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Why do some forks and frames have brake rotor size limits?



 
 
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  #381  
Old November 16th 17, 05:02 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 10,538
Default Why do some forks and frames have brake rotor size limits?

On 11/15/2017 8:26 PM, John B. wrote:
On Wed, 15 Nov 2017 14:20:32 -0500, Frank Krygowski
wrote:

On 11/14/2017 11:08 PM, jbeattie wrote:
On Tuesday, November 14, 2017 at 4:41:22 PM UTC-8, Joerg wrote:
On 2017-11-14 16:15, jbeattie wrote:
On Tuesday, November 14, 2017 at 12:37:35 PM UTC-8, Joerg wrote:
On 2017-11-13 19:02, Frank Krygowski wrote:
On 11/13/2017 7:03 PM, Joerg wrote:

[...]

They just don't want to ride.

This is true. Again, we're an unusual group. If you gave every
American a perfectly safe, absolutely level, completely separated
bike path directly from their house to their favorite grocery
store one mile away, I doubt more than 3% would ride bikes to
shop.


They would if you gave them an E-bike with a throttle-only mode.
And if it had an A/C button.

I'm dealing with an infestation of eBikes. Some woman dropped me like
a rock last night on the latest Trek super-commuter eBike while
wearing the most expensive, fully reflective Showers Pass rain
jacket.


Spandex would have been nicer if she was pretty :-)

But yeah, same here on Sunday heading up a rail trail with a buddy. We
aren't slowpokes but then we heard a whirring from behind ... zzzooom
... a guy in his 70's shot past us on an E-bike. He didn't wear fancy
clothes though.


https://www.showerspass.com/collecti...nt=27454486405
In combination with her super-bright lights, she was a human flare --
and an expensive one. She could have gotten the same dollar-to-lumen
ratio by burning $20 bills. I want all that stuff! It was he
https://tinyurl.com/y7fgaymx The "flat" route home. I was on the
better paved section to the right going up.


You guys need someone to fix those roads. A few more winters and the
underlayment is toast, meaning it can't be patched anymore.


I can't hang with the eBikes through the hills -- not without giving
myself a heart attack, and although death is part of my long-term
financial plan, I'm saving it for later.


Some guys are pushing it too far. I passed a rider last week on a hill,
probably about 65, somewhat obese but lots of leg muscles. That didn't
sit well with him so he passed me and really stepped on it, telling me
"It's on, mate!". I decided not to give chase because he was really fast
and I carried some load. Up the hill where it leveled off I closed up
quickly and he looked totally exhausted. That can't be good.

"It's on mate"(?) What a dope. I would have gone out and bought an old Silca frame pump just so I could stick it in his front wheel. "Hey, wait here; I'll be right back." I pass people all the time and couldn't imagine saying "It's on mate." I'd sign up for Death with Dignity if I did that sort of thing.

Totally OT, but I was riding up on Skyline a few months back and ran into a group of guys I raced with 30 years ago -- including a guy who was a junior prodigy back in the '70s and was in USCF development camps with Andy Hampsten and Greg LeMond. He's now CEO of a national company. We just rode along, nobody trying to prove anything, talking about the good old days. My regular cohort is like that too, except we do race each other at very predictable points in the ride. I'm slowing, so my place is no longer assured. I've learned to be more strategic, and my friends have learned to wait.


FWIW, a local mountain biker was found dead on some very tame single
track a few days ago. I didn't know him, but have friends who did. They
described him as middle aged (much younger than me), in tremendous
physical shape, built like a muscular swimmer, very low body fat, a
regular user of the YMCA etc.

Given the location, he probably wasn't pushing anywhere close to cardio
extremes. Indications are he was JRA and died instantly.

Apparently there is a correlation between long history as an endurance
athlete and atrial fibrillation and other electrical problems. Grant
Peterson has written about what he calls good exercise and bad exercise.
My views have certainly changed.


As you say, there seems to be some correlation between endurance
athletes and some heart problems, but at the same time some endurance
athletes seem to just go on for ever. "Old" John Kelly ran something
like 61 Boston Marathons, his last at the age of 84, In his 70's he
was still running 50 miles a week and some 15 races a year, while
"Young" John Kelly (the family name "Kelly" is not a rare one in South
Boston :-) ran 31 B.M.'s his last at 62 in 4:07.

On the other hand
https://www.peakendurancesport.com/e...urance-sports/
says:
"Endurance athletes who exercise for three hours or more have an
increased chance of dying from a cardiac arrest. About 1 in 50,000: if
you run marathons or participate in other forms of exercise which last
for three hours or more."

They also say the "For one thing, it's clear that regular exercise
protects you from heart attacks over broad time frames; for example,
over the course of a year regular exercisers will have fewer cardiac
failures than their sedentary counterparts.

And they go on to say that "If you are having second thoughts about
running marathons, you should know that the previously quoted rate of
one death per 50,000 marathon runners might be a bit high. For
example, there is evidence that in male runners aged 30-64 who have
not been diagnosed with heart disease, there is approximately one
death for each 800,000 person-hours of running or jogging"

And even more enlightening they add "Expressing the 800,000 statistic
in a different way, we can say that healthy, middle-aged males who run
for one hour each day can expect to die while running once every 2,192
years (800,000 hours divided by 365 hours of running per year = 2,192
years). By the same token, individuals who run two hours per day
should die while running about once every 1,096 years. When the risks
are seen in this light, many endurance athletes will consider them
acceptably low, especially as the general risk of heart disease is
reduced by strenuous training."

I think that some exercise is far better then no exercise and I think
I'll carry on as best I can :-)


I do carry on (I'm a few years younger than you), but I have a little
less fire in my belly, as they say.


--
- Frank Krygowski
Ads
  #382  
Old November 16th 17, 07:59 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default Why do some forks and frames have brake rotor size limits?

On Wed, 15 Nov 2017 23:00:03 -0500, Frank Krygowski
wrote:

On 11/15/2017 7:45 PM, John B. wrote:

On Wed, 15 Nov 2017 15:17:28 -0800, Joerg
wrote:

Anyhow, there are numerous issues here, not the least being that it is
tough to mount a thick rotor so it still lines up correctly. It may be
possible to machine a part to adapt a motorcycle caliper and I have had
parts machined for my MTB. Requires time though. As I said, first I am
going to see if the 8" rotors are good enough which they very well may
be. 6" in back was clearly not adequate.


Good Lord! A disc is just about the simplest thing that you could
design - two circles one inside the other - and almost the simplest
thing to manufacturer. Even in the wilds of California you should be
able to find either a "home machinist" or a commercial shop to make
them to your specifications.


This guy may be for hi
https://www.youtube.com/watch?v=VVV4xeWBIxE

He has lots of videos. I think one even involves repairing a chain
without a chain tool.


I get a kick out of these primitive whatever posts. Most of them
display a vivid imagination, at best.

It appears that Carthage may have smelted iron from 800-900 BCE and
certainly Rome wouldn't have been far behind. There is also evidence
dating to about the 700 - 500 BCE era in Britain. Why no primitive
iron tools :-)

As an aside The first continuous and endless power-transmitting chain
was depicted in the written horological treatise of the Song Dynasty
(960 - 1279) :-)
--
Cheers,

John B.

  #383  
Old November 16th 17, 08:07 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default Why do some forks and frames have brake rotor size limits?

On Wed, 15 Nov 2017 23:02:59 -0500, Frank Krygowski
wrote:

On 11/15/2017 8:26 PM, John B. wrote:
On Wed, 15 Nov 2017 14:20:32 -0500, Frank Krygowski
wrote:

On 11/14/2017 11:08 PM, jbeattie wrote:
On Tuesday, November 14, 2017 at 4:41:22 PM UTC-8, Joerg wrote:
On 2017-11-14 16:15, jbeattie wrote:
On Tuesday, November 14, 2017 at 12:37:35 PM UTC-8, Joerg wrote:
On 2017-11-13 19:02, Frank Krygowski wrote:
On 11/13/2017 7:03 PM, Joerg wrote:

[...]

They just don't want to ride.

This is true. Again, we're an unusual group. If you gave every
American a perfectly safe, absolutely level, completely separated
bike path directly from their house to their favorite grocery
store one mile away, I doubt more than 3% would ride bikes to
shop.


They would if you gave them an E-bike with a throttle-only mode.
And if it had an A/C button.

I'm dealing with an infestation of eBikes. Some woman dropped me like
a rock last night on the latest Trek super-commuter eBike while
wearing the most expensive, fully reflective Showers Pass rain
jacket.


Spandex would have been nicer if she was pretty :-)

But yeah, same here on Sunday heading up a rail trail with a buddy. We
aren't slowpokes but then we heard a whirring from behind ... zzzooom
... a guy in his 70's shot past us on an E-bike. He didn't wear fancy
clothes though.


https://www.showerspass.com/collecti...nt=27454486405
In combination with her super-bright lights, she was a human flare --
and an expensive one. She could have gotten the same dollar-to-lumen
ratio by burning $20 bills. I want all that stuff! It was he
https://tinyurl.com/y7fgaymx The "flat" route home. I was on the
better paved section to the right going up.


You guys need someone to fix those roads. A few more winters and the
underlayment is toast, meaning it can't be patched anymore.


I can't hang with the eBikes through the hills -- not without giving
myself a heart attack, and although death is part of my long-term
financial plan, I'm saving it for later.


Some guys are pushing it too far. I passed a rider last week on a hill,
probably about 65, somewhat obese but lots of leg muscles. That didn't
sit well with him so he passed me and really stepped on it, telling me
"It's on, mate!". I decided not to give chase because he was really fast
and I carried some load. Up the hill where it leveled off I closed up
quickly and he looked totally exhausted. That can't be good.

"It's on mate"(?) What a dope. I would have gone out and bought an old Silca frame pump just so I could stick it in his front wheel. "Hey, wait here; I'll be right back." I pass people all the time and couldn't imagine saying "It's on mate." I'd sign up for Death with Dignity if I did that sort of thing.

Totally OT, but I was riding up on Skyline a few months back and ran into a group of guys I raced with 30 years ago -- including a guy who was a junior prodigy back in the '70s and was in USCF development camps with Andy Hampsten and Greg LeMond. He's now CEO of a national company. We just rode along, nobody trying to prove anything, talking about the good old days. My regular cohort is like that too, except we do race each other at very predictable points in the ride. I'm slowing, so my place is no longer assured. I've learned to be more strategic, and my friends have learned to wait.

FWIW, a local mountain biker was found dead on some very tame single
track a few days ago. I didn't know him, but have friends who did. They
described him as middle aged (much younger than me), in tremendous
physical shape, built like a muscular swimmer, very low body fat, a
regular user of the YMCA etc.

Given the location, he probably wasn't pushing anywhere close to cardio
extremes. Indications are he was JRA and died instantly.

Apparently there is a correlation between long history as an endurance
athlete and atrial fibrillation and other electrical problems. Grant
Peterson has written about what he calls good exercise and bad exercise.
My views have certainly changed.


As you say, there seems to be some correlation between endurance
athletes and some heart problems, but at the same time some endurance
athletes seem to just go on for ever. "Old" John Kelly ran something
like 61 Boston Marathons, his last at the age of 84, In his 70's he
was still running 50 miles a week and some 15 races a year, while
"Young" John Kelly (the family name "Kelly" is not a rare one in South
Boston :-) ran 31 B.M.'s his last at 62 in 4:07.

On the other hand
https://www.peakendurancesport.com/e...urance-sports/
says:
"Endurance athletes who exercise for three hours or more have an
increased chance of dying from a cardiac arrest. About 1 in 50,000: if
you run marathons or participate in other forms of exercise which last
for three hours or more."

They also say the "For one thing, it's clear that regular exercise
protects you from heart attacks over broad time frames; for example,
over the course of a year regular exercisers will have fewer cardiac
failures than their sedentary counterparts.

And they go on to say that "If you are having second thoughts about
running marathons, you should know that the previously quoted rate of
one death per 50,000 marathon runners might be a bit high. For
example, there is evidence that in male runners aged 30-64 who have
not been diagnosed with heart disease, there is approximately one
death for each 800,000 person-hours of running or jogging"

And even more enlightening they add "Expressing the 800,000 statistic
in a different way, we can say that healthy, middle-aged males who run
for one hour each day can expect to die while running once every 2,192
years (800,000 hours divided by 365 hours of running per year = 2,192
years). By the same token, individuals who run two hours per day
should die while running about once every 1,096 years. When the risks
are seen in this light, many endurance athletes will consider them
acceptably low, especially as the general risk of heart disease is
reduced by strenuous training."

I think that some exercise is far better then no exercise and I think
I'll carry on as best I can :-)


I do carry on (I'm a few years younger than you), but I have a little
less fire in my belly, as they say.


Well, yes. However I attribute it to the growth of knowledge with
age... at least that is a handy excuse for being the last one to the
top of the hill :-)
--
Cheers,

John B.

  #384  
Old November 16th 17, 07:37 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 6,016
Default Why do some forks and frames have brake rotor size limits?

On 2017-11-15 16:45, John B. wrote:

On Wed, 15 Nov 2017 15:17:28 -0800, Joerg
wrote:

On 2017-11-14 17:31, John B. wrote:



[...]

Anyhow, there are numerous issues here, not the least being that it is
tough to mount a thick rotor so it still lines up correctly. It may be
possible to machine a part to adapt a motorcycle caliper and I have had
parts machined for my MTB. Requires time though. As I said, first I am
going to see if the 8" rotors are good enough which they very well may
be. 6" in back was clearly not adequate.


Good Lord! A disc is just about the simplest thing that you could
design - two circles one inside the other - and almost the simplest
thing to manufacturer. Even in the wilds of California you should be
able to find either a "home machinist" or a commercial shop to make
them to your specifications.


Take a look at a modern MTB, how much available clearance there is and
then think again about your statement.

One way to do it is to machine out some material in the center. And that
requires ... a machine. As I wrote several times now, if the 8" rotors
are good enough then they are good enough. I shall see.


[...]

But spending the public's taxes on building bike-ways for drunks on
bicycles might be a bit more then most politicians might be willing to
underwrite :-)



Are you prejudiced as well? I never ride drunk.

I pay enough taxes to expect something in return. And yes, that includes
road taxes. $4k alone in property taxes, part of which goes towards
traffic infrastructure. The issue is whether a community is willing to
invest in healthy modes of transportation. Ours is not, Folsom toward
the west of us is. It's that simple.


Ah, but a much healthier means of transportation is a far simpler
method that doesn't even require special paths. Just get up on your
hind legs and walk.


It will result in even higher risk because you'll end up moving along
the side of a 55mph road at 3mph versus 20mph.


Assuming a normal healthy individual you should be able to march (even
with a can of beer in your pocket) at about 3 miles per hour - about 5
kph - for hours on end.

I can assure you that a 5 Km stroll is far more invigorating then a 5
Km ride on a bicycle.



However, walking is boring and sometimes dangerous. There are no
sidewalks out here. Also, I can net 25km or so during the same time I
walk 5km and see a lot more interesting stuff while doing that.

BTW, that thought has crossed my mind as well. Some day when I am almost
competely retired I want to walk some of the singletrack I ride around
here. It's much slower but one hears more where there is none of the din
of a mountain bike. Occasionally I already do it and push my MTB for a
few miles, watching birds and such. You can't do that when having to
concentrate on ruts and stuff.

--
Regards, Joerg

http://www.analogconsultants.com/
  #385  
Old November 17th 17, 12:41 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default Why do some forks and frames have brake rotor size limits?

On Thu, 16 Nov 2017 10:37:16 -0800, Joerg
wrote:

On 2017-11-15 16:45, John B. wrote:

On Wed, 15 Nov 2017 15:17:28 -0800, Joerg
wrote:

On 2017-11-14 17:31, John B. wrote:



[...]

Anyhow, there are numerous issues here, not the least being that it is
tough to mount a thick rotor so it still lines up correctly. It may be
possible to machine a part to adapt a motorcycle caliper and I have had
parts machined for my MTB. Requires time though. As I said, first I am
going to see if the 8" rotors are good enough which they very well may
be. 6" in back was clearly not adequate.


Good Lord! A disc is just about the simplest thing that you could
design - two circles one inside the other - and almost the simplest
thing to manufacturer. Even in the wilds of California you should be
able to find either a "home machinist" or a commercial shop to make
them to your specifications.


Take a look at a modern MTB, how much available clearance there is and
then think again about your statement.

I do take a look. Just about every time I visit my LBS, and I see no
problems with installing a disc, or a bracket for the caliper for that
matter.

But I do notice that both bicycles and small motorcycles have the
caliper mounted on the back side of the front fork tubes and I have
read your posts about how that is the wrong side. Which makes one
wonder.... are all the two wheel vehicle designers in the world wrong?
Or...

One way to do it is to machine out some material in the center. And that
requires ... a machine. As I wrote several times now, if the 8" rotors
are good enough then they are good enough. I shall see.

But they are relatively small, compared to a proper "SRAM Guide
Ultimate Disc Brake" which has a 1,000 mm disc.

But perhaps the Ultimate is designed for the really fast riders?


[...]

But spending the public's taxes on building bike-ways for drunks on
bicycles might be a bit more then most politicians might be willing to
underwrite :-)


Are you prejudiced as well? I never ride drunk.

I pay enough taxes to expect something in return. And yes, that includes
road taxes. $4k alone in property taxes, part of which goes towards
traffic infrastructure. The issue is whether a community is willing to
invest in healthy modes of transportation. Ours is not, Folsom toward
the west of us is. It's that simple.


Ah, but a much healthier means of transportation is a far simpler
method that doesn't even require special paths. Just get up on your
hind legs and walk.


It will result in even higher risk because you'll end up moving along
the side of a 55mph road at 3mph versus 20mph.


Assuming a normal healthy individual you should be able to march (even
with a can of beer in your pocket) at about 3 miles per hour - about 5
kph - for hours on end.

I can assure you that a 5 Km stroll is far more invigorating then a 5
Km ride on a bicycle.



However, walking is boring and sometimes dangerous. There are no
sidewalks out here. Also, I can net 25km or so during the same time I
walk 5km and see a lot more interesting stuff while doing that.


How so? After all most people can walk and chew gum at the same time
and being on foot one is far more agile then when mounted on some sort
of wheeled device.


BTW, that thought has crossed my mind as well. Some day when I am almost
competely retired I want to walk some of the singletrack I ride around
here. It's much slower but one hears more where there is none of the din
of a mountain bike. Occasionally I already do it and push my MTB for a
few miles, watching birds and such. You can't do that when having to
concentrate on ruts and stuff.


True walking/running speed is much slower then riding a bicycle but
the level of intensity is much higher. Try running, oh say 26 miles
(43 Km), again lets say, two and a quarter hours and then do the same
thing on a bicycle.

More bang for a buck so to speak.
--
Cheers,

John B.

  #386  
Old November 17th 17, 01:19 AM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 6,016
Default Why do some forks and frames have brake rotor size limits?

On 2017-11-16 15:41, John B. wrote:
On Thu, 16 Nov 2017 10:37:16 -0800, Joerg
wrote:

On 2017-11-15 16:45, John B. wrote:

On Wed, 15 Nov 2017 15:17:28 -0800, Joerg
wrote:

On 2017-11-14 17:31, John B. wrote:



[...]

Anyhow, there are numerous issues here, not the least being that it is
tough to mount a thick rotor so it still lines up correctly. It may be
possible to machine a part to adapt a motorcycle caliper and I have had
parts machined for my MTB. Requires time though. As I said, first I am
going to see if the 8" rotors are good enough which they very well may
be. 6" in back was clearly not adequate.

Good Lord! A disc is just about the simplest thing that you could
design - two circles one inside the other - and almost the simplest
thing to manufacturer. Even in the wilds of California you should be
able to find either a "home machinist" or a commercial shop to make
them to your specifications.


Take a look at a modern MTB, how much available clearance there is and
then think again about your statement.

I do take a look. Just about every time I visit my LBS, and I see no
problems with installing a disc, or a bracket for the caliper for that
matter.


Check again, this time with glasses and measuring calipers. Between
rotor and fork there is about 1/20th of an inch on my MTB. A 3mm rotor
would barely squeeze in, a 4mm rotor would not. It would scrape.


But I do notice that both bicycles and small motorcycles have the
caliper mounted on the back side of the front fork tubes and I have
read your posts about how that is the wrong side. Which makes one
wonder.... are all the two wheel vehicle designers in the world wrong?



Often they are. Just because everybody does it a certain way does not
make it right. It's not a problem with a through-axle and certainly not
with motorcycles. There, it has the advantage that a caliper behind the
fork runs less of a chance of being hit with debris kicked up by a rider
up front. Where it is clearly the wrong design is with QR axles.


Or...

One way to do it is to machine out some material in the center. And that
requires ... a machine. As I wrote several times now, if the 8" rotors
are good enough then they are good enough. I shall see.

But they are relatively small, compared to a proper "SRAM Guide
Ultimate Disc Brake" which has a 1,000 mm disc.


Huh?


But perhaps the Ultimate is designed for the really fast riders?


Fast doesn't matter much, weight, cargo and long hills do.

[...]


Assuming a normal healthy individual you should be able to march (even
with a can of beer in your pocket) at about 3 miles per hour - about 5
kph - for hours on end.

I can assure you that a 5 Km stroll is far more invigorating then a 5
Km ride on a bicycle.



However, walking is boring and sometimes dangerous. There are no
sidewalks out here. Also, I can net 25km or so during the same time I
walk 5km and see a lot more interesting stuff while doing that.


How so? After all most people can walk and chew gum at the same time
and being on foot one is far more agile then when mounted on some sort
of wheeled device.


I could chew gum on my bikes. I just don't like chewing gum. If eating
counts then yes, I have done that while cycling. Even riding at a good
clip can be so boring at times that I turn on the MP-3 player. Once as a
kid on the way to school I even fell asleep while pedaling.

Some folks multi-task:

https://www.youtube.com/watch?v=x4nxylN4InE


BTW, that thought has crossed my mind as well. Some day when I am almost
competely retired I want to walk some of the singletrack I ride around
here. It's much slower but one hears more where there is none of the din
of a mountain bike. Occasionally I already do it and push my MTB for a
few miles, watching birds and such. You can't do that when having to
concentrate on ruts and stuff.


True walking/running speed is much slower then riding a bicycle but
the level of intensity is much higher. Try running, oh say 26 miles
(43 Km), again lets say, two and a quarter hours and then do the same
thing on a bicycle.

More bang for a buck so to speak.



Except those bucks eventually get slurped out of your bank account by
the bucket load when the hip gives out. That is what happened to a
former co-worker who used to run a lot. The doctor told him that it'll
ruin his hips. And then it did. The doctor's advice to him (besides hip
surgery): Consider cycling.

--
Regards, Joerg

http://www.analogconsultants.com/
  #387  
Old November 17th 17, 01:56 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default Why do some forks and frames have brake rotor size limits?

On Thu, 16 Nov 2017 16:19:43 -0800, Joerg
wrote:

On 2017-11-16 15:41, John B. wrote:
On Thu, 16 Nov 2017 10:37:16 -0800, Joerg
wrote:

On 2017-11-15 16:45, John B. wrote:

On Wed, 15 Nov 2017 15:17:28 -0800, Joerg
wrote:

On 2017-11-14 17:31, John B. wrote:


[...]

Anyhow, there are numerous issues here, not the least being that it is
tough to mount a thick rotor so it still lines up correctly. It may be
possible to machine a part to adapt a motorcycle caliper and I have had
parts machined for my MTB. Requires time though. As I said, first I am
going to see if the 8" rotors are good enough which they very well may
be. 6" in back was clearly not adequate.

Good Lord! A disc is just about the simplest thing that you could
design - two circles one inside the other - and almost the simplest
thing to manufacturer. Even in the wilds of California you should be
able to find either a "home machinist" or a commercial shop to make
them to your specifications.


Take a look at a modern MTB, how much available clearance there is and
then think again about your statement.

I do take a look. Just about every time I visit my LBS, and I see no
problems with installing a disc, or a bracket for the caliper for that
matter.


Check again, this time with glasses and measuring calipers. Between
rotor and fork there is about 1/20th of an inch on my MTB. A 3mm rotor
would barely squeeze in, a 4mm rotor would not. It would scrape.

Something wrong with your measuring. 1/20th of an inch is 0.050" which
is 1.27mm so your 3, 4mm disks won't fit.... or your measuring device
is off a little.

But I do notice that both bicycles and small motorcycles have the
caliper mounted on the back side of the front fork tubes and I have
read your posts about how that is the wrong side. Which makes one
wonder.... are all the two wheel vehicle designers in the world wrong?



Often they are. Just because everybody does it a certain way does not
make it right. It's not a problem with a through-axle and certainly not
with motorcycles. There, it has the advantage that a caliper behind the
fork runs less of a chance of being hit with debris kicked up by a rider
up front. Where it is clearly the wrong design is with QR axles.


Or...

One way to do it is to machine out some material in the center. And that
requires ... a machine. As I wrote several times now, if the 8" rotors
are good enough then they are good enough. I shall see.

But they are relatively small, compared to a proper "SRAM Guide
Ultimate Disc Brake" which has a 1,000 mm disc.


Huh?


But perhaps the Ultimate is designed for the really fast riders?


Fast doesn't matter much, weight, cargo and long hills do.

[...]


Assuming a normal healthy individual you should be able to march (even
with a can of beer in your pocket) at about 3 miles per hour - about 5
kph - for hours on end.

I can assure you that a 5 Km stroll is far more invigorating then a 5
Km ride on a bicycle.


However, walking is boring and sometimes dangerous. There are no
sidewalks out here. Also, I can net 25km or so during the same time I
walk 5km and see a lot more interesting stuff while doing that.


How so? After all most people can walk and chew gum at the same time
and being on foot one is far more agile then when mounted on some sort
of wheeled device.


I could chew gum on my bikes. I just don't like chewing gum. If eating
counts then yes, I have done that while cycling. Even riding at a good
clip can be so boring at times that I turn on the MP-3 player. Once as a
kid on the way to school I even fell asleep while pedaling.

Some folks multi-task:

https://www.youtube.com/watch?v=x4nxylN4InE


BTW, that thought has crossed my mind as well. Some day when I am almost
competely retired I want to walk some of the singletrack I ride around
here. It's much slower but one hears more where there is none of the din
of a mountain bike. Occasionally I already do it and push my MTB for a
few miles, watching birds and such. You can't do that when having to
concentrate on ruts and stuff.


True walking/running speed is much slower then riding a bicycle but
the level of intensity is much higher. Try running, oh say 26 miles
(43 Km), again lets say, two and a quarter hours and then do the same
thing on a bicycle.

More bang for a buck so to speak.



Except those bucks eventually get slurped out of your bank account by
the bucket load when the hip gives out. That is what happened to a
former co-worker who used to run a lot. The doctor told him that it'll
ruin his hips. And then it did. The doctor's advice to him (besides hip
surgery): Consider cycling.


Well, I can't say for you but my hips are 85 years old and still
working :-) And "Old" John Kelly was still running 50 miles a week and
entering a race a month or more when he was in his 70's. "Young" John
Kelly (no relative) was still running marathons in his 60's.

Fauja Singh, born 1 April 1911) is a British Sikh centenarian marathon
runner of Punjabi Indian descent. On 16 October 2011, Singh became
the first 100-year-old to finish a marathon, completing the Toronto
Waterfront Marathon in 8:11:06.[

Ed Whitlock, at 85, set his latest distance-running record, completing
the Toronto Waterfront Marathon in 3 hours 56 minutes 34 seconds and
becoming the oldest person to run 26.2 miles in under four hours.

Harriette Thompson, 92, became the oldest woman to complete a marathon
on Sunday when she finished the San Diego Rock 'n' Roll Marathon in
7:24:36. She surpassed the record set by Gladys Burrill, who ran
9:53:16 at the 2010 Honolulu Marathon, 19 days after her 92nd
birthday, when she was 74 days younger than Thompson is now.

Yup it is a sure thing that running is bad for you.
--
Cheers,

John B.

  #388  
Old November 17th 17, 02:16 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default Why do some forks and frames have brake rotor size limits?

On Thu, 16 Nov 2017 16:19:43 -0800, Joerg
wrote:

On 2017-11-16 15:41, John B. wrote:
On Thu, 16 Nov 2017 10:37:16 -0800, Joerg
wrote:

On 2017-11-15 16:45, John B. wrote:

On Wed, 15 Nov 2017 15:17:28 -0800, Joerg
wrote:

On 2017-11-14 17:31, John B. wrote:


[...]

Anyhow, there are numerous issues here, not the least being that it is
tough to mount a thick rotor so it still lines up correctly. It may be
possible to machine a part to adapt a motorcycle caliper and I have had
parts machined for my MTB. Requires time though. As I said, first I am
going to see if the 8" rotors are good enough which they very well may
be. 6" in back was clearly not adequate.

Good Lord! A disc is just about the simplest thing that you could
design - two circles one inside the other - and almost the simplest
thing to manufacturer. Even in the wilds of California you should be
able to find either a "home machinist" or a commercial shop to make
them to your specifications.


Take a look at a modern MTB, how much available clearance there is and
then think again about your statement.

I do take a look. Just about every time I visit my LBS, and I see no
problems with installing a disc, or a bracket for the caliper for that
matter.


Check again, this time with glasses and measuring calipers. Between
rotor and fork there is about 1/20th of an inch on my MTB. A 3mm rotor
would barely squeeze in, a 4mm rotor would not. It would scrape.


But I do notice that both bicycles and small motorcycles have the
caliper mounted on the back side of the front fork tubes and I have
read your posts about how that is the wrong side. Which makes one
wonder.... are all the two wheel vehicle designers in the world wrong?



Often they are. Just because everybody does it a certain way does not
make it right. It's not a problem with a through-axle and certainly not
with motorcycles. There, it has the advantage that a caliper behind the
fork runs less of a chance of being hit with debris kicked up by a rider
up front. Where it is clearly the wrong design is with QR axles.

But really, is there a real reason to run quick release axles on
bicycles?

If memory serves I have had two flats this year with one month to go
to make 12. The old "coaster brake" bicycles that were the only thing
available when I was a kid had conventional axles with nuts. The first
"Mountain Bikes" had solid axles.
https://mmbhof.org/mtn-bike-hall-of-fame/history/


Or...

One way to do it is to machine out some material in the center. And that
requires ... a machine. As I wrote several times now, if the 8" rotors
are good enough then they are good enough. I shall see.

But they are relatively small, compared to a proper "SRAM Guide
Ultimate Disc Brake" which has a 1,000 mm disc.


Huh?


But perhaps the Ultimate is designed for the really fast riders?


Fast doesn't matter much, weight, cargo and long hills do.

[...]


Assuming a normal healthy individual you should be able to march (even
with a can of beer in your pocket) at about 3 miles per hour - about 5
kph - for hours on end.

I can assure you that a 5 Km stroll is far more invigorating then a 5
Km ride on a bicycle.


However, walking is boring and sometimes dangerous. There are no
sidewalks out here. Also, I can net 25km or so during the same time I
walk 5km and see a lot more interesting stuff while doing that.


How so? After all most people can walk and chew gum at the same time
and being on foot one is far more agile then when mounted on some sort
of wheeled device.


I could chew gum on my bikes. I just don't like chewing gum. If eating
counts then yes, I have done that while cycling. Even riding at a good
clip can be so boring at times that I turn on the MP-3 player. Once as a
kid on the way to school I even fell asleep while pedaling.


The saying is/was "He is too stupid to walk and chew gum" as a
description of someone who is really, really, dumb. In other words,
most "normal" people CAN walk and chew gum at the same time :-)


Some folks multi-task:

https://www.youtube.com/watch?v=x4nxylN4InE


BTW, that thought has crossed my mind as well. Some day when I am almost
competely retired I want to walk some of the singletrack I ride around
here. It's much slower but one hears more where there is none of the din
of a mountain bike. Occasionally I already do it and push my MTB for a
few miles, watching birds and such. You can't do that when having to
concentrate on ruts and stuff.


True walking/running speed is much slower then riding a bicycle but
the level of intensity is much higher. Try running, oh say 26 miles
(43 Km), again lets say, two and a quarter hours and then do the same
thing on a bicycle.

More bang for a buck so to speak.



Except those bucks eventually get slurped out of your bank account by
the bucket load when the hip gives out. That is what happened to a
former co-worker who used to run a lot. The doctor told him that it'll
ruin his hips. And then it did. The doctor's advice to him (besides hip
surgery): Consider cycling.

--
Cheers,

John B.

  #389  
Old November 17th 17, 02:18 AM posted to rec.bicycles.tech
JBeattie
external usenet poster
 
Posts: 5,870
Default Why do some forks and frames have brake rotor size limits?

On Thursday, November 16, 2017 at 10:37:10 AM UTC-8, Joerg wrote:
On 2017-11-15 16:45, John B. wrote:

On Wed, 15 Nov 2017 15:17:28 -0800, Joerg
wrote:

On 2017-11-14 17:31, John B. wrote:



[...]

Anyhow, there are numerous issues here, not the least being that it is
tough to mount a thick rotor so it still lines up correctly. It may be
possible to machine a part to adapt a motorcycle caliper and I have had
parts machined for my MTB. Requires time though. As I said, first I am
going to see if the 8" rotors are good enough which they very well may
be. 6" in back was clearly not adequate.


Good Lord! A disc is just about the simplest thing that you could
design - two circles one inside the other - and almost the simplest
thing to manufacturer. Even in the wilds of California you should be
able to find either a "home machinist" or a commercial shop to make
them to your specifications.


Take a look at a modern MTB, how much available clearance there is and
then think again about your statement.

One way to do it is to machine out some material in the center. And that
requires ... a machine. As I wrote several times now, if the 8" rotors
are good enough then they are good enough. I shall see.


I found a brake that might work for you. https://www.bikerumor.com/2011/09/24...-fiber-rotors/ Skip the CF rotors and go with SS.

-- Jay Beattie.


  #390  
Old November 17th 17, 07:04 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 6,016
Default Why do some forks and frames have brake rotor size limits?

On 2017-11-16 17:18, jbeattie wrote:
On Thursday, November 16, 2017 at 10:37:10 AM UTC-8, Joerg wrote:
On 2017-11-15 16:45, John B. wrote:

On Wed, 15 Nov 2017 15:17:28 -0800, Joerg
wrote:

On 2017-11-14 17:31, John B. wrote:



[...]

Anyhow, there are numerous issues here, not the least being
that it is tough to mount a thick rotor so it still lines up
correctly. It may be possible to machine a part to adapt a
motorcycle caliper and I have had parts machined for my MTB.
Requires time though. As I said, first I am going to see if the
8" rotors are good enough which they very well may be. 6" in
back was clearly not adequate.

Good Lord! A disc is just about the simplest thing that you
could design - two circles one inside the other - and almost the
simplest thing to manufacturer. Even in the wilds of California
you should be able to find either a "home machinist" or a
commercial shop to make them to your specifications.


Take a look at a modern MTB, how much available clearance there is
and then think again about your statement.

One way to do it is to machine out some material in the center. And
that requires ... a machine. As I wrote several times now, if the
8" rotors are good enough then they are good enough. I shall see.


I found a brake that might work for you.
https://www.bikerumor.com/2011/09/24...-fiber-rotors/
Skip the CF rotors and go with SS.


I want that tire!

--
Regards, Joerg

http://www.analogconsultants.com/
 




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