Team Sky races with disc brakes for the first time

spasypaddy wrote:

how to ruin a good looking bike quickly...

Quite surprised we actually got 11 comments in before the obligatory "I don't like the look of discs, and and I want you to know that too" one...

spasypaddy wrote:

how to ruin a good looking bike quickly...

Said previously about:
- derailleur gears
- hub gears
- triple chainsets
- STI shifters
- clincher tyres
- mudguards
- rear racks
- lights
- seat packs
- non-leather saddles
- every new frame material introduced
and just about every part of a bicycle ever created.

spasypaddy wrote:

how to ruin a good looking bike quickly...

By removing the rim brakes?

Yeah, dem tings is so priddy

cdamian wrote:

What kind of wheels are those?

They look very odd, if you look at the front rim, despite the sticker saying no rim brakes, it looks like a rim brake rim, the back appears much rounder.

The sheen suggests carbon, with the shimano stickers, and the UCI regs I would guess these are what will become the new Dura Ace wheels, why 28? spokes again not sure when you can get perfectly serviceable mtb wheels with less.

well spotted - what's with all the spokes?

I think it's due to the greater stresses cause by braking forces from the discs.

graybags wrote:

I think it's due to the greater stresses cause by braking forces from the discs.

Can someone explain to me what these extra stresses I keep reading about actually are? My understanding of brakes is that you try to stop one part of the wheel from turning (or reduce its rotational speed) which is the rim in the case of rim brakes and the hub in the case of disc brakes. Because the spokes tie everything together, as you stop/slow one part of the bike the rest has to do the same. If I lock a wheel up with either a disc or rim brake, the spokes have to carry the stress which ties the whole bike together as a single unit, if they didn't then the spokes would bend or pull out of the rim or hub, everything would fall apart and different bits of bike would end up travelling at different speeds. Surely if I stop a bike from a given speed in a given distance, the stress on the spokes is the same. I know a disc can produce more stopping power but once maximum deceleration is achieved (just before a wheel locks up which is a function of tyre grip and road surface) no further loading is being applied to the spokes. Because I can lock a wheel with either type of brake, where does this extra stress come from?

extra dresses because on a rim brake system the rim is being held and the ground is trying to turn the rim. On a disc brake the hub is being held and the ground exerts a force on the rim so the spokes must resist the turning moment.

Welsh boy wrote:

graybags wrote:

I think it's due to the greater stresses cause by braking forces from the discs.

Can someone explain to me what these extra stresses I keep reading about actually are? My ....

Been a while since GCSE Physics, but I would hazard a guess at effective lever lengths between the bit doing the stopping and the contact at the road.

Welsh boy wrote:

graybags wrote:

I think it's due to the greater stresses cause by braking forces from the discs.

Can someone explain to me what these extra stresses I keep reading about actually are? ... Surely if I stop a bike from a given speed in a given distance, the stress on the spokes is the same...

With rim brakes, the brakes stop the rim and all the spokes have to do is stop the hub spinning. As the hub is light and also because its near the centre it doesn't have much angular momentum so its easy to stop. They also have to stop the hub shifting forward inside the wheel, but that's tension in the spokes at the back and spokes are very good at holding tension directed out from the hub.

On a disc brake wheel, the brakes stop the hub, and the spokes have to stop the entire bike and rider, by stopping the rim turning. (or as wycombewheeler says they have to stop the rim spinning while the ground is pushing it backwards, which is the same thing)

Welsh boy wrote:

graybags wrote:

I think it's due to the greater stresses cause by braking forces from the discs.

Can someone explain to me what these extra stresses I keep reading about actually are?

There aren't any greater or extra stresses.
You still have to stop the same bike, there are simply different stresses on different components and/or different areas.

You have to beef up the left-hand fork but you can correspondingly reduce the mass up by where the rim brake was as you no longer need a mounting point up there. Same on the chainstay - beef up the left hand stay but you can then completely redesign the seat-stays for more compliance/lighter weight etc.

Welsh boy wrote:

Can someone explain to me what these extra stresses I keep reading about actually are?

It's to do with the differential torque on each side of the bike interacting with the coriolis forces as the spokes pass through the Earth's magnetic field. For small riders on light bikes - essentially, anyone in the pro-peleton - that interaction can cause them to be thrown violently from their bikes and will turn their wheels into red-hot discs of terror. If the entire peleton were to adopt discs and were to all brake at the same time, the feedback could potentially cause the Earth to slightly increase its natural precession, causing an ice age. In the Southern Hemisphere this problem will be exacerbated unless manufacturers produce frames and hubs with the rotor and caliper on the other side of the wheel, or unless everyone rides backwards. There is no problem using discs in equatorial regions.

adamthekiwi wrote:

Welsh boy wrote:

Can someone explain to me what these extra stresses I keep reading about actually are?

It's to do with the differential torque on each side of the bike interacting with the coriolis forces as the spokes pass through the Earth's magnetic field. For small riders on light bikes - essentially, anyone in the pro-peleton - that interaction can cause them to be thrown violently from their bikes and will turn their wheels into red-hot discs.....There is no problem using discs in equatorial regions.

Quite right Welsh Boy but I think you're a little ill informed concerning equatorial braking. Disc brakes are so good that if all those tedious heroes circumnavigating the globe for charity all braked at the same time the extra traction achieved could slow the earth's spin to drop all geo-stationary satellites off by as much as 5 degrees - consequently rendering Strava next to useless as a way of trumpeting your sad pbs to those that don't give a toss.

Native types living on the equator would have no effect on thexearth's spin rate. They can't afford bikes let alone 'essentials' like disc brakes.

graybags wrote:

I think it's due to the greater stresses cause by braking forces from the discs.

Someone should tell Crank Brothers: https://www.crankbrothers.com/category/wheelsets

Gkam84 wrote:

I want to know what rotors he is running there, nothing I've seen before.

Brailsford says that they are especially round ones made in France.

oozaveared wrote:

Gkam84 wrote:

I want to know what rotors he is running there, nothing I've seen before.

Brailsford says that they are especially round ones made in France.

Froome of course will be using oval rotors.

Gkam84 wrote:

I want to know what rotors he is running there, nothing I've seen before.

Standard Shimano Icetech freeza rotors,

http://www.chainreactioncycles.com/shimano-rt99-ice-tech-freeza-cl-disc-...

Gkam84 wrote:

I want to know what rotors he is running there, nothing I've seen before.

Ice tech rotors from Shimano. I have them on my new Hunt wheels.

Gkam84 wrote:

I want to know what rotors he is running there, nothing I've seen before.

Aren't you a mechanic? The Icetech's have been out for at least 3 years in MTB versions and on road bikes for over a year