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



 
 
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  #391  
Old November 17th 17, 07:11 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 4,623
Default Why do some forks and frames have brake rotor size limits?

On 2017-11-16 16:56, John B. wrote:
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.



Fire up your calculator again. My MTB came with 2.2mm rotors. How much
wider is a 3mm rotor?



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.


I know. Grandpa never wore a safety belt in his car yet lived.


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.



My great grandpa lived to almost 103 and regularly smoked big stinking
stogies. The kind where I started to cough from just being in the same
room. So according to your "logic" cigar smoking is perfectly ok for the
health?

--
Regards, Joerg

http://www.analogconsultants.com/
Ads
  #392  
Old November 17th 17, 08:28 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 5,394
Default Why do some forks and frames have brake rotor size limits?

On 11/17/2017 1:11 PM, Joerg wrote:
On 2017-11-16 16:56, John B. wrote:


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.


I know. Grandpa never wore a safety belt in his car yet lived.


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.



My great grandpa lived to almost 103 and regularly smoked big stinking
stogies. The kind where I started to cough from just being in the same
room. So according to your "logic" cigar smoking is perfectly ok for the
health?


The above is a great example of arguing by anecdote. And I'm continually
amazed by the huge numbers of people who think one anecdote is all
that's needed to determine a universal truth. Joerg's a master at that.

For any one anecdote, it's possible to find an opposing anecdote. But
this doesn't faze the argue-by-anecdote fans. They have supreme
confidence that the anecdote _they_ prefer is the only valid one.

Should we gather data on hazards in a disciplined way from a large
sample, striving for minimal bias? Should we analyze the data as deeply
as we can, accounting for confounding factors? Should we examine the
actual magnitudes of any results, rather than treating results as a
binary, pass-fail item? Should we examine any related benefits as well
as the detriments or hazards? Should we examine data on other hazards,
to put our results in context?

The anecdote guys say "Naw. That's too much trouble. My grandpa..." or
"... my riding buddy..." or "... one time I ..." And that's all that
matters in their minds.

--
- Frank Krygowski
  #393  
Old November 18th 17, 01:12 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 3,557
Default Why do some forks and frames have brake rotor size limits?

On Fri, 17 Nov 2017 10:11:49 -0800, Joerg
wrote:

On 2017-11-16 16:56, John B. wrote:
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.



Fire up your calculator again. My MTB came with 2.2mm rotors. How much
wider is a 3mm rotor?


I don't care what calculator you use. You said that the clearance was
1/20th of an inch, i.e., 1.27mm and that you install a 3 mm rotor.

I assume that in California you have some sort of magic measuring
stick that lets you insert a 3mm rotor in a hole that is less then
half the size.

(Probably all that beer you drink)



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.


I know. Grandpa never wore a safety belt in his car yet lived.


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.



My great grandpa lived to almost 103 and regularly smoked big stinking
stogies. The kind where I started to cough from just being in the same
room. So according to your "logic" cigar smoking is perfectly ok for the
health?


No body said anything about smoking stinky cigars. You said that the
doctor told someone that running would destroy the hip joints and I
gave you examples of people that ran for 50 years or more.

Now, I can take the time and trouble to look up a few more if you
wish. There is even an "old Folks" Olympics (National Senior
Olympics). The event was first held in 1987 and the most recent event
(2007) had over 10,000 competitors, the oldest of whom was over 100
years old.

How about that? 10,000 people that were running and leaping about the
stadium compared with your one example with a bad hip.
--
Cheers,

John B.

  #394  
Old November 18th 17, 04:45 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 4,623
Default Why do some forks and frames have brake rotor size limits?

On 2017-11-17 16:12, John B. wrote:
On Fri, 17 Nov 2017 10:11:49 -0800, Joerg
wrote:

On 2017-11-16 16:56, John B. wrote:
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.



Fire up your calculator again. My MTB came with 2.2mm rotors. How much
wider is a 3mm rotor?


I don't care what calculator you use. You said that the clearance was
1/20th of an inch, i.e., 1.27mm and that you install a 3 mm rotor.

I assume that in California you have some sort of magic measuring
stick that lets you insert a 3mm rotor in a hole that is less then
half the size.


sigh

2.2mm rotor which was in there before plus 1.27mm clearance is ...
drumroll ... 3.47mm. Meaning ... trumpet blare ... a 3mm rotor will
fit. A 4mm rotor will not fit. That was easy.

https://www.youtube.com/watch?v=483wn53HDsE


(Probably all that beer you drink)


Brewing is a pretty exact science. Mess up one step and $50 plus 4h of
work go down the drain, literally .

[...]

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.



My great grandpa lived to almost 103 and regularly smoked big stinking
stogies. The kind where I started to cough from just being in the same
room. So according to your "logic" cigar smoking is perfectly ok for the
health?


No body said anything about smoking stinky cigars. You said that the
doctor told someone that running would destroy the hip joints and I
gave you examples of people that ran for 50 years or more.


I gave you an example of a guy who smoked stogies all his life and
lived. I have a lot more. You gave me a few examples of people whose hip
survived intense running. Same thing.


Now, I can take the time and trouble to look up a few more if you
wish. There is even an "old Folks" Olympics (National Senior
Olympics). The event was first held in 1987 and the most recent event
(2007) had over 10,000 competitors, the oldest of whom was over 100
years old.

How about that? 10,000 people that were running and leaping about the
stadium compared with your one example with a bad hip.



How about millions of heavy smokers who did not die from lung cancer?

--
Regards, Joerg

http://www.analogconsultants.com/
 




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