dedicated 2x deraileur on a 3x chainring

ChILd_ReBoRn

Hello everybody

I'm in a process of converting my 3x drive to 2x. I have removed the big ring and added a bash. As expected, some gear variations don't work, because the chainline sucks, but I can live with that for now. I acquired a 2x FD. I know that the CL won't get any better before i buy a true 2x drive, but will the 2x FD work at all on a 2x+bash setup (24/36)? When I flip my shifter 2/3x switch, to be used in the 2x mode, I have to move the deraileur up on the cable, because the 2x rings are differently placed than 3x. When i set it up, the shifting either sucks bad, or the chain rubs on my top and bottom gear combo.

is it worth it to put the 2x fd on? The cage is different, and that could help with the rubbing/shifting issues. or not.

thnx for the heads up.

The Rookie

As you gear size spacing is conservative a 3x would probably work better than a 2x.

Sounds like your setup was pants though.

ChILd_ReBoRn

not sure what does "conservative/pants" mean, but thnx for the info

Dirtydog11

Running a double front mech (FD-M785-10 ) on a triple chainset with bash ...

36 bash ring, 36t and 24t rings and shifter in 2x mode.

IME shifter mode convertor works best in 2x mode when paired with double FD and 3x mode when paired with a triple FD, I think the pull ratios are slightly different between 10 speed double and 10 speed triple FDs as chainring spacing is the same between double and triple chainsets.

10 speed double FD works much better than the triple did, Shimano 10 speed double front mechs are designed to work around 38t outers so butt up nice and close to the bash with out leaving a huge gap for the chain to jump through!

Tried a 10 speed triple and 9 speed double before settling on the 10 speed double.

The Rookie

ChILd_ReBoRn wrote:

not sure what does "conservative/pants" mean, but thnx for the info

Normally 2x rings would have a bigger spacing between them, yours is conservative with a small spacing similar to that between 2 gears of a triple.

Sounds like you made a hash of the install that is why you have problems, not due to an inherent deficiency in the parts.

ChILd_ReBoRn

I don't have a problem as such. I just can't use the whole cassette range as I was supposedly be able to use using a dedicated 2x drive train

I can use the lower half of the cassete with the big ring, and upper half with the granny. Not that I need to use the whole range, but sometimes it would be nice to use 24/11, instead of shifting the front up, and back up..

cooldad

The middle ring of most triples can get the whole cassette, so as Rookie said, something wrong with your set up.

ChILd_ReBoRn

What?

The bike was stock when i got it (Cube LTD SL), deore cranks, xt BB. I took off the big and the middle ring. Added a bash, and a deore 36T instead of the original 32T. And that's it. Tried to remove the bash, using spacers, but the chain kept falling off the big ring too often. Returned the bash, and all is well, except the a fore mentioned chain rub. I Tried to use my shifter in the 2x mode, but when in that mode, the shifter covers the middle and the big ring. So the chain couldn't return to the granny. I re positioned the FD on the cable so that shifter would "think" the derailleur is on the big ring, but it was on the middle. I got it to shift between the granny and the middle, but the chain rub was afwull. (24front/36rear). If I fixed the rub, then the FD couldn't pull up the chain on the front 36T. So I returned the shifter to 3x mode, and used the screws to limit the movement. I had the same setup on my giant, and two bikes before him, and it worked the same. Not all of them were set up by me. There are 2 (3 to be exact, but two of them are thin, so together they are as wide as a normal spacer) spacers on the drive side, and one on the non drive. I really don't know what could be wrong. I can't drive granny/11t without the rub, and I can't drive 36t/36t without the rub either. Theoretically, 36T on the front should cover the whole range, but it doesn't. Why? I don't know.

Dirtydog11

Already told you the best option for those given ring sizes, although I can't guarantee it won't rub in 24-11 and 36-36 as I've never tried it, I like to maintain a straight chainline .

Just because you can do something doesn't mean you should.

The Rookie

Your lengthy description makes it even more obvious that you don't know how to set up your front derailleur, if you put the lever in 2x mode you can adjust it to use either two of the three rings.

I converted my 3x to 2x with bash using a triple and then later a double FD, no issues at all, my wife's and son's bikes both run 2x with bash, again no problems at all.

ChILd_ReBoRn

well rookie, enlighten me then. I'm always willing to learn. I've got SLX shifters, and I have no clue how to select the rings it will shift to. If I leave the shifter on my granny, I can't flip the 2x switch. when i shift up to my middle ring, I can flipit, and after flipping it, I can't shift down. Only one step further up (big ring), and down from there to middle ring.

As I sad, enlighten me what I'm doing wrong...

thank yoi

cooldad

Read Parktools, disconnect everything, and start from scratch indexing the mech properly.

Mechs aren't magic - you need to tell it where to go.

ChILd_ReBoRn

I know they aren't magic. I have indexed tons of rear mechs. First ones as well, But of all the bikes I have worked on, I'm the only one with a 2x + bash combo

just for the record, I have a problem with the FRONT mech, not rear.

I did what you said, disconnected everything, and indexed it so it covers granny/and middle, but I could bet my life that the shifter has different pull ratio on 2x mode than on 3x mode. It either rubs on granny/36T combo, or it doesn't shift up. No amount of fiddling helps. The deraileur is direct mount, so I can't move it left or right.. just up and down to accommodate my rings



this is what I found on MTBR:

"The bottom line is with a Shimano 2x/3x convertible shifter, if you're going to run a 2x/bash on a 3x crank you have to leave the shifter in 3x mode and limit out the third ring. That is unless you play around with your chain line and match it to that of a dedicated 2x crank. And, of course you'd have to adjust derailleur clamp height to match the rings your were using as well."

this is one of the subject debates:

http://forums.mtbr.com/drivetrain-shift ... 69052.html

so there IS more to "me not knowing"

cooldad

That's called indexing the mech properly, the term applies to front as well as rear.

Read Dirtydog11's post up there ^^^^^^^^

I have a 10 speed triple, I removed the big ring, fitted a bash, lowered the mech as far as it would go (direct mount), adjusted the high limit screw, refitted the cable, and it worked perfectly, took 10 minutes.

ChILd_ReBoRn

Well. I'll pick up my 2x mech in a couple of days, and try it on.

thank you

The Rookie

If you can't make the 3x mech work, it's unlikely the 2x will be any different.

There are lots of things you could do wrong, it's almost impossible to just guess at the right one.

As CD says its best, if hopelessly chasing ones tail, to start all over again.

Replacing the outer ring with a bash hasn't changed anything, it should be able to operate now in the lower two chainrings just like it did before, unless somehow you made a major league hash when fitting that bash ring that is currently beyond me.

Dirtydog11

different pull ratio on 2x mode than on 3x mode.

Yes, I do believe they do, see my previous post :roll:

IME shifter mode convertor works best in 2x mode when paired with double FD and 3x mode when paired with a triple FD, I think the pull ratios are slightly different between 10 speed double and 10 speed triple FDs

I'll leave you to it!

The Rookie

Pull ratio is the same in 2x and 3x, on switcheable shifters all it does is lock out the extra click, the cable drum doesn't change

Shame people can't apply a little logic and thought.......

ChILd_ReBoRn

well logic or not, 3x mode works, 2x doesn't.

cooldad

So leave it in 3, if that works for you and adjust the limit screw.

Herdwick

The pull from granny to middle is 11mm and from middle to top 7mm if you are using a tripple crankset with just the outer ring missing you have to use the shifter at the 3x position as you need 11mm cable movement to shift the chain from granny to middle and adjust the upper limit screw accordingly. You use the 2x set up on the shifter only with a 2x crankset that uses same pull as moving from middle to top

ChILd_ReBoRn

thank you!!

I knew there was a difference

Giraffoto

I've got a similar issue with the Frankenbike I'm cobbling together, can someone answer this one for me?
If I have a 2/3 speed shifter and a 3 speed derailleur, set my 2/3 speed shifter in 2x mode, align the derailleur with the middle ring and remove the inner ring, should it work as a 32/42 double?

davidradar

Giraffoto that is a good question!

ChILd_ReBoRn

it all depends on the ring spacing. if it's 7mm..should eork

Giraffoto

And the verdict is . . . . it does work. In these precise circumstances:

• Shimano 2/3x shift lever (Deore)

• Shimano 3x front derailleur (SLX)

• Triple chainset (Suntour XCT, I think)

Remove the inner 22T chainring. Position the derailleur so it's over the old middle chainring in its low position. Set the gear shift lever to the (B) setting for 2x operation. Tension the cable. Do a practise shift onto the outer ring (it works!!) and set the outer travel limit screw. And you're done.

ChILd_ReBoRn

I mounted the dedicated 2x deraileur, and it works hell of a lot better than old 3x mech. I get a wider cassette range without the rub...

ChILd_ReBoRn

Changed my deraileur for 2x, and changed my shifters from M670 to M780. Funny thing.. SLX shifter, on a 3X position, and a "X FD works great... XT shifter on a 3X position, with that same 2X FD doesn't work. One click moves the chain all the way on my bash. When I flip the switch on 2X,, It works flawlessly