Back Brake Stuck! How Unistick?

Flyzipper's up to his tricks again. No blow-outs, touch wood, but today
I noticed a continuous plaintive whine, half mosquito, half baby, as I
was wheeling him, and a kind of grinding hesitation in the rear
quarters. He also seems considerably slower and heavier to ride.

On closer examination back in the garage, I find that the back brake pad
is squeaking against the rim of the wheel on its left side. As I move
the bike back and forth, I can see a little bit of light between the
wheel rim and the brake pad, which then disappears as the squeaking
starts. So not only is the brake not behaving properly, but perhaps the
wheel is off true.

What can I do about that? The back wheel is more problematic than the
front because of all that gear paraphernalia that is on it - derailleur
plus SRAM dualdrive. I wouldn't have a clue how to take it off, and I'm
heistant to mess with something as critical as a brake.

What behaviour on my part may have brought this about? On my new way
home, I have some very steep descents, and some nasty harsh stops. Last
night, too, I was driven home by a colleague, which means that Fly got
folded to go into the boot. Now, Fly may well be a folding bike by
vocation, but my impression is that he doesn't really like to be folded
and often develops little maladjustments as a result of frequent
folding-unfolding.

This is particuarly ****y because the weather is very suited to cycling
at the moment and I would not like to see Fly out of commission. To add
inconvenience, I have just booked another of my barge-and-cycling
holidays on the Burgundian Loire, departing in just two weeks! This
trip, the only one I could find after a number of other travel plans
fell through, is way too hard for me - 50km a day in hilly terrain with
no backup. I need Fly to be in perfect condition and I need to train my
own condition as far as I can in the small amount of time I have until then.

As always, thanks for the excellent and expert advice of the group.

EFR
Ile de France

in message , Elisa Francesca
Roselli ') wrote:

Flyzipper's up to his tricks again. No blow-outs, touch wood, but today
I noticed a continuous plaintive whine, half mosquito, half baby, as I
was wheeling him, and a kind of grinding hesitation in the rear
quarters. He also seems considerably slower and heavier to ride.

On closer examination back in the garage, I find that the back brake
pad is squeaking against the rim of the wheel on its left side. As I
move the bike back and forth, I can see a little bit of light between
the wheel rim and the brake pad, which then disappears as the squeaking
starts. So not only is the brake not behaving properly, but perhaps the
wheel is off true.

Don't panic! This one is easy.

OK, the simplest answer may be just as you say - the back wheel isn't
installed correctly into its drop-outs. In which case, with the bicycle
upright, loosen the quick release and/or nuts which hold the back axle,
apply a little weight to the saddle just to make sure the back wheel
sits down properly, and retighten the axle.

The other possibility is that the brake has been knocked squint. This
does happen. Looking at the Dahon website it seems you bike probably has
Promax V brakes like this:
http://www.dahon.com/components/deluxe/promax.htm
- there is a boss welded on to the seat stay on each side of the rear
rim, about two centimetres down from the rim. Pivoted on each of these
is a long arm which sticks up above the tyre, and the outer cable comes
into a bent which is attached to one of these arms. The inner cable goes
through the tube and is finally attached to the other arm. If you brake
does not look like this, please post us a picture of it.

V brakes are less likely to get knocked than caliper type brakes, but it
can happen. So once you've satisfied yourself that the wheel is properly
in its dropouts as described above, if the brake is still dragging you
need to adjust it.

On each arm there is a small screw located just above the pivot which
sticks out to the side of the bike. Adjust these screws half a turn at a
time, or even less. on the side which is dragging, tighten the screw
(clockwise). On the side which is not dragging, loosen the screw
(anti-clockwise) exactly as much as you've tightened the other. As I
say, do this half a turn at a time, after each adjustment spinning the
wheel to see if it still drags.

There's a picture on this page, third picture from the bottom, which
illustrates this adjustment:
http://www.parktool.com/repair/readhowto.asp?id=21


--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

Q: Whats a webmaster?
A: Like a spider, but nowhere near as intelligent.

Elisa Francesca Roselli wrote:
[snip]
On closer examination back in the garage, I find that the back brake pad
is squeaking against the rim of the wheel on its left side. As I move
the bike back and forth, I can see a little bit of light between the
wheel rim and the brake pad, which then disappears as the squeaking
starts. So not only is the brake not behaving properly, but perhaps the
wheel is off true.

First, check that the wheel hasn't shifted in its dropouts - that could
cause both issues.

What type of brakes are these - caliper or cantilever? Calipers
sometime rotate and get stuck - a bit of lube on the pivot(s) and some
'working' of the brake by hand is usually enough to get it to recenter
automatically.

Cantilevers stick too, and you usually have to remove the brake arm
(with an allan wrench), clean (with emery paper) and lube (with grease)
the pivot post and reinstall the brake arm. This doesn't affect the
adjustment of the brakes, so is actually fairly easy to do.

As to the wheel being off true, a mm or so isn't a big deal. If you
feel serious pulsing through the brakes, get it seen to. (It's actually
quite easy to do on the bike, too, but a bit fiddlely.)

- Brian "I am not a mechanic" Huntley

On Thu, 29 Jun 2006 20:05:54 +0200, Elisa Francesca Roselli
wrote:

Flyzipper's up to his tricks again. No blow-outs, touch wood, but today
I noticed a continuous plaintive whine, half mosquito, half baby, as I
was wheeling him, and a kind of grinding hesitation in the rear
quarters. He also seems considerably slower and heavier to ride.

On closer examination back in the garage, I find that the back brake pad
is squeaking against the rim of the wheel on its left side. As I move
the bike back and forth, I can see a little bit of light between the
wheel rim and the brake pad, which then disappears as the squeaking
starts. So not only is the brake not behaving properly, but perhaps the
wheel is off true.

The wheel probably is a bit out of true, yes, but if the wobble in the
wheel is less than a millimeter, I think there's a possibility that
the brakes are adjusted a bit too close as well.

What can I do about that? The back wheel is more problematic than the
front because of all that gear paraphernalia that is on it - derailleur
plus SRAM dualdrive. I wouldn't have a clue how to take it off, and I'm
heistant to mess with something as critical as a brake.

This requires no removal of the wheel. Depending on whether you have
a dual-pivot caliper or a V-brake setup, there will be one or two
small screws that adjust spring tension to center the brake. Turning
those changes the resting position of the arm and pad. It would be
good to learn how to adjust them anyway, as fiddling with this is
something that will need to be done from time to time. It is not
rocket science.

What behaviour on my part may have brought this about? On my new way
home, I have some very steep descents, and some nasty harsh stops. Last
night, too, I was driven home by a colleague, which means that Fly got
folded to go into the boot. Now, Fly may well be a folding bike by
vocation, but my impression is that he doesn't really like to be folded
and often develops little maladjustments as a result of frequent
folding-unfolding.

This is, in fact, a common problem with many folding bikes; that's
another reason why it's advisable to become familiar with the various
minor adjustments.

If you have V-brakes, this will help illuminate the subject:

http://sheldonbrown.com/canti-direct.html

As for truing the wheel, it's fairly simple in most cases. the basic
technique is this; in the area where the wheel's rim deflects to one
side, tighten the spokes on the sides *away* from the deflection.
This is done by using a spoke wrench to turn the small sleeve-like bit
at the outer end (the "spoke nipple"). If you are looking down at the
wheel from above, and the spoke is pointing from the hub towards you,
the tightening direction is clockwise. Give the nipples a
quarter-turn at a time, and check to see if the wheel is acceptably
trued after at least each pair of spokes; as you approach perfection,
check after each spoke. When the wobble is no longer great enough to
see, celebrate and go for a ride. (Recheck the truing afterwards!)

It is usually advisable to true a wheel by just tightening spokes, but
sometimes it may be necessary to loosen one. Pluck each of the
spokes, and if one hits a much higher note (a soprano amongst tenors),
and that spoke is on the side toward the deflection and is in the
region that requires attention, you may want to back off on it a
quarter-turn.


--
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Brian Huntley wrote:

What type of brakes are these - caliper or cantilever?

Uhhm, well the specs say:

BRAKES Dahon SpeedStop V brakes, stainless flex noodle, front power
modulator, mini brake bolts, stainless link and anchor bolt
BRAKE LEVER BioLogic V, ultra-smooth machined pivots, Kraton insert
CABLES AND HOUSING SIS housing, slick cable, aluminum cable stops

That's worse than computer speak, surely...

What kind of lubricant should I try? When I asked at a snooty bike shop
on my way home for a good lube for my bike, they said there were many
kinds depending on if it was for the chain, for this, for that... I know
some oils can melt some rubbers, so I wouldn't want to have the wrong
product that near the tyres.

Thanks, I'll see about checking that wheel-in-drops thingy tomorrow.

EFR
Ile de France

Damn, I've made it much worse. Decidedly the Gods are not with me.

I went down to see about the wheel shifting in its dropouts. It was only
possible to loosen the bolt on one side, because on the side with the
shifters the attachment is too complicated.

With the bike upended, the wheel is so stiff it will not even spin. When
I force it to turn, it will not freewheel, but takes the pedals with it.

I turned it upright and tried applying a little pressure to the seat as
described, but it did not resolve the problem. When I wheel the bike
around, I can actually _see_ the back brake squidging around on its own.

But to add insult to injury, I broke the computer, an essential
component in my fitness tracking. I tried re-folding the bike in the
hope that it might undo whatever evil had assailed it from last being
folded. When I unfolded again, the computer cable caught in the pedal
and snapped.

So no bike tomorrow. On Saturday I must forswear all other activity to
get him all the way to Gif, five towns away, where there is the only
bike shop in the county willing to service him. They will keep him for
at least a week, and I shall not be able to cycle on my 50th birthday
(Monday), which to my superstitious nature is a really bad omen.

Why is this bike so fragile? I love him so, he's the only bike I really
enjoy riding, but he's like Beth in Little Women, exquisitely bedridden
and tear-jerking.

EFR
Ile de France

in message , Elisa Francesca
Roselli ') wrote:


Damn, I've made it much worse. Decidedly the Gods are not with me.

I went down to see about the wheel shifting in its dropouts. It was
only possible to loosen the bolt on one side, because on the side with
the shifters the attachment is too complicated.

With the bike upended, the wheel is so stiff it will not even spin.
When I force it to turn, it will not freewheel, but takes the pedals
with it.

OK, don't panic.

The first thing is to check that it /is/ the brake that's the problem.
(Assuming V brake) the little bent piece of tube the cable passes
through clips into a sort of long stirrup which is attached to the top
of one of the brake arms. The wire then comes out of the tube and is
attached to the other brake arm. If you squeeze the two brake arms
together, you can easily unhook the bent piece of tube from the stirrup.

The two arms should now flop apart. If the brake was to blame for the
wheel binding, it should now spin freely. If it does not spin, the
problem was not the brake.

Assuming it spins, as it spins, you will be able to see whether it
appears to wobble from one side to another. If it 'wobbles' by less than
2mm, don't worry. Some degree of wobble is acceptable.

Reattach the brake by again squeezing the arms together and this time
hooking the bent pipe back into the stirrup. Ensure that it has properly
clicked into place. Again turn the wheel. Does it touch the block only
on one side, or on both?

If on both, but the wobble is less than 2mm, then I would advise
loosening the cable a bit. On this page:
http://www.parktool.com/repair/readhowto.asp?id=21
find the picture with the caption 'Use barrel adjuster to set tightness
of pads to rim'. You want to loosen the pads, so you want to unscrew the
locknut a bit, screw the barrel two or three turns into the brake lever
body, and retighten the locknut.

If, however, the brake is rubbing on one side only, there are two
possibilities:

(1) the wheel is squint in the frame, in which case looking at it you
will see that the tyre is not central between the two chainstays. If
this is the case I'm afraid you're just going to have to tackle that
axle bolt; or

(2) the brake is squint, in which case you need to adjust the brake arms
as shown in the picture with the caption 'Use centering screws to move
arms and center pads to rim' on the same page.

But to add insult to injury, I broke the computer, an essential
component in my fitness tracking. I tried re-folding the bike in the
hope that it might undo whatever evil had assailed it from last being
folded. When I unfolded again, the computer cable caught in the pedal
and snapped.

Much sympathy. I broke the cadence sensor cable on my own computer though
very similar cackhandedness.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/
;; We don't just borrow words; on occasion, English has pursued other
;; languages down alleyways to beat them unconscious and riffle their
;; pockets for new vocabulary -- James D. Nicoll

Simon Brooke a écrit :

Much sympathy. I broke the cadence sensor cable on my own computer though
very similar cackhandedness.

No more cabled computers for Flyzipper. Now I'm in the market for one of
those Polar thingys that does everything by thought transmission except
make coffee.

Fly has wanted one of those since the last MeRx. I wonder if he didn't
break his cable on purpose to get a prezzie.

EFR
Ile de France

The Bicycle Angel of Paris is coming to have a look at that brake
tomorrow. If he can't figure it, I doubt the LBS of Gif would do better.

Much relieved.

EFR
Ile de France

On Fri, 30 Jun 2006 13:48:17 +0200, Artemisia wrote:

No more cabled computers for Flyzipper. Now I'm in the market for one of
those Polar thingys that does everything by thought transmission except
make coffee.

On a small-wheeled bike check very carefully that a wireless computer
has sufficient range. They are normally rated for 75cm max, and that's
probably not enough for you.


Mike