waterrockets 

Only just starting? I would have thought they'd be doing that back in the 90s.



Great. Now I'm making speed buggy sounds and have spit spots all over my monitor.

botto 

bikes are tools, not jewels.

El Diablo Rojo

They can be both.

efficiency

Downhill mountain bikers are so far behind in understanding the importance of aerodynamics that they create a controversy over skinsuits. There was a big dust up between Rachel Atherton and Tracy Moseley that likely contributed to the UCI banning skinsuits for downhill.

https://www.bikeradar.com/racing/arti...mens-dh-18277/

https://www.bikeradar.com/news/articl...petition-19021

I'm waiting for the time when downhillers fully embrace aerodynamics. Hed can start building deep section downhill wheels again, skinsuits will be the norm, and positions will probably be narrower.

Quel

Curious. If something as small as a playdough fairing around the bb-brake made enough of a difference to clean up the wind off the front wheel, how do they account for the two rods holding up the front wheel? Wouldn't the wind coming off those affect some wheels differently than others in a way that may not be the same on the open road? That seems minor, but obviously the point of the wind tunnel is adding up lots of minor changes. Comes down to what you said that you can't find the "best", but just wondering if they do anything about that.

Racer Ex 

The supports are far enough from the bike that they don't interact. The front wheel in question is directly inline and close to the BB fairing.

Dalai

Thanks for the links. I was watching one of the World cup downhill races on TV just last week and couldn't understand why they were wearing large flapping clothing...

Dalai

I went in far less prepared than RacerEx (no field testing) just the bike and position that I thought was decent with the primary focus on position. Of my estimated 43 watt at 40 km/hr saving, only 10 watts was due to changing aero helmets.

Noting at the time my front end was a Vision Tech integrated setup (replaced this year with the UCI approved 3T Mistral Pro bars ) so couldn't change bar width etc. So 33 watts saving was just through 2cm spacer drop, shrugging and turtling...

Initial position



Final position

Cleave

Yes.

+1

However, what I meant was, "Where did I miss the demise of the Ridley Dean?"

rruff

I analyzed someone's wind tunnel (Texas A&M) data last year and concluded that... nothing could be concluded. The random scatter was >2% and there were not enough runs and repeats to determine anything with confidence.

Racer Ex 

It's still here and was tested along with the Kestrel. Kestrel, set up for me, was better.

The bike only runs were nearly identical. With me on the bike our bigger variances were in the 1% range, but mostly below that, and in some cases within a gram or three.

NateL got some of the pictures and commented that my overlay was nearly identical; pretty much what my tunnel guy also said. I've spent so much time on the TT bike that there's a lot of muscle memory there. With a lot of guys they aren't comfortable on the bike in the first place and fidget around a bunch. Tunnel can be pretty sensative to those seemingly small movements.

Quel

How'd you end up at the final position? You are sitting way farther back than most "conventional" TT positions. I was kind of expecting a big move forward from your first picture, but nothing changed there. Just a power/aero tradeoff?

Voodoo76

No socks used to be de rigueur on the track.

rruff

Ya... it seemed to be body position changes more than anything for the session I looked at. The instrumentation was good. Little things like how you hold your head can be big factors. Really have to keep your position consistent if you want to check for other variables.

What does your CdA work out to?

Dalai

Not sure what you mean by conventional TT position? Bike setup just fits within the UCI measures to which all levels of racing here in Australia must abide to - saddle tip the minimum 5cm behind the bottom bracket and the extensions right on maximum 75cm length allowed. It may look a little out of perspective as I'm just over 6 foot riding a 52cm P3?

To be consistent with the runs I am sitting square on the saddle but do drift naturally a little further forward onto the saddle tip when on the rivet. I have only fitted a wired SRM onto the TT bike in the last month, so can't say if there was a loss in power from the drop of spacers after my tunnel session. But my output from the two TT's just raced since fitting the PM is comparable with my road power output so I'm thinking my original position was just very conservative.

What the tunnel does show you is how very minor changes can make big impact to drag. When climbing on the aerobars, I tend to bring my hands further back on the extensions - this is only a minor change but increased my drag by a noticeable margin. So I'm not surprised to make the savings I did in the end mostly by shrugging and turtling. Just a matter of adapting to that position whilst racing...

Nate552

I'm sure I can guess whose test you are referring to as I was there helping and prepared the data. And you're right, consistent position was a factor. It was so slight it wasn't noticed until we created picture overlays later. But a baseline run was done towards the end and that confirmed the data was correct. And I do think some things could be determined from the testing. Ideally, you'd do repeat runs for everything, but $$$$ plays a factor

Racer Ex 

I keep certain numbers close to the vest but the improvement was substantial stacked on top of an already good number. I'm confident that going into Nats I've done my due diligence on the aero portion of the equation. Gotta get the motor in tune and the brain focused. I definitely think I have a shot at winning, but I have a lot of respect for some of the guys I'm going up against.

Nate552

Very true. This is critical, and obviously why some companies use dummies in the tunnel to check for small changes (the DZ dummy and Speedplays creepy half dummy come to mind). Looking at Ex's pics, his begin and end positions were incredibly consistent (minus the changes obviously).