C
On Thu, 15 Feb 2007 02:11:41 -0600, Ben C <[email protected]> wrote:
>On 2007-02-15, [email protected] <[email protected]> wrote:
>[...]
>> Dear Frank & Ben,
>>
>> To clarify things, disk brakes first appeared on large, heavy street
>> motorcycles--and were originally mounted with high leading calipers by
>> Honda.
>>
>> In ten years or less, the industry (including Honda) had switched to
>> overwhelmingly to low trailing calipers.
>>
>> The only modern leading calipers that I know of are found on trials
>> machines, where the high leading position helps avoid damaging
>> calipers when the bikes are dropped to one side or the other in rocks,
>> a routine hazard.
>>
>> Trials machines are not designed or certified for road use and
>> nowadays weigh under 170 pounds. Their braking can be quite savage at
>> low speeds in stunt-riding maneuvers, with the contact patches at
>> absurd angles.
>>
>> I don't know why all other machines switched to low trailing calipers
>> after the first high leading calipers, but I doubt that it had
>> anything to do with failures. More likely, the lower trailing caliper
>> improves handling at normal speeds--the motorcycle calipers and disks
>> are much larger and heavier than what's found on bicycles.
>
>Possibly there are aerodynamic advantages as well.
>
>[...]
>> Any RBT poster interested in such things should stop by a motorcycle
>> shop or just peek at a parked machine and see how much thicker,
>> heavier, and stronger motorcycle parts are.
>
>I have been getting funny looks recently as I scrutinize the caliper
>placement of every parked vehicle I walk past. All the motorbikes I've
>seen had them low and rear.
>
>Most cars I saw had them front mounted, but some were rear mounted.
>
>I saw a couple of Porsche 911s with cross-drilled discs. Grrr.
Dear Ben,
Alas, motorcycles are so hideously unstreamlined that aerodynamics are
ignored for all practical purposes. Their impressive power-to-weight
ratio tends to conceal aerodynamic characteristics that would shame a
garbage truck.
In the late 1970's, the wretched wind drag of motorcycles was
demonstrated in an amusing experiment.
A well-tuned Yamaha TZ750 racing motorcycle was put through the speed
traps.
Without even a spark plug change, the motorcycle engine was switched
into the modified engine bay of a small racing car--much heavier than
the motorcycle, but also much more streamlined.
The car went 20 mph faster on the same track.
Even well-fendered pavement-racing motorcycles with narrow handlebars
bear a strong resemblance to tumbleweeds in a wind-tunnel.
Here's a view of an ordinary street machine, showing the mirrors, turn
signals, speedometer, tachometer, fender, radiator, headlight, cables,
disk brake lever and master cylinder, and so forth that greet the
wind:
http://www.mccullagh.org/db9/10d-14/honda-919-motorcycle.jpg
For pracitcal riding, the wind drag just doesn't matter much when you
have around 100 real horsepower available at the rear tire to move
about 600 pounds of machine and rider.
Cheers,
Carl Fogel
>On 2007-02-15, [email protected] <[email protected]> wrote:
>[...]
>> Dear Frank & Ben,
>>
>> To clarify things, disk brakes first appeared on large, heavy street
>> motorcycles--and were originally mounted with high leading calipers by
>> Honda.
>>
>> In ten years or less, the industry (including Honda) had switched to
>> overwhelmingly to low trailing calipers.
>>
>> The only modern leading calipers that I know of are found on trials
>> machines, where the high leading position helps avoid damaging
>> calipers when the bikes are dropped to one side or the other in rocks,
>> a routine hazard.
>>
>> Trials machines are not designed or certified for road use and
>> nowadays weigh under 170 pounds. Their braking can be quite savage at
>> low speeds in stunt-riding maneuvers, with the contact patches at
>> absurd angles.
>>
>> I don't know why all other machines switched to low trailing calipers
>> after the first high leading calipers, but I doubt that it had
>> anything to do with failures. More likely, the lower trailing caliper
>> improves handling at normal speeds--the motorcycle calipers and disks
>> are much larger and heavier than what's found on bicycles.
>
>Possibly there are aerodynamic advantages as well.
>
>[...]
>> Any RBT poster interested in such things should stop by a motorcycle
>> shop or just peek at a parked machine and see how much thicker,
>> heavier, and stronger motorcycle parts are.
>
>I have been getting funny looks recently as I scrutinize the caliper
>placement of every parked vehicle I walk past. All the motorbikes I've
>seen had them low and rear.
>
>Most cars I saw had them front mounted, but some were rear mounted.
>
>I saw a couple of Porsche 911s with cross-drilled discs. Grrr.
Dear Ben,
Alas, motorcycles are so hideously unstreamlined that aerodynamics are
ignored for all practical purposes. Their impressive power-to-weight
ratio tends to conceal aerodynamic characteristics that would shame a
garbage truck.
In the late 1970's, the wretched wind drag of motorcycles was
demonstrated in an amusing experiment.
A well-tuned Yamaha TZ750 racing motorcycle was put through the speed
traps.
Without even a spark plug change, the motorcycle engine was switched
into the modified engine bay of a small racing car--much heavier than
the motorcycle, but also much more streamlined.
The car went 20 mph faster on the same track.
Even well-fendered pavement-racing motorcycles with narrow handlebars
bear a strong resemblance to tumbleweeds in a wind-tunnel.
Here's a view of an ordinary street machine, showing the mirrors, turn
signals, speedometer, tachometer, fender, radiator, headlight, cables,
disk brake lever and master cylinder, and so forth that greet the
wind:
http://www.mccullagh.org/db9/10d-14/honda-919-motorcycle.jpg
For pracitcal riding, the wind drag just doesn't matter much when you
have around 100 real horsepower available at the rear tire to move
about 600 pounds of machine and rider.
Cheers,
Carl Fogel