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Conference noted::bicycle

Title: Bicycling
Notice:Bicycling for Fun
Moderator:JAMIN::WASSER
Created:Mon Apr 14 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:3214
Total number of notes:31946

2825.0. "Shimano Dual Pivot Brakeset" by LUDWIG::ASMITH () Thu Aug 04 1994 16:45

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Note 2823.1                Ladies Mountain & road bike                    1 of 1
LUDWIG::ASMITH                                       27 lines   4-AUG-1994 12:41
                        -< Shimano Dual Pivot Brakeset >-
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         This is intended as a headsup on Shimano Dual Pivot brakesets 
    ( circa 1992 ).  It disappoints me to have to write this because in the 8 
    years that I have used Shimano componetry I have gotten nothing but SAFE, 
    reliable performance from it.
         Anyone who has the brakeset from the model year as mine needs to
    exercise extreme caution in the adjustment and maintenance of the 
    calipers.  The problem is that the calipers can seize the wheels,
    causing the rider to be thrown from the bike ( potentially ). There are 
    two sources of the problem.  Both seem to center around the design 
    of the Fore to Aft pivot of the calipers ( the pivot which is set with the 
    allen nut and a bolt ).  If you hit a bump when a lever is not very tight, 
    your lever may twist ( just a couple of millimeters seem to be all that is 
    needed ) causing the caliper to immediately and tightly seize the wheel
    which that caliper controls.  The second source is the fore to aft
    adjustment itself, the mechanism is a very small adjustment tolerance,
    if you tighten it just a little to much then the wheel can be seized
    when you hit a bump on the road, even if the lever is very tight - the 
    problem may not be detectable while you have the bike on a stand.
         I have had about five caliper seizures over the last 1.2 years,
    after the last one I spent a lot of time studying the brakes and
    putting them through a lot of adjustment and tests.  I have concluded
    that the brakeset is fundamentally dangerous, and I suggest that 
    anyone using it consider replacing it with something that is
    mechanically more tolerant. 
    
         Abe;
         
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2825.1Call ShimanoORION::J_CROCKERThu Aug 04 1994 17:1534
    Hi Abe,
    
    Have you called Shimano about this?
    
    They've gotten better about backing up their hardware, especially 
    Dura-Ace.
    
    I've had 3 problems in the past:
    
    1. Early Dura-Ace front brake didn't seize -- it just plain broke,
       while I was headed downhill at 40+, with a 90-degree turn at the
       bottom.  I had to rely completely on the back brake to get me through
       the turn (I'm *real* fortunate there wasn't a car coming the other
       way).
    
       I wrote a letter to Shimano, and they didn't do a thing.
       They sponsored me back then, so I guess they figured I shouldn't
       complain about a brake I didn't pay for.
    
    2. My brother broke a Dura-Ace crank.  It was an early-'80s model, so
       no luck getting that replaced.
    
    3. A set of '91 model Dura-Ace STI levers blew up on me this spring.
       I was pleasantly surprised this time.  The person I dealt with was
       cordial, and I had a new set of levers in 2 weeks (they paid the
       shipping).
    
    Wish I could give you the number, but I don't have it at hand right
    now.  However, you'll find it on any Shimano instruction sheet.
    
    These are among the most highly regarded brakes in racing, so it
    definitely sounds as if you've got a defective set. 
    
    Justin
2825.2STARCH::WHALENRich WhalenThu Aug 04 1994 20:2814
re .1  I think that the topic is reacting to exactly what has made these brakes
popular.  I've noticed that when the brakes are adjusted such that there is
minimal clearance between the pads and the rim that a significant turning of the
handlebars can cause the brakes to rub.  That's because turning the handlebars
changes the effective length of the cable.  If the brake lever were to change
position, then it too, would change the effective length of the cable.  You
don't experience a problem while riding because you don't turn the handlebars
enough to engage the brakes then.  But if your brake levers are not sufficently
tighted to the handlebars, then it is possible that they will move when you hit
a bump.  This can change the effective length of the cable and cause the brakes
to be engaged.  The "aero" (under the bar tape) routing of the cable housings
may be sufficent to hold the housing.

Rich
2825.3switch to Campy componentsWRKSYS::ROTHGeometry is the real life!Fri Aug 05 1994 02:1431
   I think Jobst Brandt commented on these brakes or something like
   them some years ago.  (He's a well known engineer at HP and serious
   rider the Bay area.)   I didn't archive or follow the bicycles
   newsgroup too closely so can't be positive it was these that he
   was discussing.

   I'll only comment by saying that I have *never* had a catastrophic
   failure of any Campy components I have used, and I have put high
   mileage on my bikes, under less than ideal conditions (like winter
   riding, through rain, etc.)

   But one of my Dura Ace pedals *came off the spindle* due to wear and
   stupidly brain dead mechanical design, something that I cannot imagine
   happening to any Campy pedal.

   I am not going to be using any Dura Ace components in the future, I've
   switched back to Campy.

   I'm not interested in having to call Shimano about stuff like this,
   I just do not want to be stranded a hundred miles from home, or worse
   yet, have my bike fail me on a dangerous descent or some such.

   I'm only venting because I think for the basic simplicity of bicycle
   components that if I pay big bucks for these components, I want
   commensurate reliability and quality, not some tweak parts that
   are obsolete in two years and can't even be repaired, because the
   next stylish new marketing fad has come along - something which is
   now the norm in bycycling, even, unfortunatly from Campy in some
   cases.

   - Jim
2825.4JURA::MACFADYENclean fresh naturalFri Aug 05 1994 09:297
Re .3:  I think you're probably wasting your time telling Abe to switch
to Campag - he's got a bit of a down on Campag too...

Never mind, there's still Mavic, Suntour, Sachs-Huret etc.


Rod
2825.5Give me a brake LUDWIG::ASMITHFri Aug 05 1994 13:1618
    Re .4
    
         Headsup, Rod, a Campy Derailleur almost cost me my sweet life once.  
    I guess that that would cause me to be down on Campy :-).  So far
    Shimano has only given me a good set of bruised ribs.
         Rich has some good points, I think the problem that the Dual
    Pivots have is due to the close tolerances, Shimano probaly will
    fix this on the next addition, but for the time being I have to stay
    alive.  I almost surely will replace the brakeset over the winter, I
    will look closely at all vendors brakesets, I just want the fear that
    I have of my equipment to go away, whichever brakeset gives me the
    confidence that I have lost is the set that I will buy.
         I agree with .3, I should not have to call Shimano on this issue
    and I WILL not call them.  I will take matters into my own hands as
    a consumer.
    
        Abe;
                                                            
2825.6GET SOME OLD RELIABLE STUFFSTOWOA::SWFULLERFri Aug 05 1994 13:396
    There are probably a ton of old center bolt campy brakes around peoples
    basements now.  You may wish to go back in time and pick up something
    like this.  They aren't quite as quick, but reliability isn't an issue.
    
    Steve
    (using circa 1982 campy record brakes)
2825.7WRKSYS::ROTHGeometry is the real life!Fri Aug 05 1994 14:4112
   Actually, my beef is not with Shimano specifically, but with the annoying
   trend I've seen that parts are not as well designed for longevity as
   the old classic designs, and that one can't even maintain them
   in later years because they have been replaced with some newer,
   incompatible, design.

   I have a Mavic roller bearing headset, which is really nice, so am not
   a purist about one brand - but the old, classic Campy gear was really
   built to last.  I still have all my origional Campy hubs, even though
   I've rebuilt and replaced the rims!

   - Jim
2825.8WMOIS::GIROUARD_CMon Aug 15 1994 15:485
    I'm noticing (and hearing from friends now) that since some of
    the Shimano componentry is reaching "maturity" it isn't holding
    up well. I hear more and more newer stuff quitting on folks too.
    
    I'll keep my Campy stuff... At least until I retire :-)