Cross Bike RD Cable Loop Question
 

I have a Jamis Nova Pro frame that I have set up for commuting with mixed Shimano 9 speed triple road group (Ultegra 6503 series triple shifters, FD and brakes, 105 long cage RD).

This is the first bike I've ever set up with this cable routing - the RD, rear brake and FD cables all run along the top of the top tube. The RD cable then runs down the seat stay with the final cable stop several inches up the seat stay.

You can see from the photo how I have the cable housing cut. It's quite a huge loop, and I have taken to fastening it to my rear rack to keep the loop from flopping around. Even with this huge loop, you can see the cable connection to the RD is not that great - it does not go straight into the RD, but there is still an angle at that point.

Any hints how to do this better? Of course, I can try to just cut the housing shorter, make the loop tighter, but I think that would make the routing to the RD even more of an angle going in and maybe make the shifting worse. (it's not bad now, but not as perfect as the same RD and shifter was on my road bike).

Thanks.

looks fine to me . smooth curve is better than a short tight one ..

there was a rollamajig it used a roller to let the rest of the housing be straighter

may not have been enough people aesthetically worried as you are ,
to sell them to, so they went out of production.
more for the under the chainstay cable runs .. actually more curved like a ? then.

Thanks for the comment.

Yea, it's partially aesthetic, although what I really don't like is that the loop is so big that if I don't have it zip tied to the leg of the rear rack, it does flop around while riding and is prone to getting caught on stuff when I move it around the garage and load it in and out of my car. But it works the way I have it zip tied.

If it shifts well you're good to go. But I've never seen a cable run this way.

My way of setting the size of the rear loop is always the same. I let the housing tell me. I put a ferrule (if using one) on the RD end, and put it into the fitting. Then I hold the other end along the line of the frame fitting and advance or withdraw housing until the RD end lines up with the fitting. That's the best length since it prevents an angle where the wire emerges.

Sometimes, however, I can't get natural alignment at both ends, so I have to cheat. I might slip the housing into a piece of tubing and curve it into a sharper bend, or sometimes I can set the sharper bend by working the housing in my fingers. If there's a practical place to tie the loop to force it to the line I want, I'll do that. (I'll often resort to a zip-tie on the stay about an inch out from the stop for this. On my commeter, I trap the housing below the QR nut which makes a good line for the chainstay, and a clean tight radius bend for the RD end.

In short there's no single best way. The object is good alignment at the ends, but how to do that is up to you and will vary bike to bike.

I believe it's common on some MTB and Cross bikes. The top tube cable routing keeps them away from mud and other damage.

Yep- not at all uncommon on cross and mtb's. Not only to keep the cables out of the crud, but to keep the cables from being damaged when you bang the bb shell on a rock or some other obstacle.

OP- FB's suggestions were good. From what I see in your pic, the exit from the ss stop is at an angle. I'd clamp the cable a bit closer to the dropout so the run is straight, then form/route the cable to the dr as FB suggested- "straight." The loop will be tighter (think 2" radius max) but any increase in friction will be less than having the cable exiting the stops at an angle.

I've never been happy with the RD loops on bikes with the seatstay routing; the cable doesn't bend around far enough to isolate the effect of the RD's movement nearly so much. Kinked ferrules more common.

I'd be inclined to experiment with a V-brake noodle; for whatever reason they seem to have surprisingly low friction for the small bend radius (at least with a fresh liner)... it must be that they're rigid.

If you can get hold of a really long one (some are 4" or more), you could straighten the terminating end and poke it in the cable stop on the frame, running down the seatstay a couple of more inches and then bending back to almost horizontal a couple of inches above the cassette (I'd go behind the seatstay). This'd give you a 180° bend of slightly smaller radius (a C rather than a ?)... might be an improvement.

V-brake noodles can do some cool stuff; they're God's gift to unreversed sidepulls on the rear of stepthroughs.

With a 9-speed Shimano MTB shadow derailleur (RD-M772 for instance) the cable runs almost exactly straight from the seat stay into the RD fitting. Of course, that's a pretty spendy fix for an aesthetically displeasing cable routing. On the downside, the cable exits directly into the spokes, so you pretty much need to bend it immediately to finish the set up. Oh, and it has no barrel adjuster so you need one inline with road levers.

Aforementioned, avid rollamajig https://www.google.com/search?q=avid...l%3B1024%3B768

I thought you were just calling it a rollamajig because you couldn't remember the name. :D

thats a whatchamacallit thingamajig ..

the op says he might shorten the cable
but the angle at which it enters the cable stops on the derailleurand frame
indicate that it should actually be slightly longer
not shorter

Unfortunately there's no great way to route these RD loops (or even chainstay RD loops IMO) without making it bend more than I'm happy with. Yours looks fine, could be a bit longer. One one setup like this I zip-tied the housing to the seatstay about an inch away from the cable stop to make it enter straight and not flop around.

The rolley thing looks nice, but I feel like if I got one I'd have to put one on all my bikes :rolleyes:

And I agree it's not aesthetic. It's critical to the function of the RD.

Thanks for the replies. Good to hear that the issue is not in my imagination. It's obvous that it's just the way these things are designed, possibly exacerbated by the fact that I'm using a road derailleur instead of a MTB derailleur. I do have a Deore RD that I'll take a look at just for grins.

A agree that my loop is too short as it is and shortening it would make it even worse for the "straight into the derailleur" criterion. I don't really care about aesthetics to get the proper loop, it's just that it's so big it gets floppy and in the way unless I zip tie it to the rack leg. So it's really better function (less floppiness) that I'm looking for (a proper loop with less length).

I get comments all the time about the loop on my other road bike that has a Sram Red RD - the loops on those things really need to be quite a bit bigger than a Shimano RD, at least based on my experience and the installation instructions.

I'm going to try zip tying the cable housing to the seat stay an inch or so below the seat stay cable stop and then cut the housing length to make a straight run into the derailleur. I also think I have an extra noodle or two laying around that I might try.

But, I might try a rollamajig just because I haven't bought a new gizmo lately....

Thanks all.