Shimano Medium Cage Derailleur Capacity

[Nigelnaturist]

Let me get this right you need to fit a 36th to your road bike can I ask what cassette your looking at i am presuming 11sp if so the only casstte I can see is the SRAM PG-1130 11-12-13-15-17-19-22-25-28-32-36 it matters not this is an example. So you fit that to a front 50/34 and this is what you get figures in ger inches on a 700x23c

my setup

In the example for the 11-36 there is 6 almost identical gears with quit big jumps between, I can see 3 maybe 4 gears close to each other, I ride almost exclusivly on the middle ring, its good upto about 23mph, the inner ring is used where I may need to spin up a hill with greater cad control, but look at the differance on the rear how close the ratios are (I actually prefer my 12-23 closer still with a low gear about 30"), just saying, but to answer your question yes a GS should work providing it clears the rear 36 cog.

 

[bondirob]

Let me get this right you need to fit a 36th to your road bike can I ask what cassette your looking at i am presuming 11sp if so the only casstte I can see is the SRAM PG-1130 11-12-13-15-17-19-22-25-28-32-36 it matters not this is an example. So you fit that to a front 50/34 and this is what you get figures in ger inches on a 700x23c

View attachment 136950

my setup

View attachment 136952

In the example for the 11-36 there is 6 almost identical gears with quit big jumps between, I can see 3 maybe 4 gears close to each other, I ride almost exclusivly on the middle ring, its good upto about 23mph, the inner ring is used where I may need to spin up a hill with greater cad control, but look at the differance on the rear how close the ratios are (I actually prefer my 12-23 closer still with a low gear about 30"), just saying, but to answer your question yes a GS should work providing it clears the rear 36 cog.

Thanks for your reply
I've actually gone for a 9 speed cassette because my other bike has a sora groups and I managed to get a cassette for under £20.
If it works out may change my 11 speed to a 36 or larger.
You can use a lindarets Road link which will allow a cassette upto about 40t

 

[Nigelnaturist]

Thanks for your reply
I've actually gone for a 9 speed cassette because my other bike has a sora groups and I managed to get a cassette for under £20.
If it works out may change my 11 speed to a 36 or larger.
You can use a lindarets Road link which will allow a cassette upto about 40t

I just stick a smaller front ring on, though not sure I can go lower than 26th due to limitation's on the FD 26th might push it to far. I rode as I say the 12-23 which is single thooth steps to 19 and I really miss the 18th, but at 32" I think it was 28x23 it was a bit high for some of the riding I am currently doing.

 

[Ajax Bay]

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?

to answer your question yes a GS should work providing it clears the rear 36 cog

Interesting data on gear lengths, @Nigelnaturist but you don't really substantively answer OP's question: your caveat is germane.

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

Of course some of the gears are the same, but that allows you flexibility to choose when to move from one chainwheel to another. Quite a few of the gears on a double set up don't just "seem the same" they are the same. There's a useful overlap from about 70" to 45" - see @Nigelnaturist 's first table (excluding the two top/bottom sprockets which are to be avoided on the 'wrong' chainring).

 

[Nigelnaturist]

@Ajax Bay I think you might find that because the RD needs to cope with 37th range that a GS cage will be ok, as mine is 39 and it works fine, providing the cage can clear the large 36th rear cog.
That clear enough, the data is on the chart but I should perhaps have made it clearer, by the way the number of gears is irrelevant its range that is important.

 

[Ajax Bay]

the RD needs to cope with 37th range that a GS cage will be ok, as mine is 39 and it works fine

OP has a compact (50-34) and wants to fit a 11-36 (could be 12-36) cassette, as a trial. Besides the issue of the jockey wheel almost certainly rubbing/interfering with/maybe not even making the change to the 36t sprocket (as I suggested at the top of the thread), even with the B screw right in, the capacity he/she needs is 16 + 25 (= 41 for me) so also beyond the specced capacity of a GS RD, and two more than you have on. I agree that if you want really short 'climbing' gears, a triple is the best option. I swapped my 30t for a 28t inner chainwheel, paired with a 12-30 cassette to improve the chances of riding up Hardknott Pass last month (300m in 2.2km), after 200km in the saddle (I made it).

 

[Nigelnaturist]

@Ajax Bay yea should have checked my formula in the spreadsheet sorry. it copied the data from the above row but not the range to the total box.

Edit
Nice one.
I do believe that the compact double is a little over sold, like you I can change the low gearing to suit quite easily, both a 26 and a 28th inner ring in the shed, plus its easy enough to change cassettes, I just keep the chain long enough for the 50x27 combination set up (not that its use, though once or twice I have forgot) but it works and works pretty well, I could go lower but I than start losing the close rear ratios even from a 12-23 to a 12-27 I lose the 18th

 

[bondirob]

Just to give anyone who's interested an update.
I've finally got round to fitting the 36t.
It does work but only just.
The jockey wheel clears the cassette but only just when pedalling forward so the chain/derailleur is under tension.
If I were to back pedal it would foul slightly.
A longer 'b' screw is required and of course a longer chain.
I've done a few rides on it and it shifts fine.
Did a local hill climb which has been used in the national hill climb championships the other day and finished much higher up the strava pecking order amongst my friends then I would have otherwise.

 

[tincaman]

Good progress. You could turn the B screw around so it screws in from the back, that might give you the clearance you need.

 

[bondirob]

Good progress. You could turn the B screw around so it screws in from the back, that might give you the clearance you need.

Thanks, but how do you screw it in from the back if it's meant to be moving the derailleur?

 

[tincaman]

Take the rear mech off the hanger, screw it in from the back just far enough to engage all the threads on the screw. The screw head will then rest on the hanger when you put it back together

 

[bondirob]

Take the rear mech off the hanger, screw it in from the back just far enough to engage all the threads on the screw. The screw head will then rest on the hanger when you put it back together View attachment 336714

Ah I get it now thanks

 

[Winnershsaint]

I've got a trip to the Alps coming up so the question of replacing both chainrings and cassette is a pertinent one. I currently run 52-36 up front with 11-28 out back. I will swap to 50-34 on the front, but then it gets a bit complicated. Ideally I reckon 11-30 would be enough gearing, but that's Dura-Ace territory only now at a price to match, so it looks like cassette wise I will probably have to go to 11-32. Now normally that would entail replacing the small cage mech with the medium, again not a cheap option with Ultegra Di2, however, I am aware that one bike mechanic I know has a work around. Unfortunately I don't know exactly what it is, but it has got something to do with the cage only. He as done this for a few club members prior to their trip to Spain last year.

 

[bondirob]

I've got a trip to the Alps coming up so the question of replacing both chainrings and cassette is a pertinent one. I currently run 52-36 up front with 11-28 out back. I will swap to 50-34 on the front, but then it gets a bit complicated. Ideally I reckon 11-30 would be enough gearing, but that's Dura-Ace territory only now at a price to match, so it looks like cassette wise I will probably have to go to 11-32. Now normally that would entail replacing the small cage mech with the medium, again not a cheap option with Ultegra Di2, however, I am aware that one bike mechanic I know has a work around. Unfortunately I don't know exactly what it is, but it has got something to do with the cage only. He as done this for a few club members prior to their trip to Spain last year.

I'm not sure about di2 but your standard short cage derailleur will work with a 32 despite what the manufacturer and your lbs might say.