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Rim brake vs Disc Brake Aero test.

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Rim brake vs Disc Brake Aero test.

Old 12-09-14, 11:48 PM
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Rim brake vs Disc Brake Aero test.

Well, for all those opposed to disc brake road bikes on aero grounds here is some wind tunnel data.

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Old 12-10-14, 12:06 AM
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Here are the problems I see with this test:

1. They only went to 10 degrees yaw.

2. They only tested the side with the disc.

For #1 I think it would have been more useful to go to 20 degrees yaw and give a fuller picture. Maybe that will come later.

For #2 what happens if the wind is coming from the side of the bike without the disc? Is there any difference? I think we then need to SPLIT those numbers as wind can come from both sides of the bike, non?

The take away, for me, is that disc brakes matter far, far less than even my most optimistic expectations and it will only improve. I would also like to see the actual numbers.
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Old 12-10-14, 12:17 AM
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If he had the caliper's QR closed the difference would then be a whopping 10 seconds.
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Old 12-10-14, 12:22 AM
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Originally Posted by hairnet View Post
If he had the caliper's QR closed the difference would then be a whopping 10 seconds.
Yeah, I saw that. Weird, non?
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Old 12-10-14, 01:50 AM
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It looks like the test with rim brakes the riders legs were unshaven....
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Old 12-10-14, 05:06 AM
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I wonder what aero-optimized rim brakes look like in comparison, those integrated/shrouded type as on the Cervelo P5, or rear fork mounted type like on Argon18 Nitrogen. I'd think those are where the aero magic happens.
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Old 12-10-14, 05:16 AM
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Originally Posted by chaadster View Post
I wonder what aero-optimized rim brakes look like in comparison, those integrated/shrouded type as on the Cervelo P5, or rear fork mounted type like on Argon18 Nitrogen. I'd think those are where the aero magic happens.
Those would be far preferable on a proper TT bike where discs would just be dumbarsed. It's always about the right tool for the job.
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Old 12-10-14, 06:19 AM
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Where are all those who blather about how horrible discs are now?

The weight penalty is evaporating and now the first real data on aero is in and this objection is withering, too.

PUNY MORTALS! Where are you now!?!
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Old 12-10-14, 06:53 AM
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Don't worry, soon someone will start doing aero tests without "people" on the bikes to magnify the differences.

The person pedaling is far too real world.
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Old 12-10-14, 06:55 AM
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Originally Posted by Bob Dopolina View Post
Where are all those who blather about how horrible discs are now?

The weight penalty is evaporating and now the first real data on aero is in and this objection is withering, too.

PUNY MORTALS! Where are you now!?!
My question is , is their a notable difference in ride/compliance comparing a optimally designed fork for each braking system. I would assume the disk fork has to be stiffer and possibly heavier?
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Old 12-10-14, 06:56 AM
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Originally Posted by Bob Dopolina View Post
Where are all those who blather about how horrible discs are now?

The weight penalty is evaporating and now the first real data on aero is in and this objection is withering, too.

PUNY MORTALS! Where are you now!?!
You're too worked up about discs. If you like them, get them. Those of us who you consider to be closed minded won't. Pretty simple.
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Old 12-10-14, 07:20 AM
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Originally Posted by Fred Smedley View Post
My question is , is their a notable difference in ride/compliance comparing a optimally designed fork for each braking system. I would assume the disk fork has to be stiffer and possibly heavier?
That's actually a really, really good question.

Certainly you have to strengthen the fork to address braking forces which, I think, would involve strengthening the back of the fork as well as the bridge, whereas the flex you want for compliance would be on the front of the fork (again, I think).

I do think this would be possible but it's early days and I think it would require a bit of experimentation to find the right balance. That may take a generation or two.

Thanks for this question. I'm going to file this away for any future development I hope to be involved in.
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Old 12-10-14, 07:31 AM
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Originally Posted by Lazyass View Post
You're too worked up about discs. If you like them, get them. Those of us who you consider to be closed minded won't. Pretty simple.
Oh come on. It's 2 for 1 margarita night at buddies pub and I have time to kill.

Worked up might be too strong a word but I am excited about this development. Other than the broader introduction of carbon as a material there hasn't been a significant product area open to real innovation in quite some time. Instead we've seen what amounts to incremental improvements for a decade or more.

Road discs have the potential to be an area of innovation so I am excited by the prospect.

If it ain't your cup o tea that's fine but I'm tired of people peeing in my cornflakes.
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Old 12-10-14, 07:48 AM
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Originally Posted by Bob Dopolina View Post
Oh come on. It's 2 for 1 margarita night at buddies pub and I have time to kill.

Worked up might be too strong a word but I am excited about this development. Other than the broader introduction of carbon as a material there hasn't been a significant product area open to real innovation in quite some time. Instead we've seen what amounts to incremental improvements for a decade or more.

Road discs have the potential to be an area of innovation so I am excited by the prospect.

If it ain't your cup o tea that's fine but I'm tired of people peeing in my cornflakes.
I hope discs on road bikes evolve nicely, but there is nothing wrong with pointing out the disadvantages as well as the advantages. And there are disadvantages. I know all about disc brakes, I've had them on mountain bikes. For me and many others, they're a solution to a problem we do not have on the road.
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Old 12-10-14, 07:59 AM
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This months Velo has a comparison of disc vs rim on two Tarmacs also. I believe they found about 8 watts difference at 20 degree yaw on the disc side with smaller differences everywhere else. Tried to find the article on the VeloNews website to link to it, but it may not be posted yet.

Last edited by TassR700; 12-10-14 at 08:00 AM. Reason: Typo
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Old 12-10-14, 08:04 AM
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Originally Posted by Lazyass View Post
I hope discs on road bikes evolve nicely, but there is nothing wrong with pointing out the disadvantages as well as the advantages. And there are disadvantages. I know all about disc brakes, I've had them on mountain bikes. For me and many others, they're a solution to a problem we do not have on the road.
That could be true for a lot of people. I hope it remains as a choice and not as a default spec as I think there are many situations where they aren't needed.

For me it does boil down to choice. I like choices (options). Depending on where you live and how you ride I think it would be great if this option was both available and evolved to maximized the benefits and eliminate the negatives for those for whom this choice made sense.

In all honestly (the margarita 2 for 1 is over so I'm on to draft...) for smaller players like us it's these niche areas where we can innovate and contend. If we can be first we have a shot. If we simply follow the big players we end up making equal or lesser "me too" products. Where's the fun in that?

I've embraced this OPTION because I see potential and because we have both ideas and manufacturing partners who are willing to work with us in this area.

Remember Gary Klein? How do you think he made his mark on the industry?
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Old 12-10-14, 08:05 AM
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Originally Posted by TassR700 View Post
This months Velo has a comparison of disc vs rim on two Tarmacs also. I believe they found about 8 watts difference at 20 degree yaw on the disc side with smaller differences everywhere else. Tried to find the article on the VeloNews website to link to it, but it may not be posted yet.
Please post it when you do. It really could move this conversation along.
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Old 12-10-14, 08:10 AM
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Originally Posted by Fred Smedley View Post
My question is , is their a notable difference in ride/compliance comparing a optimally designed fork for each braking system. I would assume the disk fork has to be stiffer and possibly heavier?
This maybe the reason I thought the Trek Domane 4 series with disks was dead feeling compared to the 4 series with caliper brakes when I test rode them.
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Old 12-10-14, 08:11 AM
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Originally Posted by Bob Dopolina View Post
the margarita 2 for 1 is over so I'm on to draft.
I'm glad to see you making good choices.
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Old 12-10-14, 08:11 AM
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Originally Posted by BigJeff View Post
Don't worry, soon someone will start doing aero tests without "people" on the bikes to magnify the differences.

The person pedaling is far too real world.
Yeah, and then they will TARE this and TARE that until it has no basis in reality at all...
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Old 12-10-14, 08:11 AM
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Originally Posted by RPK79 View Post
I'm glad to see you making good choices.
It's all about choices, baby.
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Old 12-10-14, 09:11 AM
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So the hottest topic in road cycling is about to fall off the first page? Sad.

What if we talked about asploding carbon disc brake wheel riders that waved or not?
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Old 12-10-14, 09:36 AM
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I'll go full in with discs when I can get carbon ceramic rotors. Just because they'd look dope.
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Old 12-10-14, 10:09 AM
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Originally Posted by chaadster View Post
I'll go full in with discs when I can get carbon ceramic rotors. Just because they'd look dope.
You can. There's a guy near me who is doing some. Been meaning to work with him on some setups...next season.
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Old 12-10-14, 10:11 AM
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Originally Posted by chaadster View Post
I'll go full in with discs when I can get carbon ceramic rotors. Just because they'd look dope.
Oh man, how I would love to get edjumacted enough to go there. That might be about 100 levels of overkill but it would be uber kewl.
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