On Monday, October 30, 2017 at 9:39:55 AM UTC-7, Joerg wrote:
On 2017-10-29 12:57, wrote:
On Sunday, October 29, 2017 at 10:02:12 AM UTC-7, Joerg wrote:
On 2017-10-29 09:45, wrote:
On Saturday, October 28, 2017 at 8:09:18 AM UTC-7, Joerg wrote:

And grandpa has driven his cars without safety belts yet survived
...

For people who do not shy away from unpaved roads or use a lot of
singletrack and ride in the rain there is a much more extreme
issue: Wet mud.

There is NO brake the is proof against wet mud. In fact it is perhaps
worse on a disk since the additional pressure of the pads can turn
the silicon present in most muds into cutting instruments that on rim
brakes cuts into the rubber show rather than the hard and thin disk
pad.


Actually, no. I've had mud literally dripping from the calipers which
had become barely recognizable brownish blobs. The only thing that
happens is that they make an awful grinding noise just like muddy rim
brakes do. With the two major differences that they still come on full
force immediately and that this grinding does not eat up aluminum.
Aluminum as one of the braking surfaces plain does not make any sense,
certainly not in a muddy environment.

A downside of bicycle disc brakes is that in contrast to most motor
vehicles the rotors have "vent holes" and weight weenie spiders. This
results in rather fast heat-up and in "brake mousse" when you plow
through thick vegetation on an overgrown trail. Mashed star-thistle and
other weeds get shredded and a sort of pulp develops which cakes up in
the holes of the rotor. It doesn't diminish the brake force but lets of
a bad stench. One of the reasons why I carry a Swiss Army knife in a
pocket. Not in a pannier, so I can whip it out in seconds. This also
helps in poking out the giant mud clump that forms behind the BB and can
prevent the rear wheel from turning.

Joerg - that additional noise is wear.


Sure. However, the rotors last thousands of miles, cost around $20 and
take only minutes to change. The pads cost $2/pair for ceramic-based
material (like motorcycles have) and last around 1000mi depending on
turf and weather. That is way more hassle than with a motor vehicle but
way less hassle than swapping out a shot rim.

I started riding again in fall 2013, using an older model MTB with
almost zero miles on it. By the end of 2013 it had around 1000mi on it
and the front rim looks horrible.

The problem in our area is this: Mud contains granules of decomposed
granite. Rubber pads need water diverter grooves and the granules lodge
in these grooves. They also pierce the rubber itself and lodge in there.
When pulling the lever that lets of a horrid grinding noise. Coming down
a hill you have to keep the brake engaged and you can literally hear the
rim being tortured all the way to the bottom of the hill. On flat
surfaces you have to stop and pry out the granules. On a rainy day that
means stopping every few miles. I stand by my opinion that rim brakes
are inadequate for any serious MTB riding.

Well, perhaps it was from older parts but I saw a significant number of MTB riders walking their bikes back off of hills. Those were the older cable pull brakes so that might have been when they were still developing the proper compounds.

https://www.youtube.com/watch?v=Wdb7KEc7xJI

This is comparing an 11 speed Ghost with an aluminum el-cheapo Raleigh. This was a highly unfair test to begin with: On the climbing test the Raleigh had an eight speed compact that simply didn't have the correct gearing. And the bicycle size and set-up was entirely wrong.

On the braking test it was hydraulic disks against what appeared to the the old-fashioned long throw brakes. There was so much bend in the brakes that you could bottom out the lever.

On the TT again the problem was that there simply wasn't the proper gearing.. And since the Raleigh wasn't sized correctly it was nearly impossible to get into an aero position.

Personally in the brake test I believe my Skeleton brakes would have finished not exactly with the disks but really close. There is no flex to speak of in my brakes and while I think I could lock the front wheel and allow the rear wheel to rise off of the ground there is absolutely no day I would do such a thing.

My bikes are set up similar seating position to the Raleigh. But I could merely change the stem to gain a position such as the Ghost. I personally don't give much credit to the aerodynamics of a frame.