digibud

Here are pics of two bikes (mine and wife's). Ignore the fat tire in the background - wife's pugsley wheel. As I cut new cable housing I've looked at some pics of what proper length should be and find it a fairly subtle thing. I would like to get as close to perfect as I can for my wife's bike. Thoughts on these two examples regarding housing length? Humorous snarky comments welcome , realistic suggestions also appreciated.

1.

2.

Aceldama

The first picture looks more acceptable to me. How does the friction feel with the smaller radius loop?

NatUp

I like pic one more. Number two seems too long. Basically you want that nice uniform-radius curve.

I wish my wife had a fat bike.

davidad

I would go with the shorter one. they are the same on both of my bikes.

Al1943

I've always found this an interesting subject, the length of the short housing is important to shifting performance.
I've been using the Shimano and Campagnolo cable and housing kits for our bikes. The short housings in these kits are pre-cut to length, and should not be shortened. The Shimano short housings are about 31 cm in length, the Campy short housings are about 33 cm in length. I don't know which are better but assume that something in the 31 to 33 cm (12 - 13 in.) range is considered standard and work well. If the short housing is made too long it can create a shorter reverse curvature arc just before the frame housing stop. And if so this will increase cable friction in the housing, not what you want.

fietsbob

A longer smooth curve is better than a short tight one , neither of the 2, would I call, short .

rollamajigs were a solution the last bit of cable, around a roller rather than bend the housing around..

now SRAM has re designed some of their derailleur to use a more straight line ..

dsbrantjr

I like #1 as well. I tend to judge the length by the angle at which the housing meets the frame stop; the derailleur end angle will vary some depending upon which gear you are in, the frame end less so. I like to make the length of housing obviously long, "dry" fit it without the inner wire (but with ferrules) and trim it gradually so that I can see how the angles are trending. It may take a minute and a couple of cuts more, but I get it where I want it pretty efficiently. I hold the cable in the approximate shape it will assume in service per Sheldon Brown https://sheldonbrown.com/cables.html#cutting when I cut it. Prep the ends, pop on the ferrules and it is ready to install. I leave the wire long, coil it up and ride it a bit to make sure I am happy with everything before I trim and cap off the wire.

Last ride 76 

To me, one curve. If it's got any recurve (s bend) that's too much. The shortest fully SMOOTH curve that enters the stop cleanly (basically at ninety degrees to the face of the stop).

The value judgements: Too short looks awkward, (doesn't work too well either). Too long looks lazy, or uninformed.

Regards, Eric


EDIT: I cross-posted w/ dsbrantjr, and defer to his caveat about movement affecting the angle sufficiently to require some additional fiddling...

E

Reynolds 

#1 is OK, #2 a bit long IMO. Still most come from factory shorter than #1 .

bobotech

Another vote for cable housing one.

FastJake

First one is good, cold be a bit longer. Ideally it will enter the RD nice and straight. Looks like it's coming out slightly angled.

Second picture is too long. RD housing is probably the trickiest section to cut. No matter what it's not ideal IMO. I wish the housing could enter vertically into the RD as on some models. That would make things a lot smoother. A J-Tek Shiftmate produces a similar result to what I'm talking about.

Looigi

I like the second one better because it can be trimmed a bit to make it perfect. The 1st is a bit short IMO, and of course can't be lengthened.

jowilson

Your chain looks a link or two too long.

I agree with picture #1 . #2 is definitely too long.

Josh

FBinNY 

I don't look at the curve itself. My focus is how the housing enters the fittings, especially at the RD end.

In this case, the 1st bike lines up nicely, while the second is a bit long and seems to be back up from below the fitting.

Angry_Monkey

I agree, the second looks a bit long.
I did notice that both are set to a small cog. I would also look at how they sit on a large cog as well.
The transition from lug to housing and housing to derailleur is the key. Make sure that there is no kink or binding, and then try to reduce the housing length that maintains a smooth cable path. Check at both the high and low gear extremes. Cut for the worst case scenario.
And remember to center the adjusting ferrule on the derailleur so that you have some head room to work with.

~Monkey~

Al1943

For a good comparison the derailleur cages should be in a similar position of both bikes. If the chain was on the big ring and smallest cog the lower cage should be near vertical and the housing curvatures would be more easily compared (assuming both wheels on both bikes).

IthaDan 

Top one looks just a hair too short, bottom one looks too long.

I've trimmed housing like the top loop before only to have them kink at the ferrule on the derailleur end after use.

Pepper Grinder

Voting for 1.3, just a bit over one but not quite two

bradtx

digibud, I learned years ago after my first 8S drivetrain that the RD loop needed to be a little bit longer than what I previously trimmed it to in order to alleviate some odd shifting in the middle of the cassette (primarily on a close ratio block). 7S didn't have a problem, for some reason.

I trim the RD housing so that over it's entire range of RD movement the cable housing enters the RD as straight as possible with no double bends. I learned that the plastic ferrules can split in the RD if the housing is not trimmed correctly... long enough not to effect shifting, but too short to be properly aligned at some RD positions.

Depending where the chain stay or seat stay housing stop is located and the particular RD, the loop can appear too long yet be just the right length.

Brad