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Have a question for Lennard? Please email us at veloqna@comcast.net to be included in the Technical FAQ.
Dear Lenard,
I’m switching to disc brakes and was surprised to read that they have a short lifespan. Most searches give me 500 to 1200 miles, depending on the material. I asked a friend who uses them who said it was crazy because he gets over 3,000 miles.
What is your meaning?
-I f
Dear Jeff,
In general, I agree with your friend. I usually easily get 3,000 miles or more out of organic pads, and sintered pads last much longer. However, this entirely depends on the weight of the rider, the terrain being traveled, the weather conditions while riding, and the surface of the road or trail. Under certain conditions and under certain riders, pad wear can be much faster than the rates you quoted.
For example, I have a very large client who goes through buffers very quickly. He bought me a dozen custom titanium road bikes over the years and rides them all over the world a lot. His weight fluctuated over the years between 300 and 350 pounds (135-160 kg) and he undertook numerous multi-week bicycle trips to the Pyrenees and Alps. With Shimano organic pads and 160mm rotors, he was going through a set of pads every day on these trips! With sintered pads he was usually able to spend a whole week in the Alps with one set of pads.
To imagine that, I had to recognize that he and his bike weighed the same as me, my wife and our tandem together. When descending on our tandem, we pick up speed incredibly fast and have to do a lot of hard braking on the twisty mountain descents. We, too, would go through a lot of pads if we had to do four or five passes over them day after day in, say, the Dolomites.
Another example of high bearing wear is when riding technical terrain in very light, wet mud or wet snow. For the first, I remember the Thursday and Friday races of the 2013 U.S. National Cyclocross Championships in Verona (Madison), WI, when disc brakes were just starting to arrive in cyclocross and weren’t hydraulic. Deep snow had fallen two days prior and above-freezing temperatures, combined with so many runners circling the course, turned it into thin, light mud.
Normally, disc brakes have a big advantage in the mud over cantilever brakes; sticky mud builds up around the cantilevered rims and brake pads (as happened in Saturday races in warmer temperatures at those same Nationals) while being ejected from the disc brake rotors. On the Thursday and Friday of those January Nationals, however (I ran that Thursday in 55-59, with cantilever brakes), riders with cantilever brakes didn’t necessarily have to stop (I don’t did not do). However, riders with disc brakes had to change bikes (or do maintenance if they didn’t have a second bike) every lap or two because their brakes no longer worked. They had to tighten their brake cables several times during the race and replace their brake pads at least once. I wrote this article about it.
Another time I remember racing in an early season NORBA National ATV race in Big Bear, Calif., when the mountain was covered in snow. The downhillers in the event were going through disc brake pads every run (maybe two miles).
For road riding in dry conditions on rolling, flat terrain and a rider under 180 pounds, however, pad wear can be very long, perhaps 5,000 miles with organic pads and longer with pads. sintered.
-Lennard
Dear Lenard,
The late Jobst Brandt claimed that going down a hill slowly caused more rim heating than going fast, because more of the energy was dissipated by heating the wheels, and less by wind resistance.
As usual it is very certain, but you seemed to imply that a careful descent would reduce the risk. (And no doubt, it reduces other closely related risks like a slip or a missed turn.) a few years ago.
I’m not going to go down to 60 MPH because Mr. Brandt says that makes my tires safer; I’m just curious to know what you think.
–Jon Blum
Dear Jon,
I agree with Jobst in that higher relative wind speeds will cool the brakes better. The question is what to do when descending the switchbacks. The method I use is to let the brakes go as far as possible between turns, cool them down, then brake as hard as needed (and no harder), just before the turns. This will result in a lower average brake temperature when holding the brakes the entire time when descending.
-Lennard
Dear Lenard,
Are we to believe the official weight and height listed for riders in their team profiles? Some seem to be incredibly light for their height and I suspect the runners have lighter weights listed instead, the same way basketball players want to be taller and the football lineman as tall as possible.
–Bruce
Dear Bruce,
I always take them with a grain of salt. Many times I see it the other way around, though, especially for Tour de France riders, who have slimmed down to the point of bird-like arms and sunken cheeks. I’ve seen runners in pre-race bios listed at 145 pounds who can’t weigh more than 130 when racing.
Since the power-to-weight ratio largely dictates who has a chance of winning the Tour, I can imagine that riders might exaggerate their weight so as not to be considered as seriously as a competitor, and therefore not be pursued with such determination. Their threshold power can be estimated from time trial performance or found in Strava recordings, so sandbag can be accomplished by overestimating body weight.
Also, the few really big pro riders seem to have a tendency to understate it. I don’t have a theory as to why, other than unlike basketball players who want to intimidate with their size, maybe they want to appear less standout. When I covered the Tour a lot (decades ago) I was 6’5” (I’ve lost more height since). There were a few riders I stood back to back with who were taller than me but whose bios listed them as 6’3″ or 6’4″.
-Lennard
Lennard Zinn, our longtime tech writer, joined VeloNews in 1987. He is also a custom frame builder and supplier of huge non-custom bikes , a former U.S. National Team rider, co-author of “The broken heart” and author of numerous books on cycling, including “Zinn and the art of road bike maintenance,” “DVDas good as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Introduction to Cycling: Maintenance Tips and Skill Building for Cyclists.”
He holds a bachelor’s degree in physics from Colorado College.
Follow @lennardzinn
