oldacura

I have a recumbent with a Shimano triple front crank and Shimano thumb / forefinger indexed mountain bike shifters. I swapped out the shifters after the ones that came with the bike got damaged.

It seems like the shifter has too much throw for the front derailler. If I center the cage on the center ring, it wants to throw the chain off the high side when I shift to the big ring. I have the stop adjusted to prevent this but I really have to push the shifter against the stop to get the indexer to hold it there.

I have the cable attached to derailler on the side of the clamp screw opposite the pivot point. In other words, if I move the cable attach nearer the pivot, this should cause the derailler to move even more.

It seems to me that some shifters have 5 indexed positions (instead of 3). This would allow me to half-step the derailler from the mid to big rings. However, this shifter only has 3 indexed positions.

What am I doing wrong?

JanMM

https://parktool.com/repair/readhowto.asp?id=75

Usually takes me a few tries to get the FD adjusted just right.

My SRAM trigger shifters have only 3 stops.

maddmaxx 

Were your old shifters Shimano flat bar road shifters like the R440 style? They would have had more than 3 positions to allow for trim and they would have worked with a road type front derailleur. Shimano MTB shifters have only 3 positions but pull more cable so as to work with MTB front derailleurs.

If you have a road front derailleur and MTB shifters, this would account for the "too much throw" problem.

I may be wrong but this explaination fits with all of your symptoms.

Al1943

This is what I was thinking but I couldn't remember the R440 model number.
It seems it might help to know the model number of the problem shifters.

Jeff Wills

I think you're on target, Max. The FD-R443 (older) or the FD-R453 (newer) will work with "road" size chainrings and "mountain" shifters. This is the setup I have on both my wife's and my Gold Rush recumbents:
https://home.comcast.net/~jeff_wills/...s/bike019a.htm
https://home.comcast.net/~jeff_wills/...es/bike006.htm
It works perfectly.

oldacura

I don't recall the model numbers of the derailer or the shifters. I think the derailer is a road version. I'm fairly certain that the shifter is a mountain version.

Do the ring spacing, derailer throw and shifter pull all have to match? Is the spacing on a mountain crank greater than road?

It may be the easiest (cheapest) way to go would be to replace the derailer with a mountain version.

Thanks for the help.

maddmaxx 

It's a problem of the amount of cable pulled by the shifters and the ratio of the front derailleur.

There is one other thing to check. The are some older front derailleurs out there that have what appears to be a shallow grove directly on the end of the arm that the cable attachment bolt is on. If there is such a groove there, the cable goes over the end of the arm through that groove before it gets pinned under the attachment bolt. this will make the derailleur move a little less for each movement of the shifter.

If you could provide the model numbers of the parts involved and possibly even pictures, we could help more.

oldacura

Finally got around to looking at the shifter / derailer models.

The derailer is a Tiagra. The shifters are Alivio (I think) model ST-MC18. I think the derailer is original. I know that the shifters were replaced.

Are these incompatible?

Jeff Wills

Yes. Tiagra is "road", Alivio is "mountain". You need a front derailleur which is made for the larger "road" chainrings, but accepts the longer "mountain" cable pull. Shimano only makes one or two- the most common is the FD-R453: https://harriscyclery.net/page.cfm?Pa...ils&sku=FD4428 . Any bike shop should be able to get one for you. My local recumbent-oriented shop keeps a half-dozen in stock.

rmfnla

The ring size really isn't an issue.

I'm currently running a D-A 53t with an XT front and it shifts flawlessly.

I've built up numerous others like this and they all work well.

pacificaslim

And I'm doing the opposite: using a Tiagra on a mountain triple crankset and that works fine as well. They key thing is that the front derailleur has to match the shifter - road to road, mountain to mountain - so that the amount of cable pulled by the shifter is correct.

oldacura

Last night I checked both shifters: the one that came on the bike (Deore) and the one that I insalled (Alivio). Again, the reason that I replaced the old one was because they were damaged by falls.

Shifting from Low to Mid, the Deore pulls about 11mm of cable. From Mid to High, the Deore pulls about 8mm of cable. The now installed Alivio pulls almost the same amount of cable (the best I can measure).

Is it normal to pull different amounts of cable in these 2 steps?

I assume that the easier, cheaper route would be to replace the FD with a "mountain" version. Is the cable pull on my shifters appropriate for a mountain FD?

Little Darwin

Yes. You have mountain shifters, so a mountain fd would work.

Little Darwin

Just throwing in a caution... Some mountain FDs are top pull instead of bottom pull, be sure to get a bottom pull with the proper clamp diameter..

oldacura

This would be a bottom pull, ~29mm clamp diameter. Based on my measurements of the cable pull, the FD was never compatible with the shifter.

oldacura

Jeff - you were correct. I ordered & installed a mountain FD that will accept a 50t ring and it works great.

Thanks for the help.

Panthers007

Regards the bottom-pull - you can also use a dual-pull FD for the same effect. I use a Shimano XTR on my hybrid with dual-pull. Works great on my Ultegra-triple 52-39-30.