Some manufacturers forcing pros onto disk brakes for the 2019 season

[C36]

We were stuck behind an ambulance after watching the Mt. Hamilton stage of the ToC. I could smell its brake dust. Brakes didn’t fade after 8min of constant dragging. Some carbon rim brake riders pulled off when the shoulder got sufficiently wide to give the ambulance a bigger gap. That is an option.

I did sit up and puff my elbows and knees out to help slow me down.

I don’t have the experience you may have with discs but my last try of the Sl6 in ultegra disc had brakes “degrading” (softer brake touch) in less than this I believe (8min at 40kph that’s more than 5km dragging brakes), now braking power itself was still solid.

I have never had a disc rotor go severely out of true from warping. I have seen maybe .1mm of warping on my rotors after truing them to almost perfect condition.

Just quoting a totally independent and well respected blogger based on his tour of mechanics during last year tdf. https://www.matosvelo.fr/index.php?pos ... -du-velo-3
unsure why the disc with problems doesn’t have the cooling fans but that was not even after a mountain stage.
In all cases most of the teams changed the discs after each mountain stage, so curious if that’s still the case.

Why wouldn’t you regroup with dropped riders at the top of the climb?

Never been in a group where it was a normal practice. Stopping right after an effort at the top of the hills where it can be windy, where you may have traffic or not enough space to wait if you are a larger group, I can imagine why it’s not popular (on longer climbs use to do U-turns start going downhill just enough to catch the slower ones and finish the climb with them.)
Now you may have places, weather, roads and groups that allow to do so.


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[Gunnar]

Excessive dragging on a descent suggests poor technique more than anything.

No, can very well be:
- traffic that doesn’t allow you go as fast as you would like.
- people on the side roads
- wait for other group members that you dropped in the climbs
- just you don’t want to go too quick cause you don’t know the descent

This. Not every ride is a race, and there's plenty of situations where not dragging brake to maintain a reasonable speed would be reckless.

I used to race motorcycles so I have no issues with going fast on a road bike, I just don't have the roads cleared out for me like they do in pro races. People come peeling out of side roads and I'm not going to be that maniac passing cars on a narrow 2-way road either.

I'm sure it's possible to make rim brakes fail but its no where near as easy when compared to disc, discs have a significantly smaller surface area and material mass for heat to dissipate and spread through. Rim brakes are way more reliable than disc, not to mention they also weigh less. I can't imagine why most pros would want to run discs instead of rim brakes in competition, I certainly don't see the benefit to them.

[ND4SPD]

This whole DoT/mineral oil argument is hilarious.

In a well maintained system there is nothing between them.

If you get any water in the system with mineral oil, your boiling point is instantly reduced to 100°C.

If you use DOT fluid, and if you get any water in the system, boiling point will be reduced to the wet boiling point of the DOT fluid, let's say at 270°C (for Castrol SRF).

it's why car/bikes that are raced use ceramic/carbon discs. Brake fade is common on track days.

No, not all car/bikes that are raced use ceramic/carbon discs... I remember some F1 races from hmmm, I think mid 2000. when they were using cast-iron discs in some races (I forgot why)... WRC cars don't use ceramic/carbon discs... Etc...

And brake fade is not common if you have good/adequate brakes

[basilic]

hmm.. a couple years ago I was keen to try a disc-brake road bike, because discs were just "better". Reading these posts makes me wonder. It seems like I need to understand the weaknesses of disc brakes so as to work around them, or else be guilty of user error. Now I'm thinking I'll wait a bit until they sort this stuff out.

[TobinHatesYou]

hmm.. a couple years ago I was keen to try a disc-brake road bike, because discs were just "better". Reading these posts makes me wonder. It seems like I need to understand the weaknesses of disc brakes so as to work around them, or else be guilty of user error. Now I'm thinking I'll wait a bit until they sort this stuff out.

It's mostly just scare-mongering / FUD from the peanut gallery. Don't be 100kg and drag your brakes all the way down a 15% grade for 15 minutes straight and you'll be fine.

[Nefarious86]

I've been up to 98kg and have tried to deliberately cook brakes in the past to get an idea of their limitations. Turned rotors black and had some funky smells and noises but never made them fade past the point of being able to stop...

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[mattr]

In a well maintained system there is nothing between them.

If you get any water in the system with mineral oil, your boiling point is instantly reduced to 100°C.

If you use DOT fluid, and if you get any water in the system, boiling point will be reduced to the wet boiling point of the DOT fluid, let's say at 270°C (for Castrol SRF).

To get water in the system would suggest a significicant lack of maintenance. Seals do not suddenly and catastrophically fail in such a way to let water in. Unless they have been abused/left dirty/not serviced. Worst case is generally a few drops of water, if that, that been pulled in through the seals after several years of normal use

No, not all car/bikes that are raced use ceramic/carbon discs... I remember some F1 races from hmmm, I think mid 2000. when they were using cast-iron discs in some races (I forgot why)... WRC cars don't use ceramic/carbon discs... Etc...

From what i can remember, Carbon/ceramic don't like rapid/uneven cooling. So wet F1 races might use cast iron, and rally cars regularly get dumped in deep water and mud. They also aren't so good when they are cold. Cast iron (and MMC) works from pretty much room temperature.

[Bridgeman]

On an agressive group ride the other day, a friend was verbally upset with his dragging squealling disc brakes, while on a series of steep uphills. I've test ridden several disc brake offerings and did not like the clunky heavy response. Several friends are having reservations about their newly purchased disc brake bikes for a number of reasons.

[kgt]

I also happen to know a few who were enthusiastic about their new disc brake frame but after a few rides they changed their mind. Especially those who have not a good lbs nearby to assist them fine tune their discs and cannor stand all the squeals and creaks. They just sell their frames (even very expensive frames) and get back their piece of mind.

[RTW]

I’m going to find out this weekend as my sponsor is sending me a new bike.

I have discs on my wet weather bike. They may rub, I don’t know. It is my wet weather bike and I don’t care!

[spdntrxi]

I'm still happy with disc... I do my own work... yeah they make noise occasionally, but I cant hear it over my breathing.

[RTW]

Oh, on the wet weather bike, there are noises sometimes. Sometimes they are loud, but only when wet and under extreme braking (there’s a hill around here which is pretty much straight down and in the 15% range. There are traffic lights near the bottom). But this bike is also able to stop, in really crappy weather, really quickly. Like, super quick. Better than my carbon wheels in the dry on the other bike, or any carbon wheels I’ve ever had. Of course, there are certain finishes to rims and braking tracks which really help, but consistently braking on these finishes wears them out. And they also tend to be noisy.

[Nefarious86]

Poor setup shouldn't be used as a metric of performance for a system.

My discs are silent in the dry and rarely make a peep in the wet, why? Because the initial setup was done properly.....

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[spdntrxi]

Poor setup shouldn't be used as a metric of performance for a system.

My discs are silent in the dry and rarely make a peep in the wet, why? Because the initial setup was done properly.....

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yep... overall my disc bikes are more silent then my rim brake bikes were... (when applying the brakes)

[flying]

yep... overall my disc bikes are more silent then my rim brake bikes were... (when applying the brakes)

That is really odd !