Can't get rear canti brake to skid tire. Should it?

TomYoung

Hi all:

Still working on that bike for my daughter (it was a "freebie" that's
cost me about $50 in parts and lots of hours of work) and thanks to
the help I've received here everything seems to be working fine,
except that I can't get the rear cantilever brake to skid the tire.
I'm not sure if being able to skid the rear tire really means anything
in terms of fast and safe stops, but it seems odd that I can't
accomplish this with this bike.

The bike is an older mountain bike (26" wheels) hung with Shimano
Exage 300LX parts. The brakes themselves just read "Shimano" but I
assume they're either Exage 300LX or similar.

So... I've put on new cables and new housings and new housing
ferrules. Housing ends properly prepared as laid out at Sheldon
Brown's site. New brake pads (Ritchey Logic red) and new tires.
Brake pads properly toed in and positioned equally close to either
side of the rim. (Remarkably, the wheels were quite true for such an
old bike.) Because of the highly sloped top tube the rear brake
housing makes a fairly long reverse "S" bend to get up from the top
tube to the rear brake hanger, but friction through the system doesn't
seem too bad. A very hard squeeze of the brake handle brings the end
of the handle to within a 1/4" of the bar. The only thing I haven't
done at this point is clean the rim sidewalls, but the sidewalls
aren't particularly glazed with old brake pad material.

Anything else to be done, or is this as good as it gets?

TIA

Tom Young

Tom Kunich

"TomYoung" <tgyoung@yahoo.com> wrote in message
news:734bf6d6-09fd-44ba-800b-bb30b1493e29@v1g2000pra.googlegroups.com...
>
> Anything else to be done, or is this as good as it gets?

You should be able to pretty easily get the rear wheel to skid from brake
application.

jobst.brandt@stanfordalumni.org

Tom Young wrote:

> Still working on that bike for my daughter (it was a "freebie"
> that's cost me about $50 in parts and lots of hours of work) and
> thanks to the help I've received here everything seems to be working
> fine, except that I can't get the rear cantilever brake to skid the
> tire. I'm not sure if being able to skid the rear tire really means
> anything in terms of fast and safe stops, but it seems odd that I
> can't accomplish this with this bike.

I can't imagine a brake that can't skid the rear wheel, because
skidding the rear wheel takes little effort on any working brake. I
assume that the straddle cable is out of adjustment or the straddle
cable yoke is bottoming on the cable housing anchor.

Take the wheel out and see if pulling the hand lever can make the
brake pads close to a narrower gap than the width of the rim. Beside
that test, it wouldn't hurt to pull the cable out of the housing and
wipe its entire length in with motor oil before threading it in again
and attaching the straddle cable yoke. Do the same with the front
brake. I don't know in what condition the cables have.

> The bike is an older mountain bike (26" wheels) hung with Shimano
> Exage 300LX parts. The brakes themselves just read "Shimano" but I
> assume they're either Exage 300LX or similar.

Don't worry about that, just get the brake pads to move continuously
and smoothly to make contact with the rim brake surfaces.

> So... I've put on new cables and new housings and new housing
> ferrules. Housing ends properly prepared as laid out at Sheldon
> Brown's site. New brake pads (Ritchey Logic red) and new tires.
> Brake pads properly toed in and positioned equally close to either
> side of the rim. (Remarkably, the wheels were quite true for such
> an old bike.) Because of the highly sloped top tube the rear brake
> housing makes a fairly long reverse "S" bend to get up from the top
> tube to the rear brake hanger, but friction through the system
> doesn't seem too bad. A very hard squeeze of the brake handle
> brings the end of the handle to within a 1/4" of the bar.

That doesn't sound good. When the pads make contact with the rim,
about 3/4 of the distance to the hand lever running out of stroke
should be used. If the system is so spongy that the rest of the
stroke is mostly used up, you have an improperly installed cable
housing.

> The only thing I haven't done at this point is clean the rim
> sidewalls, but the sidewalls aren't particularly glazed with old
> brake pad material.

I don't believe the brake pads are making effective contact with the
rim.

> Anything else to be done, or is this as good as it gets?

It gets a lot better when these brakes are working.

Jobst Brandt

Dan O

On Jun 27, 12:19 pm, TomYoung <tgyo...@yahoo.com> wrote:
> Hi all:
>
> Still working on that bike for my daughter (it was a "freebie" that's
> cost me about $50 in parts and lots of hours of work) and thanks to
> the help I've received here everything seems to be working fine,
> except that I can't get the rear cantilever brake to skid the tire.
> I'm not sure if being able to skid the rear tire really means anything
> in terms of fast and safe stops, but it seems odd that I can't
> accomplish this with this bike.
>
> The bike is an older mountain bike (26" wheels) hung with Shimano
> Exage 300LX parts. The brakes themselves just read "Shimano" but I
> assume they're either Exage 300LX or similar.
>
> So... I've put on new cables and new housings and new housing
> ferrules. Housing ends properly prepared as laid out at Sheldon
> Brown's site. New brake pads (Ritchey Logic red) and new tires.
> Brake pads properly toed in and positioned equally close to either
> side of the rim. (Remarkably, the wheels were quite true for such an
> old bike.) Because of the highly sloped top tube the rear brake
> housing makes a fairly long reverse "S" bend to get up from the top
> tube to the rear brake hanger, but friction through the system doesn't
> seem too bad. A very hard squeeze of the brake handle brings the end
> of the handle to within a 1/4" of the bar. The only thing I haven't
> done at this point is clean the rim sidewalls, but the sidewalls
> aren't particularly glazed with old brake pad material.
>

What kind of levers are installed?

M-gineering

TomYoung wrote:
> Hi all:
>
> Still working on that bike for my daughter (it was a "freebie" that's
> cost me about $50 in parts and lots of hours of work) and thanks to
> the help I've received here everything seems to be working fine,
> except that I can't get the rear cantilever brake to skid the tire.
> I'm not sure if being able to skid the rear tire really means anything
> in terms of fast and safe stops, but it seems odd that I can't
> accomplish this with this bike.
>
> The bike is an older mountain bike (26" wheels) hung with Shimano
> Exage 300LX parts. The brakes themselves just read "Shimano" but I
> assume they're either Exage 300LX or similar.
>
> So... I've put on new cables and new housings and new housing
> ferrules. Housing ends properly prepared as laid out at Sheldon
> Brown's site. New brake pads (Ritchey Logic red) and new tires.
> Brake pads properly toed in and positioned equally close to either
> side of the rim. (Remarkably, the wheels were quite true for such an
> old bike.) Because of the highly sloped top tube the rear brake
> housing makes a fairly long reverse "S" bend to get up from the top
> tube to the rear brake hanger, but friction through the system doesn't
> seem too bad. A very hard squeeze of the brake handle brings the end
> of the handle to within a 1/4" of the bar. The only thing I haven't
> done at this point is clean the rim sidewalls, but the sidewalls
> aren't particularly glazed with old brake pad material.
>
> Anything else to be done, or is this as good as it gets?
>
> TIA
>
> Tom Young


Is the V of the transverse cable to acute? This give a nice sturdy lever
feel, but all you are accomplishing is you're trying to pull the brakes
off the posts. Slide the posts of the blocks as far out as they will go .
Many bikes come with the stock transverse cable doohicky in too big a
size. Reverting to the old fashioned cable and cablehanger gives you
more options
--
/Marten

info(apestaartje)m-gineering(punt)nl

TomYoung

On Jun 27, 1:18*pm, Dan O <danover...@gmail.com> wrote:
> On Jun 27, 12:19 pm, TomYoung <tgyo...@yahoo.com> wrote:
>
>
>
> > Hi all:
>
> > Still working on that bike for my daughter (it was a "freebie" that's
> > cost me about $50 in parts and lots of hours of work) and thanks to
> > the help I've received here everything seems to be working fine,
> > except that I can't get the rear cantilever brake to skid the tire.
> > I'm not sure if being able to skid the rear tire really means anything
> > in terms of fast and safe stops, but it seems odd that I can't
> > accomplish this with this bike.
>
> > The bike is an older mountain bike (26" wheels) hung with Shimano
> > Exage 300LX parts. *The brakes themselves just read "Shimano" but I
> > assume they're either Exage 300LX or similar.
>
> > So... I've put on new cables and new housings and new housing
> > ferrules. *Housing ends properly prepared as laid out at Sheldon
> > Brown's site. *New brake pads (Ritchey Logic red) and new tires.
> > Brake pads properly toed in and positioned equally close to either
> > side of the rim. *(Remarkably, the wheels were quite true for such an
> > old bike.) *Because of the highly sloped top tube the rear brake
> > housing makes a fairly long reverse "S" bend to get up from the top
> > tube to the rear brake hanger, but friction through the system doesn't
> > seem too bad. *A very hard squeeze of the brake handle brings the end
> > of the handle to within a 1/4" of the bar. *The only thing I haven't
> > done at this point is clean the rim sidewalls, but the sidewalls
> > aren't particularly glazed with old brake pad material.
>
> What kind of levers are installed?

They look to me to be standard flat bar levers of the era. The
sticker on them reads "Shimano Short Reach" but it doesn't look like
any of the lever stroke has been adjusted out as the adjusting screws
are fully withdrawn and the levers snap shut tight against the lever
body. Maybe some sort of V-brake lever is what I have with attendant
mechanical advantage issues?

TomYoung

On Jun 27, 12:41 pm, jobst.bra...@stanfordalumni.org wrote:
I
> I assume that the straddle cable is out of adjustment or the straddle
> cable yoke is bottoming on the cable housing anchor.

I don't think the link wire/main cable setup (button/fixed length wire/
main cable through button) is grossly out of whack. Picture of pads
and rim are here (http://tinyurl.com/6qpprf) and link wire setup here
(http://tinyurl.com/64fy3v). I could bring the pads *slightly* closer
to the rim but would run up against a wheel that isn't *that* straight
as well as lose the "quick release" aspect of the link wire setup.
With the brake handle pulled tight against the handlebar the distance
from the top of the link wire button to the hanger is 2 - 3
centimeters.

>
> Take the wheel out and see if pulling the hand lever can make the
> brake pads close to a narrower gap than the width of the rim. Beside
> that test, it wouldn't hurt to pull the cable out of the housing and
> wipe its entire length in with motor oil before threading it in again
> and attaching the straddle cable yoke. Do the same with the front
> brake. I don't know in what condition the cables have.

With the wheel out the pads pull to within 23 - 24 mm of each other,
measured center of pad to center of pad. The rim itself looks to be
right at 28mm. The new cables are a Jagwire product with a PVDF
coating and advise against lubing. I've used these successfully on
other bikes but may try a standard lubed cable.
>

> > A very hard squeeze of the brake handle
> > brings the end of the handle to within a 1/4" of the bar.
>
> That doesn't sound good. When the pads make contact with the rim,
> about 3/4 of the distance to the hand lever running out of stroke
> should be used. If the system is so spongy that the rest of the
> stroke is mostly used up, you have an improperly installed cable
> housing.

Hand lever stroke is just at 6cm. Good solid pad/rim contact is at
3cm. The "hard squeeze" I mentioned was with me squeezing the lever
just about as hard as I can.

I'd bet you money and give you odds that the cable housing setup when
I got the bike was just as it was when the bike was sold, and that's
what I copied in my installation. In any case, the arrangement seems
right: housing from lever to to front top tube cable stop, then bare
cable along the top tube to the rear cable stop, then housing from
rear cable stop to hanger via reverse "S" bend with the middle of the
"S" secured to the seat tube with a small collar. At this point the
only change I can think of is shortening the first length of housing,
which is probably a little long.

Tom Young

TomYoung

On Jun 27, 2:34*pm, M-gineering <ikmotgeens...@m-gineering.nl> wrote:
> TomYoung wrote:
> > Hi all:
>
> > Still working on that bike for my daughter (it was a "freebie" that's
> > cost me about $50 in parts and lots of hours of work) and thanks to
> > the help I've received here everything seems to be working fine,
> > except that I can't get the rear cantilever brake to skid the tire.
> > I'm not sure if being able to skid the rear tire really means anything
> > in terms of fast and safe stops, but it seems odd that I can't
> > accomplish this with this bike.
>
> > The bike is an older mountain bike (26" wheels) hung with Shimano
> > Exage 300LX parts. *The brakes themselves just read "Shimano" but I
> > assume they're either Exage 300LX or similar.
>
> > So... I've put on new cables and new housings and new housing
> > ferrules. *Housing ends properly prepared as laid out at Sheldon
> > Brown's site. *New brake pads (Ritchey Logic red) and new tires.
> > Brake pads properly toed in and positioned equally close to either
> > side of the rim. *(Remarkably, the wheels were quite true for such an
> > old bike.) *Because of the highly sloped top tube the rear brake
> > housing makes a fairly long reverse "S" bend to get up from the top
> > tube to the rear brake hanger, but friction through the system doesn't
> > seem too bad. *A very hard squeeze of the brake handle brings the end
> > of the handle to within a 1/4" of the bar. *The only thing I haven't
> > done at this point is clean the rim sidewalls, but the sidewalls
> > aren't particularly glazed with old brake pad material.
>
> > Anything else to be done, or is this as good as it gets?
>
> > TIA
>
> > Tom Young
>
> Is the V of the transverse cable to acute? This give a nice sturdy lever
> feel, but all you are accomplishing is you're trying to pull the brakes
> off the posts. Slide the posts of the blocks as far out as they will go .
> Many bikes come with the stock transverse cable doohicky in too big a
> size. Reverting to the old fashioned cable and cablehanger gives you
> more options

The link wire setup on this bike, front and rear, is the old-fashioned
button with a fixed-length wire and the main cable running through the
button to the other brake arm. The link wire for both brakes is the
shortest one available, 73mm.

You're suggesting (if I'm reading you right) that I slide the pads as
far "away" from the brake arms as I can, thereby moving the tops of
the brake arms away from the bike, compensating for this by lowering
the link wire/main wire junction? So that the angle of the "V"
increases?

Tom Young

TomYoung

On Jun 27, 2:34*pm, M-gineering <ikmotgeens...@m-gineering.nl> wrote:
> TomYoung wrote:
> > Hi all:
>
> > Still working on that bike for my daughter (it was a "freebie" that's
> > cost me about $50 in parts and lots of hours of work) and thanks to
> > the help I've received here everything seems to be working fine,
> > except that I can't get the rear cantilever brake to skid the tire.
> > I'm not sure if being able to skid the rear tire really means anything
> > in terms of fast and safe stops, but it seems odd that I can't
> > accomplish this with this bike.
>
> > The bike is an older mountain bike (26" wheels) hung with Shimano
> > Exage 300LX parts. *The brakes themselves just read "Shimano" but I
> > assume they're either Exage 300LX or similar.
>
> > So... I've put on new cables and new housings and new housing
> > ferrules. *Housing ends properly prepared as laid out at Sheldon
> > Brown's site. *New brake pads (Ritchey Logic red) and new tires.
> > Brake pads properly toed in and positioned equally close to either
> > side of the rim. *(Remarkably, the wheels were quite true for such an
> > old bike.) *Because of the highly sloped top tube the rear brake
> > housing makes a fairly long reverse "S" bend to get up from the top
> > tube to the rear brake hanger, but friction through the system doesn't
> > seem too bad. *A very hard squeeze of the brake handle brings the end
> > of the handle to within a 1/4" of the bar. *The only thing I haven't
> > done at this point is clean the rim sidewalls, but the sidewalls
> > aren't particularly glazed with old brake pad material.
>
> > Anything else to be done, or is this as good as it gets?
>
> > TIA
>
> > Tom Young
>
> Is the V of the transverse cable to acute? This give a nice sturdy lever
> feel, but all you are accomplishing is you're trying to pull the brakes
> off the posts. Slide the posts of the blocks as far out as they will go .
> Many bikes come with the stock transverse cable doohicky in too big a
> size. Reverting to the old fashioned cable and cablehanger gives you
> more options

You may have hit the nail on the head here.

One thing I didn't mention, because it just didn't seem relevant, was
that the bike has front and rear reflectors mounted to the fork crown
and rear brake bridge. I ended up bending both of them down to give
me a little more room for the link wire button when the brake was
released but I didn't think a lot about the issue because my reasoning
was "that's how they sold the bikes and the brakes must have worked OK
when they sold them." However, in looking more closely at the front
and rear brakes (the fronts seem to work OK) was that the brake arms
up front formed a wider angle, by a good margin, then the brake arms
in the rear. The limiting factor for the narrow angle in the rear is
that rear reflector.

Tomorrow I'll try again, either bending that rear reflector a heck of
a lot more or removing it all together and widen the angle of the
brake arms.

Tom Young

jim beam

TomYoung wrote:
> On Jun 27, 1:18�pm, Dan O <danover...@gmail.com> wrote:
>> On Jun 27, 12:19 pm, TomYoung <tgyo...@yahoo.com> wrote:
>>
>>
>>
>>> Hi all:
>>> Still working on that bike for my daughter (it was a "freebie" that's
>>> cost me about $50 in parts and lots of hours of work) and thanks to
>>> the help I've received here everything seems to be working fine,
>>> except that I can't get the rear cantilever brake to skid the tire.
>>> I'm not sure if being able to skid the rear tire really means anything
>>> in terms of fast and safe stops, but it seems odd that I can't
>>> accomplish this with this bike.
>>> The bike is an older mountain bike (26" wheels) hung with Shimano
>>> Exage 300LX parts. �The brakes themselves just read "Shimano" but I
>>> assume they're either Exage 300LX or similar.
>>> So... I've put on new cables and new housings and new housing
>>> ferrules. �Housing ends properly prepared as laid out at Sheldon
>>> Brown's site. �New brake pads (Ritchey Logic red) and new tires.
>>> Brake pads properly toed in and positioned equally close to either
>>> side of the rim. �(Remarkably, the wheels were quite true for such an
>>> old bike.) �Because of the highly sloped top tube the rear brake
>>> housing makes a fairly long reverse "S" bend to get up from the top
>>> tube to the rear brake hanger, but friction through the system doesn't
>>> seem too bad. �A very hard squeeze of the brake handle brings the end
>>> of the handle to within a 1/4" of the bar. �The only thing I haven't
>>> done at this point is clean the rim sidewalls, but the sidewalls
>>> aren't particularly glazed with old brake pad material.
>> What kind of levers are installed?
>
> They look to me to be standard flat bar levers of the era. The
> sticker on them reads "Shimano Short Reach" but it doesn't look like
> any of the lever stroke has been adjusted out as the adjusting screws
> are fully withdrawn and the levers snap shut tight against the lever
> body. Maybe some sort of V-brake lever is what I have with attendant
> mechanical advantage issues?
>

could well be. but you'd notice that same problem with the front brake
as well, and that's not an issue you've raised so far...

jim beam

TomYoung wrote:
> Hi all:
>
> Still working on that bike for my daughter (it was a "freebie" that's
> cost me about $50 in parts and lots of hours of work) and thanks to
> the help I've received here everything seems to be working fine,
> except that I can't get the rear cantilever brake to skid the tire.
> I'm not sure if being able to skid the rear tire really means anything
> in terms of fast and safe stops, but it seems odd that I can't
> accomplish this with this bike.
>
> The bike is an older mountain bike (26" wheels) hung with Shimano
> Exage 300LX parts. The brakes themselves just read "Shimano" but I
> assume they're either Exage 300LX or similar.
>
> So... I've put on new cables and new housings and new housing
> ferrules. Housing ends properly prepared as laid out at Sheldon
> Brown's site. New brake pads (Ritchey Logic red) and new tires.
> Brake pads properly toed in and positioned equally close to either
> side of the rim. (Remarkably, the wheels were quite true for such an
> old bike.) Because of the highly sloped top tube the rear brake
> housing makes a fairly long reverse "S" bend to get up from the top
> tube to the rear brake hanger, but friction through the system doesn't
> seem too bad. A very hard squeeze of the brake handle brings the end
> of the handle to within a 1/4" of the bar. The only thing I haven't
> done at this point is clean the rim sidewalls, but the sidewalls
> aren't particularly glazed with old brake pad material.
>
> Anything else to be done, or is this as good as it gets?
>
> TIA
>
> Tom Young


from those pictures, it would appear that the toe is excessive* and the
pad/rim angle is not close enough - just a little contact area means
just a little braking friction, and this is especially noticeable under
load. try re-setting the pads accordingly. and double check to make
sure the cables slide easily in their housings. a little friction in a
long cable run takes a lot out of the force transfer.


* you don't really need toe unless the brakes are squealing. trying to
achieve the "modulation" effect toe creates is something of a
misinformed objective since natural pad wear ensures the pads are
parallel with the rim anyway, so you may as well get used to operating
the brakes properly in the first place.

jim beam

jobst.brandt@stanfordalumni.org wrote:
<snip uninformative waffle>


> In any event, a rear wheel
> should skid easily with moderate hand force, so there is something
> amiss here.

why did you bother jobst? the o.p. had figured that bit out on their own.

but i guess we should be grateful you're not making stuff up this time.

Tom Kunich

"TomYoung" <tgyoung@yahoo.com> wrote in message
news:c59e37c5-141f-462a-9b1a-2f248c8eede5@c19g2000prf.googlegroups.com...
>
> A simple response of "Tom, you ignorant slut" would have been
> sufficient.

The problem is that you aren't ignorant, just misinformed.

Tom Kunich

"TomYoung" <tgyoung@yahoo.com> wrote in message
news:12cc30f5-fc77-4178-8815-f309f3e4a76e@i36g2000prf.googlegroups.com...
>
> Tomorrow I'll try again, either bending that rear reflector a heck of
> a lot more or removing it all together and widen the angle of the
> brake arms.

Try this - when the brakes engage the wheel rim you should have
approximately 45 degrees on the cable connector.