It depends on the disc but I use a Sigma Speed sensor and a magnet.(The SRM speed sensor is pretty much the same as this but more expensive in the Uk)

https://www.amazon.co.uk/...ROKL5A1OLE&psc=1

On my Aerocoach Disk have managed to fit a spoke magnet on one of the internal spokes just to the side of the opening for the valve.
Have just bought a Zipp900 to have as a spare and have ordered one of these with built in magnet.

https://www.racewaredirect.co/...ry/zipp-disc-covers/

Ahhh, I never considered using the valve hole sticker for a magnet. Or spoke just beside the hole.

Thanks.

How realistic you all feel it is for a hobbyist with “all” the go fast you can buy and the fit parts with using the sensor for testing to go below 0.200?

Totally realistic? Tough?

What about to 0.190?

I’m about to ditch weeknight run group for a few weeks and do testing. I have three “superhelmets” and million fit things on the list.

Realistic for sure. But it can be frustrating and a lot of work. Things that I've thought would be great test like crap and sometimes you find something that just shouldn't be good but is.
Still one of the fastest helmets for me is a Rudy Wingspan, and that helmet is almost universally panned on ST. (and for good reason if you look at the data on most folks)

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My Blog - http://leegoocrap.blogspot.com

If you are a medium-sized person, without super broad/manly shoulders, sub-0.2 it is totally do-able. I was listening to a Dan Bingham interview this week and he said his hour record CdA was right at 0.160. That is a difference of 20% or 40ish watts at 30 mph. If you can get your frontal area to be roughly equivalent, you can make some bad equipemnt choices and still not lose 40 watts. However, pretty much all of his equipment is stuff us schmoes and Joe-s can buy and you almost never hear of anyone coming out of a tunnel session with those kind of gains from swapping a good skinsuit or helment for an optimal one.

Sounds interesting

I did a Google search and found many of his interviews

Which one are you taking about?

Either the cycling Dane or Matt Stephens. What I thought was interesting was that he talked about what he needs to do for the hour record. It is 7 watts and it didn't sound like he thought he would get there on equipment improvements alone. That probably indicates where he thinks the floor is for CdA. Maybe 0.155 could be achieved with the next round of technology improvements, but no guarentees. He also said Ganna could break the record at a 0.2 CdA. Yikes.

He said the same on endurance innovation

I'd like to here him compare his track numbers to road. I did some work on some world champs files and while he is slippery I think there is a difference

Maybe MTM who is also very slippery and has road results could compare.

No way you will hold Dan's hour record position on the road.

I used to drag race pocket rocket cars. We could make 1.8L of displacement fly. I once got a 1.8L turbo VW engine to 500whp with a catalytic converter, muffler, and pass emissions without shennanigans. Maybe a wink and a 6 pack. Rev to 9000 rpm.

But…..big boys still ran more displacement. And big boys went faster.

I plan to run 5 to 7 pounds heavier this year as long as skinsuit fits. It is flat and watts matter.

So do you care to comment on your CdA estimates now that you have your fancy bars set up?

In rough numbers there's around 0.01 m2 between track and road. That's for me (though positions are not 100% equal), I think around the same for Dan, and around the same too from what I remember hearing from other people.

Thanks. I have very little data of track vs road with riders than know how to ride the track like you two.

I'd be curious on the difference in "effective CDA" on the road is vs their "tunnel CDA", ie when you don't have to steer, look, accelerate....If you spend a ton of time in the tunnel, get an optimal CDA, how close will you get that on the road ? I know for a few riders I've worked with it's "considerable". One more reason it makes sense for complement tunnel testing with road testing

Bars were to get fit coords I was tired of "hacking" together with a thousand shims or metal angles and weird stuff. I didn't do a before/after on exact fit dimensions as the install is long enough the field data would have been impossible to get by trying to assemble then trim things in a parking lot.

I have a list to test. This week looks good weather wise after work, so will be doing some stuff. I'll post up what I see there.

A didn't have the sensor with me at work the other day, but did a little lunch ride and my out/back "speed trap" averaged using the Aeroweenie calculator had me at 0.205 assuming a CRR of .0035 and that day's weather info. Seems about right. But I'll post a Notio figure after I do some laps.

I've been working on a little fun project I'll post up as a topic in forum later today. It's relevant. It's been too cold to ride outdoors and test so been indoors on Zwift and trying to "hack-a-day" on the bike.



I see all these Facebook time trial photo posts that make me just shake my head. I love folks trying and being collaborative, but there's a lot of both ignorant folks and outright trolls responding with bad info in there. Like, a dude posting up "go buy a Tempor" to a guy who explicitly said "this is for Ironman". That's like the last helmet I'd tell someone to go buy for that.

I say that as watching the video posted up even riding a trainer for 30 seconds they're looking up, down, up, down, stare at the front hub and hit a car, rock all over the place. Folks not realizing outdoors it isn't a track or tunnel where if you can see the black line and have ridden thousands of track laps, you'll be good but outdoors you have to look up (and ruin your aero). I've never ridden track, but imagine there is some muscle memory of holding the black line.

One hammer ride last year I let them leave and chased on the TT bike from a few minutes back. I needed a long TT workout but wanted to see teammates after the ride. I caught and passed the drop group as they headed back into town with sad faces but my one teammate was able to latch on. I asked him to watch me the next 5mi while I went at it all out to see if I moved or not. He said it was really still........excellente!!! That's important.

The amount of people who are trying pretzel positions, relying on FB comments to position themselves and listen to "experts" who don't have a clue what they are talking about is staggering.

This whole "fashion" of high hands and fancy extensions is the perfect example. I would say less than 2% of people spending hundreds if not thousands have not even tested if their position is faster.

And BTW, I don't see a trend of it improving. I am not convinced aero testing equipment will be big money maker.

Is there a theory why “low stack is faster, till it isn’t” can be true? Like what gets in the way of what?

Otherwise I am at like 10cm rise to hands and modest reach, not laid out.

I had slammed the new setup in install just to see where I could go, down.

Today I ran a lot of Notio runs of that, then adding back about 40mm of stack.

No matter how I analyzed the laps, every indication was the higher stack was worth from .004 to .005 faster.

I haven’t tried “mega stack” yet, but I was surprised the lowest was slower.

I am not an expert in how air flow etc gets manipulated, etc. I'm more of a "let's measure this" guy, but here is my n=1

We have a grad student that did some video/image analysis. He developed tools for measurement of frontal area from video/pictures. What we saw was frontal area was not decreasing as expect by dropping stack. In an over simplistic example, imagine your shoulder line dropping but your head staying in the same place. An over simplification but you get the idea.

We also measure head position with sensors in the helmet. We only saw a significant drop when the person consciously did something measurable with his head and the head did not change as much as expected with stack drop.

I suspect this is part of the equation.


PS : with your device make sure your calibration is correct after cockpit changes. This can skew the numbers

I apply cal factor in Golden Cheetah selecting the relevant laps for each. I've been finding the "field cal" pretty much impossible to satisfy on the app during ride. Is that what you mean? Selecting the out/back laps in GC then "compute cal factor"? I did that.

Otherwise all I can figure is the lowest stack dams up the air from going under the arms but over the base bar and top tube of the bike. But raising stack provides a nicer little "hole" for it to flow freely.

Today is helmets and 9+ vs. open mold Revolver trispoke. Tempor, Aerohead, Aeroswitch. IMO an easier test as I don't have to fuck with a bunch of little parts while sweating in my bike clothes beside the road to reassemble the cockpit.

Do you see consistency in your calibration numbers ?

Do you see them changing in a consistent way as you change your stack ?

When comparing numbers you have to have strong confidence in that calibration number which means consistency.

If you do a run and get a 1.38 then change nothing and get a 1.37 you cannot compare the two numbers if you use different factors.

I think you have kind of answered your own question with some of your previous comments. Given that you value actually seeing where you are going, realize that to maintain the same field of view, your head has to stay up while your body drops. So not only are you not realizing the drop in A you thought you were getting, you are raising the wings of the Tempor above their intended position of shielding your shoulders, which would likely result in an increase in Cd.

Now if you pulled on a old Kask Bambino and stared at your top tube, I bet you would see your CdA drop as you lowered the stack.

The one suggestion I would give you is to see what stack height does to your FTP. I hit a point where my sustained power output drops by about 20 watts and the power comes back up with an increase in pad height by about 5mm (I.e., a super narrow window of optimum aero and power output). Maybe the drop would be less dramatic if I changed around some other fit parameters like crank length, but it is a good example of how optimizing aerodynamics without considering the effect on power output can make you slower.

Different days and roads the factor may change, but same day same road and doing a test of things I do not see it change. It stays.

Today I pit the Aerohead, Aeroswitch, and Tempor against each other at the modestly higher stack. Number crunch tonight.

One way or another, the power drop off would matter with the lowest stack. As I'm slow enough versus a "pro" that if a pro loses 5w or 7w of power from stack height hip angle stuff, that's 5w out of 400w+. 5w for me is out of like 280. So more difference.

I feel like the lowest stack also isn't good as looking at a photo of it, it doesn't seem to get me any favors in a side view of my frontal area and my chest/back at all. Like, the higher stack is "already low enough".

Thoughts on those helmets:
-Aerohead has less visibility with that little point between your eyes but with such a giant visor than I would have assumed. I like it as a helmet, but didn't find wearing it life changing at all. I'll change my mind if the data favors it. Road/wind noise with it was average I would say.
-Aeroswitch has better visibility due to how the helmet cocks back to your back and you've got that whole visor. I didn't care for the wonky optics closer to the road in front of you versus further down road. Road noise was highest of the three. Felt quality, liked wearing it. Maybe a bit warm/snug on the ears for a summer lid.
-Tempor, neutral visibility. Again, since it is cocked back you can see where you want. By far quietest to the point you don't really have a sense of how fast you're going or not versus the other two. Other two you can kind of hear the wind noise enough changing it you could kind of gauge your air speed.

Overall, all sat fine for the fit. Sun on this road this time of day is "just so" that on the outbound test leg you can without moving your head see out of your side eye a shadow of your position.

I may have to do the same helmet test again another day as today would have qualified as "high yaw". I would be shocked if today the Tempor still did well at all. Not really a day for that lid.

So your saying lower doesn't seem to improve frontal area ? If so, that is exactly what we measured.

1. tempor
2. Aeroswitch
3. Aerohead

Very surprised a windy day yielded that. I totally thought Aerohead would win in the “at higher yaw” windy day testing.

The cal factors rock steady, the Aerohead lost pretty measurable. I did a good job holding speed/watts fairly. Lap times were money.

The Aeroswitch lost but just some. The Aerohead really disappointed me. Good, but like not remotely close to the others.

Revolver won. But pretty close to the 9+ on windy day higher yaw.

I will repeat these tests on a still day. For posterity. As I bet the results stick but get worse on a still day.

I just can’t ride at 95 to 100% for 100 min in a day. So couldnt ride hard enough to cut the yaw down.

Choice now is what to keep.

Tempor to race and Aeroswitch for funsies probably.

What was the difference in watts between the 3?

Watts depend on what speed you're personally going.

For me the CdA difference POC to Aeroswitch was .007 to .009 (depending on tossing statistical outliers of lap data). The POC to the Giro was more like the Giro being .014 to .016 slower.

Again, that could be a small amount at a slow riding speed making the difference for someone in longer events like triathlon largely irrelevant. OR if you're doing just 3km or 4km individual pursuit.......the watt delta could start to grow into a fairly meaningful amount.

You'd have to plug those deltas into an online calculator with your desired speed and CdA to see what happens.

Aeroweenie's calc at 25mph the best to worst is about 13w, the middle was 7w. I time trial a 10 excluding the u-turn at about 28mph..........so more loss.

I already owned the POC. So really just proved to myself something to not LOSE. Not really a gain at all.

Then again, not sure how relevant 28mph or even 25mph is for someone that isn't a pro or really quick amateur triathlete. As you're largely in Z2 or Z3 bike power for those, not Z4 and low Z5. So it's almost an order of magnitude different scenario.

So interesting

You have really gotten into this congratulations

Thank you for taking the time to post such a detailed answer