Road Discs

On Wed, 27 Sep 2017 00:37:12 -0400, Frank Krygowski
wrote:

On 9/26/2017 11:32 PM, John B. wrote:
On Tue, 26 Sep 2017 22:57:03 -0400, Frank Krygowski
wrote:

On 9/26/2017 8:34 PM, John B. wrote:
On Tue, 26 Sep 2017 07:18:28 -0700 (PDT), jbeattie wrote:

"Braking is also more rapid and positive with a well adjusted disc."

I would really like to see the dynamics of that statement explained as
during the 20 years or so that I worked on aircraft it was always
explained to us that maximum braking force is generated just before
the tire starts to skid which I have always assumed applied to any
rubber tired wheel and thus any brake that could actual stop the wheel
from turning must be capable of generating maximum braking force.

I've thought a bit about the descriptions of brake behavior. What you
say about maximum deceleration occurring very near skidding is certainly
correct. But what about statements like Jay's "rapid and positive," or
others' descriptions of "progressive" or "controllable" and the like?

On one hand, I don't think they're necessarily just ad-speak. I think
ideally, you'd want the braking force on the wheel to be perfectly
proportional to the force applied to the levers. There are various
practical effects that could destroy that proportionality.

Cable friction is certainly one such phenomenon, if it's got any
stick-slip component to it. (My antique motorcycle suffered from that
until I replaced its front brake cable.) Pivot friction in both the
lever and the brake's pivots could do the same. Some brakes have return
springs that tend to slide a bit where they contact the brake arm as the
arms move, and that causes a little jerk in the movement. Some brakes
(e.g. the notorious Campy Deltas) had geometry that was inherently
non-linear. And I can see that hydraulic discs inherently remove
several of those possibilities.

And I certainly won't say that a person who rides a lot could never
detect those effects. I know that musicians can detect and be bothered
by incredibly tiny imperfections in an instrument's action.

On the other hand, exactly when does that non-linearity matter? I think
unless a person is frequently diving into corners, trying to brake at
the last second and maintain the maximum possible speed through the
corner, the difference can't possibly be very important.


I wonder.

Basically I have three different braking systems on four different
bikes. In Bangkok both bikes have conventional dual pivot brakes and
in Phuket the utility bike has vee brakes and the road bike has center
pull brakes (at the moment).

Switching from one bike to another does, momentarily, result in a
difference in "brake feel", for want of a better description, but
after the first corner I don't notice any difference.

The Bangkok bikes are much the same and ridden on essentially the same
roads but the Phuket bikes are very different as the utility bike's
vee brakes are surprisingly effective, I can skid either or both
wheels on dry asphalt roads, while the center pull brakes are less
powerful. But still, I might notice the difference the first time I
apply the brakes but other than that I don't remember every thinking
"Oh yes, this is the yellow bike the brakes are different", in fact
generally speaking I don't think much about braking at all.

I would comment that I do spend time "tuning" the brakes on all the
bikes to ensure that there is minimal cable drag, the pads are aligned
and then the brakes apply equal pressure to each side of the rim, but
that shouldn't be unusual (I hope) :-)

I think this is the main reason I don't think much about the different
brake types I use: I almost never have to brake hard at all.

In fact, it's sort of an objective to use the brakes the least amount
possible. I mean, almost by definition, using the brakes slows you down,
right?

But some times it is nice to have them :-)
A hill in Phuket Thailand:
https://postimg.org/image/bqeh6mn1b/
--
Cheers,

John B.

On Wednesday, September 27, 2017 at 4:57:06 AM UTC+2, Frank Krygowski wrote:
On 9/26/2017 8:34 PM, John B. wrote:
On Tue, 26 Sep 2017 07:18:28 -0700 (PDT), jbeattie wrote:

"Braking is also more rapid and positive with a well adjusted disc."

I would really like to see the dynamics of that statement explained as
during the 20 years or so that I worked on aircraft it was always
explained to us that maximum braking force is generated just before
the tire starts to skid which I have always assumed applied to any
rubber tired wheel and thus any brake that could actual stop the wheel
from turning must be capable of generating maximum braking force.

I've thought a bit about the descriptions of brake behavior. What you
say about maximum deceleration occurring very near skidding is certainly
correct. But what about statements like Jay's "rapid and positive," or
others' descriptions of "progressive" or "controllable" and the like?

On one hand, I don't think they're necessarily just ad-speak. I think
ideally, you'd want the braking force on the wheel to be perfectly
proportional to the force applied to the levers. There are various
practical effects that could destroy that proportionality.

Cable friction is certainly one such phenomenon, if it's got any
stick-slip component to it. (My antique motorcycle suffered from that
until I replaced its front brake cable.) Pivot friction in both the
lever and the brake's pivots could do the same. Some brakes have return
springs that tend to slide a bit where they contact the brake arm as the
arms move, and that causes a little jerk in the movement. Some brakes
(e.g. the notorious Campy Deltas) had geometry that was inherently
non-linear. And I can see that hydraulic discs inherently remove
several of those possibilities.

And I certainly won't say that a person who rides a lot could never
detect those effects. I know that musicians can detect and be bothered
by incredibly tiny imperfections in an instrument's action.

On the other hand, exactly when does that non-linearity matter? I think
unless a person is frequently diving into corners, trying to brake at
the last second and maintain the maximum possible speed through the
corner, the difference can't possibly be very important.

So: Top level road racers? Yeah, I can see them wanting the very best,
and detecting a positive difference between a hydraulic disc vs. a top
shelf caliper brake. I suppose some may gain a very slight advantage in
a fast, curvy descent with a better brake.

But I doubt it's ever made a difference in who actually won a race. And
except for Jay-style commuters (doing hills during six months of wet
weather) I doubt the differences make a practical difference to many
non-racers.

--
- Frank Krygowski

Frank, the constant improvement of rim brakes is all about improving the brake force - applied handforce/travel curve. Stiffer calipers, low friction cables, Dual pivots, leverage in caliper and brake lever etc. etc. Compare 1978 Dura Ace with the new DA rim brakes and you notice a huge improvement.

Lou

On Tuesday, September 26, 2017 at 5:49:38 PM UTC-7, Doug Landau wrote:

Oh, stop putting up straw men and then bickering with what nobody said.
It is perfectly clear that those with whom you are pretending to argue are in fact discussing either a)the behavior of various brakes up to the point of locking the wheel, or b)the situation wherein [wet] conditions are preventing the brakes from being able to lock the wheel at all.

Also - a vehicle with no brakes still has tires with a coefficient of traction, but no braking ability at all, so your definition of braking ability is not correct.

I don't know about you but I'd just as soon that my tire not skid in wet conditions.

And all this talk about rim brakes overheating and exploding tires makes me nervous as hell too. I've never seen that happen but if it can under what conditions would it? Here I am going down a 3 mile hill that's pretty steep and now I'm slowing the bike down because I don't want to have to ride the brake hard and explode a tire.....

On Tuesday, September 26, 2017 at 7:57:06 PM UTC-7, Frank Krygowski wrote:
On 9/26/2017 8:34 PM, John B. wrote:
On Tue, 26 Sep 2017 07:18:28 -0700 (PDT), jbeattie wrote:

"Braking is also more rapid and positive with a well adjusted disc."

I would really like to see the dynamics of that statement explained as
during the 20 years or so that I worked on aircraft it was always
explained to us that maximum braking force is generated just before
the tire starts to skid which I have always assumed applied to any
rubber tired wheel and thus any brake that could actual stop the wheel
from turning must be capable of generating maximum braking force.

I've thought a bit about the descriptions of brake behavior. What you
say about maximum deceleration occurring very near skidding is certainly
correct. But what about statements like Jay's "rapid and positive," or
others' descriptions of "progressive" or "controllable" and the like?

On one hand, I don't think they're necessarily just ad-speak. I think
ideally, you'd want the braking force on the wheel to be perfectly
proportional to the force applied to the levers. There are various
practical effects that could destroy that proportionality.

Cable friction is certainly one such phenomenon, if it's got any
stick-slip component to it. (My antique motorcycle suffered from that
until I replaced its front brake cable.) Pivot friction in both the
lever and the brake's pivots could do the same. Some brakes have return
springs that tend to slide a bit where they contact the brake arm as the
arms move, and that causes a little jerk in the movement. Some brakes
(e.g. the notorious Campy Deltas) had geometry that was inherently
non-linear. And I can see that hydraulic discs inherently remove
several of those possibilities.

And I certainly won't say that a person who rides a lot could never
detect those effects. I know that musicians can detect and be bothered
by incredibly tiny imperfections in an instrument's action.

On the other hand, exactly when does that non-linearity matter? I think
unless a person is frequently diving into corners, trying to brake at
the last second and maintain the maximum possible speed through the
corner, the difference can't possibly be very important.

So: Top level road racers? Yeah, I can see them wanting the very best,
and detecting a positive difference between a hydraulic disc vs. a top
shelf caliper brake. I suppose some may gain a very slight advantage in
a fast, curvy descent with a better brake.

But I doubt it's ever made a difference in who actually won a race. And
except for Jay-style commuters (doing hills during six months of wet
weather) I doubt the differences make a practical difference to many
non-racers.

Funny you should talk about those Campy Deltas. Over on Steel Is Real I said that I hated them because they wouldn't stop a bike. And everyone went crazy. One person said that I must have used the Croi d'Aune (spelling?) brakes and the Record Deltas worked fine.

Another said that you have to set the Deltas up properly to work well.

Well, setting them up properly consisted of either using very narrow rims so that the brake was almost entirely expanded when it contacted the rim, or sanding the brake shoes down to the same condition on a normal rim.

The problem with that of course is just like with disks - a little normal wear puts them out of operation.

One of the things with disks is that you can chip the edge of the pad when inserting the wheel and this causes faster than normal wear. Also in order to get them to work well in very wet condition you have to have disks that have a lot of cut-outs. Well by doing that to push water off of the disk more rapidly you are reducing the surface area of the disk so that IT now wears rapidly.

On a heavy full suspension bike you can find a balance but for very light bikes such as road bikes or cross bikes I don't like the extreme sensitivity of the braking.

On Wednesday, September 27, 2017 at 5:25:40 AM UTC-7, wrote:
On Wednesday, September 27, 2017 at 4:57:06 AM UTC+2, Frank Krygowski wrote:
On 9/26/2017 8:34 PM, John B. wrote:
On Tue, 26 Sep 2017 07:18:28 -0700 (PDT), jbeattie wrote:

"Braking is also more rapid and positive with a well adjusted disc."

I would really like to see the dynamics of that statement explained as
during the 20 years or so that I worked on aircraft it was always
explained to us that maximum braking force is generated just before
the tire starts to skid which I have always assumed applied to any
rubber tired wheel and thus any brake that could actual stop the wheel
from turning must be capable of generating maximum braking force.

I've thought a bit about the descriptions of brake behavior. What you
say about maximum deceleration occurring very near skidding is certainly
correct. But what about statements like Jay's "rapid and positive," or
others' descriptions of "progressive" or "controllable" and the like?

On one hand, I don't think they're necessarily just ad-speak. I think
ideally, you'd want the braking force on the wheel to be perfectly
proportional to the force applied to the levers. There are various
practical effects that could destroy that proportionality.

Cable friction is certainly one such phenomenon, if it's got any
stick-slip component to it. (My antique motorcycle suffered from that
until I replaced its front brake cable.) Pivot friction in both the
lever and the brake's pivots could do the same. Some brakes have return
springs that tend to slide a bit where they contact the brake arm as the
arms move, and that causes a little jerk in the movement. Some brakes
(e.g. the notorious Campy Deltas) had geometry that was inherently
non-linear. And I can see that hydraulic discs inherently remove
several of those possibilities.

And I certainly won't say that a person who rides a lot could never
detect those effects. I know that musicians can detect and be bothered
by incredibly tiny imperfections in an instrument's action.

On the other hand, exactly when does that non-linearity matter? I think
unless a person is frequently diving into corners, trying to brake at
the last second and maintain the maximum possible speed through the
corner, the difference can't possibly be very important.

So: Top level road racers? Yeah, I can see them wanting the very best,
and detecting a positive difference between a hydraulic disc vs. a top
shelf caliper brake. I suppose some may gain a very slight advantage in
a fast, curvy descent with a better brake.

But I doubt it's ever made a difference in who actually won a race. And
except for Jay-style commuters (doing hills during six months of wet
weather) I doubt the differences make a practical difference to many
non-racers.

--
- Frank Krygowski

Frank, the constant improvement of rim brakes is all about improving the brake force - applied handforce/travel curve. Stiffer calipers, low friction cables, Dual pivots, leverage in caliper and brake lever etc. etc. Compare 1978 Dura Ace with the new DA rim brakes and you notice a huge improvement.

Imagine the difference in feel with the old long reach Mavic brakes and a modern Campy Record.

I think we're just arguing tin man. Disks have taken this connection of hand and brake to it's ultimate limit. I don't like that but certainly others do.

Il 10/09/2017 00:28, jbeattie ha scritto:
So, my SuperSix was crushed in a roof-rack accident and last weak my
Roubaix was stolen out of the garage that I left open all night. I've
done that many times -- apparently one too many. I'm down to a
gravel bike and my commuter -- the reborn warranty CAADX (which is a
great bike).

The gravel bike is a pig, but I'll use that for fall/winter/spring
sport riding. I want a fast bike, though -- and I've got a line on
a nice bike that I can get with rim brakes or discs, but the disc
model will not be available until December -- which really means that
I get to ride it in dry weather some time around May. I can get a
rim brake model by the end of the month.

All the shops are pushing discs, and I did like the discs on the
Roubaix and on my gravel bike. I know this is absolutely the wrong
group to ask because it's wall-to-wall curmudgeons, but if you were
buying your last nice road bike, would you go rim brakes or discs?
It will be a dry weather bike or ridden in the rain only because of
bad luck. There would be no real weight penalty because the bike is
so light to start with. I'm not aero, so I don't care about the aero
penalty with discs.

My concern with getting rim brakes is not really even a performance
issue because in dry weather, I've never had a problem with rim
brakes -- but to listen to the guys at the local shop, rim brakes
are going the way of the dodo. I'm worried about buying an antique!

-- Jay Beattie.

Let me first say hi to you all: I'm Stefano, 56, from Piacenza, Northern
Italy. I'm a hobby-cycle-traveller... and a cycle commuter.
I'm mainly lurking, but let me give you my personal experience.

I have 2 bikes, now. An ancient but still perfect city bike (a Bianchi
Stelvio, bought used in 1987!), used for commuting: Campagnolo 5x2, all
aluminum wheels (Ambrosio) very tiny 23x622, Campagnolo aluminum wheel
brakes. A race bike (of its age) with lights and dyno added, basically. :-)

And a "travel bike": a Kalkhoff Sting, with aluminum frame, very robust
(and heavy), much larger tyres (37-622), hydraulic disk brakes.
I have choosen disks because I use it fully loaded. When I travel, me,
the bike, the bags and their contents are easily exceeding 120-130 kg...

So, brake power and resistance is a much more complicated business, with
that weight.

But, surprisingly, the biggest difference that I experienced, in the
end, is the effort needed to brake (much, much lower with disks,
obviuosly) and the sensitivity. I mean: I am able to brake as much as I
want. Easily. Very easily.
It's not the same with rim brakes, even with very powerful V-brakes. I
had excellent v-brakes on an MTB: they are powerful. They brake quite
well under the rain (if you use the right rubber "shoes"...). But you
cannot brake so precisely as a hydraulic disc brake can. Sorry, no way.

So, in my experience, I'll never more go back to a bike without disc
brakes. Not for the power of braking. But surely because it's effortless
and very easy to manage.
Yes. It requires more maintenance. But nothing more complicated than the
usual effort to get a good response, squeezing levers on a v-brake
system. Not to talk about cantilever!!! Or pure rim brakes... :-(

In my opinion, for race bikes it's a little bit early. Maybe some
systems are not yet 100% fit the application: they all are derivated
from MTB systems. You're right: race bikes have very small wheels, thus
the braking force MUST be adapted to that level of tyre surface on
ground. But if you can find a good system, correctly balanced and
manufactured, there's no story. That's the future, in my opinion,
definitely.
Look to the MTB: more and more bikes come with disks. Once it's
available and you've tested it, it's difficult to say that it doesn't
matter.

On 9/27/2017 8:25 AM, wrote:
On Wednesday, September 27, 2017 at 4:57:06 AM UTC+2, Frank Krygowski wrote:
On 9/26/2017 8:34 PM, John B. wrote:
On Tue, 26 Sep 2017 07:18:28 -0700 (PDT), jbeattie wrote:

"Braking is also more rapid and positive with a well adjusted disc."

I would really like to see the dynamics of that statement explained as
during the 20 years or so that I worked on aircraft it was always
explained to us that maximum braking force is generated just before
the tire starts to skid which I have always assumed applied to any
rubber tired wheel and thus any brake that could actual stop the wheel
from turning must be capable of generating maximum braking force.

I've thought a bit about the descriptions of brake behavior. What you
say about maximum deceleration occurring very near skidding is certainly
correct. But what about statements like Jay's "rapid and positive," or
others' descriptions of "progressive" or "controllable" and the like?

On one hand, I don't think they're necessarily just ad-speak. I think
ideally, you'd want the braking force on the wheel to be perfectly
proportional to the force applied to the levers. There are various
practical effects that could destroy that proportionality.

Cable friction is certainly one such phenomenon, if it's got any
stick-slip component to it. (My antique motorcycle suffered from that
until I replaced its front brake cable.) Pivot friction in both the
lever and the brake's pivots could do the same. Some brakes have return
springs that tend to slide a bit where they contact the brake arm as the
arms move, and that causes a little jerk in the movement. Some brakes
(e.g. the notorious Campy Deltas) had geometry that was inherently
non-linear. And I can see that hydraulic discs inherently remove
several of those possibilities.

And I certainly won't say that a person who rides a lot could never
detect those effects. I know that musicians can detect and be bothered
by incredibly tiny imperfections in an instrument's action.

On the other hand, exactly when does that non-linearity matter? I think
unless a person is frequently diving into corners, trying to brake at
the last second and maintain the maximum possible speed through the
corner, the difference can't possibly be very important.

So: Top level road racers? Yeah, I can see them wanting the very best,
and detecting a positive difference between a hydraulic disc vs. a top
shelf caliper brake. I suppose some may gain a very slight advantage in
a fast, curvy descent with a better brake.

But I doubt it's ever made a difference in who actually won a race. And
except for Jay-style commuters (doing hills during six months of wet
weather) I doubt the differences make a practical difference to many
non-racers.

--
- Frank Krygowski

Frank, the constant improvement of rim brakes is all about improving the brake force - applied handforce/travel curve.

Give me that again, please. Is this what you mean?

((brake force) - (hand force))/travel

And if so, what specific "travel" are you using there?

Stiffer calipers, low friction cables, Dual pivots, leverage in caliper and brake lever etc. etc. Compare 1978 Dura Ace with the new DA rim brakes and you notice a huge improvement.

There have certainly been improvements over the years.

--
- Frank Krygowski

On Wednesday, September 27, 2017 at 7:57:57 AM UTC-7, Cordy wrote:
Il 10/09/2017 00:28, jbeattie ha scritto:
So, my SuperSix was crushed in a roof-rack accident and last weak my
Roubaix was stolen out of the garage that I left open all night. I've
done that many times -- apparently one too many. I'm down to a
gravel bike and my commuter -- the reborn warranty CAADX (which is a
great bike).

The gravel bike is a pig, but I'll use that for fall/winter/spring
sport riding. I want a fast bike, though -- and I've got a line on
a nice bike that I can get with rim brakes or discs, but the disc
model will not be available until December -- which really means that
I get to ride it in dry weather some time around May. I can get a
rim brake model by the end of the month.

All the shops are pushing discs, and I did like the discs on the
Roubaix and on my gravel bike. I know this is absolutely the wrong
group to ask because it's wall-to-wall curmudgeons, but if you were
buying your last nice road bike, would you go rim brakes or discs?
It will be a dry weather bike or ridden in the rain only because of
bad luck. There would be no real weight penalty because the bike is
so light to start with. I'm not aero, so I don't care about the aero
penalty with discs.

My concern with getting rim brakes is not really even a performance
issue because in dry weather, I've never had a problem with rim
brakes -- but to listen to the guys at the local shop, rim brakes
are going the way of the dodo. I'm worried about buying an antique!

-- Jay Beattie.

Let me first say hi to you all: I'm Stefano, 56, from Piacenza, Northern
Italy. I'm a hobby-cycle-traveller... and a cycle commuter.
I'm mainly lurking, but let me give you my personal experience.

I have 2 bikes, now. An ancient but still perfect city bike (a Bianchi
Stelvio, bought used in 1987!), used for commuting: Campagnolo 5x2, all
aluminum wheels (Ambrosio) very tiny 23x622, Campagnolo aluminum wheel
brakes. A race bike (of its age) with lights and dyno added, basically. :-)

And a "travel bike": a Kalkhoff Sting, with aluminum frame, very robust
(and heavy), much larger tyres (37-622), hydraulic disk brakes.
I have choosen disks because I use it fully loaded. When I travel, me,
the bike, the bags and their contents are easily exceeding 120-130 kg...

So, brake power and resistance is a much more complicated business, with
that weight.

But, surprisingly, the biggest difference that I experienced, in the
end, is the effort needed to brake (much, much lower with disks,
obviuosly) and the sensitivity. I mean: I am able to brake as much as I
want. Easily. Very easily.
It's not the same with rim brakes, even with very powerful V-brakes. I
had excellent v-brakes on an MTB: they are powerful. They brake quite
well under the rain (if you use the right rubber "shoes"...). But you
cannot brake so precisely as a hydraulic disc brake can. Sorry, no way.

So, in my experience, I'll never more go back to a bike without disc
brakes. Not for the power of braking. But surely because it's effortless
and very easy to manage.
Yes. It requires more maintenance. But nothing more complicated than the
usual effort to get a good response, squeezing levers on a v-brake
system. Not to talk about cantilever!!! Or pure rim brakes... :-(

In my opinion, for race bikes it's a little bit early. Maybe some
systems are not yet 100% fit the application: they all are derivated
from MTB systems. You're right: race bikes have very small wheels, thus
the braking force MUST be adapted to that level of tyre surface on
ground. But if you can find a good system, correctly balanced and
manufactured, there's no story. That's the future, in my opinion,
definitely.
Look to the MTB: more and more bikes come with disks. Once it's
available and you've tested it, it's difficult to say that it doesn't
matter.

Thanks Cordy. That is pretty much my idea as well. On heavy bikes where you might have to stop suddenly - Full Suspension MTB's or in your case a Touring bike fully loaded - I can see them but I would still be concerned about pad wear.

On 9/27/2017 9:47 AM, wrote:

And all this talk about rim brakes overheating and exploding tires makes me nervous as hell too. I've never seen that happen but if it can under what conditions would it? Here I am going down a 3 mile hill that's pretty steep and now I'm slowing the bike down because I don't want to have to ride the brake hard and explode a tire.....

There were extended discussions on this back when Jobst was with us.

I can recall six blowouts in my 45 or so years of adult cycling. I don't
think most were caused by rim overheating, but I can't say for sure what
the mechanisms were on several of them.

First one was a borrowed set of tubulars. I did a solo ride on a hot
day, parked the bike in the sun while I cooled down, and heard what
sounded like a shotgun blast. It was really the expensive Clement
tubular blowing a hole in itself, dead center of the tread right at the
top. So no rim involvement.

Second was in 1979, when I mounted the first set of tires on our new
tandem's rims. After I mounted the tires, I parked the bike indoors in
our bedroom. Maybe an hour later, we were startled by another shotgun
blast, and the tube was shredded where the back tire was off the rim. No
heat involvement.

Third was on that same tandem, same rims (Weinmann, non-hook rims) maybe
five years later. We slowly descended a steep (15% to 20%) short (1/4
mile?) hill, braking as we went down toward a stop sign, and blew the
back tire. I don't think it was heat, because the hill was so short. I
don't remember the rim being hot as I replaced the tube.

Fourth was when my wife, daughter and I did a three week tour around
Ireland. We rode a few miles on a multi-use path that was originally a
canal towpath. It was pretty bumpy. At the path's end, we parked the
bikes and paused for a snack in a little village square. About ten
minutes after we stopped, a tire exploded on my daughter's bike as it
stood there parked. That was 1992.

Fifth was a club mate, about five years ago. We'd just descended a
mile-long hill, maybe 8% grade, with a stop sign at the bottom. As we
pulled away from the stop sign onto a level road, he blew out one of his
tires. Again, I don't recall anyone saying the rim was hot, but it may
have been. I wasn't the one changing that tire.

Six was about two years ago. Our Bikes Friday came with trailer hardware
for towing the bike-containing suitcases. I modified one trailer to tow
little kids. I was putting air into the 12" trailer tires mounted on
plastic wheels, and I misread the recommended pressure. Instead of 35
psi, I put in 85 psi. (Hey, I was sleepy.) One tire blew off the rim
hours later as it was parked in the hot sun.

It's not that I doubt that hot rims can cause a tire to dismount and
blow a tube. But there must be other mechanisms that can cause the same
thing.

BTW, I've gotten quite religious about checking the registration line
all around the rim, both sides, when I mount tires.

--
- Frank Krygowski

On Tuesday, September 26, 2017 at 7:57:06 PM UTC-7, Frank Krygowski wrote:
On 9/26/2017 8:34 PM, John B. wrote:
On Tue, 26 Sep 2017 07:18:28 -0700 (PDT), jbeattie wrote:

"Braking is also more rapid and positive with a well adjusted disc."

I would really like to see the dynamics of that statement explained as
during the 20 years or so that I worked on aircraft it was always
explained to us that maximum braking force is generated just before
the tire starts to skid which I have always assumed applied to any
rubber tired wheel and thus any brake that could actual stop the wheel
from turning must be capable of generating maximum braking force.

I've thought a bit about the descriptions of brake behavior. What you
say about maximum deceleration occurring very near skidding is certainly
correct. But what about statements like Jay's "rapid and positive," or
others' descriptions of "progressive" or "controllable" and the like?

In a straight line. He is still only considering the situation of moving in a straight line. While turning, maximum braking will occur at a lower point than the coefficient of friction of the tires, and the result of exceeding the available traction will be a spin and fall, rather than a skid.