Tuesday, October 26, 2010

My Anecdotal History of Tandem Braking

(Originally Posted on Tandem@Hobbes 5/28/2010)

This is based on 35 years of tandem riding experience and observation. 
First, keep in mind that a rear brake can slow a bike, but a front brake is what stops one.
In the the beginning, Cantilevers alone were inadequate (design, pad material and steel rims), so a third brake was added. (And there were some tire roll-out and blow-out stories on rim brakes alone.)
At first came some internal hub brakes (our first Gitane Interclub), then improved pads (Scott-Mathauser), Shimano had an early mechanical disc (originally on the Sting Ray and Orange Crate), Phil had a disc brake, and others.
Arai Drum "discovered" - became drum standard for the first "production" tandems of the early `80s.
Mountain bike boom, dramatically improved cantilevers, eventually leading to V-Brakes,
Which led the to the Third Brake no longer being "needed",
Which then led to new (anecdotal) tire blow-out stories due to overheating rims.
At the same time Performance tandem buyers speced improving side pulls on their 2nd and 3rd tandems.
At the same time Mountain bike market was driving more Disc Brake Improvement.
And Discs were being speced by weight conscious performance tandem buyers.
Probably some minor quibbles by some on the exact timeline, this is all IMHO, and YMMV.
The tandem braking paradox (or "Judicious" use) is this:
The faster you are willing to descend, the less likely you are to ever need a "drag" brake.  
For the faster descending team, aero braking, which increases at the square of velocity (overly simplified), takes care of all the potential energy that a slower descending team turns into heat with a drag brake. 
Now this works fine for the fast team until conditions (inclement weather, route, slower traffic, etc) place them in a situation where they need to rely on "drag" braking rather than aero braking, and they have no where to dump the potential energy (as heat) of their descent.  The laws of physics (even arm-chair physics) can be a harsh mistress.
(Other variable enter, of course.  Steeper, shorter descents in the midwest and eastern US, team weights on this forum from vary 230 to 450 lbs, rider skills, perceived risk and acceptance of risk. etc. etc.)
A follow-up comment resulted from the dialog that ensued.
Single to tandem braking comparison don't work, each has a unique braking dynamic. The single bike rider of the same weight will go into a header with the front braking force that can be applied on a tandem, due to the single bikes higher and more forward center of gravity. A descending tandem is capable of putting a much greater load on the brakes than is physically possible for a single. It isn't the total weight, but where the weight is located.
Just wanted it on file for future reference.

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