Brake Cable Routing = Which way is best for performance?

AMuzi writes:

On 2/18/2014 9:42 PM, Sir Ridesalot wrote:
When routing cables there have been many ways to do it.First was over the handlebars brake cable housig with long swooping curves. They usedcable clips on the top tube and then later brace on cable housing guides were used. Next there were cable housings routed through tthe top tube. Then there were aero brake cable routing the cable housing under the handlebar tape which meant a tighter radius in each of the curves of the cable housing.

Given identical cables and cable housing with each type of routing, which one would theoreticlly if not practically give the best performance? Assume too that the actual brake calipers are the samefor every setup.

Cheers


That's easy.
Outside the handlebar with traditional levers.
You want a large radius while avoiding recurves.

For the most part, the radius doesn't matter unless it's quite small.
What does matter is total curvature, that's what you want to reduce.
The cable friction loss is proportional to exp(mu*theta), where mu is
the cable coefficient of friction and theta is the total curvature, in
radians (a circle has a total curvature of 2*Pi radians). The modern
brake routing has a smaller total curvature than the old, swoopy, over
the bar routing.

--
Joe Riel

On Wed, 19 Feb 2014 17:34:02 -0800 (PST), jbeattie
wrote:

On Wednesday, February 19, 2014 4:55:19 PM UTC-8, John B. wrote:
On Wed, 19 Feb 2014 11:41:09 -0800 (PST), jbeattie

wrote:



On Wednesday, February 19, 2014 10:58:50 AM UTC-8, AMuzi wrote:

On 2/19/2014 12:35 PM, wrote:



AMuzi wrote:



Sir Ridesalot wrote:



When routing cables there have been many ways to do it.First was over the handlebars brake cable housig with long swooping curves. They usedcable clips on the top tube and then later brace on cable housing guides were used. Next there were cable housings routed through tthe top tube. Then there were aero brake cable routing the cable housing under the handlebar tape which meant a tighter radius in each of the curves of the cable housing.



Given identical cables and cable housing with each type of routing, which one would theoreticlly if not practically give the best performance? Assume too that the actual brake calipers are the samefor every setup.







That's easy.



Outside the handlebar with traditional levers.



You want a large radius while avoiding recurves.







AAAAAAAAAAAAAAAAAA



yup



http://www.raydobbins.com/molteni_replica/photo19.jpg







FRICTION LEVERS ! Shimano housing(s) mated with Shimano cable(s) run in soaked Finish Line Wax and Teflon..



a big turn into the deray with a section of Ultra Housing if separate.



continual end housing lubing with liquid silicone



but there are bar bags amd I doahno for Bikepacking....dirt road but trail ?



when there at the end use trail level does response design qualify or dirt proofing....pick.



I'm pleased getting the right gear, brake release ahhhhhhh brake release let me count the ways.......











OMG that's a gorgeous thing and a beautiful photo.



I've got one of those Unicanitor saddles on my commuting bike. No Benotto death tape -- not up here in the wet PNW. I need something with more traction.



Speaking of cable routing, with all the muck, I would be better off with the old over the BB routing, or maybe something super-modern, like this: http://www.trekbikes.com/us/en/bikes...ross/crockett/ I get lots of sticking with the under the BB route. I would like to find a cable guide that has closed tubes.



-- Jay Beattie.



Tubing guides under the Bottom Bracket get all full of gorp, sometimes

to the point where shifting is effected.

--

Cheers,

I might experiment with running my rear derailleur cable through a length of liner and see if that helps at all -- or just gets gunky. The winter muck causes the bare cable to hangs up on the BB guide which gives me ghost shifting.

-- Jay Beattie.

Actually (I hate to say it) the best under Bottom Bracket guide seems
to be those cheap plastic gizmos. Mounts on the bottom of the B.B.
with one screw and are pretty much self lubricating - wire on plastic
:-)

There are also B.B. guides that mount on the top of the B.B. but that
pretty much requires a steel B.B. and a bit of silver solder, and the
cable stop on the chain stay also needs to be moved to the top of the
stay.

I've also seen reference to an internal cable routing which exited the
chain stay where the usual cable to the derailer stop is. But I don't
remember where the cable enters the system.
--
Cheers,

John B.

On Thursday, February 20, 2014 1:06:03 AM UTC-5, JoeRiel wrote:
AMuzi writes:



On 2/18/2014 9:42 PM, Sir Ridesalot wrote:

When routing cables there have been many ways to do it.First was over the handlebars brake cable housig with long swooping curves. They usedcable clips on the top tube and then later brace on cable housing guides were used. Next there were cable housings routed through tthe top tube. Then there were aero brake cable routing the cable housing under the handlebar tape which meant a tighter radius in each of the curves of the cable housing.



Given identical cables and cable housing with each type of routing, which one would theoreticlly if not practically give the best performance? Assume too that the actual brake calipers are the samefor every setup.



Cheers





That's easy.

Outside the handlebar with traditional levers.

You want a large radius while avoiding recurves.



For the most part, the radius doesn't matter unless it's quite small.

What does matter is total curvature, that's what you want to reduce.

The cable friction loss is proportional to exp(mu*theta), where mu is

the cable coefficient of friction and theta is the total curvature, in

radians (a circle has a total curvature of 2*Pi radians). The modern

brake routing has a smaller total curvature than the old, swoopy, over

the bar routing.



--

Joe Riel

***************

rear deray cable effectiveness increases with 2-3x more diameter than stock as with stock bars, pedal shafts, rim width...

reducing curvature directly decreases radii, right ?

what cable system does JB use commuting in that slosh ? 'like' urnot pinching pennies over there.

the prob for us DIY is how to lay in the cable n stops...seems the effective solution is experience reduced to particular bikes. we have no experience.

On 2/19/2014 9:32 PM, Phil W Lee wrote:
Sir Ridesalot considered Tue, 18 Feb 2014
19:42:08 -0800 (PST) the perfect time to write:

When routing cables there have been many ways to do it.First was over the handlebars brake cable housig with long swooping curves. They usedcable clips on the top tube and then later brace on cable housing guides were used. Next there were cable housings routed through tthe top tube. Then there were aero brake cable routing the cable housing under the handlebar tape which meant a tighter radius in each of the curves of the cable housing.

Given identical cables and cable housing with each type of routing, which one would theoreticlly if not practically give the best performance? Assume too that the actual brake calipers are the samefor every setup.

Cheers

If brake performance were the only factor, the ideal would be whatever
gives the least total amount of curvature in the cable, as that is
what produces both friction and compressibility of the outer.

But then that may have aerodynamic implications, or catch on stuff you
don't want it to.
Then there's aesthetic considerations, and ease of maintenance.
Whatever route is used is a compromise between all those factors.


The aspect I noticed most is the ease of slipping a bike
into a car. Cables under tape make that much simpler. Other
differences were less dramatic.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On 20/02/14 17:06, Joe Riel wrote:

The modern
brake routing has a smaller total curvature than the old, swoopy, over
the bar routing.


Really? How do you measure that?

ISTM the old had about a 180 degree total curve. Vertical up from the
caliper to vertical down at the lever.

The new has vertical up from the caliper, through 90 deg to the bars,
and through another 90 deg under the tape to the lever.

All in all about the same, really.

--
JS

On Thursday, February 20, 2014 1:06:03 AM UTC-5, JoeRiel wrote:

For the most part, the radius doesn't matter unless it's quite small.
What does matter is total curvature, that's what you want to reduce.
The cable friction loss is proportional to exp(mu*theta), where mu is
the cable coefficient of friction and theta is the total curvature, in
radians (a circle has a total curvature of 2*Pi radians).

The other factor is the presence of return springs inside modern levers.
Old ones relied on the brake caliper springs to return the levers home.
That required a strong caliper spring, so a stronger high-side tension
on the cable.

With the little spring returning the lever to home, caliper springs
can be weaker, high side tension is less, so friction loss is less.
Control is better. At least, that's how it seems to me.

- Frank Krygowski

On Thursday, February 20, 2014 8:31:58 AM UTC-5, AMuzi wrote:


The aspect I noticed most is the ease of slipping a bike
into a car. Cables under tape make that much simpler. Other
differences were less dramatic.

I appreciated easier access to a clip-on aero bar, and/or easier access
to a handlebar bag. That was actually what motivated me to go to
"aero" levers.

- Frank Krygowski

James writes:

On 20/02/14 17:06, Joe Riel wrote:

The modern
brake routing has a smaller total curvature than the old, swoopy, over
the bar routing.


Really? How do you measure that?

ISTM the old had about a 180 degree total curve. Vertical up from the
caliper to vertical down at the lever.

There isn't much different in the front brake, though the modern
routing is shorter, which helps, but probably is not significant.
The routing to the back is definitely better, it eliminates almost
90 degrees of bend.

The new has vertical up from the caliper, through 90 deg to the bars,
and through another 90 deg under the tape to the lever.

All in all about the same, really.

--
Joe Riel

On 21/02/14 15:32, Joe Riel wrote:
James writes:

On 20/02/14 17:06, Joe Riel wrote:

The modern
brake routing has a smaller total curvature than the old, swoopy, over
the bar routing.


Really? How do you measure that?

ISTM the old had about a 180 degree total curve. Vertical up from the
caliper to vertical down at the lever.

There isn't much different in the front brake, though the modern
routing is shorter, which helps, but probably is not significant.
The routing to the back is definitely better, it eliminates almost
90 degrees of bend.

Really? How do you figure? I get;

180 + 90 + 70 for old

Up from the lever through 180 degrees, then bend toward the back of the
bike with 90 degrees and through another 70 or so to get to the back
caliper.

90 + 90 + 90 + 70 for new

Out from the lever and through 90 degrees around the bend in the bars,
then through 90 degrees to point almost straight down and through
another 90 to point toward the back of the bike, and another 70 to the
caliper as before.

Seems identical!

--
JS

On Fri, 21 Feb 2014 16:08:41 +1100, James
wrote:

On 21/02/14 15:32, Joe Riel wrote:
James writes:

On 20/02/14 17:06, Joe Riel wrote:

The modern
brake routing has a smaller total curvature than the old, swoopy, over
the bar routing.


Really? How do you measure that?

ISTM the old had about a 180 degree total curve. Vertical up from the
caliper to vertical down at the lever.

There isn't much different in the front brake, though the modern
routing is shorter, which helps, but probably is not significant.
The routing to the back is definitely better, it eliminates almost
90 degrees of bend.

Really? How do you figure? I get;

180 + 90 + 70 for old

Up from the lever through 180 degrees, then bend toward the back of the
bike with 90 degrees and through another 70 or so to get to the back
caliper.

90 + 90 + 90 + 70 for new

Out from the lever and through 90 degrees around the bend in the bars,
then through 90 degrees to point almost straight down and through
another 90 to point toward the back of the bike, and another 70 to the
caliper as before.

Seems identical!

Additionally I believe you will have to make some allowance for radius
of bend. At least it appears self evident that a large diameter bend,
say from the top of the brake lever to the first cable guide on the
top tube will have less frictional losses then a small radius bend,
say from an aero brake lever around the bend of the handlebar.

--
Cheers,

John B.