Originally Posted by
pdlpsher
mtseymour,
Once again, you have forgotten about the external variables such as vehicle traffic. The gradient and descent length is only part of the story. The reason why Tour do these tests is because these are not really extreme conditions. Have you personally descended on Mt. Evans or Pikes Peak? These mountains are open only for a short time due to inclement weather and the tourists jam pack the mountain on the weekends when the roads are open to traffic.
By the way, I have already stated Tour's brake test protocol, which is "The test was done with a 220lb system weight (bike plus rider) with a 245 meters altitude loss at a 13% average gradient." You went on to describe a different protocol which is not what Tour had used.
I have the Tour's test results but I don't plan on sharing it here because the publication is copyrighted.
You keep digging yourself a hole and don't know when to stop and listen. You can ride more safely and reduce equipment failure by using proper braking technique. Let's resume the fact checking.
"
They tested the previous version of Shimano's Ice-Tech 160mm rotors on a single bike and they failed spectacularly. The aluminum core that is sandwiched inside the stainless steel braking surface had melted and the disk collapsed."
Neither Bike or Tour magazine said that the Ice-tech rotors "failed spectcularly", or that the disk rotor "collapsed". The grueling tests ended up with the Shimano XT brakes and Ice-Tech rotors receiving a "Very Good" rating, along with several other hydraulic brakes (eg. Sram Guide).
"
Recently they tested the latest improved Dura Ace 160mm rotors and the front brake also failed but it didn't collapse like the previous version."
In 2017, Tour magazine did a "first test" of the Dura Ace R9170 disc brakes (w flat mount) and RT900 Freeza rotors (160mm) on a Pinerello Dogma with ZIPP carbon wheels. The rider and bike weighed 220 lbs (100kg). The test track was 13% for 245 meter drop, which translates to a continuous descent of 1.2 miles. The Freeza rotor has substantially more material for heat dissipation, but has limited use for tandems because of its 160mm limit and new flat mount. The Not surprisingly, the Tour liked the Freeza rotors and didn't mention any "failure". The video is a a bit mundane because the test rider completed the descent without any drama. My German-speaking friend was disappointed that there was no spectacular crash or failure in the video.
As for your excuse of "copyright" restrictions, the "fair use" rule allows anyone to quote copyrighted materials for limited discussion purposes, especially in a non-commercial setting. Without the fair use rule, we would not have a free press, internet forums, or academic research. So please show us the data or test summary!
I doubt that you can because the real problem is your braking technique. When discussing your new 2017 titanium Santana in this forum, you stated that
"Disk brake is imperative for our riding. We had a front tire blowout on a steep descent and that led to us to replace our 1987 Sovereign with a 2012 Team Scandium with a disk brake. We do a lot of climbing and with a rim brake the rim will also probably wear out very quickly. We use the rear disk brake 95% of the time. The front brake is only used when quick stopping is needed."
It doesn't make sense that you would buy an expensive titanium tandem (with ti bolts, no less), and then avoid using the front brake to avoid rim wear! This is a good example of misplaced priorities. By mainly your rear brake, you double your stopping distance and consistently overheat the rear rotor. This will lead to severe brake fade or failure just when you really need both brakes.
Here are two videos that show that simultaneous use of F & R brake is TWICE as effective as using just the front brake. The GCN ("Brake like A Pro") shows that a single bike using just the rear brake requires twice the stopping distance as a bike using F & R brakes:
Since a tandem is heavier than a single, the it's even more important to use F & R brakes. Look at this video of a motorcycle using only rear braking:
So stop blaiming the brakes and use them properly.
BTW, I've been skiing and mtn biking at Whistler for over 30 years. Doing 20-30% off-road descents is fairly routine around here. So a 7 or 13% road descent is fun but not particularly challenging, even when dodging cars and other riders.