Re: [CR] Brakes and flex


Example: Framebuilders:Chris Pauley

From: "paccoastcycles" <paccoastcycles@sbcglobal.net>
To: "Jon Spangler" <jonswriter@att.net>, "Dale Brown" <classicrendezvous@bikelist.org>
References: <D27D31E1-60E1-4C2F-BDBD-FCCD546DDD7B@att.net>
Date: Wed, 5 Jan 2011 08:11:04 -0800
Subject: Re: [CR] Brakes and flex


What is referred to as cable stretch, that is, the need to take up some cable after any new set-up, is the settling in of cable housing ends into the ferrules, the ferrules into their respective homes, etc.

Of the engineers here, I'd like to ask a question. If we were to have a cable that stretched, say two millimeters over the distance of a rear brake run, would the cable stretch just those two millimeters and then stabilize? And, if so, why wouldn't it keep stretching?

At the Interbike show a few years ago, I happened upon the Sram booth where, unless I misinterpreted what I walked in on the middle of, the guy was telling his audience that Sram had studied cable behavior and that they do not stretch in the use they recieve on bicycles.

Chuck Hoefer
Pacific Coast Cycles
Oceanside, Ca.


----- Original Message -----
From: "Jon Spangler"
To: "Dale Brown"
Sent: Tuesday, January 04, 2011 10:58 PM
Subject: Re: [CR] Brakes and flex



>
> Jon Spangler
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>
> Dear All,
>
> If brake cables are not stretching when new (and requiring re-attachment
> to take up the slack), what is it that is causing this
> need for readjustment after installing any new brake cables?
>
> I am all ears (and eyes), folks....
>
> Jon Spangler
> Curious in Alameda, CA USA
> and still at a late-night City Council meeting
>
>
> Message: 13
> Date: Tue, 4 Jan 2011 22:10:44 -0800
> From: "paccoastcycles" <paccoastcycles@sbcglobal.net>
> Subject: Re: [CR] Brakes and flex
> To: "Ken Freeman" <kenfreeman096@gmail.com>, "John Betmanis"
> <johnb@oxford.net>
> Cc: classicrendezvous@bikelist.org
> Message-ID: <280940BA0D074C1EBE759E250580C329@ownerd556865ac>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
> John Betamus, thank you for making me not feel alone in the world of
> bicycle
> mechanics with regard to cables not stretching. I'm always shagrined (not
> crestfallen) when I hear someone who says their mechanic said this or that
> about cable stretch. I think of it this way: If you try to hang a car from
> a
> bridge with a bicycle cable, it will stretch...and then break. But the
> forces we put on these cables are not stretching them.
>
> Chuck Hoefer
> Pacific Coast Cycles
> Oceanside, Ca.
> ----- Original Message -----
> From: "Ken Freeman" <kenfreeman096@gmail.com>
> To: "John Betmanis" <johnb@oxford.net>
> Cc: <classicrendezvous@bikelist.org>
> Sent: Tuesday, January 04, 2011 6:08 PM
> Subject: Re: [CR] Brakes and flex
>
>
>> I've made a lot of improvement in the feel of previously bad brakes by
>> replacing with modern inner and outer cables, carefully terminated by
>> filing
>> and with ferrules.
>>
>> On Tue, Jan 4, 2011 at 4:42 PM, John Betmanis <johnb@oxford.net> wrote:
>>
>>> On 04/01/2011 3:53 PM, Harry Travis wrote:
>>>
>>> Please someone, show me that new design stainless steel cables stretch
>>>> less
>>>> than old-skool zinc-plated ones (any more than bicycle chains
>>>> "stretch.")
>>>> Which is to say: Show me that they measurably stretch at all, as
>>>> against
>>>> simply having the ends bed and the housings move.
>>>>
>>>
>>> Springiness or lost motion in brake cables is no more due to "stretch"
>>> than
>>> a worn-out chain is "stretched". It's the housing that's the culprit
>>> when
>>> it
>>> appears to "compress". If there is excessive clearance between the inner
>>> cable and the housing, the housing will "buckle" in a series of "S"
>>> curves
>>> before any serious tension reaches the brake caliper. Moreover, if the
>>> housing is made of round section wire rather than rectangular, the coils
>>> can
>>> also "slip" allowing more "compression". I believe the reason the better
>>> modern cables have less "stretch" is due to better design and closer
>>> tolerances.
>>>
>>> --
>>> John Betmanis
>>> Woodstock, Ontario
>>> Canada