Front derailleur compatibility
 

I’m one that seems to like to learn the hard way. Converting my old Trek 850 into a “gravel” bike…economically. Put on some tourney A070 shifters and a shimano M361 triple crankset, because I stripped the old one. The derailleur that’s on the bike doesn’t have enough travel to reach the big ring. Trying to find out what does. Bought an Altus FD-M310 derailleur, and it is shy of the reach too…also had the wrong pull direction. That’s me doing it the hard way. Can someone tell me what will work?

Before you go chasing down the derailleur rabbit holes, make sure you are using a bottom bracket with the correct length spindle. Install your crank and rear wheel with your intended cassette. Then lay a yardstick across the center ring and the centerline of your cassette. Verify that the yardstick lies parallel to the centerline of the bike. I'm betting that your spindle is too long for the new crankset.

First, is your new crankset sitting as far in as the old one? Where a crankset sits is a function of both the crankset and the bottom bracket. If the new crankset is sitting significantly further out, finding a derailleur that can reach the big ring may be a challenge. (There are tricks but some come with big cans of worms. I won't pass on what I did to bring an FD significantly further in than is standard because I intentionally set my crankset up to be narrower than standard. My knees like very small Q-factors. They cost considerably more than chains and cassettes. My trick can be done just as well to bring the FD outboard.)

Do you have clearance between the inside most part of the crankset and chainrings and the bottom bracket shell and chainstay? Enough to run a narrower bottom bracket? That could be a very simple fix. $30 for a basic (and rather good) Shimano bottom bracket.

This is the foreign object to the body, and I bet is pushed out away from the frame vs the original stock one.

My opinion is to find another crankset that the frame likes.

Yes, the FD is attached to said happy frame.

this is the tell. Look over the rear cassette / freewheel and get a "gun sight view" of the alignment of the crankset

Ideally the middle ring should line up with the middle cog, and the inner ring should clear the chainstay by 3-4 mm

/markp
https://cimg1.ibsrv.net/gimg/bikefor...a96a38101e.jpg

Is the problem you're having is that the 'throw' of the FD not getting out far enough with the high limit screw loosened as far as possible? The Shimano specs for your crank (with the proper BB) and the Altus FD should be able to handle a 50mm chainline.

Another possible issue is that the shifter may not have enough cable pull to actuate the FD properly. Most road shifters, prior to 11 speed, have less cable pull than MTB shifters. This will mean that the FD does not move as much as needed with a road shifter, and the 'trim' positions will not work properly. Assume that you're using the 3x version of the shifter (ST-A073). Have you researched the compatibility of the shifter & FD?

"In General" Shimano front road and mountain shifters and derailleurs don't play well together. A070 is road series and Altus is mountain series.

You also need to learn what deraileur specifications to pay attention to. Here is a link to one site that will help you understand them. It's a site for Di2 and electronic shifting, but the same thing applies to cable pulled DR's.

https://bettershifting.com/installat...pecifications/

There are probably other sites that explain it better, but this will get you started so you know at least what kind of questions to be asking and what terms to search on.

The Shimano website will have the spec's listed with all their current products and the specs and compatibilities and all sorts of other information can be found at their documentation website. https://si.shimano.com

FD-M310 says 47.5mm chainline

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[QUOTE=dedhed;22905052]FD-M310 says 47.5mm chainline

Shimano's specs list it as "47.5/50mm" chainline. Probably since these level FDs are typically used with cranksets that uses square taper or Octalink V2 BB. Shimano list some these cranksets with 47.5 or 50 chainlines depending on which of the 2 recommended BB length used.