Pretty compelling data and setup. Used TriRig front brake, etc., standard disc equipment, and no obvious holes in the experiment design other than it’s not an “independent” test. Cannondale, as indicated by previous statements, pretty clearly wants disc brakes to work on aero bikes.
other than it’s not an “independent” test. Cannondale, as indicated by previous statements, pretty clearly wants disc brakes to work on aero bikes.
That’s the rub.
So even if it turns out the disc brakes are aero neutral to rim brakes in an independent test, is that reason enough to upgrade wheels and frames?
Not for me.
other than it’s not an “independent” test. Cannondale, as indicated by previous statements, pretty clearly wants disc brakes to work on aero bikes.
That’s the rub.
So even if it turns out the disc brakes are aero neutral to rim brakes in an independent test, is that reason enough to upgrade wheels and frames?
Not for me.
It might be for me. This past weekend I ended up in the middle of an intersection because I forgot to swap out the pads on my TriRig-front/under-BB rear brakes. Had my carbon-surface pads in with aluminum training wheels. And I learned that it really matters. Just one of lots of little annoyances with my TT brakes. Yes, that’s partially my fault for having two different rim brake surfaces.
And I tried out the Cervelo P5x and the brakes are a dream.
So I’ll consider disc brakes if other tests corroborate this. Specialized has indicated similar results. (And let’s face it, the Venge ViAS proprietary rim brakes have all kinds of problems). And the TriRig Omega, while a nice product, doesn’t hold a candle to a Dura-Ace 9000 rim brake. Just doesn’t.
and no obvious holes in the experiment design other than it’s not an “independent” test.
All runs were conducted with a bicycle only. The same wheelset was used in both configurations; however, rotors were removed for the rim brake test.
Some will see this as a pretty big “hole”…that is not an “optimized” wheelset for the rim brake variation (i.e. non-radial lacing on the front wheel, less aero hub for attaching the rotor, etc).
You can argue the “right” way to test stuff until the cows come home…optimized set-up for each vs. keeping all variables to a minimum. Don’t think there is a “right” answer personally…i can see merits on both sides.
If you do, get some rotor shims to put the rotor in same spot on both your training and race wheels. Otherwise you have to realign your brakes when you swap wheels, far bigger PITA than swapping rim brake pads.
Did anyone else notice the lack of cables? Seems like that may be important
If you do, get some rotor shims to put the rotor in same spot on both your training and race wheels. Otherwise you have to realign your brakes when you swap wheels, far bigger PITA than swapping rim brake pads.
If I buy, say, HED Ardenne/Jet disc wheels at the same time (or the equivalent Zipp/Enve, etc) , shouldn’t the alignment on those be the same?
Also you’ve never changed the rear pads on my Felt DA. I have yet to do it without profanity. 
Did anyone else notice the lack of cables? Seems like that may be important
Hmm…yeah, if they skipped cabling for convenience, they should have mention that. However I would speculate that the hydraulic lines for the disc brakes could be made aero neutral on a frame designed for discs.
Pretty standard when doing a lot of tunnel testing. I guess it would have been better to have two identical bikes in there all cabled up. Seems like these were prototypes and time and money adds up very quickly. With the level of integration in today’s bike I’m guessing it would be pretty much a wash.
I do agree with a post above that called out the wheels. Disc brake wheels generally have to be over built from the hub to the rim to counter brake torque. I think where we’ll see improvements is with rim shapes not being dependent on brake tracks. All that being said I’m not a fan of having disc brakes on TT bikes.
“if they skipped cabling for convenience, they should have mention that.”
they did. in an image caption i did not include. i suppose i should find someplace to make that note.
The rim brakes were tested with no cables; the disc brakes were tested with cables.
Always wanting more, now I would like to see aero data on different approaches to the disc design itself. Multi-spoke, curved spoke, star designs, tri-spoke, solid, bigger surface areas with less cooling holes, etc.
Pretty standard when doing a lot of tunnel testing. I guess it would have been better to have two identical bikes in there all cabled up. Seems like these were prototypes and time and money adds up very quickly. With the level of integration in today’s bike I’m guessing it would be pretty much a wash.
I do agree with a post above that called out the wheels. Disc brake wheels generally have to be over built from the hub to the rim to counter brake torque. I think where we’ll see improvements is with rim shapes not being dependent on brake tracks. All that being said I’m not a fan of having disc brakes on TT bikes.
Smaller head tubes and forks too.
" The results show that disc brakes do not necessarily result in an increase in drag."
Cool… seems more like a ‘if you buy them you’re not sacrificing much… maybe… under some conditions… that don’t really apply to you…’
I understand the value of a disc brake, I really do. I have them on my commuter and mountain bikes and can name more than a couple of times its kept me from being under a bus or in a tree. That said, in the years (decades) of riding a road bike and/ triathlon bikes I can think of only one time when I would have liked a disc brake, one. I for one will not be rushing out and making the switch. Will I eventually (in years) be riding a bike with disc brakes? Sure.
Assuming for a moment that disc brakes are aerodynamically neutral to a rim brake and understanding that bicycle manufactures want to sell whole bikes I’d like to see manufactures offer an option for people to update their front end with a disc brake, or sell new bikes with a split brake system. I feel that this both offers manufactures something to ‘sell’, kit for people to geek out over, an advanced braking system and saves people from buying a completely new bikes/wheelset(s).
I’m sure its wishful thinking, but seems like a reasonable ‘solution’ to this ‘problem’.
Dan, I’m curious as to why manufacturers of bike frames and wheels have just figured out now that Disc are faster? Its puzzling that they have spent so much time and money in the wind tunnels for years that they just now figured out that Disc are faster. Can you share your thoughts on this?
Thanks,
Rex
other than it’s not an “independent” test. Cannondale, as indicated by previous statements, pretty clearly wants disc brakes to work on aero bikes.
That’s the rub.
So even if it turns out the disc brakes are aero neutral to rim brakes in an independent test, is that reason enough to upgrade wheels anNot for you maybe, but there will always be people who are new to the sport who may well prefer the added stopping power that disc brakes give over rim brakes.
Similarly, people like me who will be looking to upgrade within the next 18months may also like the same. Especially if as it seems with this test that there is little to no aero difference.
Pretty standard when doing a lot of tunnel testing. I guess it would have been better to have two identical bikes in there all cabled up. Seems like these were prototypes and time and money adds up very quickly. With the level of integration in today’s bike I’m guessing it would be pretty much a wash.
I do agree with a post above that called out the wheels. Disc brake wheels generally have to be over built from the hub to the rim to counter brake torque. I think where we’ll see improvements is with rim shapes not being dependent on brake tracks. All that being said I’m not a fan of having disc brakes on TT bikes.
Why aren’t you a fan? I’m genuinely interested?
I get the whole ‘need new race wheels’ argument. But if the overall result is a bike that is no slower but you get better stopping power what’s not to like?
I think we’re at the ‘discs may not be slower’ stage.
This is what I found interesting:
http://i64.tinypic.com/nnv6dj.jpg
IOW, the TriRig brake plus Shimano direct-mount brake under the bottom bracket added 0.0021, 0.0026, and 0.0026 m^2 of effective frontal area at +/- 5, +/-10, and +/- 10 deg of yaw, respectively.
By comparison, here’s what I found in my wind tunnel tests for the TriRig brake alone: 0.0014, 0.0011, and 0.0014 m^2 of effective frontal area at +/- 5, +/-10, and +/- 10 deg of yaw, respectively.
Given the differing test conditions, these results seem to match up rather well.
“I’m curious as to why manufacturers of bike frames and wheels have just figured out now that Disc are faster?”
i’ll take my best crack at it. there were a number of problems leading up to this:
-
no hydraulic pursuit levers and we still have this problem, except it’s easier now with eTAP because you don’t need an integrated shift/brake pursuit lever for hydraulic brakes.
-
flat mount made it much more likely you could create a reasonably aero disk brake caliper.
-
a lot of people just assumed discs were slower.
-
nobody wanted to be first.
but i ALWAYS thought they were viable! and said so. here. but then again i’m just an ignorant slut!
Hello Damon,
Allthough you were not the author of the article thank you for posting. Since i always read the ‘aerodynamics issues’ discussions with some feelings that some maybe even most people are overreacting. More in the sense that for example in this case on a given course with drag throughout the bike leg in neg and pos yaw how much actual time will be gained or lost on an ironman bike leg. I know, each course will have different circumstances but i just wonder how much time difference we are talking about between rim versus disc brakes if we should take both cdale bike set ups from the main article on let’s say the Kona bike leg?
Regards,
Jeroen