On Sunday, February 3, 2019 at 5:14:00 PM UTC-8, James wrote:
On 1/2/19 7:48 am, wrote:
On Wednesday, January 30, 2019 at 7:27:08 PM UTC-8, James wrote:
On 31/1/19 5:02 am, wrote:
On Tuesday, January 29, 2019 at 2:59:39 PM UTC-8, James wrote:
On 30/1/19 6:13 am, wrote:
On Tuesday, January 29, 2019 at 6:07:16 AM UTC-8, Roger
Merriman wrote:


You’d think it would be so, but really quite differing
brakes don’t seem to cause confusion. I will admit that
first time I use the MTB with is 180mm etc disks they are
so instant, but actually you don’t lock, it’s a very easy
system to use to it’s full, ie tyres at the point of
locking but not quite etc.


If you're applying the disk brakes and hit a bump it is WAY
too easy to lock the brakes up.


Disk brakes are normally associated with better brake
modulation than rim brakes. That means with disk brakes you
can achieve more brake effort without locking a wheel. You
seem to be contradicting that.

-- JS

Not really. A full suspension MTB has a different center of
gravity and weighs twice what a road or cross bike does. When you
have 2" wide tires and a great deal of weight disks do modulate
much better because you can retain traction most of the time.

Whether the bike weighs 10 kg or 20 kg does not change much when
the rider weighs 80 - 90kg.

The biggest difference is that a full suspension MTB will retain
tyre contact with the road or track surface better - however, as
you start to brake the suspension forks should compress which
starts to rotate you over the bars, which is bad.

There are two problems with a xcross bike - it weighs very little
- a 32 mm cross knobbie can easily have so much traction that the
bike can rotate around it's much high center of gravity. And on
hard surfaces you can lock the brakes very easily since there is
less traction.

Regardless of bike weight, if you're going to brake hard you must
move your body backwards as much as possible, to prevent the rear
wheel from lifting. Even motorcycle riders who do defensive riding
courses learn this.

My gravel bike comes standard with 42mm tyres. It can handle
slightly wider. Not dissimilar to many MTB tyres.


With road bikes they reduced the size of the disks dramatically.
The reason that they even went to disks was to not wear out
expensive carbon rims. So instead they wear out easily and
cheaply replaceable metal disks. Using Campy skeleton brakes I
can easily lock the brakes if I wish to. So what would I gain
using disks other than cheaper replacement costs?

Smaller disks on road bikes is because there is significantly less
tyre on the road - but it should still be possible to lock the
front brake and send yourself over the bars, especially if you
don't move your body backwards.


I am not anti-disk brakes but there are horses for courses. If
you are building a superlight bike with superlight components why
would you put an very un-aerodynamic and heavy disk brake systems
on it?

3 months of riding my Colnago with carbon wheels show less wear
that a single month on aluminum wheels. Though I have to replace
the basalt brake pads all the time.


It facilitates easier CF rim use, and doesn't require rim brakes to
have a quick release so the brake pads can be moved out of the way
of wide tyres. You know the pros use 27 - 28 mm tyres for cobbled
classics? They won't get past properly adjusted rim brakes without
a quick release.

-- JS

I don't think we agree on this: I weigh 84 kg and a 20 kg bike most
assuredly climbs slower than snot on a cold day. With my cross bikes
I would come up behind a FS 29er and try to pace him because I don't
like blowing by people as if I were better than they. But eventually
I just can't go that slow and have to pass. Though I try to do it
mildly until I'm out of sight.

I will say that really rough, steep climbs that you have to carry a
cross bike up these long wheelbase MTB's can carry such a low gear
that they can climb almost anything.

I have 28's on my Time VX Elite with an Ultegra group on it and the
brake releases work fine. Let's remember that today's disk brake
bikes have 10 mm one piece axles and so there is no such thing as a
quick release. Plus you have to thread the wheel between the forks
plus carefully insert the disk through the brake pads without
knocking them off.

That's why most of the road racing teams are not using disks


Earlier the conversation was about braking performance. Now you are
talking about climbing.

Just how often do you have to brake hard while riding up a steep hill?

--
JS

Maybe I got lost in the conversation - I was talking about MTB's being a good place to use disks because they can use them for their very heavy downhill loads whereas my cross bike can pass them easily on hard climbs save the very hardest in which the long wheelbase and low gears of an MTB win out.