Far more important to GC contenders is inter-operability and speed of wheel change, and rim brakes win there. Team car availability for a bike swap on a descent can be multiple chase groups behind. Mavic neutral cars and support motos have rim brake wheels. Teammates can swap wheels with rim brakes without team car assistance. Disc brakes mean a slow change, or far more likely, a full bike swap from the team car when it can finally get to the rider in need.

Did you see Alaphillipe's failed wheel change and eventual full bike swap during one of first stages of this tour. He was completely helpless and teammates could not help. It was early in the stage and he had plenty of time to get back in the field. Something like that on a mountain stage ends the the GC aspirations for a contender if it happens at wrong time.

These guys don't give a crap about stopping power of rim vs disc. Both are fine for them. They care about instantly getting a wheel swap from a teammate or neutral car when they need it and not losing the race over inability to get a through-axle out.

Not sure about the the Colnago, but Ineos and Jumbo-Visma have trouble getting the Dogma and Oltre under the UCI weight limit. Ineos have been swapping out their sponsored wheels on critical climbing stages. (Though I'm not sure about this year with the lighter frame). And Jumbo-Visma have resorted to stripping the Oltre of paint. Disc brakes would make that even harder. And other teams apparently haven't had as much trouble getting their disc brake bikes to the weight limit.

Also wheel changes are a bit slower with disc brakes (a problem few recreational riders worry about).

I'm still rim brake on the road with no immediate plans to change. But pointing at Roglic, Pogacar, and Bernal to point out the superiority of rim brakes is kinda silly.

What about Hirschi yesterday! Absolute masterclass climbing, descending, then "TTing" on a disc brake S5. :)

Opinions are kinda split, just like they are with us, amongst the pros I've talked to (and I think honestly, outside sponsor-pleasing PR-speak).

Exactly. If a guy that descends faster than 60mph doesn't give a crap, why should your average cyclist do? Are they better? Just as super boost is better than boost and boost better than regular in MTB. But only by a tiny fraction that doesn't justify the expenses and hassles of upgrading.

I am not saying rim brakes are superior, they are probably inferior by a micron. But the upgrade is hard to justify in a road bike.

I hear you. I recently shattered a chainstay on my race bike - perfect excuse to upgrade. And after looking at the internal routing of hydraulic lines through the bars and headtubes of all the bikes I'd want, I instead got my old bike carbon repaired. Just don't want to deal with that. Yet.

On the other hand I adore the disc braking on my gravel bike. It's hands-down superior to rim brake.

And, unfortunately, my race team wheels are carbon-rimmed. My first race in this (shortened) season was a crit in torrential rain, with a short-steep downhill into a sharp turn. It was stark terrifying because I had no brakes at all on that downhill. I had to spend the whole race in the front so I wouldn't have to worry about going right over the top of someone slowing in front of me. People thought I was taking crazy risks on the turn. But I wasn't intentionally. When you can't brake you take the turn full gas.

But probably only a handful of races out of hundreds where I would have cared either way.

Are they 100% on electric shifting now? You never see issues. I remember a few years ago when it was just taking off seeing riders whose batteries would die or otherwise fail wildly calling for team cars as they try to get up mountains at 20rpm in their 11 tooth. You never see that anymore.

Curious, has there been more development and studies on aerodynamics of disc vs rim where the disc bikes are optimized for them? I haven't been paying attention to this debate for a while but the last I did, i thought I saw that as of yet, rim brakes were better but that disc brake bikes haven't yet been optimized.

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808 > NYC > PDX > YVR
2024 Races: Taupo

I just purchased AXS for my mountain bike and GRX Di2 for my gravel bike. I LOVE AXS but I do need to watch that battery. The Di2 battery lasts twice as long (if not longer). I've been caught out on my mountain bike with a dead battery. My mountain bike became a single speed. Thankfully I was only a few miles from my car. I now check the app before I ride. That gives me battery life.

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The curious task of economics is to demonstrate to men how little they really know about what they imagine they can design.

It's tough to decipher because there hasn't been much independent analysis. But Cervelo says, for example, that their new S5 is more aero than the prior S5's. So disc brakes weren't so much of an impediment that they can't at least match the aero-ness of prior bikes. I think others, like Specialized and Trek, have said the same. But these are often with "tricks" like flush-mounted thru-axle systems without built-in levers.

My suspicion is that disc brakes will always be a marginal detriment in both weight and aero in terms of absolute design space. But only very marginal.

A guy stopped yesterday with iFailure

Teammate was in a 2 day stage race last weekend. The TT winner in his AG and favorite for overall didn't start the RR because his Di2 was flat. I don't know if this is more common than riders snapping their Shimano derailleur cables at inopportune times - seen quite a bit of this as well.

Better braking and better comfort are marginal gains, though.

While I personally think the UCI weight rule is stupid, but unintended benefit is that it has allowed new tech to develop. Riders can add big head units, power meters, aero frames, deeper wheels, disc brakes, etc. etc. without being at a weight disadvantage to their peers. These items start out being heavy/clunky, but eventually evolve into elegant solutions (remember when STI was so heavy that Lance ran one STI lever and one downtube lever to save weight?). Without a min weight limit, riders would be stripping a lot of these off their bikes.

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ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

The weight limit is stupid in that it is unfair to light riders. They should have a different bike weight limit for each 5 kilo ride weight bracket. Quintana is penalized more than Dumoulin

Grand Tour obsession with mountain top finishes and neglect of TTs is unfair to everyone bar the 10% skinny buggers. This only started in the 90s. Before that riders looked merely thin. If the mountain stages all ended with a descent into the nearest village we'd never hear a murmur about the UCI weight rule again. If they matched every mountain top finish with a TT stage we might see riders blitzing the mountain for all they were worth to gain advantage over the TT guys instead of waiting to attack the final climb. A bit ridiculous that GTs are often decided by who can diet closest to the razor's edge without getting sick.

Is the first one a serious question?? You can’t understand why a lawyer, doctor, dentist!, or whatever profession you are in doesn’t care more about their bodily safety than someone who gets paid to race bikes for a living?? This is a hobby for me. And I highly likely make more money than most pro cyclists in that profession so of course I care about my safety more. I’m not saying I need disc brakes. I don’t. But I do care about braking in general more than I care about going an extra .1 MPH in a group ride.

Typically in a forum focused on racing , marginal gains are defined in speed. not peace of mind or personal comfort.

Do disc brakes give you better braking performance? Yes, DB is more consistent and a well setup DB feels nice than a well setup RB

Are RB as safe as DB? Absolutely, unless it is very wet, then you need to reduce speed with RB to compensate for worse braking performance.... having said that you probably should reduce your speed with DB too, unless racing

Can you descend faster with DB: No, in the dry I am just as fast decending on a RB. When I ride my DB bike, I do think "ooo this is nice" however it is just the feel is better, I don't brake noticeably later with DB or descend faster

What about the wet: DB is better, in light rain a RB on carbon rims doesn't respond instantly as it needs to shift the water first. In torrential rain, it sometimes feels that RB don't work at all... some pads and rims are better, but none come close to DB performance in the wet

Weight? My Specialized Tarmac SL6 Disc weighs in at 6.7kgs with pedals, cage and garmin mount, under UCI limit. my 2018 Cervelo R5 with Rim brakes was 6.4kg, There's not much in it now, could switch to Carbon Titanium discs and save 100g

Are disc brakes more aero? Contraversial here, but we are seeing wheel builders designing more aero wheels as they are not constrained by having a flat braking surface on the rim. Frame designers can now accomodated super wide rims and don't have to worry about space for calipers.

What about maintenance. As an experienced bike builder, I still find it a PITA to setup DB for the first time. Whatever I do, I always end up with fluid on the floor and on the brake hoods and on the bike. Its essential to keep pads and discs away from any potential contamination. Once setup, brakes are pretty much maintenance free for 15,000km - possibly a change of pads, but that is really simple

It doesn't really make sense for manufacturers to design 2 models of bikes, one for disc and one for Rim brakes. Rim brakes are not dead yet, and some pro teams will continue to use them

I doubt that I have bought my last RB bike, however, DB will be dominant in the market for the forseeable future

Disc brakes win for a couple of reasons:

1) They allow bikes to be more aero. Disc brakes allow a cleaner setup with less flapping brake lines. I'm gonna get some haters saying that disk brakes are less aero. They might be when you consider bikes from 5 years ago. Not anymore. The most aero road bikes are all disk brakes.

2) They let you run wider tires with lower pressures. In ten years pros are going to be racing on 32+ mm tires in the tour. Wheel designers will miraculously figure out that wider tires can be just as fast as skinny tires. And not destroy your taint at the same time. It'll take a slightly different rim shape.

3) Wider tires let you run tubeless setups that work. 25mm tubeless tires need to be run at like 80+ PSI. 32 mm can be run at 55 PSI and sealant works at that pressure. Say goodbye to flats on the world tour (functionally)

4) They brake better.

5) Modern disk brakes are really good and require functionally no maintenance. They are only going to get more reliable.

It depends though. First, better braking isn't just "peace of mind." The later you can brake, the faster you go. This is why race cars have outstanding brakes relative to normal cars.

And comfort, while difficult to quantify, can likely be important. Though dependent on course. Did you see the Tirreno-Adriatico TT this morning? Savage road conditions. With the high-rate slow-mo footage you could see riders bouncing pretty violently in the TT position. The days of 19-21mm tires pumped to 130PSI or higher are over. Not just because it turns out that pressure is just plain higher rolling resistance, but just because being vibrated to death probably isn't fast.

Granted, most of the fastest guys had rim brakes. I'd bet most of them chose relatively wider tires at the cost of marginal aero gains. I could be wrong - haven't seen a bike review of that race yet.

I think for most triathlons, you're probably right. Non-technical courses on good roads, typically. But with the pure bike racing community turning a bit away from tarmac and towards rougher, more technical, race courses, comfort and braking will likely play an increasing role in pure speed. Just one that's harder to measure.

Regardless of whether you consider the peace of mind and comfort to BE marginal gains or to facilitate marginal gains isn't too important. The result will likely be the same, more speed.
That is, of course, assuming the aerodynamic losses are minor and the comfort improvement is significant. There's a balance to be achieved.

A rider who doesn't trust their brakes, or their skill with them, will be slower on a technical descent; and an uncomfortable rider will get progressively slower.
Has the idea that fast positions and equipment tend to be uncomfortable gotten twisted into the idea that discomfort is not detrimental to speed, or am I misunderstanding?