v-brakes

[Emanuel Berg]

Here are a couple of pics to facilitate the
discussion:

http://user.it.uu.se/~embe8573/bike/brake/

I've heard that

1) the long spring pin should be in the
middle boss hole

2) the pads/shoes/blocks should be slightly
pointing inward on the rim on the front
end

3) the arms should be vertical

4) between the cable anchor bolt/cable
clamp and the noodle/guide should be
39mm of cable

Is there a trick/algorithm to achieve all this?
I have put together several but 1, 2, 3 don't
come automatically for me :)

--
underground experts united
http://user.it.uu.se/~embe8573

[Ned Mantei]

On 25-02-18 00:07, Emanuel Berg wrote:
> Here are a couple of pics to facilitate the
> discussion:
>
> http://user.it.uu.se/~embe8573/bike/brake/
>
> I've heard that
>
> 1) the long spring pin should be in the
> middle boss hole
>
> 2) the pads/shoes/blocks should be slightly
> pointing inward on the rim on the front
> end
>
> 3) the arms should be vertical
>
> 4) between the cable anchor bolt/cable
> clamp and the noodle/guide should be
> 39mm of cable
>
> Is there a trick/algorithm to achieve all this?
> I have put together several but 1, 2, 3 don't
> come automatically for me :)
>

Concerning point 2, "toe-in", I just use the Kool-Stop brake shoes. The
back end is slightly raised, so the toe-in comes automatically. Another
possibility would be to put a piece of very thin cardboard under the
back end of the brake shoe when tightening the bolt.

What hasn't worked for me is a special tool like this one:
https://www.veloplus.ch/AlleProdukte/Werkstatt/TUNEREinstell-LehrefuerBremsschuhevonTacx.aspx
In theory that tool holds the brake shoes just where they should be,
including with proper toe-in. However, I always ended up with the brake
shoes at the lower/inner edge of the rim (towards the hub). This isn't
good, because as the brake shoes wear and get thinner the brake will
engage farther down in the rim. If it starts at the edge, later it will
be partly off the rim towards the center**. So this could be a point 5
in your list.

**And many years ago a friend crashed when the brake shoes went
completely off the rim into the spokes.


For your point 3, the only adjustment for the arms being more or less
vertical is, at least for the Shimano BR-M750 that I have, whether the 3
mm washer is on the rim side and the 6 mm one on the outer side, or vice
versa. You might want to check this with an inflated tire in place, to
make sure that there is clearance further up on the brake. Otherwise,
closer to vertical gives more mechanical advantage.

I haven't worried at all about your point 4, and just adjust the cable
so that there is minimal clearance between pads and rim. Whether more or
less than 39 mm would depend on rim width, so not a constant for all
bikes (and for my BR-M750 the service instructions anyhow say to have 45
mm or more).

With the older cantilever brakes things were more complicated. See
http://www.sheldonbrown.com/cantilever-geometry.html

Ned

[John B.]

On Sun, 25 Feb 2018 00:07:01 +0100, Emanuel Berg <moa...@zoho.com>
wrote:

>Here are a couple of pics to facilitate the
>discussion:
>
> http://user.it.uu.se/~embe8573/bike/brake/
>
>I've heard that
>
> 1) the long spring pin should be in the
> middle boss hole
>
> 2) the pads/shoes/blocks should be slightly
> pointing inward on the rim on the front
> end
>
> 3) the arms should be vertical
>
> 4) between the cable anchor bolt/cable
> clamp and the noodle/guide should be
> 39mm of cable
>
>Is there a trick/algorithm to achieve all this?
>I have put together several but 1, 2, 3 don't
>come automatically for me :)

The three little holes at the hub are to adjust the brake arms. Try to
get the brake arms parallel. The small bolts are for fine tuning the
adjustment. Start with them screwed in about half way. (Or out about
half way, if you prefer :)

The pads should be installed so that the face is parallel to the wheel
rim and if possible with the leading edge "toed in", the front end
slightly closer to the rim then the rear.

Adjust the cable length to give you the brake lever movement that you
are comfortable with and then use the small hub screws to center the
brake pads on the rim.

Finally, ride the bike down a steep hill 30 kph and grab the back
brake. If the rear wheel skids the brakes are working. Congratulations
:-)

You could also try to skid the front wheel but that is a little "iffy"
so I won't recommend that as a test :-)
--
Cheers,

John B.

[Frank Krygowski]

On 2/25/2018 6:01 AM, John B. wrote:
>
> The three little holes at the hub are to adjust the brake arms. Try to
> get the brake arms parallel. The small bolts are for fine tuning the
> adjustment. Start with them screwed in about half way. (Or out about
> half way, if you prefer :)

Half way in vs. half way out? This could be the next r.b.tech controversy!


--
- Frank Krygowski

[Tosspot]

On 25/02/18 00:07, Emanuel Berg wrote:
> Here are a couple of pics to facilitate the
> discussion:
>
> http://user.it.uu.se/~embe8573/bike/brake/
>
> I've heard that
>
> 1) the long spring pin should be in the
> middle boss hole
>
> 2) the pads/shoes/blocks should be slightly
> pointing inward on the rim on the front
> end
>
> 3) the arms should be vertical
>
> 4) between the cable anchor bolt/cable
> clamp and the noodle/guide should be
> 39mm of cable
>
> Is there a trick/algorithm to achieve all this?
> I have put together several but 1, 2, 3 don't
> come automatically for me :)

All a matter of taste. I used to use the top boss hole, I liked a bit
of toe-in so as per 2, 3) they always seemed to be about that. 4 is a
bit of a mystery. I just threaded the inner and cut with cable cutters
leave about 5cm 'spare'.

[Tosspot]

On 25/02/18 11:36, Ned Mantei wrote:
> On 25-02-18 00:07, Emanuel Berg wrote:
>> Here are a couple of pics to facilitate the discussion:
>>
>> http://user.it.uu.se/~embe8573/bike/brake/
>>
>> I've heard that
>>
>> 1) the long spring pin should be in the middle boss hole
>>
>> 2) the pads/shoes/blocks should be slightly pointing inward on the
>> rim on the front end
>>
>> 3) the arms should be vertical
>>
>> 4) between the cable anchor bolt/cable clamp and the noodle/guide
>> should be 39mm of cable
>>
>> Is there a trick/algorithm to achieve all this? I have put together
>> several but 1, 2, 3 don't come automatically for me :)
>>
>
> Concerning point 2, "toe-in", I just use the Kool-Stop brake shoes.
> The back end is slightly raised, so the toe-in comes automatically.
> Another possibility would be to put a piece of very thin cardboard
> under the back end of the brake shoe when tightening the bolt.
>
> What hasn't worked for me is a special tool like this one:
> https://www.veloplus.ch/AlleProdukte/Werkstatt/TUNEREinstell-LehrefuerBremsschuhevonTacx.aspx

A cigarette packet is made of just the right thickness card...

<snip>

[Tosspot]

I'm an all out man meself...

[Emanuel Berg]

> Is there a trick/algorithm to achieve all
> this? I have put together several but 1, 2, 3
> don't come automatically for me :)

It should be 2-4 that don't come automatically.
Getting the long pin of the spring into the
middle bass hole is actually quite easy :)

Here is a printable A4 "poster" pic for
V-brakes:

http://user.it.uu.se/~embe8573/bike/brake/v-brake-a4-poster-gs.jpg

http://user.it.uu.se/~embe8573/bike/brake/v-brake-a4-poster.jpg

I wrote a zsh program [1] to produce such
graphics from singular imgs, and God willing
I will do a couple more from other aspects of
bike mechanics!

[1] http://user.it.uu.se/~embe8573/conf/.zsh/gfx

[John B.]

Well, one does try to be politically correct and given all the claims
of indecent conduct occurring 20 or 30 years in the past a certain
level of prudence seems to be called for. After all some will
certainly argue that half way in is a whole different matter then half
way out :-)
--
Cheers,

John B.

[John B.]

On Sun, 25 Feb 2018 22:06:06 +0100, Emanuel Berg <moa...@zoho.com>
wrote:

Why? There are the brakes attached to the bicycle and there are you
sitting there looking at them. Why for you need a poster.
--
Cheers,

John B.

[Emanuel Berg]

John B. wrote:

> Why? There are the brakes attached to the
> bicycle and there are you sitting there
> looking at them. Why for you need a poster.

Because this is a wood house, the work shop
must look advanced and hi-tech to compensate :)

[AMuzi]

In the famously heroic words of Capt. Lloyd Bucher,
"penetration however slight is sufficient to complete the act."

Right up there with Gen McAuliffe for catchy composition
under fire.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[John B.]

On Mon, 26 Feb 2018 03:01:01 +0100, Emanuel Berg <moa...@zoho.com>
wrote:

>John B. wrote:
>
>> Why? There are the brakes attached to the
>> bicycle and there are you sitting there
>> looking at them. Why for you need a poster.
>
>Because this is a wood house, the work shop
>must look advanced and hi-tech to compensate :)

So a wall covered with Posters.... in lieu of competency?
--
Cheers,

John B.

[Ian Field]

"Emanuel Berg" <moa...@zoho.com> wrote in message
news:868tbiq...@zoho.com...

> Here are a couple of pics to facilitate the
> discussion:
>
> http://user.it.uu.se/~embe8573/bike/brake/
>
> I've heard that
>
> 1) the long spring pin should be in the
> middle boss hole
>
> 2) the pads/shoes/blocks should be slightly
> pointing inward on the rim on the front
> end
>
> 3) the arms should be vertical
>
> 4) between the cable anchor bolt/cable
> clamp and the noodle/guide should be
> 39mm of cable

Most brake arms seem to be curved - so which bit needs to be vertical.

I frequently have a problem with no clearance between cable clamp and noodle
guide.

The steel rims seem to be slightly wider than the aluminium ones, so I can
usually use the blocks down to their wear limits without stacking washers on
the brake block studs when the noodle hits the clamp.

Arms bolt upright gives optimum leverage, so worth aiming for if you can get
it. Maybe set them leaning out a bit so they wear in to vertical.

"toeing in" the brake blocks is to prevent brake noise - leave it and its as
good as a horn/bell for dumbass pedestrians wandering about in the road.

[Emanuel Berg]

Ian Field wrote:

> "toeing in" the brake blocks is to prevent
> brake noise - leave it and its as good as
> a horn/bell for dumbass pedestrians wandering
> about in the road.

Really? That's it?

OTOH I really dislike any kind of noise from
riding a bike tho.

[Emanuel Berg]

Ned Mantei wrote:

> What hasn't worked for me is a special tool
> like this one:
> https://www.veloplus.ch/AlleProdukte/Werkstatt/TUNEREinstell-LehrefuerBremsschuhevonTacx.aspx
> In theory that tool holds the brake shoes
> just where they should be, including with
> proper toe-in. However, I always ended up
> with the brake shoes at the lower/inner edge
> of the rim (towards the hub). This isn't
> good, because as the brake shoes wear and get
> thinner the brake will engage farther down in
> the rim. If it starts at the edge, later it
> will be partly off the rim towards the
> center**. So this could be a point 5 in
> your list.

... OK, how would you phrase that, except the
tool doesn't work as intended?

I thought about such a tool myself, a small
clamp basically, and not just for this brake in
particular, but just ended up with squeezing
them together manually so far...

> I haven't worried at all about your point 4,
> and just adjust the cable so that there is
> minimal clearance between pads and rim.
> Whether more or less than 39 mm would depend
> on rim width, so not a constant for all bikes
> (and for my BR-M750 the service instructions
> anyhow say to have 45 mm or more).

OK, great, thanks!