My $0.02: I think custom and semi-custom frames will be far more disruptive to the bike industry than disc brakes. There are a lot of interesting concept floating around out there such as Bastion Cycles carbon/titanium concept below. There's nothing stopping them from making an aero bike using this approach. If they were to make such a bike in large volumes they could have a mandrel made to filament wind the tubes and then simply cut them to length (I'm sure there's a way you could work around the seat tube cutout). Could you imagine going in for a Retul-like fit and then having a bike with geometry that's specifically optimized for you show up a week later in whatever color and with whatever components you want? LBSs wouldn't have to carry inventory other than example frames and replacements for wear/tear items.

Depends on the application...still.

If I was buying a TT/Tri or road racing bike, and my concern was the fastest setup possible? No way I'd buy a (separate braking) disc equipped bike.

However, if it was something I might want to throw some 30mm+ tires on and do some off-pavement exploring on? Disc might be the best solution...

Besides, if you're commenting on my "lack of choice" statement above, the point isn't about not being able to choose to keep what I have...the point is having a smaller (or no) selection to choose from if I'm looking for something new. There's a difference.

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This is not really a 'tipping point'. More of a 'we're holding your head underwater until you comply' point.

87% of OEM sales.
Onlly 13% of afternarket.

All that shows is that retailers/shops are not putting rim-brake bikes on the sales floor.
The consumer doesn't really have a choice, so duh, obviously disc sales will dominate.
We already knew this.

IMO, the more telling stat is that folks who already own functional bikes don't really want this sh*t.
(13% are curious, lemmings, or are building-up a gravel bike.)

Heck..I know someone who had a custom aero road bike made out of steel...using "off the shelf" tubing, no less.

Ended up arguably faster than a 1st gen Venge and nearly as fast as a Venge Vias ;-)

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...and they all can't figure out why sales have been so bad over the past few years :-/

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Actually...to be fair, I'm sure a big part of the low aftermarket %-age is because the stuff isn't backwards compatible to the vast majority of existing bikes.

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I’ve NEVER had to true a rotor on a mountain bike or my cross bike....ever. Not saying they can’t get bent, but I think that’s pretty remote. Now I do agree there will or can be some fiddling. My cross bike brakes do get to tinging at times.

They make shims for this.

It's a lot like cassette position variations between wheels.

Also, like 98% of existing bikes are no disc bikes, so of course the aftermarket will not reflect the same % as the new market.

I have...so, we cancel each other out ;-)

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Isn't that what I said?

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I've had to do it once or twice on my mountain bike, in about 2000 miles. It's always stick getting jammed in there somewhere. On the road, it should be a non issue.

No

I've done some pretty gnarly gravel on my aero road bike with 23C Conti 4000S tires but it beat the hell out of me.
I have been looking at a new aero road with hydraulic disc purely so I have an "all road" bike.

This is a tipping point -- in the same way the Coke "Zero Sugar" has absolutely dominated Coke Zero recently.

Hell, I can't even find Coke Zero on the shelves anymore.... The consumer has spoken!

Hmmm...OK :-/

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However, a huge percentage of OEM rim brake spec on SRAM and Shimano equipped bikes, especially the lower and mid range, is from Tektro and Promax...

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"I'm thinking of a number between 1 and 10, and I don't know why!"

You can run ~28mm tires with most conventional, dual-pivot road brakes. You can run up to 40mm tires with road/cx linear pulls (TRP CX-8.4, CX-9, Tektro RX5, Paul's Mini-V, etc.), most of which have excellent braking performance when set up properly. Rim brakes aren't keeping you from running bigger tires on an all-road bike. Did I mention they're also lighter, (generally) cheaper, easier to set up and maintain?

The brakes may not be, but an older frame probably is.

I wonder if this means it's only a matter of time before UCI allows disc brakes for all road racing.

I'm not in a hurry to replace my ar5 but my next bike will more than likely have disc brakes. Or I just keep the felt for a handful of UCI races a year.

Tire clearance is definitely not something that (road) frame designers have been focused on in the last couple decades, since most people were using tires no bigger than 25mm until the last few years.

Good point.

Yup...lack of clearance on road frames is a fairly recent issue. My '86 Bianchi steel frame (and brakes!) can easily accommodate tires measuring ~28mm+ wide.

It's funny...but all the current road brakes which everyone complains can't fit 28mm wide tires are known as "short reach". Older "standard reach" calipers can easily clear that.

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The only time I've knocked a rotor out of true was when I ran over my front wheel with my car.

There seem to be two distinct sets of experiences with rotors coming out of true, those who have it happen routinely, and those who don't. I think there are some rotors that are untrue out of the box, or that develop a small problem under hard usage due to the heating up and cooling that happens (and often being used while they're hot). Like a poorly built wheel that comes out of true just with the normal stress of riding.

Also, hydro calipers have very little pad clearance, even less than mechanical calipers from what I can tell. That's going to make any tiny 1-2mm bend in the rotor result in rubbing.

So if you combine a hydro caliper with cheap rotors that are prone to bend under normal usage, you get a fairly high maintenance braking system. These are the things that I expect will be improved upon in the next several years as the road disc brake systems get more refined and user friendly. Who remembers trying to center road calipers (rim brake) in the days before Shimano dual-pivots? Huge PITA, and you'd still get rub from time to time. Eventually the components got more user friendly. Disc brake systems probably will as well.