Possible to have brake pads too close to rims?

On 20/11/2014 03:19, Joe Riel wrote:
Clive George writes:

On 20/11/2014 01:34, Sir Ridesalot wrote:
On Wednesday, November 19, 2014 6:28:41 PM UTC-5, JoeRiel wrote:
AMuzi writes:

On 11/19/2014 4:32 PM, Sir Ridesalot wrote:
Okay, you've got very nearly perfectly trued wheels, single pivote calipers brakes and decent quality tires.

Braking isn't that great. Flip open the brake caliper quick relese and braking becomes much more effective.

Is it possible to have brakes so finely adjusted with the pads so close to the rim that braking ability is degraded whereas moving the pads further from the rim actually improves the braking?

Cheers


Some QR designs did indeed change the cable leverage slightly,
although nothing currently made.

More likely you just are able to get a better grasp of the lever when
it's closer to the handlebar.

Yeah, my wife has small hands and sets her brakes up so they don't
engage until the brake lever is quite close to the bars. Worries me,
since there isn't much room for wear. With them engaging earlier she
cannot apply as much force.

Not much difference with the brake lever travel when the brake caliper QR is open just a much more positive feel and effect when the brakes are applied.

Presumably the bite point changes? If it doesn't then the QR is pretty
pointless :-)

Campy Record Ergo levers have the QR in the lever, which doesn't change
the contact point. The Shimano 600 brakes have the QR on the caliper,
so your point is valid, just not universal.

My Mirage levers have it there too. But he did say "brake caliper QR" :-)

On 11/19/2014 7:32 PM, Sir Ridesalot wrote:
On Wednesday, November 19, 2014 6:05:29 PM UTC-5, AMuzi wrote:
On 11/19/2014 4:32 PM, Sir Ridesalot wrote:
Okay, you've got very nearly perfectly trued wheels, single pivote calipers brakes and decent quality tires.

Braking isn't that great. Flip open the brake caliper quick relese and braking becomes much more effective.

Is it possible to have brakes so finely adjusted with the pads so close to the rim that braking ability is degraded whereas moving the pads further from the rim actually improves the braking?

Cheers


Some QR designs did indeed change the cable leverage
slightly, although nothing currently made.

More likely you just are able to get a better grasp of the
lever when it's closer to the handlebar.

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

Shimano 600 Arabesque brake calipers and matching brake levers. New brake blocks.

Cheers


That design does indeed have a very slight change of
leverage when open:
http://www.yellowjersey.org/SH83G.JPG
Not sure a human could feel that difference.

That image is poor, here's a different finish on the same
caliper:
http://www.yellowjersey.org/SH83H.JPG


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

On Wed, 19 Nov 2014 15:28:39 -0800, Joe Riel wrote:

Yeah, my wife has small hands and sets her brakes up so they don't
engage until the brake lever is quite close to the bars. Worries me,
since there isn't much room for wear. With them engaging earlier she
cannot apply as much force.

I was getting wrecked hands because when you need to brake, not being
able to reach the levers doesn't come into your calculations. The
problem was solved by two engineers, one Dremel moto-tool, and a pair
of child's brake levers.

I've forgotten how many decades ago that was, but I'm still using
them.

Not working too well at the moment; it's past time to scrub my blocks
and rims again.

And its *cold* out there!

--
joy beeson at comcast dot net
http://joybeeson.home.comcast.net/
The above message is a Usenet post.
I don't recall having given anyone permission to use it on a Web site.

On 11/20/2014 9:51 AM, Joy Beeson wrote:
On Wed, 19 Nov 2014 15:28:39 -0800, Joe Riel wrote:

Yeah, my wife has small hands and sets her brakes up so they don't
engage until the brake lever is quite close to the bars. Worries me,
since there isn't much room for wear. With them engaging earlier she
cannot apply as much force.

I was getting wrecked hands because when you need to brake, not being
able to reach the levers doesn't come into your calculations. The
problem was solved by two engineers, one Dremel moto-tool, and a pair
of child's brake levers.

I've forgotten how many decades ago that was, but I'm still using
them.

Not working too well at the moment; it's past time to scrub my blocks
and rims again.

And its *cold* out there!

On one of my wife's bikes, I was able to bend the brake levers so they
better fit the size and shape of her hands.

--
- Frank Krygowski

Frank Krygowski wrote:
On 11/20/2014 9:51 AM, Joy Beeson wrote:
On Wed, 19 Nov 2014 15:28:39 -0800, Joe Riel wrote:

Yeah, my wife has small hands and sets her brakes up so they don't
engage until the brake lever is quite close to the bars. Worries me,
since there isn't much room for wear. With them engaging earlier she
cannot apply as much force.

I was getting wrecked hands because when you need to brake, not being
able to reach the levers doesn't come into your calculations. The
problem was solved by two engineers, one Dremel moto-tool, and a pair
of child's brake levers.

I've forgotten how many decades ago that was, but I'm still using
them.

Not working too well at the moment; it's past time to scrub my blocks
and rims again.

And its *cold* out there!

On one of my wife's bikes, I was able to bend the brake levers so they
better fit the size and shape of her hands.

I also 'suffer' from small hands and I never understood why manufacturers
don't offered different brake levers. Instead they messing around with
shims and other kludges. This problem doesn't exists with ATB brakes. They
have adjustable reach from the beginning at least the better ones. Thank
god we got rid of the ergo dropbars (with a straight section) that puts you
hands ever further away from the levers.

--
Lou

On Wednesday, November 19, 2014 2:32:57 PM UTC-8, Sir Ridesalot wrote:
Okay, you've got very nearly perfectly trued wheels, single pivote calipers brakes and decent quality tires.

Braking isn't that great. Flip open the brake caliper quick relese and braking becomes much more effective.

Is it possible to have brakes so finely adjusted with the pads so close to the rim that braking ability is degraded whereas moving the pads further from the rim actually improves the braking?

Cheers

High MA of V brakes is different than the lower MA on say Mafac's Cantilevers

what you got , specifically?

On Wednesday, November 19, 2014 2:32:57 PM UTC-8, Sir Ridesalot wrote:
Okay, you've got very nearly perfectly trued wheels, single pivote calipers brakes and decent quality tires.

Braking isn't that great. Flip open the brake caliper quick relese and braking becomes much more effective.

Is it possible to have brakes so finely adjusted with the pads so close to the rim that braking ability is degraded whereas moving the pads further from the rim actually improves the braking?

Cheers

Ah these? a single pivot side pull .


http://velobase.com/ViewComponent.as...57052&Enum=117

Id put Kool Stop's Continental brake shoes on,

maybe upgrade cables to slick ones , use some of the new Jagwire housing
for Cable Disc brakes , to minimize the compression losses ,

I will also subscribe to the notion that where the grip strength is best, is mid arc
in pulling the lever to the bars.
its part of my brake setup preferences..

On Thursday, November 20, 2014 3:47:16 PM UTC-5, Zarniwoop wrote:
On Wednesday, November 19, 2014 2:32:57 PM UTC-8, Sir Ridesalot wrote:
Okay, you've got very nearly perfectly trued wheels, single pivote calipers brakes and decent quality tires.

Braking isn't that great. Flip open the brake caliper quick relese and braking becomes much more effective.

Is it possible to have brakes so finely adjusted with the pads so close to the rim that braking ability is degraded whereas moving the pads further from the rim actually improves the braking?

Cheers

Ah these? a single pivot side pull .


http://velobase.com/ViewComponent.as...57052&Enum=117

Id put Kool Stop's Continental brake shoes on,

maybe upgrade cables to slick ones , use some of the new Jagwire housing
for Cable Disc brakes , to minimize the compression losses ,

I will also subscribe to the notion that where the grip strength is best, is mid arc
in pulling the lever to the bars.
its part of my brake setup preferences..

The point is that the braking is extremely positive with tthe brake caliper quick release opened and the brake shoes a bit further from the rim than when the QR is closed.

The wheels are very true and with the QR closed there's just enough room for a piece of newspaper to slip between each brake block and the rim.

The issue wasn't needing to change anything to gain better braking but whether it's possible to have brakes so finely adjusted and the pads so close to the rim that braking suffers. I think that's the case here. I'm going to adjust the caliper so that the shoes are a bit further from the rim in the QR closed position.

Cheers

Phil W Lee writes:

Frank Krygowski considered Wed, 19 Nov 2014
18:48:44 -0500 the perfect time to write:

On 11/19/2014 5:32 PM, Sir Ridesalot wrote:
Okay, you've got very nearly perfectly trued wheels, single pivote calipers brakes and decent quality tires.

Braking isn't that great. Flip open the brake caliper quick relese and braking becomes much more effective.

Is it possible to have brakes so finely adjusted with the pads so close to the rim that braking ability is
degraded whereas moving the pads further from the rim actually improves
the braking?


I suppose it's possible, but that's in the same sense that "anything is
possible."

I'm trying to visualize the geometry of different brakes, and wondering
if some resulting change in geometry might increase mechanical
advantage. So - What model of brakes? What model of brake lever? What
type of quick release?

That is certainly possible - braking designs have been trying for ages
to give geometries which give maximum pad movement (with low
mechanical advantage) at the start of lever travel, to move the pads
quickly into contact with the braking surface, and lower movement with
high mechanical advantage toward the end of lever travel, to maximise
force applied between pad and braking surface.
In fact, understanding this is the key to getting maximum performance
out of cantilever brakes.

Similar "rising rate" geometries have been at the heart of vehicle
suspension design for many years as well.

So it's certainly above the level of "anything is possible".

But the Shimano 600 brakes don't have any mechanism to do this. The
only clear mechanical difference is that opening the QR slightly
increases the leverage, probably not enough to be significant. As has
been speculated, the more likely cause is that Sir is more comfortable
braking with his hands slightly clenched; that isn't unusual. I find
that with the brakes freshly adjusted, to allow for the most wear,
braking seems effective. An analysis of the changing mechanical
advantage of the hand, as it closes, might be interesting.


I'm also wondering about other weird factors. Maybe something like a
strand of cable that's broken away, and is restricting motion somehow.
Is it both front and rear brakes? Can we see a photo?

--
Joe Riel

On 21/11/14 08:15, Sir Ridesalot wrote:

The point is that the braking is extremely positive with tthe brake
caliper quick release opened and the brake shoes a bit further from
the rim than when the QR is closed.

The only thing that changes is the position of the lever when the shoe
reaches the rim.

Effectively, by opening the QR lever on the caliper, you've lengthened
the cable, which means the lever has to be moved further before the pad
touches the rim.

It could be that your levers provide more mechanical advantage at that
point, or simply that your hand is better at applying force.

Either way, there's no change to the caliper performance in isolation.

--
JS