"Actually you are the first person to bring up this issue"

[Alan Hoyle]

On Thu, 25 Mar 2004 17:37:06 -0600, Jim Adney wrote:

> OTOH, even if threadlocking cured the main problem,
> repositioning would still add some protection for those
> who fail to secure the QR properly, so it's hard to see
> how this could be viewed as a bad thing.

Absolutely. Even if QRs don't loosen on their own, the
"disc brake ejection force" appears to make an
improperly tightened QR more dangerous than on a bicycle
with conventional brakes. Here's an experiment for the
shop owners:

Check all the bikes that come in to see if the QRs are
properly tightened. I would suspect the number of improperly
installed wheels will be above zero. It might also be
interesting to see what % of each category have disc brakes.

Repositioning the brakes would make the bike less likely to
exhibit dangerous failures with what I suspect is a common
user-maintenence error. From what I can tell, the only draw-
back is from a manufacturing perspective: that is a minor
re-design and re-tooling of their QR forks and chainstays.

-alan

--
Alan Hoyle - [email protected] - http://www.alanhoyle.com/
"I don't want the world, I just want your half." -TMBG
Get Horizontal, Play Ultimate.

 

[Carl Fogel]

Benjamin Lewis <[email protected]> wrote in message news:<[email protected]>...
> Ryan Cousineau wrote:
>
> > Benjamin Lewis <[email protected]> wrote:
> >> - loose surfaces don't lend themselves well to hard
> >> front braking. (I suppose this holds for most
> >> mountain biking though.)
> >
> > This is true in all mountain biking, and means that you
> > can stop faster from a given speed on pavement with a
> > road bike than on dirt, possibly excepting some
> > extremely high-traction surfaces; I'm thinking deep sand
> > or very tacky mud.
>
> (For the record, I said "most" rather than "all" to stave
> off pedants bringing up scenarios of riding over bare
> rocks or some such. I might have known one would come
> along and bite me anyway )
>
> >> - you can't brake as hard going downhill before lifting
> >> your rear wheel (maybe this isn't true; that's just
> >> my immediate intuition).
> >
> > Yes, but you can slide off the back of the seat. This
> > puts your weight very far back.
>
> I've always wondered how significant this effect is, and
> whether it's worth what I imagine would be some amount of
> loss of control. I'm still too lazy to do the vector
> analysis for the former, and have no idea how to determine
> the latter.
>
> In any case, one can slide off the back of the seat
> anywhere, not just while bombing downhill. Or does
> coasting downhill lend itself more to this practice, since
> one doesn't need to pedal as much?
>
> Just a clueless roadie, me.

Dear Benjamin,

The effect of the rearward position can be enormous, at
least on motorcycles. The cover of "Sammy Miller on Trials"
gives a good example:

http://tinyurl.com/283wh

The really awful part is that the only place that I could
find the famous cover picture turned out to be WalMart, of
all places.

Carl Fogel

 

[Dvt]

Carl Fogel wrote:
> I've been asking about how hard the braking really is
> elsewhere in this thread and would love to see more
> comment on it. The figure of 0.6 g has been used for hard
> braking in calculations about this thread, but it seems to
> come from dry pavement stops done with excellent road
> tires and riders able to throw their weight well back in
> an absolute panic stop.

So let's pretend the actual number is half that; 0.3g is the
max deceleration rate. The downward force on the caliper
goes down by a factor of two, which is still 910 N
(according to James' calculation). That's about 909 N more
than there *should* be, since things could be corrected with
a minor design change.

--
Dave dvt at psu dot edu

 

[G.T.]

Carl Fogel wrote:
> "G.T." <[email protected]> wrote in message
> news:<[email protected]>...
>
>>Carl Fogel wrote:
>>
>>>
>>>The front tire is also likely to have less traction
>>>downhill than on a flat stretch--the friction should be
>>>less, since gravity is not acting at right angles to
>>>press it against the ground, but instead is pressing it
>>>partly "forward" from the point of view of motion. (Or so
>>>it seems to me--I wish that some folks who know about off-
>>>road downhill braking physics would confirm or dispel my
>>>fantasies.)
>>
>>You're not always pointed down a hill steep enough for
>>gravity to not have an effect.
>>
>>
>>>I've been asking about how hard the braking really is
>>>elsewhere in this thread and would love to see more
>>>comment on it. The figure of 0.6 g has been used for hard
>>>braking in calculations about this thread, but it seems
>>>to come from dry pavement stops done with excellent road
>>>tires and riders able to throw their weight well back in
>>>an absolute panic stop.
>>>
>>
>>My panic stops on a mtn bike on fast, rocky terrain are
>>much shorter than my panic stops on a road bike on dry
>>pavement.
>>
>>
>>>It seems unlikely that as much traction will be available
>>>on a rough downhill, particularly when heavy braking
>>>effectively collapses telescopic front suspension. And
>>>paradoxically, the best downhill bicyclists might turn
>>>out to be those who brake the least, being able to jump
>>>and corner at higher speeds.
>>>
>>
>>Stopping quickly is just as important in downhill racing
>>as it is any wheeled sport with turns and obstacles.
>>
>>
>>>What I keep wondering about is whether there's a
>>>substantial difference between actual force (0.6 g, for
>>>example) and our careless impression of desperate braking
>>>on rough downhills. Loss of traction is not the same
>>>thing as braking force, whether it's on a loose descent
>>>or a sheet of ice.
>>>
>>
>>Why do people wonder about stuff they've never done and
>>ignore those who have done it?
>>
>>Greg
>
>
> Dear Greg,
>
> We wonder about such things precisely because we haven't
> done them. And it leads to interesting responses and
> further questions.
>
> If, as you indicate, you can indeed stop with much greater
> force on a rocky descent on a mountain bike than you can
> stop with a touring bike on flat dry pavement, should it
> follow that you can stop even faster on flat dry pavement?
> That is, do treaded tire mountain bikes have a tremendous
> braking advantage on the road?

As we all know treaded tires are not an advantage on the
road, but the bigger contact patch due to lower pressures
gives them an advantage. I can stop fastest on good, dry
pavement on my mtn bike than I can on any of my other bikes.

>
> Incidentally, do you have any figures? A 0.6 g pavement
> stop, for example, is usually shown as stopping in 20
> feet from 20 mph. If your bike has a speedometer, you
> could find a convenient downhill stretch, pick a mark,
> approach it at about 20 mph, and let us know how far past
> it you end up.
>

I will, maybe even tomorrow.

Greg

 

[G.T.]

Carl Fogel wrote:
>
>
> While wide knobby tires offer grip, what I'm wondering is
> whether they offer enough grip for greater braking than
> normal thin smooth street tires on flat dry pavement. As I
> understand it, street bikes are limited by the force that
> the brake can apply and by how well the rider can avoid
> flipping over, not by loss of traction on the front wheel.

Well, I've locked up my front wheel on flat dry pavement on
my road bike so I don't think that's always true.

>
> That is, ridiculously steep slopes can be descended quite
> slowly trials-fashion, but I'm not sure that this is the
> same force involved in a 0.6 g flat stop from 20 mph in
> 20 feet.

Slopes aren't always ridiculously steep. I can go quite fast
on a 3% grade.

> Frequently, there is no deceleration on a trials-type
> descent, just a steady rate. This must apply some steady
> force to counter the equally steady force of gravity
> acting at an angle, but I have no idea whether this
> amounts to as much as the 0.6 g forces used in James
> Annan's example for the wheel ejection.
>
> I suspect that the kind of braking involved will turn out
> to be trickier than presented so far, which is why I keep
> asking about it.
>
> Do disk brakes on bicycles actually offer more braking
> force than rim caliper brakes?

Yes.

> If so, is the greater force useful?

Yes, for me it is useful to prevent hand fatigue. On
long bumpy descents I only have to take one finger off
of the grip.

> That is, would a street bike be able to stop shorter with
> a disk brake than with a caliper brake?
>

No, not in general, only during muddy and wet conditions.

Greg

 

[G.T.]

Tony Raven wrote:
> G.T. wrote:
>
>>My panic stops on a mtn bike on fast, rocky terrain are
>>much shorter than my panic stops on a road bike on dry
>>pavement.
>>
>
>
> Using a tree is cheating ;-)

I am going to try to do some tests this weekend, and I will
try to avoid using a tree or large rock.

>
> Anyone remember Travis and his 4G stops off-road?
>

But of course.

Greg

 

[G.T.]

Benjamin Lewis wrote:
> G. T. wrote:
>
>
>>>- loose surfaces don't lend themselves well to hard front
>>> braking. (I suppose this holds for most mountain biking
>>> though.)
>>
>>Surfaces aren't always loose.
>
>
> Of course not. I'm not sure what your point is. Downhill
> racers are much more likely to be doing much of their
> braking on loose surfaces than people riding on pavement.
>

Because your blanket statement sounds like the bulk of a
downhill course is loose.

>
>>>- you can't brake as hard going downhill before lifting
>>> your rear wheel (maybe this isn't true; that's just my
>>> immediate intuition).
>>
>>It's very easy to lift a rear wheel on anything but the
>>slipperiest of surfaces.
>
>
> ... and my point was that it's even easier (requires less
> braking force) when descending. Again, I'm not sure what
> your point is.
>

I don't know how I misread that.

Greg

 

[Bomba]

On Fri, 26 Mar 2004 10:33:52 -0800, Benjamin Lewis wrote:

>>> - loose surfaces don't lend themselves well to hard
>>> front braking. (I suppose this holds for most mountain
>>> biking though.)
>>> - you can't brake as hard going downhill before lifting
>>> your rear wheel (maybe this isn't true; that's just my
>>> immediate intuition).
>>
>> Sorry, but you're way out.
>
> Well, I'm sorry too, but just telling me I'm wrong without
> attempting to explain why is hardly likely to convince me.

Sorry, I hadn't realise we were trying to convince you of
anything. I figured a certain amount of humility on your
part would prevail when discussing a subject, of which you
have little/no experience, with a group that has it by the
bucketload.

Ok, on the first point, truly loose surfaces that create a
roll-over effect are pretty rare. You're unlikely to get
front wheel skidding. You have to bear in mind that
mountain bike tyres run at lower pressures, have a much
greater contact area with the ground and have 'knobbles'
that are designed to dig in and give traction. In the
context of this (part of the) thread, downhill riders run a
minimum of 2.3" soft compound tyres run with extra thick
tubes at pressures of approx. 20psi. Combine this with 4-
pot hydraulic brakes and you have a pretty powerful braking
force. Because you're pointed downhill, all the forces are
going through the front end of the bike, and consequently,
most of the braking performance comes from there. In
addition to the total lack of power that you'll get by
using a back brake, you also have little control because
you'll just be locking up the rear. Typical braking on a
downhill is 80-100% through the front.

As for the second point, again, in the context of this
thread (DH racing), the bikes are designed with much slacker
angles. This allows more braking force to be applied to the
front of the bike without over-balancing the rider over the
front of the bike. Even normal mountain bikes have slacker
head and seat angles than which you're used to, for exactly
this reason.

Now, one may not be able to apply the brakes with the same
immediate force that one could on flat ground, but the
forces involved are greater, occur over longer periods and
on a more frequent basis.

Anyway, as I pointed out earlier, this test is unlikely to
produce any results because downhill racers all use bolt-
through axles anyway.

 

[Bomba]

On Fri, 26 Mar 2004 12:06:36 -0800, Carl Fogel wrote:

> Do disk brakes on bicycles actually offer more braking
> force than rim caliper brakes? If so, is the greater force
> useful? That is, would a street bike be able to stop
> shorter with a disk brake than with a caliper brake?

Yes, yes and yes.

 

[James Annan]

G.T. wrote:

> Carl Fogel wrote:
>
>>
>> Incidentally, do you have any figures? A 0.6 g pavement
>> stop, for example, is usually shown as stopping in 20
>> feet from 20 mph. If your bike has a speedometer, you
>> could find a convenient downhill stretch, pick a mark,
>> approach it at about 20 mph, and let us know how far
>> past it you end up.
>>
>
> I will, maybe even tomorrow.

I've been reluctant to wade into this particular detail
until now but maybe this year-old comment from Chris Juden
will set your minds at rest:

---begin quote

James

You are on solid ground with 0.6g. It's the limiting
deceleration for typical bicycles, at which the rear wheel
lifts (so front brake only is assumed). That's because 0.6
(or something like it) is the tangent of the angle of a line
joining the combined (bike+rider) c-of-g to the front tyre
contact point. Since the coefficient of friction between
tyre and ground usually exceeds 0.6, solo bikes usually tip
over before the front wheel slides - unlike cars, motorbikes
or tandems, which generally slide their front wheels first
and can brake at more than 1.0g, given good enough tyres,
road surface and brakes. (Which is interesting because it
means you can get some stupendous hub ejection forces out of
a tandem with discs.)

A skilled rider may well brake at very close to the 0.6g
limit (who hasn't sometimes felt their rear wheel lift in an
emergency stop?) and a very skilled mountain-biker, by
lowering his saddle, hunkering down and sliding off the back
of it, can sufficiently recline the vector joining front
tyre contact to his c-of-g so as to get 0.7 or even 0.8g -
though more commonly this is done to offset the reduction in
limiting deceleration that comes from tipping the whole
frame of reference forward, i.e. when riding downhill.

BS6102/1 calls for a dry stop from 24km/h in 5.5m. That
computes to a deceleration of 0.41g. So our 0.6g is only 50%
more severe than the absolute minimum standard that an
ordinary shopping bike should achieve.

---end quote

Given the potential for brake judder, the peak force is
actually substantially higher than the steady one (consider
adding a vibrating component on top of a steady force).
However it was not necessary to include this factor into the
description, which is fortunate as it would have given
another nit for the trolls to pick at. In fact, having now
mentioned it, I predict they won't be able to resist picking
at it anyway...

James

 

[James Annan]

G.T. wrote:

> Carl Fogel wrote:
>
>>
>> Incidentally, do you have any figures? A 0.6 g pavement
>> stop, for example, is usually shown as stopping in 20
>> feet from 20 mph. If your bike has a speedometer, you
>> could find a convenient downhill stretch, pick a mark,
>> approach it at about 20 mph, and let us know how far
>> past it you end up.
>>
>
> I will, maybe even tomorrow.

I've been reluctant to wade into this particular detail
until now but maybe this year-old comment from Chris Juden
will set your minds at rest:

---begin quote

James

You are on solid ground with 0.6g. It's the limiting
deceleration for typical bicycles, at which the rear wheel
lifts (so front brake only is assumed). That's because 0.6
(or something like it) is the tangent of the angle of a line
joining the combined (bike+rider) c-of-g to the front tyre
contact point. Since the coefficient of friction between
tyre and ground usually exceeds 0.6, solo bikes usually tip
over before the front wheel slides - unlike cars, motorbikes
or tandems, which generally slide their front wheels first
and can brake at more than 1.0g, given good enough tyres,
road surface and brakes. (Which is interesting because it
means you can get some stupendous hub ejection forces out of
a tandem with discs.)

A skilled rider may well brake at very close to the 0.6g
limit (who hasn't sometimes felt their rear wheel lift in an
emergency stop?) and a very skilled mountain-biker, by
lowering his saddle, hunkering down and sliding off the back
of it, can sufficiently recline the vector joining front
tyre contact to his c-of-g so as to get 0.7 or even 0.8g -
though more commonly this is done to offset the reduction in
limiting deceleration that comes from tipping the whole
frame of reference forward, i.e. when riding downhill.

BS6102/1 calls for a dry stop from 24km/h in 5.5m. That
computes to a deceleration of 0.41g. So our 0.6g is only 50%
more severe than the absolute minimum standard that an
ordinary shopping bike should achieve.

---end quote

Given the potential for brake judder, the peak force is
actually substantially higher than the steady one (consider
adding a vibrating component on top of a steady force).
However it was not necessary to include this factor into the
description, which is fortunate as it would have given
another nit for the trolls to pick at. In fact, having now
mentioned it, I predict they won't be able to resist picking
at it anyway...

James

 

[Chris B .]

On Fri, 26 Mar 2004 22:28:48 GMT, "G.T." <[email protected]>
wrote:

>Carl Fogel wrote:
>>
>>
>> While wide knobby tires offer grip, what I'm wondering
>> is whether they offer enough grip for greater braking
>> than normal thin smooth street tires on flat dry
>> pavement. As I understand it, street bikes are limited
>> by the force that the brake can apply and by how well
>> the rider can avoid flipping over, not by loss of
>> traction on the front wheel.
>
>Well, I've locked up my front wheel on flat dry pavement on
>my road bike so I don't think that's always true.

Yeah, sure you did.

 

[Simon Brooke]

in message <[email protected]>, Carl Fogel
('[email protected]') wrote:

> Simon Brooke <[email protected]> wrote in message news:<bmjdj1-
> [email protected]>...
>> in message <[email protected]>, Benjamin
>> Lewis ('[email protected]') wrote:
>>
>> > G. T. wrote:
>> >
>> >> Benjamin Lewis wrote:
>> >>> Mark Hickey wrote:
>> >>>
>> >>>> That was the beauty of the test I proposed. A bunch
>> >>>> of grass-roots riders on an unregulated newsgroup
>> >>>> could collect real data. Mike J's suggestion to test
>> >>>> skewers at downhill racing events is even better. No
>> >>>> kind of riding would produce the skewer movement
>> >>>> more quickly.
>> >>> Really? As a non-mountain-biker, I wouldn't expect
>> >>> there to be a lot of hard front braking in this
>> >>> environment.
>> >>
>> >> Why would you think that?
>>
>> If high braking forces weren't possible, MTBs would still
>> be using caliper brakes - there wouldn't have been any
>> push for progressively more effective braking
>> technologies.
>>
>> > - loose surfaces don't lend themselves well to hard
>> > front braking. (I suppose this holds for most
>> > mountain biking though.)
>>
>> Not all off-road surfaces are loose. I do a lot of my
>> riding on big granite outcrops. Even on loose surfaces
>> large, knobbly tyres can deliver a lot of grip.
>>
>> > - you can't brake as hard going downhill before lifting
>> > your rear wheel (maybe this isn't true; that's just
>> > my immediate intuition).
>>
>> You get your **** off the saddle and hang it over the
>> back wheel. Obviously there are limits, but you'd be
>> surprised how steeply you can safely descend.
>
> Dear Simon,
>
> I vaguely recall comments that disk brakes are popular for
> off-road bicycling not so much because they offer
> increased braking power, but because they get the brake
> surface up out of the muck that ruins rims from caliper
> braking, because they offer smoother control, and because
> they can offer increased mechanical advantage for the same
> braking force (your forearm muscles last longer).

All these are true. Add better modulation with hydraulic
brakes. However, that would not explain the progressive
shift from caliper brakes to cantilevers, and then to V
brakes, and then to hydraulic rim brakes which we have seen
in mountain bike development. All these developments came
about because earlier braking technologies could not achieve
sufficient braking force. Locking my front wheel on a hill
bike is a very rare experience (prolly a good thing because
that's a most excellent way of doing a face-plant). With
good knobbly low pressure tures you get phenomenal grip even
on loose and slimey surfaces.

> While wide knobby tires offer grip, what I'm wondering is
> whether they offer enough grip for greater braking than
> normal thin smooth street tires on flat dry pavement.

Speaking as one who rides more or less equally on and off
road, and who runs very narrow 100psi tyres on his road
bike, I can achieve higher braking forces on my hill bike
than on my road bike - but the latter does have rather
crummy old single pivot calipers and it's possible that with
more modern brakes it would stop quicker. But the contact
patch is *much* smaller.

> As I understand it, street bikes are limited by the
> force that the brake can apply and by how well the rider
> can avoid flipping over, not by loss of traction on the
> front wheel.
>
> That is, ridiculously steep slopes can be descended quite
> slowly trials-fashion, but I'm not sure that this is the
> same force involved in a 0.6 g flat stop from 20 mph in 20
> feet. Frequently, there is no deceleration on a trials-
> type descent, just a steady rate. This must apply some
> steady force to counter the equally steady force of
> gravity acting at an angle, but I have no idea whether
> this amounts to as much as the 0.6 g forces used in James
> Annan's example for the wheel ejection.

Downhilling one achieves much higher speeds than are normal
on road bikes; certainly higher than your quoted 20 mph.
While at some times (on particularly loose or uneven
sections) you may have less traction, at other times you
will have equal or more traction than on a road bike.

> Do disk brakes on bicycles actually offer more braking
> force than rim caliper brakes?

Yes, a lot more.

> If so, is the greater force useful?

Yes, very much so.

> That is, would a street bike be able to stop shorter with
> a disk brake than with a caliper brake?

Provided the rider shifted his weight to compensate, yes, in
my opinion.

Returning home from going west, I come down the village
street which is fairly steep and brake to a stop outside the
house. I know from experience that I can leave the braking
much later on my disk equipped hill bike than on my single-pivot-
caliper equipped road bike, to stop from similar speeds.

Disk brakes do have disadvantages. They're undoubtedly
heavier, they're more expensive, I suspect there's more drag
when the brake is disengaged, the spoke angle is steeper so
the wheels may be laterally weaker... but they are hugely
effective at stopping, wet or dry.

--
[email protected] (Simon Brooke)
http://www.jasmine.org.uk/~simon/

;; all in all you're just another click in the call
;; -- Minke Bouyed

 

[Jobst Brandt]

Carl Fogel writes:

> I vaguely recall comments that disk brakes are popular for
> off-road bicycling not so much because they offer
> increased braking power, but because they get the brake
> surface up out of the muck that ruins rims from caliper
> braking, because they offer smoother control, and because
> they can offer increased mechanical advantage for the same
> braking force (your forearm muscles last longer).

> While wide knobby tires offer grip, what I'm wondering is
> whether they offer enough grip for greater braking than
> normal thin smooth street tires on flat dry pavement. As I
> understand it, street bikes are limited by the force that
> the brake can apply and by how well the rider can avoid
> flipping over, not by loss of traction on the front wheel.

I think the term braking power means different things to
various people and that needs to be defined before and
answer can be given to brake performance questions.

The greatest retardation (negative acceleration) is limited
by overturning the bicycle forward, regardless of tire grip,
soft ground, or dry pavement. people talk of hanging off the
back of the saddle to achieve a lower center of gravity, but
that cannot be done except on a long sooth surface or the
saddle will give the rider a painful kick in the belly.
Besides, this is not a position that is easily entered or
left in situations where hard braking is demanded.

The advantage of disc brakes is not in braking "power", the
conversion of kinetic energy to heat, but in repeatable
reliable braking wet or dry and in dirty conditions. A good
disc brake can also do this with less lever force than a rim
brake because it can make use of low pad clearance to offer
a higher mechanical advantage to the hand lever.

> That is, ridiculously steep slopes can be descended quite
> slowly trials-fashion, but I'm not sure that this is the
> same force involved in a 0.6 g flat stop from 20 mph in 20
> feet. Frequently, there is no deceleration on a trials-
> type descent, just a steady rate. This must apply some
> steady force to counter the equally steady force of
> gravity acting at an angle, but I have no idea whether
> this amounts to as much as the 0.6 g forces used in James
> Annan's example for the wheel ejection.

Steep slopes are usually rough ones from water erosion and
thus such descents can achieve high momentary retardation,
higher than on level ground considering that braking while
landing on a rock outcropping can give high traction. It
isn't smooth long term braking as on a fast highway that is
under discussion. Therefore, rough steep descents can give
more up and down forces on the wheel attachment than on a
level course because there is more energy available and the
course is rough and fast.

> I suspect that the kind of braking involved will turn out
> to be trickier than presented so far, which is why I keep
> asking about it.

I wouldn't worry about it because active off road riding
generally involves high demands on brakes and is usually
involves steep rough descents, whether racing or not, but it
always sounds better if it is competition. One should think
where racers get their practice if it isn't in many miles of
the same but not officially sanctioned events.

> Do disk brakes on bicycles actually offer more braking
> force than rim caliper brakes? If so, is the greater force
> useful? That is, would a street bike be able to stop
> shorter with a disk brake than with a caliper brake?

As I said, it's the "over the top" effect that limits
braking. Most road riders do not brake near that limit so it
isn't a parameter.

Jobst Brandt [email protected]

 

[Tcmedara]

[email protected] wrote:
>
> As I said, it's the "over the top" effect that limits
> braking. Most road riders do not brake near that limit so
> it isn't a parameter.
>
Isn't that an inherent design flaw? Perhaps we should refer
to it as the OTB force from this point on and ask ourselves
why the manufacturers continue to market such a product. And
why hasn't the CPSC stepped in?

Just wondering....

Tom

 

[Ambrose Nankive]

In news:OI39c.10303$oH2.7396@lakeread01,
tcmedara <[email protected]> typed:
> [email protected] wrote:
>>
>> As I said, it's the "over the top" effect that limits
>> braking. Most road riders do not brake near that limit so
>> it isn't a parameter.
>>
> Isn't that an inherent design flaw? Perhaps we should
> refer to it as the OTB force from this point on and ask
> ourselves why the manufacturers continue to market such a
> product. And why hasn't the CPSC stepped in?
>
> Just wondering....
>
Yes. Maybe they should outlaw diamond frame bikes. Everyone
on a recumbent from now on, guys!

A

 

[Mark Thompson]

> perhaps pumice or slickrock might equal or exceed cement
> pavement.

<ahem> pavement?

 

[Jobst Brandt]

Tom C Medara writes:

>> As I said, it's the "over the top" effect that limits
>> braking. Most road riders do not brake near that limit so
>> it isn't a parameter.

> Isn't that an inherent design flaw? Perhaps we should
> refer to it as the OTB force from this point on and ask
> ourselves why the manufacturers continue to market such a
> product. And why hasn't the CPSC stepped in?

> Just wondering....

The hell you say! Maybe bicycles should be banned because
you can fall over if you stop and don't put your foot
down... on the side to which the bicycle leans.

Coming up with such remarks makes me doubt that there is
anything more behind much of this "there is no problem" talk
than a desire to be contra. Either that or it is a defense
of having bought a disc brake bicycle and making a defense
of how good a decision that was. Other than something on
that vein, I don't see why all this ad hominem is crudely
rising against the concept that current disc brakes pose a
hazard and one that could be easily fixed.

Jobst Brandt [email protected]

 

[Tom Sherman]

[email protected] wrote:

> Tom C Medara writes:
>
>
>>>As I said, it's the "over the top" effect that limits
>>>braking. Most road riders do not brake near that limit so
>>>it isn't a parameter.
>
>
>>Isn't that an inherent design flaw? Perhaps we should
>>refer to it as the OTB force from this point on and ask
>>ourselves why the manufacturers continue to market such a
>>product. And why hasn't the CPSC stepped in?
>
>
>>Just wondering....
>
>
> The hell you say! Maybe bicycles should be banned because
> you can fall over if you stop and don't put your foot
> down... on the side to which the bicycle leans....

Since I have a recumbent trike, I am well prepared for this
contingency.

--
Tom Sherman - Quad Cities (Illinois Side)

 

[Tom Sherman]

Ambrose Nankivell wrote:

> In news:OI39c.10303$oH2.7396@lakeread01, tcmedara
> <[email protected]> typed:
>
>>[email protected] wrote:
>>
>>>As I said, it's the "over the top" effect that limits
>>>braking. Most road riders do not brake near that limit so
>>>it isn't a parameter.
>>>
>>
>>Isn't that an inherent design flaw? Perhaps we should
>>refer to it as the OTB force from this point on and ask
>>ourselves why the manufacturers continue to market such a
>>product. And why hasn't the CPSC stepped in?
>>
>>Just wondering....
>>
>
> Yes. Maybe they should outlaw diamond frame bikes.
> Everyone on a recumbent from now on, guys!

Some of us have already figured that out without the
assistance of any regulatory agency.

--
Tom Sherman - Quad Cities (Illinois Side)