New brake won't stop slipping!
Colin B.
Just put new brake cables, levers, and cable housing on my ancient road
bike. Everything went fine, except that I cannot tighten the back brake
anchor enough to keep the cable from slipping under very minor pressure.
I mean, I've tightened that bolt HARD, and the cable slips on a single pull
of the brakes.
The brakes themselves are old Shimano SLRs, and the cables are teflon-coated
Nervz.
Any suggestions here? I'm thinking of putting contact cement on the anchor
surface and the cable, but I don't know if that'll help or not.
Thanks,
Colin
jim beam
> Hey folks;
>
> Just put new brake cables, levers, and cable housing on my ancient road
> bike. Everything went fine, except that I cannot tighten the back brake
> anchor enough to keep the cable from slipping under very minor pressure.
> I mean, I've tightened that bolt HARD, and the cable slips on a single pull
> of the brakes.
>
> The brakes themselves are old Shimano SLRs, and the cables are teflon-coated
> Nervz.
>
> Any suggestions here?
yes, don't use teflon coated cable! also, be sure you have the pressure
block on the correct way around.
Jeff Starr
Hi, without damaging the actual cable, you might try removing, or
roughing up the teflon surface. Try some steel wool. Also, not the
mating surfaces, but the bolt itself should be greased.
Life is Good!
Jeff
Lou Holtman
Burn of the teflon on the part of the cable that is under the bolt. It
has no use there.
Lou
--
Posted by news://news.nb.nu
jim beam
hard to do without risking cable softening [and the health risks of
toxic vapor ingestion] - caught between a rock & a hard place. best to
not use teflon cable at all.
Lou Holtman
It was quit easy with my teflon coated derailleur cables on my ATB. Just
used a cigarette lighter and hold my breath for a couple of seconds.
> best to not use teflon cable at all.
I agree.
jim beam
so did the steel soften? or did you not test? the temperature to burn
off teflon is high enough for this to be a factor. it's fine if it's
beyond the anchor point like the soldered end debate earlier, but here,
the affected area is load bearing. i definitely wouldn't do it.
Lou Holtman
To be honest I didn't test it. As I said it was a derailleur cable and
the pulling forces aren't that high. Maybe it isn't a good idea for a
brake cable. Good point. So the OP better remove the teflon coating with
a hobby knife.
jim beam
yes, derailleur is much less of a problem.
believe it or not though, the knife thing is not a great idea! it'll
end up scratching the strand surfaces which can initiate fatigue. if i
were the o.p., i'd look for some clamping assembly problem. i've used
teflon coated cable in the past and experienced no slippage issues, so
while i don't think it's great idea, i do know that it works. if teflon
is to be the magic bullet, it needs to be in the liner, not coating the
cable.
Mark Janeba
I don't get it. I know I have a bad tendency to over-tighten things,
but the brake cable clamps I can remember physically deform the cable,
so that it is mechanically restrained from slipping. Maybe I'm just
remembering the old center-pull and canti cable clamps.
I suspect a washer or some such has been mislaid, which would provide
the "pinch" I mention above. Certainly worth checking into.
Mark
Phil, Squid-in-Training
Yes, this is the exact problem I had with my old SLRs and one of the primary
reasons that I dispensed with single-pivot brakes. The cable must be
pinched between two *steel* surfaces. If you have a missing washer, it's
easy to get the cable pinched between steel and aluminum or
aluminum/aluminum. This would most definitely cause slippage.
--
Phil, Squid-in-Training
jtaylor
"jim beam" <nos...@example.net> wrote in message
> > It was quit easy with my teflon coated derailleur cables on my ATB. Just
> > used a cigarette lighter
>
> so did the steel soften? or did you not test? the temperature to burn
> off teflon is high enough for this to be a factor. it's fine if it's
> beyond the anchor point like the soldered end debate earlier, but here,
> the affected area is load bearing. i definitely wouldn't do it.
>
No.
Typical teflon melting points are in the neighbourhood of 300 degrees
Celcius. It is unlikely that typical steels wil "soften" at such low
temperatures (4130 for example needs something over 800 degrees Celcius, and
that usually for an extended period of time).
Colin B.
Thanks to all. I scraped the teflon off, and then roughed up the surface of
the cable. It's true that this can weaken the cable, but if that's the only
way I can get it to clamp properly, then so be it.
As an aside, I took a good look at the pinch-clamp washer. It has a groove
for the cable to sit into, and in that groove are two pins which are
presumably there to hold the cable tight. Those pins are worn down to
about nothing, so the cable is free to ride in the groove. Looks like I need
to get some more new bits now.
Thanks,
Colin
Ted Bennett
That's "Celsius". My God, the disinformation here is astounding.
(Just a little joke, no need for firing off an angry reply.)
I think Jim meant that much lower temperatures than the "softening"
temperature will alter the structure of the steel for the worse.
--
Ted Bennett
jtaylor
"Ted Bennett" <tedbe...@earthlink.net> wrote in message
news:tedbennett-8E4B3...@news.west.earthlink.net...
By "softening" I did assume that jim "I used to be a metalurgist, but now
I'm an anonymous jerk on the net" beam DID mean annealing; which DOES
require the 800 degrees indicated above.
Werehatrack
<cbi...@somewhereelse.nucleus.com> wrote:
Does the bolt have a square shoulder on it? If so, I suspect that
it's rotated a little off from the correct alignment, and become
jammed in the hole.
--
Typoes are a feature, not a bug.
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