I have bought a replacement FD for an old Shimano Alvio der that is showing signs of wear. The replacement I bought is a Shimano Altus FD-M313 and appeared to be compatible as it was sold as dual pull. However, I now find that the cable clamp is at the front of the pull lever, whereas the Alivio was at the back. There is a cable router at the back to enable the cable to pull the derailleur in the same direction as the Alivio but I am wondering if this will work or if there will be differences in the amount of pull, travel of cage, etc. By finding more online I learn that the Altus is described as top swing and wonder if this is different from top pull. So a bit confused.

Pics of the Altus below:

Top pull vs. bottom pull refers to the cable routing whether down from the top tube or up from the bottom bracket.

Top swing vs. bottom swing refers to how the derailleur is clamped onto the seat tube. Top swing derailleurs are clamped right next to the bottom bracket.

That particular derailleur is definitely a bottom swing, the more common configuration. It looks to me like it was designed to be a replacement for either top pull or bottom pull cable routing.

Many thanks, Retro Grouch. It is a top pull routing on the bike fitted directly to the clamp. However, this one would seem to require routing through the cable guide and then fixed to the clamp to enable the correct pivot action to work. The existing der does not sit on the bottom bracket but in the traditional position next the rings. So, it may - hopefully - do the job so long as the cage does not travel more or less than the original. I am not even sure if that is possible. I suppose the only way to kn ow is to fit it and see.

If your cable comes from above (i.e. top pull), you would just affix it to the bolt in the front and the cable would pull up on the lever. If your cable comes from under the bottom bracket (i.e. bottom pull), you would route the cable over the pin and then affix the cable to the anchor bolt. That would allow the cable to pull down on the lever to move it up.

Your existing derailer sounds like it is a top swing meaning that it swings above the derailer cage. This one is a bottom swing which means that the derailer pivot is below the cage.

Thanks, cyccommute. I am not sure. I think the existing one swings below the cage. Here is a rather poor photo of it.

These differences speak to exactly what I mentioned in your other thread Sutable FD Replacement Shimano has kept their lever/crankset ring spacing/ft der compatibility the same for the 7/8/9 speed systems (within the MtB side of their offerings). So one can interchange a bottom swing for an top swing if the other specs match up. Andy

Thanks, Andy. I panicked a bit and more than a little confused over top/bottom swing and compatibility.

Cable routing for bottom pull is indirect, over the knob, then, to cable clamp..
so it pulls down..
top pull is direct, from above..

Many thanks.

That's a bottom swing. A top swing would have the clamp on the frame higher up.

On a personal note, I prefer top swing (either bottom pull or top pull) over bottom swing. The bottom swing tends to have more problems with fitting all that metal in a fairly confined space. Additionally, for Shimano, the cheaper front derailers tend to work better and be more forgiving in set up then the more expensive ones. I actually prefer SRAM over anything Shimano offers. They just work better.

MAYBE.

I've always found issues with the clamping points. Water bottle cage mounting points or something always seem to be located exactly where I need to clamp the derailleur whenever I've tried to replace a top swing with a bottom swing or vice versa.

I agree completely. This is why when I build a frame I want to have the components on hand to insure everything plays nice together. I was speaking specifically WRT the shifter/der/crankset relationships, which seemed to me to be the OP's focus too. Good point though. Andy

I had this issue today when I fitted the derailleur in place. The clamp lies between both bolt holes. It could have been worse and been right over the lower bolt hole. I can live without using the seat post holes.

If you ever decide that you want to install a water bottle cage there, that's a pretty easy problem to solve. Take apart one of the spare sections of chain that you have laying around. Save a couple of the rollers. They're exactly the right length and diameter to spacer your water bottle cage over the derailleur clamp.

Are they? I have loads of bits of chains in the garage. Thanks for the tip.

Presta valve stem nuts are good too
not a fast to rust as bare steel chain rollers (which you could paint before using)

We use PV rim nuts all the time. Just uses a couple as spacers for a home made fork die handle. Andy