One interesting side effect I have noticed:

Whatever sort of interaction between spokes, rim, and frame cause wheels to rub the rear brake under power: the reverse will make them rub when the brake is mounted down below.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

I refuse to buy a road bike with chainstay mounted brakes.

Can you elaborate on why you've reached that conclusion? Are you also going to avoid disc brakes?

-SD

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https://www.kickstarter.com/...bike-for-the-new-era

I tend to avoid road bikes with chainstay brakes, though it wouldn't be a total deal breaker, reason being that it is so common you check to make sure brakes are adjusted well before a ride and I Don't want to have to flip the bike over to make adjustments or see how close they are. Also problematic if you grab a neutral wheel in a race.

The aero benefit seems to be so small, I'm guessing, ~2 to ~3 seconds per 40k at best? That not worth it on a road bike.

Disc on the other hand, more like 60-90 seconds per 40k kind of penalty, for no real advantage to me.

more neutral wheel problems. I hope disc road goes away.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Kind of agree, but don't exactly understand your sentence. Is it more, 'when standard rear brakes rub (such as when standing or sprinting), chainstay mounted brakes rub even more'? Or something else?

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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It is more like, when wheel doesn't rub on a regular brake, it might on chainstay brake.

When it does rub on a regular brake, probably still rub on a chainstay brake.

I've spent hours staring at a zipp 404 rubbing a trek madone rear brake.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Not an owner of a bike with chain stay mounted brakes... While not a deal-breaker, I'd definitely try to avoid them. I end up fiddling with my brakes often enough (though really not that often) that I'd really find it a hassle to have chain stay mounted ones. If i had a bike with those brakes, I'ld probably leave them wide open and grumble every time I use them. I have zero interest in road discs.

jackmott answered it nicely. And ease of maintenance too.

Road disc needs to die an early death. I swear the only reason they exist is because wheel designers hate having to design around a brake track.

I have the Bontragers on my Madone 5.2. Only about 600 miles so far, but some pretty crappy roads. No problems so far. I read about how they were so difficult to adjust. I just followed the instructions and bingo, 5 min later I was done. IF I was planning on riding this bike in the rain and on muddy roads a lot it might be different, not sure.

I love the rear brake on the AR; it is fantastic. Easy to adjust and manipulate, good power and modulation (same as their "regular" brake). The only thing I don't like is the inline "quick release" up by the stem. In fact, I just removed it. Adjust the caliper width using the cable itself.

I have not tried shimano direct mount brakes, but have tried a few bikes with chainstay-mounted (TRP and clones) brakes. I was not impressed with the braking action or feel. While there is little doubt that shimano brakes are likely effective, the under BB mounting location is not ideal (for maintenance, for road grit accumulation, for brake pad rubbing, for quick visual inspections, for on-bike adjustment, etc.). Also, the proprietary mounts (to shimano specs) really limit brake changes and upgrade options.

It seems like regular cable-actuated brake technology could progress much further to create far more aero and more powerful calipers (I am a fan of the classic eebrakes, they seem to be far far more advanced than almost anything else out there). Focusing on these kind of improvements on traditional brake calipers would make any aero advantage of under BB brakes essentially zero, and but with no performance losses, and all the benefits of the traditional brake locations.

Greg @ dsw

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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None of these are issues on the AR + Shimano brakeset.

Good to know. Haven't tried that set up.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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Hear, hear!

Kind of curious, how would you do an on-bike adjustment on your rear brake while riding?

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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I have about 2000 miles on my first bike with chain stay mounted brakes (Trek Madone). I can't say I was excited about them, but, that is the way the bike came. If anything, I was concerned going in about them. But so far have had no issues. The release mechanism and barrel adjuster are up front where the cable goes into the downtube so adjustment and opening them up to change wheels is not an issue. It easier actually. They're direct mount so they don't get knocked out of line and rub but, if for some reason I did tweek a wheel and have to open them up while riding it would actually be easier to do on the move now with the release up front. I thought they would get dirtier down there and that would affect performance but that does not seem to be an issue in practice. The braking performance is fine.

After riding with them a bit, I don't hate anything about them but things I have a negative feeling about are that you do have to bend over and make a point of looking at the pads if you want to check wear and I have not changed the pads yet but it does look like that will be mildly more difficult due to the location.

A big negative for me is that I can not run a Stages power meter since on my particular bike the brake will cross paths with the pod on the crank. I fear that may also be the case with some of the cheaper new power meters coming down the pike. That frankly is my biggest beef. These brakes are going to cost me several hundred bucks for a more expensive power meter.

Well, I guess if I wanted to do something I've never had to do ever in all my years of riding I'd rely on an inline barrel adjuster.

Ok that is a good point about direct mount not being able to get bumped out of alignment. I had not considered that.

Direct mount + some sort of remote QR/adjustment mechanism would allay most of my concerns.

Not being able to run Stages also a plus. =)

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

And you can get your eecycleworks upgrade, too on the AR!



-SD

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https://www.kickstarter.com/...bike-for-the-new-era

How often have you checked your brakes and they've needed immediate attention that wouldn't have been revealed by grabbing the lever or just spinning the wheel and verifying function non-visually?
How often do you adjust the brakes without the bike in a repair stand?
2-3w @50kph seems a reasonable estimate but the advantages are beyond the aerodynamic boost. There are structural requirements to mounting calipers that can be eliminated on the seat stays but do not need to be added to the chainstays because they already handle the bulk of the drivetrain loads.

As for the wheel rub, if you think about the deflection of the wheel as a result of twist a chainstay brake is more susceptible to this lack of wheel and frame stiffness because the chain tension is trying to pull the wheel forward on the drive side causing the deflection perpendicular to the vector to be greater the farther away from the chain/cassette. A caliper on the seat stays is closer to this axis so the deflection is less.

-SD

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https://www.kickstarter.com/...bike-for-the-new-era

Well if they are anything like the crappy Tektro brakes on my B12...no thanks. I have tried everything and they are just plain mushy. Not a huge issue on tri bike but for road bike i do sort of like the idea of braking. As for discs, bring them on as i have no issues there. Just make rims designed for them with lower weight and no brake track.

Unhappy with the braking power, hard to see if they are rubbing if you hit a bump and the wheel goes out of true, harder to adjust on a workstand.

The rear brake was already drafting the seat stays and seat tube, so these seem like a lot of negatives for very minor (is it even measurable?) aero gains.

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

This is why I'm generally not a fan of chain stay mounted brakes at all. Lots more movement between the frame and wheel in that area and I've yet to try a frame with this brake placement where I didn't need to open up the rear brake more than I'd like.

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BA coaching http://www.bjornandersson.se

Which bike did you ride that had a lack of braking power?
When you hit a bump and your wheel went out of true on your seat stay mounted bike, what did you experience and how was it remedied easier/quicker than if the brakes were on the chainstays?
The workstand position of the bike can be important but not "harder"; just rotate the frame fork down:


A well designed seat stay and seat tube doesn't leave enough "draft" for the caliper to fit into. Aerodynamic improvement is just one of the benefits. Structural flexibility is the greater gain IMO.

-SD