Need Help Lowering CdA

[cruzKurt]

Two days in a row I am pushing pretty hard, hitting 19 mph over a 25-28 mile ride. Windsock says my CdA is .259 yesterday and .265 today. Seems to me if I could lower my CdA, I could pass that 20 mph barrier. Looking for ideas on what you have done to lower your CdA.

I am running Schwalbe Pro One Tubeless.

 

[Lief]

At those speeds air resistance and turbulence will be the biggest differences.
* no flappy clothing. Everything tight
* clean up the air behind you. Rear wheel cover is the biggest option in this pic.

If you can rotate those bullhorns forward and still be comfy, that’ll put your arms straighter and do a lot of good too.

 

[Andrew Wilson]

FWIW, I really didnt notice a measurable difference running a rear wheel cover. I had one for the SR State games and did back to back testing on a 10k course using speed and power meter. Looks cool though If you are still running the stock bars, you might look into something narrower with less flare. I run the Gary bars

Perfect handlebar for a V20

Since four or five months I'm owner of a V20. I started with the stock handlebar, which eases to learn to handle a Cruzbike (its my first MBB). But I didn't really like that handlebar, I didn't feel comfortable with the hand angle and it was not aero enough. I switched to a 400 mm Zipp course...

forum.cruzbike.com

 

[Jeffers]

I've gotten more aero by raising the front of my seat. But I don't know how feasible that is on a Vendetta.

 

[Frito Bandito]

Every thing you can do is going to be "Marginal gains" now. Bars, as was mentioned to get the brifters from poking up. Turning the bars so they sit level and similar to how they sit on a road bike is what I would do first.

Moose pack, or cover the area it sits so less air will hit the the top of the wheel where the spokes are rotating forward.

Those Boyd wheels are nice, but there are faster options. Cheapest is Monokoting at least the rear, and if you aren't afraid of side winds, might as well Monokote the front too. Not many people want to fork out money for new wheels, but doing so is 1 of the first thing riders do to save a few watts. Schwalbe Pro One Tubeless are very good tires, but you can probably save a few more watts by switching to GP5000 tubeless in the same size.

I'd probably have the bottle in the front of the Race Case as opposed to the rear as long as it doesn't touch your helmet. Speaking of helmets, what do you currently have and does it have a lense?

Riding position. My elbows tend to stick out when I am not focused as well as I should be, so you may want to check that also. Lief mentioned clothes, and I'll second that. No loose clothing. I even tuck my sleeves into my gloves, use a rubber band to keep them from billowing, or pull them up a little until they are tight so they don't act like a parachute.

 

[cruzKurt]

Speaking of helmets, what do you currently have and does it have a lense?

I do not have a good helmet and no lens. What type of helmet is recommended?

 

[Frito Bandito]

There are plenty of good ones, Giro Air Attack, the Oakley Aero 7, Jeffer's helmet looks alright, Cairbull, Casco, I have a Limar 007 with several different types of lenses I put magnets on, but the Limar Speed King covers the ears a bit better which I have 1 of those in Texas that will be used unless I wind up buying the Icaro Nero Hero.

Cycling | Casco Helme

Bike Helmets, Eyewear and Accessories, SPEEDairo 2, SPEEDtime, Warp Sprint

casco-helme.de

Icaro helmet NeroHero

 

[ratz]

As the other said;

1. close the triangle up under the seat,
2. get the brifters lower,
3. If you are tall enough for that long chainstay then you might need more volume behind your shoulders to get the turbulence down
4. Lower the tire pressure if you can

That all said; If you have the medium chainstay, you might want to test that we've see people because less aero if they are too small of the long chain stay.

If you still aren't breaking 19 with ease we we can talk about looking at you training and riding data; it could be as simple as needing 8 weeks of purely aerobic riding to rebuild your base; it's truly possible to ride daily and slightly too hard and thus make yourself slow.

 

[DavidCH]

I was thinking about this all day. I have a number of helmets but it all depends where that air flow goes behind me. It was mentioned in another thread something that got me thinking...

I get a big box of sand and make an upside down impression of a fender that I want to extend my neck rest and to be a hanger for a bladder.

Plaster of Paris... wait for it to set and then get the carbon cloth out and epoxy and start my winter project.

 

[DavidCH]

There are plenty of good ones, Giro Air Attack, the Oakley Aero 7, Jeffer's helmet looks alright, Cairbull, Casco, I have a Limar 007 with several different types of lenses I put magnets on, but the Limar Speed King covers the ears a bit better which I have 1 of those in Texas that will be used unless I wind up buying the Icaro Nero Hero.

Cycling | Casco Helme

Bike Helmets, Eyewear and Accessories, SPEEDairo 2, SPEEDtime, Warp Sprint

casco-helme.de

Icaro helmet NeroHero

View attachment 16155
View attachment 16156

That last one looks like 400g plus... how heavy is it?

 

[Frito Bandito]

That last one looks like 400g plus... how heavy is it?

Yeah, it is heavy David. Icaro quotes as 790g. What I like about it are the better crash protection (EN 966 flight rated), full UV protection on the lense with anti-fog and anti-scratch, and it comes with pads of various sizes to get a precise fit. I am no aerodynamicist, but that back end looks pretty aero. I tested it on my V20, and while it seems like overkill, it didn't interfere with my neck rest. I didn't buy the 1 in the pic because that specific helmet is an "Asian fit" meaning it is more round than oval, so I couldn't get it to sit lower because the pointy end of my head was digging into the helmet. However, I like the transition between my hydration bag and the bottom of the helmet seems pretty nice. Additionally, the design of the helmet leaves a huge unobstructed view, perfect for a V20.

 

[vosadrian]

Your bike looks pretty good to me. But if you are running stock bars, you need narrower lower bars. I hit CdA much lower than what you are getting with traditional drop bars (with a little flare) with the bars much lower (curved slider) than your and just wide enough to fit my upper legs between them. I hit CdA on mywindsock of around 0.17 average.

 

[-don1]

have a look at the 'standard' handlebar setup and Larry's set up, nice level arm extension

 

[-don1]

look at what you're wearing... no wrinkles, TT gloves race spec jersey......

 

[DavidCH]

have a look at the 'standard' handlebar setup and Larry's set up, nice level arm extension

That's an unusual photo of Larry. I don't see his glasses and he's lost his disc wheel. Where was it taken?

 

[LarryOz]

That's an unusual photo of Larry. I don't see his glasses and he's lost his disc wheel. Where was it taken?

haha - yes, this was no doubt the last few days of the BRAG 2022. I mounted my T50E wheel to the back of my V20. This was to "assure" I rode the last few days easy, as the very next day after BRAG I was to attempt a 100 Mile record in Savannah. You can see the battery pack strapped to the botom on the frame. It was a lot of fun and the battery lasted the entire day. I still pedaled but maybe only 100W or less.
Here is my report on that record attempt: https://ultracycling.com/record/larry-oslund-100-mile-road-record-recumbent-2022-06-12/

 

[cruzKurt]

I experimented with arm position today while I was riding and I can definitely see how getting my arms straighter will be a huge help. I am shifting to a 1x12 SRAM eTap sometime in the near future and will be able to experiment with handlebars after that. The microshift levers hit my thighs on my current handlebars, so I have to keep them rotated like they are.

Thanks everyone and I will update this thread when I get some more data.

 

[DavidCH]

(The tradeoff with straight arms I found was tendernitus which I had for 2 seasons), if you go this route, try not to strain /sprint uphill.

This week I had a great ride and came to a roundabout junction. There were 2 road bikes at the roundabout and I slotted in between them. The first one took off like a rocket but the second one tried to draught off me. No matter what I tried I could only hit 34kph which wasn't enough to catch the guy in-front, but the person behind me blew up. Even with slightly bent elbows you can still go reasonably fast.

 

[vosadrian]

There seems some debate between V20 riders as to whether straight and high arms are quicker than low (and bent arms). I chose to follow the Larry approach which is well proven as I am not sure there are any V20 riders hitting the CdA numbers he achieves. This is my setup, and I also hit very low CdA numbers (though not as low as Larry). My bar width is such that my legs brush about 5mm from my fingers and about 5mm from the horizontal bar, so about as low as I can manage without interference:

 

[cruzKurt]

There seems some debate between V20 riders as to whether straight and high arms are quicker than low (and bent arms). I chose to follow the Larry approach which is well proven as I am not sure there are any V20 riders hitting the CdA numbers he achieves. This is my setup, and I also hit very low CdA numbers (though not as low as Larry). My bar width is such that my legs brush about 5mm from my fingers and about 5mm from the horizontal bar, so about as low as I can manage without interference:

What kind of helmet is that, pretty snazzy looking.