1x11 Conversion - Rear Mech's

gmacd51

I am currently running 46/36T with a 11-28 cassette and Ultegra 11 speed rear mech (short cage I think) and am considering converting to to a single chainring.

I ride a bit of singletrack/trails and a bit of CX racing (and not on road), but never really use the big ring and could do with being able to spin a tad more up the steep stuff. I am considering fitting 40T/11-32 or 38T/11-32.

I have browsed, but struggled to find all the answers to the following questions (apologies if it has been covered many times before!):

1. Could I use 11-32 on the rear with the Ultegra rear mech?
2. If I wanted anything larger than 32 on the rear (maybe 36), would a long cage or MTB rear mech be needed? Is a clutched mech worth considering?
3. Can a Shimano MTB mech be used with 105 levels I.e. would the pull ratio be the same as a road mech? I assume a SRAM mech couldn't be used with 105 shifters?

Many thanks in advance!

joey54321

1). Not sure, but I know Shimano's official recommendation is sometimes on the conservative side
2). I would say larger than 32 you are definitely in long cage territory.
3). I don't think you can use a Shimano MTB mech in place of a road one. I remember when SRAM first released with its 1:1 ratio it made a big fuss of being able to swap road and mtb parts around which makes me think you can't with SRAM but I am sure someone more informed will be along soon.

What I will say is I have run both converted 1x system and genuine 1x systems (both SRAM Rival) and I think I preferred the converted (just slapped a SuperstatComponenets I/O chainring on). I am sure the clutch mech is a more secure fit but for cross and bridleway type riding the chain never came off with just the narrowwide chainring.

raisinberry777

gmacd51 wrote:

1. Could I use 11-32 on the rear with the Ultegra rear mech?
2. If I wanted anything larger than 32 on the rear (maybe 36), would a long cage or MTB rear mech be needed? Is a clutched mech worth considering?
3. Can a Shimano MTB mech be used with 105 levels I.e. would the pull ratio be the same as a road mech? I assume a SRAM mech couldn't be used with 105 shifters?

Many thanks in advance!

1. Yes
2. No. Cage length choice is dependent on total chain wrap. A 105 5800 RD with a short cage has a total recommended max of 33T (being 50-34 = 16 and 28-11 = 17, add together is 33). With only one ring at the front, even with an 11-36 the total chain wrap is only 25T, well within spec. 11-36 would probably require a derailleur hanger extender, like a Wolftooth Roadlink.
3. No. Different pull ratios (to both parts of the question).

joey54321

raisinberry777 wrote:

gmacd51 wrote:

1. Could I use 11-32 on the rear with the Ultegra rear mech?
2. If I wanted anything larger than 32 on the rear (maybe 36), would a long cage or MTB rear mech be needed? Is a clutched mech worth considering?
3. Can a Shimano MTB mech be used with 105 levels I.e. would the pull ratio be the same as a road mech? I assume a SRAM mech couldn't be used with 105 shifters?

Many thanks in advance!

1. Yes
2. No. Cage length choice is dependent on total chain wrap. A 105 5800 RD with a short cage has a total recommended max of 33T (being 50-34 = 16 and 28-11 = 17, add together is 33). With only one ring at the front, even with an 11-36 the total chain wrap is only 25T, well within spec. 11-36 would probably require a derailleur hanger extender, like a Wolftooth Roadlink.
3. No. Different pull ratios (to both parts of the question).

Spec also includes max gear ratios:

Model Number : RD-5800 GS
Series : 105
Cassette Compatibility : 11
Maximum Sprocket : Low sprocket 32T/ Top sprocket 12T
Minimum Sprocket : Low sprocket 28T / Top sprocket 11T
Maximum Front Difference : 16T
Total Capacity : 37T

Model Number : RD-5800 SS
Series : 105
Cassette Compatibility : 11
Maximum Sprocket : Low sprocket 28T/ Top sprocket 12T
Minimum Sprocket : Low sprocket 23T/ Top sprocket 11T
Maximum Front Difference : 16T
Total Capacity : 33T


So even the long cage (GS I think) is out of spec when you go over 32T. Not to say it won't work, it most likely will, but just to make OP aware.

gmacd51

Great, thanks for the responses.

I think I'll just give 11-32 on the rear a go with the existing mech (with 38T on the front) and see how that goes before considering anything further.

raisinberry777

joey54321 wrote:

raisinberry777 wrote:

gmacd51 wrote:

1. Could I use 11-32 on the rear with the Ultegra rear mech?
2. If I wanted anything larger than 32 on the rear (maybe 36), would a long cage or MTB rear mech be needed? Is a clutched mech worth considering?
3. Can a Shimano MTB mech be used with 105 levels I.e. would the pull ratio be the same as a road mech? I assume a SRAM mech couldn't be used with 105 shifters?

Many thanks in advance!

1. Yes
2. No. Cage length choice is dependent on total chain wrap. A 105 5800 RD with a short cage has a total recommended max of 33T (being 50-34 = 16 and 28-11 = 17, add together is 33). With only one ring at the front, even with an 11-36 the total chain wrap is only 25T, well within spec. 11-36 would probably require a derailleur hanger extender, like a Wolftooth Roadlink.
3. No. Different pull ratios (to both parts of the question).

Spec also includes max gear ratios:

Be that as it may, the upper body geometry between the two (which determines max clearance) is identical.

Alex99

I ran 11-34 on a holiday with a 9s Tigra medium cage rear mech. It was fine. Just try it, but make sure your chain length is OK.

Jterrier

If you go 1x for general use, be careful you dont get rid of half your gear range. Its easy to get it wrong.

As regards using your exisiting rear mech, you can do it but may need to wind the b screw in to avoid the guide pulley hitting the 32 tooth sprocket.

The clutch mech question is moot as to get that you would need to go to a sram groupset, as shimano dont make a road clutch mech and their mtb stuff doesn't work with road shifters. So clutch mech equals new bike tbh. Its also a question of how much chain slap you can tolerate; once the going gets a bit rough those shimano rear mechs start slapping about quite a lot. On basic trail and gravel they are ok.

trek_dan

In my experience Shimano road stuff setup 1x isn't very robust, especially 11 speed. By not using a clutch mech you loose most the advantage of going 1x anyway. I'd either sell the lot and go SRAM or stick with Shimano and go 1x9 so you can use a MTB mech with road shifters.

joey54321

trek_dan wrote:

In my experience Shimano road stuff setup 1x isn't very robust, especially 11 speed. By not using a clutch mech you loose most the advantage of going 1x anyway. I'd either sell the lot and go SRAM or stick with Shimano and go 1x9 so you can use a MTB mech with road shifters.

What would you say the biggest advantage is of going 1x if you loose it without the clutch?
For me its lack of maintenance, more mud clearance and easier to clean, all of which you get without a clutch mech.

Jterrier

joey54321 wrote:

trek_dan wrote:

In my experience Shimano road stuff setup 1x isn't very robust, especially 11 speed. By not using a clutch mech you loose most the advantage of going 1x anyway. I'd either sell the lot and go SRAM or stick with Shimano and go 1x9 so you can use a MTB mech with road shifters.

What would you say the biggest advantage is of going 1x if you loose it without the clutch?
For me its lack of maintenance, more mud clearance and easier to clean, all of which you get without a clutch mech.

You do get all those things, and will have no probs generally, but a clutch basically holds the chain super taut meaning if it gets ragged, i.e you want to throw it down a bumpy descent, then the drivetrain stays silent, you get less chainslap, and your mech hanger doesnt break suddenly, potentially writing your bike off.

trek_dan

joey54321 wrote:

trek_dan wrote:

In my experience Shimano road stuff setup 1x isn't very robust, especially 11 speed. By not using a clutch mech you loose most the advantage of going 1x anyway. I'd either sell the lot and go SRAM or stick with Shimano and go 1x9 so you can use a MTB mech with road shifters.

What would you say the biggest advantage is of going 1x if you loose it without the clutch?
For me its lack of maintenance, more mud clearance and easier to clean, all of which you get without a clutch mech.

One less thing to break. Not really a massive anti clogging measure if you have to run a chain catcher anyway which most people racing on Shimano seem to do.

tsarouxaz

you can use the new r8000 ultegra rear mech which is made for up to 34t so I bet it will work with a 36t too. the new ultegra mechs are quite generous with gear range compatibility.

antonyfromoz

I run sora 9speed as a single ring system and, although I haven't done it yet, I seem to recall reading that there are two settings for the spring in the rear derailleur so you can set it to have firmer resistance (which should reduce chain slap). Aha, found the thread: viewtopic.php?t=13035004

penguin_of_death

If you did want clutched mtb mech for 1x and increased range on the cas JTek make a pulley called a Shiftmate which allows all kinds of weird combinations of shifter and mech as it alters the cable pull

milese

Does 10 speed mtb mech not work with 11 speed road?

964cup

To give you an idea, I've got a 1 x Ultegra Di2 setup on my CX. 46T SRAM CX1 front ring, 11-40 Shimano SLX M7000 cassette, Ultegra 6800 GS derailleur. I had to modify (extend, reverse and bend) the b-screw to get it to clear the 40T, but it works beautifully. I have a 40T front I switch to for more serious off-road or light bike packing type riding. I'm sure it would be better still with one of the new clutch derailleurs, but I've not had a single chain drop incident, nor any serious slap.