Weak Braking - Shimano 105
 

Since I exfoliated the more padded area of my anatomy on a stretch of
wet tarmac, my rear brake has been acting up. I have a full and
unrestricted range of moment in the lever (Shimano 105) but seem
unable to apply sufficient pressure to the brake.

The brake mechanism (and pads) are fine. However, the shifter took a
knock when I fell and scraped a bit along the road. Whilst it's
scratched up a bit, there's no visible mechanical damage to the lever
and I have no problems changing gear with it.

Pulling the brake cable away from the top-tube puts a good amount of
pressure on the brakes. However, using just the lever I just can't
get enough pressure on the brakes to stop the bike. The problem must
therefore lie somewhere in the lever, or in the cable around the
lever.

I'd be very grateful for any insight. I presume I must have damaged
the gear lever, but it feels normal to use (apart from not stopping me
properly!)

Weak Braking - Shimano 105
 

Weak Braking - Shimano 105
 

in message . com,
') wrote:

Since I exfoliated the more padded area of my anatomy on a stretch of
wet tarmac, my rear brake has been acting up. I have a full and
unrestricted range of moment in the lever (Shimano 105) but seem
unable to apply sufficient pressure to the brake.

The brake mechanism (and pads) are fine. However, the shifter took a
knock when I fell and scraped a bit along the road. Whilst it's
scratched up a bit, there's no visible mechanical damage to the lever
and I have no problems changing gear with it.

Pulling the brake cable away from the top-tube puts a good amount of
pressure on the brakes. However, using just the lever I just can't
get enough pressure on the brakes to stop the bike. The problem must
therefore lie somewhere in the lever, or in the cable around the
lever.

I'd be very grateful for any insight. I presume I must have damaged
the gear lever, but it feels normal to use (apart from not stopping me
properly!)

Investigate everything else first, as those Shimano shift levers are not
cheap, and are not repairable - service parts are not available. I would
try changing the cable outer - the sheath - of the rear brake cable. This
will mean retaping your bars, which is a nuisance; but damage to the
sheath could produce the symptoms you describe. Also inspect all the
points on the bike where the sheath terminates - i.e. (typically) at frame
stops either end of the top tube, at the lever itself, at the brake
calliper itself.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/
Iraq war: it's time for regime change...
... go now, Tony, while you can still go with dignity.
[update 18 months after this .sig was written: it's still relevant]

Weak Braking - Shimano 105
 

You have either stretched that cable, or it has slipped through the nut
at the actual brake.

That's what I thought at first, but even with the cable very (i.e.
too) tight, I can't get the brake to work properly. I should have
said that in my post. The sensation is much like having an oily brake
pad (I don't) - I'm gripping hard and getting a firm response from the
lever, but it just doesn't stop the wheel from turning.

Fortunately, I got away with little more than scratches, a slightly
bent wheel and the dodgy brake. That's jolly lucky - my GPS was
doing 40 when it hit the road and turned off!

Weak Braking - Shimano 105
 

wrote in message
oups.com...
You have either stretched that cable, or it has slipped through the nut
at the actual brake.

That's what I thought at first, but even with the cable very (i.e.
too) tight, I can't get the brake to work properly. I should have
said that in my post. The sensation is much like having an oily brake
pad (I don't) - I'm gripping hard and getting a firm response from the
lever, but it just doesn't stop the wheel from turning.

Mine feel like that - I assumed my brake blocks are crap though and/or oily.

Have you got crud in the outer tubes on the cable which is making it hard
for the cable to slide? Or - perhaps due to a bump - has the outer tubing
got a kink/sharp bend in it which the cable is struggling to pull around?
--
peter

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http://www.petereverett.co.uk/tickets/

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Visit website if you want to contact me

Weak Braking - Shimano 105
 

Weak Braking - Shimano 105
 

Weak Braking - Shimano 105
 

Pete Biggs wrote:
wrote:

Since I exfoliated the more padded area of my anatomy on a stretch of
wet tarmac, my rear brake has been acting up. I have a full and
unrestricted range of moment in the lever (Shimano 105) but seem
unable to apply sufficient pressure to the brake.


What happens when you pull the lever as hard as you can when not riding the
bike?

If you are not able to make the lever touch the handlebar, then there is
nothing wrong its ability to transmit force from you to the brake.

Not really a kink in the cable or something trapping it preventing full
movement, maybe a broken strand.

I'm no expert, but I'd take all the inner/outers off and check them.
Then the toe of the brake to make sure it didn't get smacked and is out
of line, lastly I'd take the lever apart. But I'm no expert.

I might get someone else to have a go as well, just to verify.

Weak Braking - Shimano 105
 

Thanks for the all responses - they're very helpful.

I've already taken the bar tape off to inspect the exterior of the
cables (no visible damage or kinks) but haven't had the insides out
yet. I'll take a look tonight.

Re. pulling the brake cable at the top tube, what that shows me is
that the brake + pads are working okay. The lack of tension from the
levers is dramatic - I can put all my weight on the left lever and
still push the bike forward relatively easily, wheras pulling the
cable by hand is much more effective.

The lever itself appears to be working correctly - if I take all the
pressure off the cable it has a full range of movement, and with the
cable set correctly I can't pull the lever all the way back. However,
it is very slightly spongier than I remember it being before.

I'm beginning to think there must be an obstruction between the inner
and outer cables at their front ends. That would make sense and be a
lot cheaper to fix than a broken lever!

Thanks again!

Weak Braking - Shimano 105