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Unnerving braking experiences; sudden braking increase.



 
 
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  #1  
Old January 25th 07, 01:21 AM posted to rec.bicycles.tech
Michael Press
external usenet poster
 
Posts: 9,202
Default Unnerving braking experiences; sudden braking increase.

I experienced something a bit unnerving yesterday on a
bike I have been riding a couple years. The bike is a
nifty steel sport frame. The brakes are Ultegra 49 mm
reach with Kool Stop pads. On descents I was waiting a
bit longer before braking at turns, using more braking
force, but still using progressive force, rather than
slamming them. At a later point in the brake
application, the braking force suddenly increased
sharply. This happened more than once. Had not seen
this before, and need more experiments. Any comments on
this sketchy account?

--
Michael Press
Ads
  #2  
Old January 25th 07, 02:32 AM posted to rec.bicycles.tech
ddog
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Posts: 273
Default Unnerving braking experiences; sudden braking increase.

Michael,

Just a guess, but by riding on the brakes it made the (rust pad?) Kool
Stops hot.
They expanded and added pressure to brake surface. Then if they got
slightly cocked
when they were hot, soft, and draging pads the rear pads could catch
and jam the wheel.

It would be logical the rears would heat, expand, and grab more since
the front of the pads
would get direct air cooling.

But that's just a guess. Dragging bike brakes seems dangerous.
Are those Salmon color rust pad Kool Stops? That may have been what
happened to Jobst going
down the Alps. Good experience to pass on. So for cooling the pads, the
AL fins wouldnt' do much since furtherst
away from hot pad surface: air scoops need to divert air on the back of
the pad surfaces on the rear end,
top rear half, and bottom rear half of each pad. Interesting puzzle for
an air dam.

I may be way off, but it sounds logical any way.


Thanks

Michael Press wrote:
I experienced something a bit unnerving yesterday on a
bike I have been riding a couple years. The bike is a
nifty steel sport frame. The brakes are Ultegra 49 mm
reach with Kool Stop pads. On descents I was waiting a
bit longer before braking at turns, using more braking
force, but still using progressive force, rather than
slamming them. At a later point in the brake
application, the braking force suddenly increased
sharply. This happened more than once. Had not seen
this before, and need more experiments. Any comments on
this sketchy account?

--
Michael Press


  #3  
Old January 25th 07, 02:34 AM posted to rec.bicycles.tech
Mark Hickey
external usenet poster
 
Posts: 1,083
Default Unnerving braking experiences; sudden braking increase.

Michael Press wrote:

I experienced something a bit unnerving yesterday on a
bike I have been riding a couple years. The bike is a
nifty steel sport frame. The brakes are Ultegra 49 mm
reach with Kool Stop pads. On descents I was waiting a
bit longer before braking at turns, using more braking
force, but still using progressive force, rather than
slamming them. At a later point in the brake
application, the braking force suddenly increased
sharply. This happened more than once. Had not seen
this before, and need more experiments. Any comments on
this sketchy account?


Something sounds very wrong here... Perhaps you've got the pads toed
out (with a wider gap at the leading edge of the pad than the trailing
edge). That can cause this kind of thing (though normally it'll still
be somewhat progressive in nature).

Maybe it's just contamination on the rim or brake pad? A bit of
water? If you go into a corner on the brakes hard with a wet rim, the
braking WILL "improve" sharply when the water is removed by the first
couple revolutions of the wheel (give or take).

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame
  #4  
Old January 25th 07, 04:55 AM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 216
Default Unnerving braking experiences; sudden braking increase.



On Jan 24, 7:21 pm, Michael Press wrote:
At a later point in the brake
application, the braking force suddenly increased
sharply. This happened more than once. Had not seen
this before, and need more experiments. Any comments on
this sketchy account?


I had something similar happen when I was using different sets of
wheels with rims that didn't match in the rim brake path (Nisi Mixer
with triangular profile, switching to box-section tubies to race on).
Brake pads worn on the Mixers contacted "boxer: rims unevenly. Going
for more stopping power, more shoe area would contact the rims as the
brakes were pulled tighter, so I got more squeeze plus more brake pad.
One emergency slow-down to avoid a crashing rider sent me over the bars
when the front brake worked all too well, all of a sudden. It hadn't
been a problem (the usual multi-turn crit race) until I tried to use it
real hard. (You've probably checked pad-to-rim "engagement" already,
posting "JIC") --D-y

  #5  
Old January 25th 07, 07:59 AM posted to rec.bicycles.tech
Michael Press
external usenet poster
 
Posts: 9,202
Default Unnerving braking experiences; sudden braking increase.

In article
.com
,
"ddog" wrote:
Michael Press wrote:
I experienced something a bit unnerving yesterday on a
bike I have been riding a couple years. The bike is a
nifty steel sport frame. The brakes are Ultegra 49 mm
reach with Kool Stop pads. On descents I was waiting a
bit longer before braking at turns, using more braking
force, but still using progressive force, rather than
slamming them. At a later point in the brake
application, the braking force suddenly increased
sharply. This happened more than once. Had not seen
this before, and need more experiments. Any comments on
this sketchy account?


Just a guess, but by riding on the brakes it made the (rust pad?) Kool
Stops hot.
They expanded and added pressure to brake surface. Then if they got
slightly cocked
when they were hot, soft, and draging pads the rear pads could catch
and jam the wheel.

It would be logical the rears would heat, expand, and grab more since
the front of the pads
would get direct air cooling.

But that's just a guess. Dragging bike brakes seems dangerous.
Are those Salmon color rust pad Kool Stops? That may have been what
happened to Jobst going
down the Alps. Good experience to pass on. So for cooling the pads, the
AL fins wouldnt' do much since furtherst
away from hot pad surface: air scoops need to divert air on the back of
the pad surfaces on the rear end,
top rear half, and bottom rear half of each pad. Interesting puzzle for
an air dam.

I may be way off, but it sounds logical any way.


Do not top post. I fixed it for you.

In the cases reported I spent _less_ time with the
brakes on. I was not dragging the brakes as you say.

--
Michael Press
  #6  
Old January 25th 07, 11:26 PM posted to rec.bicycles.tech
Mamba
external usenet poster
 
Posts: 38
Default Unnerving braking experiences; sudden braking increase.

"Michael Press" wrote in message
...
In article
.com
,
"ddog" wrote:
Michael Press wrote:

snip

Do not top post. I fixed it for you.

In the cases reported I spent _less_ time with the
brakes on. I was not dragging the brakes as you say.

--
Michael Press


I am curious about the "top post" comment. It appears that bottom posting
encourages bandwidth waste and the inclusion of way too much verbiage,
especially in longer threads. Since all prior occurances in the thread
would likely contain the same stuff, seems redundant.

I realize that some folks use readers that make this desirable, and I'm not
flaming. Just curious about why this became the "way" to do it on usenet?


  #7  
Old January 26th 07, 12:31 AM posted to rec.bicycles.tech
John Forrest Tomlinson
external usenet poster
 
Posts: 6,564
Default Unnerving braking experiences; sudden braking increase.

On Thu, 25 Jan 2007 15:26:52 -0800, "Mamba"
wrote:

I am curious about the "top post" comment. It appears that bottom posting
encourages bandwidth waste and the inclusion of way too much verbiage,
especially in longer threads. Since all prior occurances in the thread
would likely contain the same stuff, seems redundant.


Top posting practically guarantees longer messages and wasted
bandwidth, since there is no incentive to trim out unnecessary stuff.

In long threads, or any thread, the proper thing to do is to bottom
post while removing information not needed to understand the post
you're writing.
--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************
  #8  
Old January 26th 07, 12:47 AM posted to rec.bicycles.tech
Bill Sornson
external usenet poster
 
Posts: 4,098
Default Unnerving braking experiences; sudden braking increase.

Does this help?

Mamba wrote:
"Michael Press" wrote in message
...
In article
.com
,
"ddog" wrote:
Michael Press wrote:

snip

Do not top post. I fixed it for you.

In the cases reported I spent _less_ time with the
brakes on. I was not dragging the brakes as you say.

--
Michael Press


I am curious about the "top post" comment. It appears that bottom
posting encourages bandwidth waste and the inclusion of way too much
verbiage, especially in longer threads. Since all prior occurances
in the thread would likely contain the same stuff, seems redundant.

I realize that some folks use readers that make this desirable, and
I'm not flaming. Just curious about why this became the "way" to do
it on usenet?



  #9  
Old January 26th 07, 01:11 AM posted to rec.bicycles.tech
John Forrest Tomlinson
external usenet poster
 
Posts: 6,564
Default Unnerving braking experiences; sudden braking increase.

On Thu, 25 Jan 2007 16:47:25 -0800, "Bill Sornson"
wrote:

Does this help?


You're such a dick. Stuff like that was funny in grade school.
--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************
  #10  
Old January 26th 07, 01:39 AM posted to rec.bicycles.tech
Mike Jacoubowsky
external usenet poster
 
Posts: 2,972
Default Unnerving braking experiences; sudden braking increase.

I experienced something a bit unnerving yesterday on a
bike I have been riding a couple years. The bike is a
nifty steel sport frame. The brakes are Ultegra 49 mm
reach with Kool Stop pads. On descents I was waiting a
bit longer before braking at turns, using more braking
force, but still using progressive force, rather than
slamming them. At a later point in the brake
application, the braking force suddenly increased
sharply.


Check both the rim and pads for signs of unusual wear; specifically, if the
rim is significantly worn, you can end up with a lip near the top and
bottom. As the brake pads wear, pressure is at first applied to the very
small surface area of the lip, after which it drops down into the main
section... which can suddenly increase the braking forces.

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA


 




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