I figure I may as well make my first topic about a hot button issue. There’s obviously a lot of debate surrounding internal routing in the bike world in general. Working in the design field, I’m a sucker for clean lines, but keeping the cables on the outside has huge benefits.
Of course, the materials that most of us are working with make internal routing more of a challenge. Sleeving, stress risers, all that good stuff.
I recall hearing about an issue with the Rodeo Flaanimal with buckling downtubes. My eyeball FEA tells me that those two ports are awfully large, close to each other, and in the load path. However, I assumed that this frame passed all the ISO standards
FYI our port is a 3/8x.72in slot in a (usually) 38x1.0 butt. The 3D printed port has a pretty large flange and is located in a pretty “chill” stress area:
Without doing a lot of testing it would be hard to say where your designs are hanging out along this curve. You could be totally fine, or playing with fire. And even if you did a lot of testing, every tube diameter and butt thickness would yield a shifted curve.
My personal feeling is that internal for dropper is fine, everything else on the outside.
I don’t even want to own a bike with an internally routed hydraulic brake hose that runs through the frame and through the rear triangle let along make one! A friend of mine decided to change the brakes on his trek fuel from Shimano to hope and spent half a day pulling all the linkages and whatnot apart. What a pain!
Thanks a ton @Daniel_Y those FEA shots are super interesting. If you ever feel the desire to make a quick’n dirty FEA tutorial, I think a lot of us would find it super useful
FEA is not in my realm of Mechanical Engineering. I know enough to make colorful pictures to develop intuition, but not enough to get analytical results. Also, you need the paid version of Fusion360 to use their simulation tools.
Until a real FEA expert steps up, I can generate colorful pictures for people:
Kinda related to the topic, here is a comparison of a fore-aft load on a fork 25.4x1.2x.9 fork leg w/ and w/o bosses:
The bosses on the side are not directly in the load path. This is why I also question the efficacy of the Willits style brake tabs (Disk Fork Question - #12 by bushtrucker). Seems like they just move a stress riser to an area with higher stress (higher up the leg).
Gotcha. I’m lucky enough to still have a few months left of Fusion EDU. Are you willing to share some of the force before data you’re using as inputs? Some of the info I’ve found online has been conflicting but I would also like to make some pretty pictures and make unqualified judgements based off of them
I only build with internal routing. I do non-sleeved routing throughout the frame.
Fully internal for everything besides flat mount bikes. For flat mount bikes I do internal through the front triangle and then external along the bottom of the chain stays for both the brake and derailleur.
I silver braze little laser cut .03” thick stainless reinforcements to the outside of the tube, then slot ~7x15mm ports with the mill. For the dropper I slot the bb from the down tube into the seat tube - with a bit of a notch sloted in the front of the seat tube.
The lack of places for cables to get caught inside the frame makes routing these bikes very quick and it can be done without magnets or any tools really. I provide them with foam tubes that slide over the hoses for a rattle free life.
Below is a dorky video of me running hoses and what not for one of my frames. (With some more words about why I do internal routing)
I’m a huge fan of internal routing, particularly in my usual domain of bikes that get covered in mud. External cables and hoses are a real mess when it comes to build-up, and make cleaning the bike a little more difficult. We haven’t had any issues with it for the team bikes this year, and they basically live in a state of always being wet. I don’t really see a case in which I wouldn’t at least partially route the cables internally.
I am curious about trying full internal routing, but I kind of hate the way it would make the head tube look. I do think it would have a lot of advantages for cyclocross though, where reducing exposed everything is always good. It would be a small annoyance for replacing headset bearings, but those need doing so rarely I’m not worried about it.
Anyway, these cable ports from @Carl_Snarl are the bee’s knees.
I don’t love internal routing for frames. The one experience I had (hydro cable through downtube) was fine but defo slower to install and didn’t seem worth it. I guess I’ve never looked at a bike and thought the cables made it look ugly. Actually, I’d say that when done well they actually add to the look of a bike. So yeah, if builders wanna do it for a frame that’s fine but I wouldn’t ask for it or pay more. The directions things are now going with internal routing through headsets/stems/bars though, that’s a disaster.
I always say internal routing is for folks that don’t work on their own bikes.
I did it on my MK2. Just extra headache every time you work on it, for the benefit of clean looks. Just not worth it in my opinion. I did do stainless tubing all the way for each line, but that’s also just a big headache in the building process.
Also, if there’s a single noise on my bike (even the hub, lol. I run an Onyx) it’s a travesty. I can’t stand rattles and noises going down the trail.
But I’m also one of those weirdos that would even run a externally routed dropper if that was an option on the good ones.
I refuse to put gnarly stress risers all over my downtube just to make a bike look cool. And I have seen them (both mine and others) break because of the ports.
But then I do not care at all about looks, just function and fit. So I’m an outlier there.
Forgive me if this is a silly question/perspective. I’ve always been curious what the real motivation for chainstay mounted disc brakes is? Purely aesthetics to keep the lines of the rear triangle maintained? or is it just the lack of brake bridge?
On an mtb: Routing the derailleur and brake line along the underside of the top tube and down the seat stays just seems to me to be a very elegant solution (aesthetically and practically) and housing is fairly shielded from mud kicked up from your front wheel.
It feels like the moment you move the brake to the chainstay. The ideal routing gets compromised a bit and then everything shifts to the downtube. Externally routing all of this along the downtube is kind of ugly and a mud collector.
I’m not really wow’d by internal routing, so most of this I guess purely from the perspective from someone who has a preference for external routing.
For mountain bikes, I prefer the TT routing, but I can see a few reasons for CS-mounted brakes (or DT brake routing with SS mounted brake)
It allows you to group the brake, dropper, and shifter cable into a single paragon clip
this saves maybe 30min of time?
The cable system is versatile. The bike looks good with wireless shifting, dropper, no dropper, etc…
It allows you to use a thinner SS
how much smaller and its impact is up to debate, but that’s the theory
I actually prefer internal routing when done right. I have a few 3D-printed port designs that do this, but it’s not feasible from a production standpoint.
For my last hardtail I went with CS mount for the brake because I wanted to give the rear end every opportunity to flex. I was undecided on if the whole “frame compliance” thing was actually a thing so I didn’t put in a seat stay brace and I put the brake on the chainstay so I didn’t have to triangulate the Cs to SS for braking force reasons.
Re: weatherproofing, I don’t know what the mud is like where everyone else is but here it sticks to the bike regardless of cables and hoses off fine regardless of cables. And if you run full length housing then weatherproofing is again irrelevant, housing is waterproof. Maybe get the ferrules with rubber grommets in them if you do a lot of wet riding.
To me part of the beauty and joy of a bike is the simplicity and practicality of it. Anyone can and should be able to maintain their own bicycle. As a teen I fell in love with cars, and pursued a career as a mechanic, I did that for about 6 months before realizing that they are just awful to work on and I didn’t want to do it. I don’t want my bikes to be like that.
My current choice for mtb and gravel is full external below the DT and above the CS, with the dropper cable entering near the bottom of the seat tube. I use the Paragon triple aluminum guides on the DT and zip tie guides on the stays. I find it aesthetically pleasing as well as practical. Internal can make maintenance a PITA, especially hydro hose, and I don’t want to do something on purpose to make my bikes harder to work on (for me or a customer).
Someone mentioned that bundling housing/hoses below the DT was unsightly and created a mud trap, but I disagree. At least in my part of the world I’ve never had trouble cleaning this area - dirt just hoses right off. Also, if you’re standing near a bike you are sort of looking down on it and this cable configuration hides them pretty well, keeping the upper half of the bike really clean and simple.
I can’t explain why exactly I like routing along the top side of the chain stays, other than it seems to provide the most direct line. Plus the housing on the drive side protects against chain slap, which is a bonus.
The housing is steel with some plastic covering it. You could slap the chain for 1,000 years and not cause a problem (though it might look bad after a while).
Thanks, Nick! Walt is right, housing is pretty bomber stuff. On a mtb the chain slap definitely wears the shiny surface down a bit, but no big deal. You’re going to change your cables and housing once in a while anyway. On a gravel bike with a clutch derailleur the housing barely ever gets touched - unless you ride your gravel bike like a mtb…
to develop intuition, but not enough to get analytical results. Also, you need the paid version of Fusion360 to use their simulation tools.
