Outer brake casing diameter ?

[FINNEY1973]

http://jagwire.com/products/v/road_pro - say's 5.0mm on all road outers, 4.0mm on gear outers. Possibility that the ebay sales pitches aren't correct?

I have a hunch it's my frame and not the cable outers that are the issue.

As Richard has just suggested internal guides on some frames may differ to the norm?

I've spent 30 minutes looking at brake cables online :facepalm:

You're right, the industry standard seems to be 5mm brake, 4mm gear. Maybe 4mm is some old stock size but I can't find anything about 4mm brake online.

I do suspect that some cablesets are sold as something they're not, i.e. cheap production, cheap materials then bagged up as a known manufacturer - that's why the 'proper' cablesets are emblazened with manufacturer names and have some impressive construction for something so simple. 4.0mm could well be an older specification but my hunch is it's gear outer though in theory a brake cable shouldn't then fit should it?

I always assumed (very dangerous I know) that the inner cable guide in a TT was brazed in and made of metal - am I wrong in thinking this or are there plastic & metal ones out there subject to the frame builder?

Confusion reigns....

 

[TGR]

I am now more confused! Is Ian saying that the cable outer he has tried is too big for the stop in the top tube? Or is he using a 5mm aluminium outer end on the cable outer and it is too big? I really think that pics would help and some input from a frame builder.

Richard

 

[Ian Raleigh]

Richard the steel ferrule has been cut off the outer cable casing and the plastic covering has been
neatened up so it would go through the hole but just didn't as its too wide!

Had a reply from an ebay seller:

''Thankyou for the enquiry unfortunately 5mm is now the standard size for all outer cables but you could buy narrower brake cable casing years ago which was about 4.5mm but has not been around for many years now. Using 4mm outer gear cable could be possible but you would have to try and pull out the entire nylon liner for the larger brake cable to fit through the casing, This is not the most ideal way as there will be friction inside the casing and will wear faster, Also the brake lever will feel rough as you brake, So you would have the fill the casing with grease and then thread the cable through.

Hope this helps you somewhat''

 

[Ian Raleigh]

Update on the find a suitable brake cable quest :roll:

Fibrax 4.9mm outer goes in to the hole but jams further in.

Clarks 4.6mm outer casing slips into the hole goes that bit further then that jams.

Went to local bike shop and took the bike, they tried all their cables, then tried 4mm outer gear casing, fits through :roll:

Talk about waste money on friggin outer bloody cable casing :facepalm:

 

[Ian Raleigh]

Question for you guys !

Instead of trying to use the thick inner brake cable inside the gear cable casing
could I use a gear cable instead ? Would they be strong enough ?

I'm all ears!

 

[Jezmellors]

I'm probably teaching you guys to suck eggs here but my understanding is that gear and brake outers are made differently, gear outers have linear wires and brake outers have spiral wires to resist compression.
Brake inners and outers are bigger and stronger because there is a greater safety factor built in, forces used in braking are much greater and a failure in a breaking system is potentially much more serious than in a gear system.
Having said all this, if you are routing brake cable through the frame you are probably talking about the rear brake and i read somewhere that upto 80% of braking force is achieved with the front brake (I only have a front brake on my single speed bike) so how important is the rear brake's performance to you?
I'm certainly not advising you to do this, i never have and i'm not sure if it will work or not, but it may be that you decide that using a gear inner and outer on the rear brake is ok in this situation.

 

[Wold Ranger]

Loving this and chuckling to myself, sadly I'm old enough to have the answer, which won't help you much!!!!
Modern style is 4mm gear 5mm brake simples, OK?
Old bikes utilised Imperial sized cabling which was 5/32" diameter, both brake and gear the same, or near as dammit 4mm :mrgreen:
The trouble was, old 5/32" brake cables were prone to snapping, as inners were way thin, hence why the 5mm standard came about.
You could use gear inners and outers but thread a collett down to the nipple (you may need a fabricate one) so that it doesn't pull through the lever's aperture stop.

 

[Woz]

"I'm probably teaching you guys to suck eggs here but my understanding is that gear and brake outers are made differently, gear outers have linear wires and brake outers have spiral wires to resist compression."

Slight correction; gear cables with linear wires are "compressionless" to simply aid new fangled indexing. They can not be used for brakes; the plastic outer casing will split under load. Brake outers that use coiled wire compress slightly.

My suggestion would be to source some old NOS gear cable that uses coiled wire - I'm pretty sure the Shimano XT stuff from the early 90s was coiled.