zeta

Updated: Turns out these Soma levers I have are quite different from the TTs, so does not apply to Cane Creek...

I am very happy to ride on my newly assembled bike but the brakes give my quite a headache (and some worries)! The brake cable of the rear brake failed three times within just three month. By failing I mean the little metal head inserted into the lever rips off while braking (with pretty little force). I think the wires rip out of the head one by one as I can feel the brake becoming more and more mushy during the days before a failure.

My brake setup is a bit bizarre, so let me describe it quickly.

Parts: I use a bullhorn handle bar with Soma bar end levers and additional Cane Creek cross top levers as interrupter levers. However, I mostly use the bar end levers. My brakes are low-profile Paul touring cantis. The brake cable is from Clarks and the housing is from Jagwire.

Cable routing and adjustment: Obviously I need to route the cables below the handlebar tape to the interrupters. In addition the cable is routed internally through the top tube and ends in a cable hanger soldered to the frame. So yes, there are a few turns but I made sure to bend the cable as little as possible. When I pull the cable by hand, I do not feel any drastic friction but that's hard to measure. The cable housing at the Soma levers ends right at the end of the handlebar.
As Sheldon Brown suggests for low profile cantis, I set up the traverse cable with a pretty low yoke angle of around thirty degrees or so. The traverse cable is almost rectangular to the brake arms (which lean a bit outwards of course).


Did anyone experience something similar with the Soma levers? Or would you rather suspect the setup? Do I have to much mechanical advantage? I noticed that the Soma levers allow quite some travel and to brake heavily I need to pull them quite far - but not to the max. This way I can modulate the brakes quite well.

Any kind of feedback welcome...

wschruba

This is a dippy question, but I have to ask, having seen it on bikes that have rolled in to me...

You are using a brake cable, not a derailleur cable, right?

zeta

Yes :-)

Andrew R Stewart 

While cable ends do break or come off the cables it's not a common experience. To have this happen 3 times means either each cable had the same defect or the set up is somehow wrong.

First is the question as to where, exactly, does the cable fail. Is the head pulling off the cable or the head cracking? Or is the cable fraying just past the head? I suspect the second is happening. Since cables can and do fray as they get bent back and forth (like a paper clip fails) look for that reason first. Does the cable head fit in the lever properly (there are more then two different cable hear shapes put there)? Does the casing fit square to the lever's seat and is the casing in line with the cable's needed path? Is the casing end cut square or is a coil of the casing cut so the casing wags back and forth with the cable being pulled? Good levers allow the cable end seat to pivot slightly, keeping the cable and end straight WRT to each other during the lever's range. Do your levers have this feature?

Brake cables have far more tension on them and the failure results are far worse that a gear cable failure. If you can't figure this out you owe it to your friends and family (and the poor guy you run into when the cable fails at the wrong moment) to see that this problem is resolved by someone else. Andy

FBinNY 

Brake lever cable anchors are almost universally on a swivel, so the cable doesn't bend as the lever moves through it's arc. I suspect that either you have the cable fitted or routed improperly, or the swivel is binding, so the wire bends at the head every time you use the brake.

Take a good close look at what you're doing and see if you can dope out where and why it's bending. Correct that and you should be OK.

fietsbob

this type: Lickbike.com | Cane Creek 200TT reverse brake levers

not this : Lickbike.com | Tektro RL726 top mount brake levers Right?

the 1st has a straight cable pull with a brake cable end anticipated .. the 2nd is made to go in the middle of the cable run.. splitting the housing.

zeta

Update: Turns out the Soma levers I have are quite different from the Creek TT levers.

Thanks a lot for your comments!

@fietsbob yes, it's the first kind of lever - a reverse lever. But I also have type 2 as interrupter brake.



@Andrew Your are absolutely right and I don't take it easy. That's why I posted here.The cable frays slightly towards the head and the head pops off without being damaged. I found the last failed cable in the trash bin and attached a photo. I totally agree with your point about how a good lever should pull the cable and I think this could be the reason for the failures. I use cable heads of type B (see here https://www.bikeman.com/bicycle-repa...bles-a-housing). The further the lever is pulled the more the cable bends right below the head as the head cannot rotate in the lever. I tried to capture it in the shot below.

I see two options
- Either I setup the brakes so that a very small travel is sufficient to brake properly. (That means I don't have the nice modulation I had so far)
- Or I look for bar end levers that take those barrel-like heads that are able to rotate while the lever is being pulled. That should solve the problem as well. Does anyone know such a lever?

I just wonder why nobody else has this problem....

fietsbob

^^ That looks Like a Top mount Cross lever my 2nd link of type made to spread the Housing ,
interrupting the housing bu t the running length of the cable is continuous, Through It.

and is Mis applied putting it at the end of the Bar. (but done far too Often) , Buy a real reverse Lever ..

I have had one made to use with a Barrel end commonly used on MTB..
it is free to rotate so always Pulls straight ,

and does not force any bending where bonding the end to the cable makes it stiffer..
and flexing it is the source of your failures.


SOMA is a Merry Sales Imports Brand name , Cane Creek is a different company , though both may have manufacturing done in Taiwan , a country,
the Go To Place for a Lot of Bike stuff Under various brand names .

andr0id

In your first post, you say you have a Cane Creek TT lever, but your photo says SOMA on the side.

These are not the same, I have the Cane Creek and you use the other end of the brake cable. I've never had any problems with it. There is enough free space in the cable slot that the barrel rotates as you pull the lever.

That SOMA lever looks to me and it doesn't look like either of the Cane Creek TT brake levers.

https://www.canecreek.com/resources/...structions.pdf

zeta

Mea culpa, you are right! Now that I see the specs and the drawing of the TT levers I must say they are much better engineered than the Soma ones... Already ordered! I am sure that will fix the problem.

Thanks a lot for your help!

I also changed the title of the thread accordingly - no reasons to blame Cane creek...