[Closed] 2x10 help

I run 3 speed shifter as all my 2x setups are 3x with a ring removed. A combination of the bash ring and not doing it stops me from over shifting.

Adjust the limit screws on your front mech to dial out the extra shift. Or, just don't shift into the the non existent ring.

As suggested, you can use 3x10, tho I changed to SLX m670 as the left shifter can be either 3 or 2 without the expense of XT.

Got mine for £15 off pinkbike.

I run M670's (I think- early dynasys SLX) with the limit trick in 2x10 on my Spicy and SRAM X7 2x10 specific on my Chameleon.
No functional difference other than usual SRAM vs Shimano ergonomics/feel.
Both have double specific FD's (M785 on the Spicy, X7 on the Cham)
I guess you *could* monster the limited triple shifter and break it/the derailleur but really any sensible shifter pushing would be fine.
I believe double/triple switchable SLX/XT only exist in the new ISpec models if you really want to change, but I wouldn't bother personally.
The only advantage of the double specific FDs is the shorter cage - more worth having than the specific shifter but make sure it's got enough capacity for your ring setup.

If they were proper 2x10 shifters, there would be a small screw that turns 90deg and says 3x and 2x on the bottom of the shifter.

I think 770's aren't 2x10, gotta have 780's

You can run 2*10 with a triple shifter as said. The jump between rings is the same, but after a long thread on this a couple of months back and some experimentation, seemed that the better option if using a triple shifter is to set the shift to be between middle and outer stops on the shifter and leave the inner stop alone. Kind of makes sense, then the redundant shift just slackens the cable further and the mech does nothing because it is held by the limit screw, as opposed to the extra shift trying to pull the mech against the outer stop.

I was under the impression my 2 x10 specific chainset is different to a normal 3 ring setup in that the 2 rings are spaces slightly closer together?

If I use a 3 speed shifter won't it be over shifting slightly?

Pretty sure not. Certainly hasn't been an issue on the double chain set / triple shifter set up I have been running

Thanks for the replies so far.

This has thrown me now though as I thought the purpose of 2x10 was that you can use all the gear combinations and effectively get the same ratios as 3x9.

If a 2x10 chainset chainline is no different to a 3x10 chainset chainline whats the point.

I well known bike shop did tell me that the smallest ring on a 2x10 is sort of inbetween the granny ring and middle postion of a 3x10, and the biggest ring on a 2x10 is in the middle compared to the middle and big ring of a 3x10 chainset.

Was this all bull?

Nobody mentioned chainline, just the chainrings on 2x and 3x are the same distance apart, hence you can use the same shifters.

For all of us using a bashring instead of an outer, then the bike shop is right - my 'outer' is just the middle on a triple. The granny being in a different position sounds a bit flakey.

You can always swap the spacers about on your bb to play with chainline a touch, but yes, welcome to the world of hype and the next emperors clothes that require sane men and women to ditch perfectly good drivetrains in search of some new 'nivarna'...

Was this all bull?

Yes.... and no!

The rear chainline (middle of the cassette) on a typical (135mm OLD) mountainbike is 47.5mm. So, for the ideal chainline - middle of cassette lines up with middle of crankset - you'd want the front to be 47.5 also.

However, because of the oversize tubes of MTB pushing the FD outwards, and the need for clearance of the larger chainrings on chainstays, a standard Shimano triple has a chainline of 50mm. So this is further out than ideal, but it doesn't matter too much as most of us rarely use the big ring anyway. It does mean however, that if you convert a triple into a double by just taking the big ring off, your new chainline (hlf way between the granny and middle) is magically 47.5 - the ideal!

Then you get the double specific cranks. For example Shimano's M785 XT double has a chainline of 48.8mm. Again, this is a compromise - further out than ideal so that if running the 40T outer ring there's enough clearance of chainstays. But, its better than a triple, but not quite as good as a triple converted to a double.

Hope that all makes sense... 🙂

And to address some of the other points made above...

The spacing between the rings on double and triple cranksets is the same, as is the spacing between rings on 9 speed and 10 speed cranksets (despite it being widely reported on forums that 10sp cranksets have closer spacing).

A Shimano front shifter (9 speed or 10 speed) will pull exactly 11mm of cable with the first shift, and 7mm with the second. All the 2x3 converter switch does on the newer shifters is make sure you use the middle to top position instead of the bottom to middle, so that you have the right cable pull (7mm) for the 2x FD. So, if using an older shifter without the mode switch, and a 2x FD, just make sure you're using the middle to top position to get the right cable pull. The notable exception to this is if you are using a 9 speed 2x FD (like the M665/7), which were designed for a cable pull of 11mm, so you need to use the bottom to middle position on an old shifter, and switch the mode switch off on the recent shifters.

Adjust the limit-screw and (if you can be arsed) shorten the cable so it won't physically shift in to the non-existent big-ring.

Thanks PerthMtb, I think I understand.

So are the crank arms I have just bought (m785) double, the same as the triple, as in could I convert it to triple should I ever want to?

So are the crank arms I have just bought (m785) double, the same as the triple, as in could I convert it to triple should I ever want to?

The M780 triple and M785 double are the same in some ways and different in others.

The crank [i]arms[/i] themselves are identical. The rings in the middle and inner positions are interchangeable as they are 64 and 104 BCD respectively.

The chainline on the M785 is 48.8mm versus the chainline on the M780 of 50mm, which means the two rings of the M785 are slightly further out (1.3mm) than the equivalent granny and middle ring on an M780. This is for clearance reasons, not to improve the chainline, as the M785 can have up to a 40T chainring in the middle position, versus the M780 only 32T. So, if you then added a big ring to your M785 the chainline would become 51.3mm, and you might have problems using the bottom half of the cassette when in the big ring.

But, that's irrelevant anyway, because you can't physically add a big ring to the M785 because the crank spider is different and doesn't have the cut-outs for fitting a big ring/bash.

So, if you're likely to be swapping between double and triple, or want to run a bash with your double, then you're better off getting an M780.