 32.
The max your supposed to use with a medium cage is a 32t so will it too take an extra 4 teeth enabling me to fit a 36t to my road bike?

 

[Ajax Bay]

will it too take an extra 4 teeth enabling me to fit a 36t to my road bike?

No. A 36t sprocket's radius is ~8mm greater than a 32t. You can screw the B screw right in with the 32t on and see how many mm you have 'spare' (will be very small distance between the 32t and the jockey wheel already). Now imagine a sprocket 8mm lower (ie towards the RD cage).

 

[bondirob]

No. A 36t sprocket's radius is ~8mm greater than a 32t. You can screw the B screw right in with the 32t on and see how many mm you have 'spare' (will be very small distance between the 32t and the jockey wheel already). Now imagine a sprocket 8mm lower (ie towards the RD cage).

Thanks for the reply

 

[Cubist]

No. A 36t sprocket's radius is ~8mm greater than a 32t. You can screw the B screw right in with the 32t on and see how many mm you have 'spare' (will be very small distance between the 32t and the jockey wheel already). Now imagine a sprocket 8mm lower (ie towards the RD cage).

However, some add-on for larger cogs in MTB world involve adding a longer B screw. This enables long cage 10 speed mechs to reach over 42t, so if the difference is only a few mm, there may be a case for simply sourcing a longer B tension screw. Worth a try.

That said, One Up Components designed an add-on cage for Shimano clutch mechs that changes the direction the cage moves as you reach higher cogs. Called the RAD cage, it replaces the outer cage plate, and pivots on a slightly different point to swing the cage away from the biggest cogs. If the arc taken by the standard swinging cage still fouls the cogs despite a longer B screw then that would indicate max capacity.

 

[Ajax Bay]

What chainrings have you got, @bondirob and what rear derailleur?

 

[tincaman]

I have a Shimano 105, 5800 medium GS rear mech running a 36T successfully on my 1x11

 

[bondirob]

Thanks for your advice everyone ive ordered a 12/36 and I'll give it a go when it arrives
I've got 50/34 chain rings and a 105 medium cage

 

[Ajax Bay]

Either the length of chain you use will NOT go round large to large (so if you inadvertently do try that then either it just won't go there, or the chain or the RD will break), OR: the RD will not be able to 'wind up' the spare chain and in small to the smaller sprockets (if you go there) the chain will start fouling the RD cage. You'll be able to hear this racket and will prompt you to change up to the large chainring, pronto.
This is irrespective of whether the jockey wheel fouls up against the 36t sprocket. @tincaman 's experience suggests you might get away with this. But he hasn't got the associated capacity issue (above) because he's on a 1x11 so the cage has no problem wrapping sufficient chain.
Best of luck.

 

[bondirob]

Thanks for the advice it's only an experiment so I'm not fussed if it doesn't work

 

[tincaman]

You will probably have to wind the B screw on the rear mech all the way in

 

[davidphilips]

why not consider fitting a triple chainset at the front and keeping the 32 max or even a 28 at the back you then would have a big range of gears with less of a jump between gears.

 

[al-fresco]

Be interested to hear how you get on. I've got a 34/48 front and an 11-32 rear with a 105 medium cage.

 

[Nigelnaturist]

What's the absolute maximum size cassette I can use with a Shimano medium cage gs derailleur?
I do know that with the short cage the maximum spec is a 28t cassette but in reality it will work fine with a 32.
The max your supposed to use with a medium cage is a 32t so will it too take an extra 4 teeth enabling me to fit a 36t to my road bike?

I think I would be fitting a triple if I want gearing that low, I run a triple 50/38/26 with a 12-27 10sp 25-110" gear range with 12-13-14-15-16-07-19-21-24-27 on the rear, though I do miss the 18th from the 12-23 setup I had, its just I am carrying 5kgs more weight (baggage) and a tad bit more elevation per mile.
I am toying with the idea of creating an 11sp triple when funds allow.

 

[bondirob]

Be interested to hear how you get on. I've got a 34/48 front and an 11-32 rear with a 105 medium cage.

I'll let you know once i get my act together.
I've got a cassette just need a new chain then I'm good to go

 

[bondirob]

I

I think I would be fitting a triple if I want gearing that low, I run a triple 50/38/26 with a 12-27 10sp 25-110" gear range with 12-13-14-15-16-07-19-21-24-27 on the rear, though I do miss the 18th from the 12-23 setup I had, its just I am carrying 5kgs more weight (baggage) and a tad bit more elevation per mile.
I am toying with the idea of creating an 11sp triple when funds allow.

I've already got a triple but i find a few of the gears seem the same that's why I prefer the double