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



 
 
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  #331  
Old November 11th 17, 10:39 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 2017-11-11 11:55, jbeattie wrote:
On Saturday, November 11, 2017 at 10:47:10 AM UTC-8, Joerg wrote:
On 2017-11-11 08:59, jbeattie wrote:
On Saturday, November 11, 2017 at 8:34:13 AM UTC-8, Frank
Krygowski wrote:
On 11/11/2017 10:37 AM, Joerg wrote:
On 2017-11-11 07:21, jbeattie wrote:

... I don't think most people need discs with giant rotors,
but Joerg is a special case.


All one has to do is go down French Creek Road and then
Holly Drive out here on a loaded bike and the li'l 6-incher
in back starts to smell. Can't use the front too much because
it's loose gravel. Similar for some of the long hills in the
Sierra east of here. The 8" rotors I mounted yesterday will
allow me to roll down many of the long downslopes without a
cooling-off break or spritzing water onto the rotors.

A friend had 8" on the front and still lost the front brake
at the last curve on a long hillside. One of those "Oh
s..t!" experiences.

Hmm. So even 8" isn't sufficient. Good to know.

My brakes are about 25" diameter. I'm keeping them! ;-)

In Joerg's neighborhood but much further into the Sierra, I did
Monitor Pass, Ebbetts, Carson and Luther multiple times on loaded
and unloaded bikes with either single pivot Campy NR or Mafac
cantis. Tioga, too. Ebbets has some 20% pitches. I never once
had brake problems.


Very different scenario because there you can just "let'er rip"
most of the time. I described a road that has a long downhill
stretch and is gravel. You have to hold the brakes the whole time
because there is forest left and right. Sure enough about 70% down
a Shepherd and a smaller dogs came out of the woodwork and were
totally unfazed but my brightly lit aluminum horse. They sauntered
across. At 40mph that would have been a nasty crash. At 15mph I
could even greet the dogs properly. There are also diagonal ruts
and washouts that you won't see in time at high speed. A reminder
could be seen in one curve where a car driver must have thought
differently, flew off the road and chopped some trees. The wreckage
was already hauled off but there still was a torn-off front axle
and a ripped out coil spring way out in the bushes. Ghastly.


Actually, you can't let 'er rip down Ebbetts. My son, who is about
200lbs, 6'5" and basically all leg muscle, descends Guardsman's Pass
on CF rims and caliper brakes.
https://www.youtube.com/watch?time_c...&v=hRM3bFXlyNk



Right, and three guys crashed. That is not my definition of a safe ride.


https://www.youtube.com/watch?v=NKdVMYo1H38 Basically the whole world
descends much hairier descents than French Grade Road on pretty
mundane equipment.



And crashes, hard. What I do not understand why the riders braked so
late when they were obviously far off the ideal line for that curve and
then did not drop behind their seats. No wonder the rear wheel comes
off, you've got to move the CG as far back and as low as possible.
Staying on or above the seat that does not work. Maybe some of the road
bikers would need MTB training. "Belly riding" is an almost instinctive
and instant reaction when a crisis situation like in the video comes up
for a mountain biker.


... Having forest to the left and right is basically
SOP around here. I could commute to work on Fire Lane 5 if I were so
inclined. https://www.youtube.com/watch?v=XbWCFwIxgnw&t=62s (on a CX
bike). It gets nasty at 3:00. Anyway, get to the bottom, turn right
and you're practically down town. I've done that on a SuperSix.


That's singletrack, yet even there it can happen:

https://www.youtube.com/watch?v=a07sV453Qaw

I had a close one with a buck. Thank God for disc brakes which came on
hard and instantly.

Here I was talking about a gravel road wit a long descent. There are
houses left and right in the trees and people out there let their
animals run free. A collision with an animal at 40mph can end badly.


Speaking of climbing, my son's friend Luke did an Everest the other
day -- almost 34,000 feet in 120 miles in 11 hours. 100 times up an
11% neighborhood road in the upper Avenues in SLC. The guy is a
phenom.



He sure is. Like this long distance bike commuter:

https://www.youtube.com/watch?v=G52mQpoheL8

I couldn't do that anymore.


... He's on track for over a million feet of climbing this year,
and he was off his bike due to a serious injury for a month. His last
Everest was up every canyon in SLC, including the Midway side of
Guardsman Pass, which is one of the most difficult climbs/descents in
the US. All on caliper brakes. Yes, it's not Cameron Park, but still
some serious climbs.


On wide open roads I don't have a problem with rim brakes (unless it rains).

A problem arises on gravel or dirt roads with long continuous descents.
Nearly all the braking happens in back then and almost the whole time.
Bikes don't have jake brakes.

--
Regards, Joerg

http://www.analogconsultants.com/
Ads
  #332  
Old November 12th 17, 12:08 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 11/11/2017 4:39 PM, Joerg wrote:
On 2017-11-11 11:55, jbeattie wrote:
My son, who is about
200lbs, 6'5" and basically all leg muscle, descends Guardsman's Pass
on CF rims and caliper brakes.
https://www.youtube.com/watch?time_c...&v=hRM3bFXlyNk


Right, and three guys crashed. That is not my definition of a safe ride.


The first guy to crash had his rear wheel about a foot in the air. He
was decelerating at the limit. Disc brakes would have added nothing.

https://www.youtube.com/watch?v=NKdVMYo1H38 Basically the whole world
descends much hairier descents than French Grade Road on pretty
mundane equipment.


And crashes, hard.

No, Joerg. One video of a bad crash does not mean that such crashes are
normal.

What I do not understand why the riders braked so
late when they were obviously far off the ideal line for that curve ...


The commentator on the second video claims that the support vehicles
blocked views of the turns and prevented the riders from taking proper
lines. It was odd that the rider who crashed first entered the scene so
far to his left, but we can't say why he did that. Perhaps it had
something to do with obstruction from a support car.

and then did not drop behind their seats. No wonder the rear wheel comes
off, you've got to move the CG as far back and as low as possible.


Sliding way back helps a bit, but it's not magical. More important, it's
often just not possible to do quickly. Sure, you can do it if you're on
a mountain bike peeking over the rim of a steep downhill. That's not the
case here.

All the riders in the videos were on the ragged edge of control in one
way or another. They may not have had any reflexes left to initiate
sliding back. Alternately, they may have realized doing so might
destabilize their steering.

Staying on or above the seat that does not work. Maybe some of the road
bikers would need MTB training. "Belly riding" is an almost instinctive
and instant reaction when a crisis situation like in the video comes up
for a mountain biker.


I would think these guys could outride you in any situation, including
mountain biking. Very few "Monday morning quarterbacks" ever make it
into the pro ranks, despite their legendary expertise around a water cooler.

--
- Frank Krygowski
  #333  
Old November 12th 17, 12:38 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 Saturday, November 11, 2017 at 1:38:59 PM UTC-8, Joerg wrote:
On 2017-11-11 11:55, jbeattie wrote:
On Saturday, November 11, 2017 at 10:47:10 AM UTC-8, Joerg wrote:
On 2017-11-11 08:59, jbeattie wrote:
On Saturday, November 11, 2017 at 8:34:13 AM UTC-8, Frank
Krygowski wrote:
On 11/11/2017 10:37 AM, Joerg wrote:
On 2017-11-11 07:21, jbeattie wrote:

... I don't think most people need discs with giant rotors,
but Joerg is a special case.


All one has to do is go down French Creek Road and then
Holly Drive out here on a loaded bike and the li'l 6-incher
in back starts to smell. Can't use the front too much because
it's loose gravel. Similar for some of the long hills in the
Sierra east of here. The 8" rotors I mounted yesterday will
allow me to roll down many of the long downslopes without a
cooling-off break or spritzing water onto the rotors.

A friend had 8" on the front and still lost the front brake
at the last curve on a long hillside. One of those "Oh
s..t!" experiences.

Hmm. So even 8" isn't sufficient. Good to know.

My brakes are about 25" diameter. I'm keeping them! ;-)

In Joerg's neighborhood but much further into the Sierra, I did
Monitor Pass, Ebbetts, Carson and Luther multiple times on loaded
and unloaded bikes with either single pivot Campy NR or Mafac
cantis. Tioga, too. Ebbets has some 20% pitches. I never once
had brake problems.


Very different scenario because there you can just "let'er rip"
most of the time. I described a road that has a long downhill
stretch and is gravel. You have to hold the brakes the whole time
because there is forest left and right. Sure enough about 70% down
a Shepherd and a smaller dogs came out of the woodwork and were
totally unfazed but my brightly lit aluminum horse. They sauntered
across. At 40mph that would have been a nasty crash. At 15mph I
could even greet the dogs properly. There are also diagonal ruts
and washouts that you won't see in time at high speed. A reminder
could be seen in one curve where a car driver must have thought
differently, flew off the road and chopped some trees. The wreckage
was already hauled off but there still was a torn-off front axle
and a ripped out coil spring way out in the bushes. Ghastly.


Actually, you can't let 'er rip down Ebbetts. My son, who is about
200lbs, 6'5" and basically all leg muscle, descends Guardsman's Pass
on CF rims and caliper brakes.
https://www.youtube.com/watch?time_c...&v=hRM3bFXlyNk



Right, and three guys crashed. That is not my definition of a safe ride.


https://www.youtube.com/watch?v=NKdVMYo1H38 Basically the whole world
descends much hairier descents than French Grade Road on pretty
mundane equipment.



And crashes, hard. What I do not understand why the riders braked so
late when they were obviously far off the ideal line for that curve and
then did not drop behind their seats. No wonder the rear wheel comes
off, you've got to move the CG as far back and as low as possible.
Staying on or above the seat that does not work. Maybe some of the road
bikers would need MTB training. "Belly riding" is an almost instinctive
and instant reaction when a crisis situation like in the video comes up
for a mountain biker.


... Having forest to the left and right is basically
SOP around here. I could commute to work on Fire Lane 5 if I were so
inclined. https://www.youtube.com/watch?v=XbWCFwIxgnw&t=62s (on a CX
bike). It gets nasty at 3:00. Anyway, get to the bottom, turn right
and you're practically down town. I've done that on a SuperSix.


That's singletrack, yet even there it can happen:

https://www.youtube.com/watch?v=a07sV453Qaw

I had a close one with a buck. Thank God for disc brakes which came on
hard and instantly.

Here I was talking about a gravel road wit a long descent. There are
houses left and right in the trees and people out there let their
animals run free. A collision with an animal at 40mph can end badly.


And yet, people ride that stuff all the time on normal bikes with rim brakes and paltry 160mm rotors on disc brakes. Jobst was riding down an unpaved Gavia Pass on racing gear. https://rayhosler.files.wordpress.co...via-4-best.jpg Fifty years ago, riders were descending French Creek Road on balloon tire bikes and hub brakes. The first mountain bikers -- not a disc in sight: https://www.mmbhof.org/wp-content/up...c-1500x700.jpg I'm sure gravity has increased in the last 50 years (particularly in Cameron Park), so now discs with 10" rotors are necessary for gravel road riding.

-- Jay Beattie.

  #334  
Old November 12th 17, 01:07 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 Saturday, November 11, 2017 at 3:08:36 PM UTC-8, Frank Krygowski wrote:
On 11/11/2017 4:39 PM, Joerg wrote:
On 2017-11-11 11:55, jbeattie wrote:
My son, who is about
200lbs, 6'5" and basically all leg muscle, descends Guardsman's Pass
on CF rims and caliper brakes.
https://www.youtube.com/watch?time_c...&v=hRM3bFXlyNk


Right, and three guys crashed. That is not my definition of a safe ride..


The first guy to crash had his rear wheel about a foot in the air. He
was decelerating at the limit. Disc brakes would have added nothing.

https://www.youtube.com/watch?v=NKdVMYo1H38 Basically the whole world
descends much hairier descents than French Grade Road on pretty
mundane equipment.


And crashes, hard.

No, Joerg. One video of a bad crash does not mean that such crashes are
normal.

What I do not understand why the riders braked so
late when they were obviously far off the ideal line for that curve ...


The commentator on the second video claims that the support vehicles
blocked views of the turns and prevented the riders from taking proper
lines. It was odd that the rider who crashed first entered the scene so
far to his left, but we can't say why he did that. Perhaps it had
something to do with obstruction from a support car.

and then did not drop behind their seats. No wonder the rear wheel comes
off, you've got to move the CG as far back and as low as possible.


Sliding way back helps a bit, but it's not magical. More important, it's
often just not possible to do quickly. Sure, you can do it if you're on
a mountain bike peeking over the rim of a steep downhill. That's not the
case here.

All the riders in the videos were on the ragged edge of control in one
way or another. They may not have had any reflexes left to initiate
sliding back. Alternately, they may have realized doing so might
destabilize their steering.

Staying on or above the seat that does not work. Maybe some of the road
bikers would need MTB training. "Belly riding" is an almost instinctive
and instant reaction when a crisis situation like in the video comes up
for a mountain biker.


I would think these guys could outride you in any situation, including
mountain biking. Very few "Monday morning quarterbacks" ever make it
into the pro ranks, despite their legendary expertise around a water cooler.


All of my son's riding companions and all of my regular riding companions also race MTB and CX. I'm the only one without a mountain bike. I'm sure most of the racers in the Tour of Utah have experience riding mountain bikes.

Anyway, the rider who crashed on Guardsman took a bad line and was carrying too much speed. Also keep in mind that they were probably hallucinating from the climb and not getting much rest on the descent, which is hair raising. There is a place at the top that scares me in a car and on a bike. No guard rails, narrow, 20% grade -- and oblivion if you miss a turn. Some of the descents in the Wasatch are just not very fun because they are steep, twisting and super narrow. You can't let the bike run for fear of whacking a car around some corner, which has happened to a couple of my son's friends..

-- Jay Beattie.
  #335  
Old November 12th 17, 01:15 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 2017-11-11 15:08, Frank Krygowski wrote:
On 11/11/2017 4:39 PM, Joerg wrote:
On 2017-11-11 11:55, jbeattie wrote:
My son, who is about
200lbs, 6'5" and basically all leg muscle, descends Guardsman's Pass
on CF rims and caliper brakes.
https://www.youtube.com/watch?time_c...&v=hRM3bFXlyNk


Right, and three guys crashed. That is not my definition of a safe ride.


The first guy to crash had his rear wheel about a foot in the air. He
was decelerating at the limit. Disc brakes would have added nothing.


And was fully seated. Big mistake. You've got to move far behind the
seat for max deceleration.


https://www.youtube.com/watch?v=NKdVMYo1H38 Basically the whole world
descends much hairier descents than French Grade Road on pretty
mundane equipment.


And crashes, hard.

No, Joerg. One video of a bad crash does not mean that such crashes are
normal.


Three guys in a row crashed.


What I do not understand why the riders braked so late when they were
obviously far off the ideal line for that curve ...


The commentator on the second video claims that the support vehicles
blocked views of the turns and prevented the riders from taking proper
lines. It was odd that the rider who crashed first entered the scene so
far to his left, but we can't say why he did that. Perhaps it had
something to do with obstruction from a support car.


Then he should have slowed down earlier, hard.


and then did not drop behind their seats. No wonder the rear wheel
comes off, you've got to move the CG as far back and as low as possible.


Sliding way back helps a bit, but it's not magical. More important, it's
often just not possible to do quickly. Sure, you can do it if you're on
a mountain bike peeking over the rim of a steep downhill. That's not the
case here.


It has nothing to do with the type of bike and these riders had plenty
of time to move behind. Yet they didn't. My definition of quickly is a
split second, not five seconds.


All the riders in the videos were on the ragged edge of control in one
way or another. They may not have had any reflexes left to initiate
sliding back. Alternately, they may have realized doing so might
destabilize their steering.


It doesn't destabilize steering when you are going straight. You've got
to make a quick decision whether to lay the bike and risk major road
rash or go straight but initiate max deceleration.


Staying on or above the seat that does not work. Maybe some of the
road bikers would need MTB training. "Belly riding" is an almost
instinctive and instant reaction when a crisis situation like in the
video comes up for a mountain biker.


I would think these guys could outride you in any situation, including
mountain biking.



Doubtful. An experienced mountain biker never stays in or above the seat
in a situation that requires shedding speed fast, especially downhill.


... Very few "Monday morning quarterbacks" ever make it
into the pro ranks, despite their legendary expertise around a water
cooler.


It is rather clear that all three made several major mistakes. Happens
to all of us but we usually make only one at a time.

The first crashed rider would have crashed even without any obstacles in
the way. His speed was way too high, he'd have over-cooked the curve.

Look at the rider at 0:05min. He approaches the curve at reasonable
speed _and_ belly-rides behind the saddle. That is how it's done. He'd
be a good MTB rider, as would some others in the video.

--
Regards, Joerg

http://www.analogconsultants.com/
  #336  
Old November 12th 17, 01:39 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 2017-11-11 15:38, jbeattie wrote:
On Saturday, November 11, 2017 at 1:38:59 PM UTC-8, Joerg wrote:
On 2017-11-11 11:55, jbeattie wrote:



[...]


... Having forest to the left and right is basically SOP around
here. I could commute to work on Fire Lane 5 if I were so
inclined. https://www.youtube.com/watch?v=XbWCFwIxgnw&t=62s (on
a CX bike). It gets nasty at 3:00. Anyway, get to the bottom,
turn right and you're practically down town. I've done that on a
SuperSix.


That's singletrack, yet even there it can happen:

https://www.youtube.com/watch?v=a07sV453Qaw

I had a close one with a buck. Thank God for disc brakes which came
on hard and instantly.

Here I was talking about a gravel road wit a long descent. There
are houses left and right in the trees and people out there let
their animals run free. A collision with an animal at 40mph can end
badly.


And yet, people ride that stuff all the time on normal bikes with rim
brakes and paltry 160mm rotors on disc brakes. Jobst was riding down
an unpaved Gavia Pass on racing gear.
https://rayhosler.files.wordpress.co...via-4-best.jpg Fifty
years ago, riders were descending French Creek Road on balloon tire
bikes and hub brakes. The first mountain bikers -- not a disc in
sight:
https://www.mmbhof.org/wp-content/up...c-1500x700.jpg



Sure, I did that as well. But you either go slow or take breaks so you
won't have a tire pop from an overheating rim.


I'm sure gravity has increased in the last 50 years (particularly in
Cameron Park), so now discs with 10" rotors are necessary for gravel
road riding.


Bicycle technology has (finally!) inched up towards motor vehicle
technology. Meaning now I can go down that road the same way as in my
car without concern that the brakes might not hold up. What's wrong with
that?

Yes, if 10" were more mainstream I'd probably have taken those but 8"
seems fine because I am not towing a brake-less trailer. A friend of
mine does though.

The extra cost is minimal. The adapters cost me $5.56 for both. The
rotors were around $23.70 each and the cost difference towards the
smaller versions will almost be made up by extended service life.

BTW there is a new bike shop in Placerville and one of the owners had
his MTB there the other day. 10" rotors on both wheels. He weighs less
than I do and said 8" was too iffy on some of his rides. These guys know
their stuff.

--
Regards, Joerg

http://www.analogconsultants.com/
  #337  
Old November 12th 17, 06:10 PM 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 11/11/2017 7:39 PM, Joerg wrote:

Yes, if 10" were more mainstream I'd probably have taken those but 8"
seems fine because I am not towing a brake-less trailer. A friend of
mine does though.

The extra cost is minimal. The adapters cost me $5.56 for both. The
rotors were around $23.70 each and the cost difference towards the
smaller versions will almost be made up by extended service life.

BTW there is a new bike shop in Placerville and one of the owners had
his MTB there the other day. 10" rotors on both wheels. He weighs less
than I do and said 8" was too iffy on some of his rides. These guys know
their stuff.


Let's look at the big picture. How do we decide which disc size is big
enough? And how do we decide how much how much tire puncture protection
is enough? How do we decide how bright one's lights need to be? How do
we decide how strong wheels need to be, how strong frames need to be, etc.?

In each of those categories (as well as in everything else being
designed) there is a tradeoff of benefits vs. detriments. Everyone else
recognizes this, and shoots for some optimal compromise. Example: I had
a flat about three days ago, but I prefer dealing with a few flats per
year rather than riding tires that noticeably slow me.

In each of those categories, Joerg's claim has been: if it's not as
robust as an automobile it's not good enough. But A) that's total
nonsense, because bikes and cars have very different uses and
parameters. And B) he really doesn't believe it anyway; otherwise he'd
be pedaling the de-motorized motorcycle that Sir Ridesalot has proposed
many times.

Joerg's real attitude is different. He's decided that the only
acceptable equipment is what he desires or approves, and that the entire
bicycle industry should cater to his wishes.

But in its wisdom, the bicycling industry realizes there's only one Joerg.

--
- Frank Krygowski
  #338  
Old November 12th 17, 06:37 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 2017-11-12 09:10, Frank Krygowski wrote:
On 11/11/2017 7:39 PM, Joerg wrote:

Yes, if 10" were more mainstream I'd probably have taken those but 8"
seems fine because I am not towing a brake-less trailer. A friend of
mine does though.

The extra cost is minimal. The adapters cost me $5.56 for both. The
rotors were around $23.70 each and the cost difference towards the
smaller versions will almost be made up by extended service life.

BTW there is a new bike shop in Placerville and one of the owners had
his MTB there the other day. 10" rotors on both wheels. He weighs less
than I do and said 8" was too iffy on some of his rides. These guys
know their stuff.


Let's look at the big picture. How do we decide which disc size is big
enough?



Big enough so they won't overheat on the longest descent on the usual
routes on a 105F day without overheating. Now that was simple.

If still not clear to you I mean descents where you have to "hang in the
brakes" most of the time because of many sharp turns or too much gravel.


... And how do we decide how much how much tire puncture protection
is enough?



When there are no more flats except for the dreaded side wall blow-outs
but I have almost fixed that problem as well.


... How do we decide how bright one's lights need to be?



1. When I can see the trail well enough to continue night travel at
15mph and debris in the road well enough for 25mph at night.

2. When the number of times where drivers see my too late drops to a
minimum. For me, it has.

Both objectives accomplished.


... How do
we decide how strong wheels need to be, how strong frames need to be, etc.?


So nothing gets bent during the gnarliest rides typically encountered.
Simple.


In each of those categories (as well as in everything else being
designed) there is a tradeoff of benefits vs. detriments. Everyone else
recognizes this, and shoots for some optimal compromise. Example: I had
a flat about three days ago, but I prefer dealing with a few flats per
year rather than riding tires that noticeably slow me.


Well, I don't. It's bad enough when I have to stop because other riders
have flats. I do that out of courtesy, plus because I have on-board
tools and they often don't.


In each of those categories, Joerg's claim has been: if it's not as
robust as an automobile it's not good enough. But A) that's total
nonsense, because bikes and cars have very different uses and
parameters.



For some people bicycles are not just rolling gyms but real
transportatiuon devices. Where if people say they will be there at 1300
hours they are there by that time. The fact that you don't seem to
understand this does not mean anything to those people.


... And B) he really doesn't believe it anyway; otherwise he'd
be pedaling the de-motorized motorcycle that Sir Ridesalot has proposed
many times.


Wrong again. I have now reached almost "unflattable" tire performance.
Objective achieved.

This was evidenced for the umpteenth time during my most recent MTB ride
where I met a couple with decent riding skills. We rode together for
about 10mi. Two miles into that I heard "Oh dang, got a flat". We all
had goat's head thorns in our tires, quite normal for that stretch of
singletrack. It is a bit overgrown and you can't see the thorns. My MTB
was completely unfazed, I didn't even bother pulling them out. Both of
their bikes had green slime oozing out of the front tires and it didn't
want to stop. Got it stopped by spinning the wheels and pumping up. Sort
of, somewhat, and not for long.


Joerg's real attitude is different. He's decided that the only
acceptable equipment is what he desires or approves, and that the entire
bicycle industry should cater to his wishes.


They should make bicycles as reliable as motor vehicles. That is my firm
opinion and it is not rocket science to do that.


But in its wisdom, the bicycling industry realizes there's only one Joerg.


Nope. Why do you think Kenda, Sunlite and some others offer thick tubes?
Why do you think product lines such as Mr.Tuffy have good success in the
marketplace? Why do you think Shimano sells 8" rotors? All out of pure
altruism?

More and more riders in my area realize that and start equipping their
bikes in a similar way. Then you hear comments such as "Man, I haven't
gotten a flat in a year now!".

BTW, the most common excuse I hear from cyclists not to have made a
particular trip by bike is "It's got a flat right now". I have never
heard that from a motor vehicle user, ever.

--
Regards, Joerg

http://www.analogconsultants.com/
  #339  
Old November 13th 17, 02:46 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 Sun, 12 Nov 2017 12:10:38 -0500, Frank Krygowski
wrote:

On 11/11/2017 7:39 PM, Joerg wrote:

Yes, if 10" were more mainstream I'd probably have taken those but 8"
seems fine because I am not towing a brake-less trailer. A friend of
mine does though.

The extra cost is minimal. The adapters cost me $5.56 for both. The
rotors were around $23.70 each and the cost difference towards the
smaller versions will almost be made up by extended service life.

BTW there is a new bike shop in Placerville and one of the owners had
his MTB there the other day. 10" rotors on both wheels. He weighs less
than I do and said 8" was too iffy on some of his rides. These guys know
their stuff.


Let's look at the big picture. How do we decide which disc size is big
enough? And how do we decide how much how much tire puncture protection
is enough? How do we decide how bright one's lights need to be? How do
we decide how strong wheels need to be, how strong frames need to be, etc.?

In each of those categories (as well as in everything else being
designed) there is a tradeoff of benefits vs. detriments. Everyone else
recognizes this, and shoots for some optimal compromise. Example: I had
a flat about three days ago, but I prefer dealing with a few flats per
year rather than riding tires that noticeably slow me.

In each of those categories, Joerg's claim has been: if it's not as
robust as an automobile it's not good enough. But A) that's total
nonsense, because bikes and cars have very different uses and
parameters. And B) he really doesn't believe it anyway; otherwise he'd
be pedaling the de-motorized motorcycle that Sir Ridesalot has proposed
many times.

Joerg's real attitude is different. He's decided that the only
acceptable equipment is what he desires or approves, and that the entire
bicycle industry should cater to his wishes.

But in its wisdom, the bicycling industry realizes there's only one Joerg.


I don't think that you understand :-) You see, if it is "mine" then it
must be better then anyone. My brakes are better; my legs are
stronger; my beer is better; and on and on and on.

As an aside, I just measured the front discs on my wife's Honda Jazz
(I think it is called a "Fit"in the U.S.) and to my horror I find that
they are only 240mm (9.4") in diameter. As the nominal weight of the
car is about 1100 Kg (2400lb), as opposed to (probably) an all up
weight of less then 250 lbs for a bicycle, it is obvious that they
can't possibly be large enough to be safe. And Horrors, there isn't
any room to fit larger :-(
--
Cheers,

John B.

  #340  
Old November 13th 17, 02:58 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 Sun, 12 Nov 2017 09:37:54 -0800, Joerg
wrote:

On 2017-11-12 09:10, Frank Krygowski wrote:
On 11/11/2017 7:39 PM, Joerg wrote:

Yes, if 10" were more mainstream I'd probably have taken those but 8"
seems fine because I am not towing a brake-less trailer. A friend of
mine does though.

The extra cost is minimal. The adapters cost me $5.56 for both. The
rotors were around $23.70 each and the cost difference towards the
smaller versions will almost be made up by extended service life.

BTW there is a new bike shop in Placerville and one of the owners had
his MTB there the other day. 10" rotors on both wheels. He weighs less
than I do and said 8" was too iffy on some of his rides. These guys
know their stuff.


Let's look at the big picture. How do we decide which disc size is big
enough?



Big enough so they won't overheat on the longest descent on the usual
routes on a 105F day without overheating. Now that was simple.


I guess I'd have to ask "what is over heating"? You see a F1 car's
brakes work perfectly when they are red hot, around 1200 degrees (C),
in fact I understand that at ambient temperatures they are less
effective then when hot.

So, what is too hot?

If still not clear to you I mean descents where you have to "hang in the
brakes" most of the time because of many sharp turns or too much gravel.






... And how do we decide how much how much tire puncture protection
is enough?



When there are no more flats except for the dreaded side wall blow-outs
but I have almost fixed that problem as well.


... How do we decide how bright one's lights need to be?



1. When I can see the trail well enough to continue night travel at
15mph and debris in the road well enough for 25mph at night.

2. When the number of times where drivers see my too late drops to a
minimum. For me, it has.

Both objectives accomplished.


... How do
we decide how strong wheels need to be, how strong frames need to be, etc.?


So nothing gets bent during the gnarliest rides typically encountered.
Simple.


In each of those categories (as well as in everything else being
designed) there is a tradeoff of benefits vs. detriments. Everyone else
recognizes this, and shoots for some optimal compromise. Example: I had
a flat about three days ago, but I prefer dealing with a few flats per
year rather than riding tires that noticeably slow me.


Well, I don't. It's bad enough when I have to stop because other riders
have flats. I do that out of courtesy, plus because I have on-board
tools and they often don't.


In each of those categories, Joerg's claim has been: if it's not as
robust as an automobile it's not good enough. But A) that's total
nonsense, because bikes and cars have very different uses and
parameters.



For some people bicycles are not just rolling gyms but real
transportatiuon devices. Where if people say they will be there at 1300
hours they are there by that time. The fact that you don't seem to
understand this does not mean anything to those people.


... And B) he really doesn't believe it anyway; otherwise he'd
be pedaling the de-motorized motorcycle that Sir Ridesalot has proposed
many times.


Wrong again. I have now reached almost "unflattable" tire performance.
Objective achieved.

This was evidenced for the umpteenth time during my most recent MTB ride
where I met a couple with decent riding skills. We rode together for
about 10mi. Two miles into that I heard "Oh dang, got a flat". We all
had goat's head thorns in our tires, quite normal for that stretch of
singletrack. It is a bit overgrown and you can't see the thorns. My MTB
was completely unfazed, I didn't even bother pulling them out. Both of
their bikes had green slime oozing out of the front tires and it didn't
want to stop. Got it stopped by spinning the wheels and pumping up. Sort
of, somewhat, and not for long.


Joerg's real attitude is different. He's decided that the only
acceptable equipment is what he desires or approves, and that the entire
bicycle industry should cater to his wishes.


They should make bicycles as reliable as motor vehicles. That is my firm
opinion and it is not rocket science to do that.


But in its wisdom, the bicycling industry realizes there's only one Joerg.


Nope. Why do you think Kenda, Sunlite and some others offer thick tubes?
Why do you think product lines such as Mr.Tuffy have good success in the
marketplace? Why do you think Shimano sells 8" rotors? All out of pure
altruism?

More and more riders in my area realize that and start equipping their
bikes in a similar way. Then you hear comments such as "Man, I haven't
gotten a flat in a year now!".

BTW, the most common excuse I hear from cyclists not to have made a
particular trip by bike is "It's got a flat right now". I have never
heard that from a motor vehicle user, ever.


But to be honest, I never heard a bicyclist say that, or a
motorcyclist say that, or a auto driver say that, or even a big 18
wheel trucker say that.

Is that something they say in Germany?
--
Cheers,

John B.

 




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