[miles e]

Trying to figure out what options there might be for running a dropper cable completely internally from where it enters near the head tube all the way to the seat tube. Most mass produced metal bikes have it pop out briefly between the down tube/seat tube right above the BB shell, but I'm sure some custom builders have figured out creative work arounds. Anyone seen this done, and if so where/how?

 

[stuartm2]

I have a Giant Stance in the workshop at the moment which does this. The cable enters at the top of the DT. They've cut a section out of the BB shell, DT and ST to route the cable then covered it over with a plate. Their covering plate has the lower shock mount on it but you could imagine doing something similar with some kind of covering gusset on a hardtail.

 

[NorCal_In_AZ]

On my Giant Talon, I just run the cable from the down tube, through the BB shell, and into the seat tube. It took a while to fish the housing over the top of the BB, but its been in there for two years now working fine.

You can also have the housing pop out the bottom of the down tube then back into the back side of the seat tube. That would give you a clean run, that doesn't visibly stand out.

 

[Ben.land101]

It's a little unconventional, but here's how I've been doing it.
Doing the seat tube this way solves multiple problems. Super easy dropper routing is one of them.

 

[natzoo]

Based on the space available BB junction, there are really only two options:

1. Route it inside of a T47 bottom bracket
2. Route it through a "gusset"/offset seat tube like stuartm2 and Ben showed

For option 1 (blue line), the housing has JUST enough room to fit between the shell and the bottom bracket sleeve. It runs the risk of snagging on the BB shell

Depending on your tube diameters and geometry, a third option may be available to you, the red line.

I have been trying to figure out a way to run a stainless tube internally that directs the housing straight up the seattube, but it runs into two issues: how to secure stainless tube inside of the seattube, and what to do about water getting into the stainless tube (it might get trapped in the u-shaped bend).

 

[rideit]

AXS? (I’ll show myself out)

 

[AdamR83]

View attachment 1957649

I have been trying to figure out a way to run a stainless tube internally that directs the housing straight up the seattube, but it runs into two issues: how to secure stainless tube inside of the seattube, and what to do about water getting into the stainless tube (it might get trapped in the u-shaped bend).

Red solution looks best.

In terms if process, I should think the following will work...

Weld DT fully to BB shell.

Drill hole at bottom of DT, close to BB shell.

Insert / braze in hockey stick shaped internal sleeve for routing (will stick up into seat tube 'cavity'), with tiny hole at the bottom apex to allow water to drain.

Weld seat tube on afterwards.

Simples.

 

[miles e]

You can also have the housing pop out the bottom of the down tube then back into the back side of the seat tube. That would give you a clean run, that doesn't visibly stand out.

I've seen that, and definitely find it preferable to just "cutting the corner" above the BB shell- although I suppose the latter does have the benefit of keeping the holes in the frame further away from the ground/rear wheel. Would still prefer to keep it internal the whole way once it enters.

 

[miles e]

It's a little unconventional, but here's how I've been doing it.
Doing the seat tube this way solves multiple problems. Super easy dropper routing is one of them.

Very nice, reminds me of an early Knolly! Can I ask what other problems it solves?

 

[miles e]

Based on the space available BB junction, there are really only two options:

1. Route it inside of a T47 bottom bracket
2. Route it through a "gusset"/offset seat tube like stuartm2 and Ben showed

For option 1 (blue line), the housing has JUST enough room to fit between the shell and the bottom bracket sleeve. It runs the risk of snagging on the BB shell

Depending on your tube diameters and geometry, a third option may be available to you, the red line.

Good info, thanks. I'm guessing option 1 is what Bingham Built has done here?

The red line idea is intriguing too, but seems like routing the housing through that tight space with limited access could be quite challenging.

 

[Ben.land101]

Very nice, reminds me of an early Knolly! Can I ask what other problems it solves?

It's accomplishing the same goal as bending the seat tube (Offsetting it) But without the bend.
So, Tire clearance in other words. For reference, that bike in the pictures has a 410mm rear center.

But having the tube straight eliminates the problems with bent seat tubes. Mainly, dropper clearance. The name of the bent seat tube game is smaller and smaller CLR's and tighter degrees of bend, etc, all to get the bend as low as possible. There's a pretty hard limit with conventional methods. That bike can run a theoretical ~250mm dropper (for a tall person) or a proper 210mm or similar for shorter riders.

I'm also starting to question the current trend of super steep seat tube angles.
Gently places tin foil hat on my head
I'm convinced they exist for the same reason that mullet bikes exist.

But anyways, the not-bent offset tube makes whatever seat tube angle you want easier also, without compromising the other stuff.

 

[natzoo]

Good info, thanks. I'm guessing option 1 is what Bingham Built has done here?

The red line idea is intriguing too, but seems like routing the housing through that tight space with limited access could be quite challenging.

It is possible that the Bingham may have a TI tube running all the way to the seat tube.

In my experience, routing either the red and blue line always involve some snagging if you forget and tug on the seatpost too hard, which fouls the cable, and is followed up by immediate regret and 30min getting the BB out.

It would be great to get an internal tube from the DT entrance into the seat tube, but I think the min bend radius of the internal tube starts becoming a factor. Also, I think most people weld the ST to the BB first, then miter the downtube around the seat tube. This makes the internal tube an even harder proposition.

 

[jsudar]

I milled a 3/8 slot in the BB shell, then attached the ST and milled it to match. Probably wouldn’t be too hard to put a guide in the to help navigate around the BB before the DT is installed.
I have also used a spherical rotary file on a die grinder to make a similar cut on a frame I didn’t build myself. My 1990 Redline Forty Four has internal dropper routing that exits near the head tube.