Miles2go

I don't know what pressure you run your tubulars at, but I start every ride with my tubeless tires at 60-65 psi, and that leaves room for increased pressure and no resulting problems.
It just happens that I (along with 4 others, 2 more with carbon rim brakes) descended over 12 miles and 4,000 feet with an average of 7% on Sunday with both brakes on very nearly 100% of the time.
I didn't die and my tire pressure didn't change, no fade, no overheat situation. Reason why we had to brake all the way down was because sudden variable high gusting tailwinds came up, and my average speed for that segment was 29.4 mph...with both brakes applied nearly 100% of the 12 mile descent. These wheels have 2 years of use on them at this point.

tomato coupe

I guess that depends on how you define "rim brakes let you down." I've never crashed because of rim brakes, but I've certainly had some really exciting moments when braking in wet conditions.

Miles2go

Oh, I could say the same if I think back to the days riding a bike with a lousy pads/brake surface combo, though I don't remember any really hairy situations. You could diminish a disc brake system too. My modern rim brake bikes have been great in the dry and wet. I guess I should add that I've never weighed more than 180 pounds, and currently hang out around 155lbs.

ls01

I use Reynolds pads. I have 2 sets of Reynolds and 3 sets of SuperTeam. They work well on both brands. I don't live in a hilly area but do go to Kentucky to ride once a year. Hasn't been a problem.

TheKillerPenguin

In the dry, my newest set of carbon race wheels somehow brake better than my aluminum training wheelset. I have also not encountered any sketchiness with heat buildup and have complete confidence in them on even the gnarliest downhills (though the mountains here only feature 3-4 mile descents tops, not sure how the santa monica mountains are). I say this as someone that has melted the epoxy and buckled a brake track on an older pair of carbon rims. Don't fear the reaper, modern carbon rims are fine.

SoSmellyAir

Can anyone else comment on the slight pulsing during initial braking which I experienced on my first ride? I read somewhere else (Trainer Road?) that this phenomenon is unavoidable on carbon fiber wheels because (1) a carbon fiber brake track surface is inherently grabbier and (2) a carbon fiber wheel, even if perfectly true, would have slight width variance around its perimeter because, unlike an alloy brake track, it cannot be further milled so that the thickness is perfectly even around its perimeter. These reasons make perfect sense to me, but I would like to know (a) what everyone's actual experience is, and (b) whether this phenomenon diminishes after I have used the wheels more.

ls01

yes, I can. I have had one front wheel fail and that was the symptom that presented before I stopped riding it. The brake lever actually started to pulse in my hand because the bed was beginning to separate. I also had another wheel blow apart due to manufacturers defect. The side wall blew out of the rim in the back of my truck on the way to a ride. It launched carbon Fibre confetti all over the back of my pick up.
Neither one crashed me.

SoSmellyAir

Oh, dear. I don't think mine is the same. The slight pulsing I described above only happens during initial braking (e.g., maybe the first two revolutions of the wheel after I apply the brakes) and goes away thereafter even I keep squeezing the brake lever. Also, I have only ridden 60 miles on these wheels, so I sure hope that no part is separating from any other part.

smashndash

A video is worth a million words. Do you have a textured brake track?

SoSmellyAir

Let me figure out how to take one while braking.

No, the brake tracks feel perfectly smooth underneath my fingertips.

ctak

My rule of thumb, as a 160-lb guy who averages 20-25k ft of climbing per week (10k miles last yr), has been to go with Dura Ace c24s (aluminum brake track with carbon laminate) on my rim brake climbing bike or my slightly heavier aero disc bike on rides with over 5k ft of elevation. Otherwise, spending a lot of time on a non-disc Roubaix with Mavic 40mm carbon hoops (DA 9000 calipers). Also have a set of deeper Roval clx carbon clinchers and Easton carbon tubulars.

I've used carbon clinchers on plenty of dry 5k+ days and they've been totally fine but, as another poster stated above, quality carbon pads aren't cheap and don't last as long. OTOH, if I was only ascending 10k elevation per week or weighed less, I'd exclusively move over the carbon clinchers.

Be sure to use the right pads with your rims. Mavic has an excellent new-ish grey compound pad for their textured TgMAX rims. Black Prince for the Rovals and Eastons, which can be a bit "grabby" at times but work great.

superdex

I descend Colorado mountains (not as steep, but a LOT longer, and I'm 84kg-ish) with LightBicycle carbon wheels and Swiss Stop Black Prince pads (on Campy Potenza brakes). Works great, and other than some squeal when I'm really clamping on them, I've had no issues. Like mentioned, stick with reputable brands and enjoy....

superdex

could be a slight out-of-true, and/or the pads are contacting at slightly different times (not quite centered)...?

SoSmellyAir

Ouch, $40 per pair, so $80 for a full set.

Many describe rim braking on carbon clinchers as grabby; maybe what I experienced as slight pulsing is just grabby to everyone else, because the brake levers are not pulsing.