brake cable housing < 5 mm, does it exist?
 

I have an no-name time trial bike from the 90s (track ends, rd hanger, someone on C&V suggested it might be an older time trial bike) that has internal routing for brakes, gears, etc.

The problem I'm having is that the guides in the top tube for the rear brake are too tight for 5 mm housing. I can push the housing in about an inch, but applying the brake causes the housing to start to shred against the edges of the "port" so there doesn't seem to be a "stop" inside the top tube.

Using any sort of step down ferrule also seems out of the question because the ferrule itself would "float" along the edge of the "port" <-- does this make sense?

It seems like the internal routing for this frame requires cable housing < 5 mm... of which I've only been able to find the compression-less variety.

I've currently "solved" this by stripping the plastic cover from a length of housing which allows it to fit through the internal guide and then using double ended ferrules to complete the housing runs to the lever and brake. It works, but appearance-wise, it's not idea.

Is there brake cable (or non-compressionless) housing that is less than 5 mm in diameter? Has anyone else come across a frame with internal routing like this (e.g. odd diameter guides)?

Thanks for any help/suggestions,
James

Clark's and some Dia Compe cables of that era had slightly smaller OD's. I don't know if current production stuff still does. I have some NOS Clarks kits, and DiaCompe roll housing that might be what you need a various colors, but no black or white.

If you want I could send you a small length to try out.

Shimano Dura Ace cable set is 4mm housing with the 5mm ferrules, about $15 - $20 a set.

you sure the 4 mm DA housing isn't compressionless? i.e. just for shifter cables?

Yeah - cable housing diameters seem to be inconsistant between manufacturers anyway.

If you don`t find any other options - Jagwire Ripcord is Kevlar reinforced compressionless cable housing and is suitable for both shifters AND brakes. It has a dia of 4.5mm.

Good to know.. thanks.

dang, it looks like it's just the derailleur housing is that is 4.5 mm and is only nylon reinforced (at least all that I could find online)...

Sorry I was recommending DA because I knew it would fit with a ferrule, hadn't herd of compression less housing before. I was wondering if there is a stop in the frame and I knew the DA should fit but it is precut,not full length. A lot of shops carry both housings in 4 and 5 mill. A lot of the older bikes and custom bikes also used full length housing internally.

My Quality book lists 4.5mm Jagwire brake housing (not Ripcord) in 4 different colors. That's all that I can tell you about it because I've never used it. I can tell you that I've been very pleased with Jagwire 5mm Ripcord universal brake/derailleur housing. It greatly improves the "feel" of mechanical disc brakes.

LOL OK So maybe I`m being a little imaginative here to help out the OP. The Ripcord that Jagwire produces for shifter cables is 4.5mm and the Ripcord that Jagwire produces for brake cables is 5mm.

The key question is: Can a current SS inner BRAKE cable easily slide through the L3 liner in that 4.5mm Ripcord intended for SHIFTER cable?

And the answer is "YES!" I have some here and checked before posting.

Most modern bikes would be set up to interface best with 5mm brake cable and ferrules but the OP has an unusual situation. So if nothing else works - guarantee that combo of Ripcrd derailleur housing and SS brake inner cables will work like a charm if thats the size needed to do a continuous run through the frame tubing.

Take a small rat tail file and open up the holes to fit bigger housing?

using derailleur housing for brakes is something that is always stated in ALL CAPS as a DON'T. The rip chord brake housing claims kevlar reinforcement since it is also compressionless... otherwise this is what I'd do.

it's a tube brazed into the top tube so this wouldn't work. In fact, I have no idea if it's the same diameter through out the length... all I know is that housing with the plastic stripped off slides right in.

Do you have a stock number or upc or something so I can try to order it?

Wild! Usually they're just two short sections of tube one for the entry and one for the exit. Sometimes they're curved which would rule out filing also, but...

QBP parts numbers:
CA4327 - black
CA4328 - gold
CA4329 - silver
CA4330 - titanium

FWIW, 4.5mm derailleur housing has different part numbers.

Agreed and any Jagwire compressionless shifter housing EXCEPT the Ripcord would also be a no-no. The Kevlax exterion on both the 5mm and the 4.5mm housing is identical. The reason I`m guessing they didn`t offer both sizes as off the shelf items for brakes as well is the vast selection of Jagwire ferrule styles and colors already offered for 5mm brake housing. As well thats the standard interface size for modern bikes. You have an unusual situation and will have to use a little inginuity to deal with it. As it is, its possible that you would be better off using 4.5mm ferrules on your bike (you could check) in which case it might make sense to use ferrules designed for shifter cable, drop the internal O-rings and run a small drill through the exit hole to provide clearance for the larger cable.

Your bike - your decision.

thanks everybody for the suggestions and input. This is what I've done, let me know what you think.

1. take a full run of standard brake housing
2. cut in half (roughly) after measuring which section would be incased in the top tube.
3. strip the casing off both ends that would go in the tube

I figure since both ends are metal, and will be incased in the routing tube, there shouldn't be a problem with flex. Looks pretty much like I'm running the entire housing through the tube and seems to work fine. What do you think?

Just wish I knew what the original spec/configuration was for this particular bike.