That is a crapton faster than I go at similar power outputs. Like 2 MPH faster. I would kill to get that aero.

What was your average power? NP is a physiological number. But, average power relates to the physical work you performed.

Oh okay, I didn't realise that. Are you a similar weight to me?

My average power overall for the 4 laps was 246w.
Any ideas about whether a disc wheel would have a big impact?

Cheers

To many variables. My speed can be as high as 26 mph on a race course to as low as 22mph. I can tell you at 250w on a flat road with good road conditions I am going well over 25mph for 15 min. A disk gives you sail effect (this is debatable) so its most effective in a cross wind. If you are super concerned go get some testing done and then you can live with knowing you are making the right aerodynamic decisions.

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2024: Bevoman, Galveston, Alcatraz, Marble Falls, Santa Cruz

Define big. There’s lots of online data to give you these estimates (Flos site for one).

Thanks for your replies.

-Would love to get some testing done, however not readily available where I live, but will look into it.

-When I said 'big' impact, the question was more- how much of an impact would a disc have over a deep section rear wheel over a 40km?
I've just checked out Flo's website, thanks- I'll have a read around.

I am around 80 kg in race weight, so definitely a bit heavier. A disc makes a very big difference. My speed jumped a lot when I went from a 90mm rear to a disc. I did a couple other bike tweaks at the same time, so I cannot quantify the disc alone, but I got 30W faster (i.e. I rode the same speed on 30W less power).

I understand that is framing the issue....but that doesn’t answer the question of how much of an impact is “big” for you. 30”? 1’? 2’? You can find data to show you the time improvement you can expect to achieve with a disc, but no website can define (although they will try!) what is a “big” impact for you.

That is a big impact!! What other changes did you make to your bike at the time if you don't mind me asking?

Well by 'big' impact, I suppose even a minute at 40km is loads- as extrapolated equals quite big savings over middle and long distance triathlons.

I did look at the Flo website- I could only find their comparisons to a set of mavic open pro wheels. I'd be going from a pair of DT swiss ARC 1400. Though I do accept that it is difficult to quantify time savings.

I guess I'm in the market for a disc wheel!

Hard to answer the question without knowing your bike position, but yeah those numbers look reasonable for your weight. I am a bit lighter than you 63 kg, decent bike position and can average 40 kph on flat/easy rolling out-back TTs using about 215 -230 w (depends how windy it is)

If the air density was 1.2 kg/m^3, then at CdA=0.25 m^2 and at 40.02 kph = 11.12 m/s you'd need 0.5*1.2*0.25*11.12^3 W = 206 W to overcome air resistance in still air. Tack on about 25 W of rolling resistance for crr=0.003 and 1-2% drivetrain losses and you're still about 10 W below your recorded 246 W power output -- the headwind/tailwind combo probably accounts for those extra watts.
So, roughly speaking the BBS numbers for CdA pass the smell test and you probably are around 0.25 m^2.

I upgraded my wheels from 60/90 to 90/disc, lowered my cockpit 2 cm, and added a draft box to my frame (Felt IA). That netted at least 30W efficiency based on some same-course testing and nearly identical rides in a race. The cockpit was probably the biggest gain-- just a guess-- but the disc was part of the package.

-Thanks for that! Some nifty maths up your sleeve!

-Nice, I'm thinking of making quite a few changes, going to an 82mm front as well as disc wheel. Hopefully that will help things.

You can compare the Flo disc to the Flo 60 or Flo 45 to perhaps get a closer comparison.

https://3.bp.blogspot.com/...t%2B6.11.02%2BAM.png

Is this the table you're referring to?
Am I reading it right that they're saying there is around a 20-30 second saving over an ironman using a disc over a deep section rim?

Now that you have the info the only question is whether that is a big enough impact for you to spend the money. We can’t answer that question for you.

Sorry but 0.248 kind of sucks for 66kg, so either your position sucks or the assumptions they use in BBS don’t match your situation well. Air density, road surface and Crr are the first areas to looks the problems with what comes out of BBS. A floppy jersey could be costing you 15 watts, so next time wear a ski suit and just take a cell phone.

The upside is that if the estimate is accurate, you can be a ton faster with a better position.

On the biggest German triathlon forum there is a thread where people post exactly that what you did, see

https://www.triathlon-szene.de/...?t=32666&page=74

post #588:

BMI_Größe___Gewicht__Leistung___W/kg____Name@Geschw... (Angabe der Außentemperatur in °C)
17,8_1,71m___52 kg___210 W___ 4,0 W/kg___ sandrina-illes @ 40 km/h
17,8_1,71m___52 kg___242 W___ 4,7 W/kg___ kreuzotter @ 40 km/h
20,3_1,80m___66 kg___238 W___ 3,6 W/kg___ Arminatz @ 39,9 km/h
21,0_1,70m___61 kg___255 W___ 4,2 W/kg___ kreuzotter @ 40 km/h
21,0_1,73m___63 kg___245 W___ 3,9 W/kg___ aims @ 39,9km/h (11°C, +/-1% Steigung)
21,0_1,73m___63 kg___202 W___ 3,2 W/kg___ aims @ 40,0km/h 10m hinter Feld (22°C, flach, full aero)
21,0_1,75m___64 kg___ 261 W___ 4,1 W/kg___ kreuzotter @ 40 km/h
21,1_1,78m___67 kg___ 200 W___ 3,0 W/kg___ maximgold @ 40 km/h
21,0_1,83m___70 kg___ 268 W___ 3,8 W/kg___ kreuzotter @ 40 km/h
21,0_1,88m___74 kg___ 275 W___ 3,7 W/kg___ kreuzotter @ 40 km/h
21,0_1,85m___72 kg___ 283 W___ 3,9 W/kg___ kreuzotter @ 40 km/h
21,3_2,02m___87 kg___ 303 W___ 3,5 W/kg___ deirflu @ 40,2 km/h 1h Zeitfahren Straße
21,4_1,80m___69,5kg___210 W___ 3,02 W/kg___ be fast @ 40 km/h (2x1 km pendeln, avg. aus 5 Fahrten, 26° C)
21,5_1,74m___65 kg____243 W___ 3,74W/kg___ glaurung @41,3km/h;16,3km;71HM
21,5_1,74m___65 kg____212 W___ 3,25W/kg___ glaurung @40,3km/h; 16,6km;74HM
21,5_1,74m___65 kg____251 W___ 3,86W/kg___ glaurung @41kmH; 16,0km; 73HM
23,0_1,84m___78 kg____258 W___ 3,3 W/kg___ heshsesh @ 40,3 km/h (22°C, 16km, Full Aero Equip, Garmin Vector)
21,6_1,76m___67 kg____264 W___ 3,94 W/kg___ suze @ 40,4 km/h
21,6_1,83m___73 kg____253 W___ 3,5 W/kg___ michael skjoldborg @ 39,9 km/h
21,0_1,91m___77 kg____290 W___ 3,8 W/kg___ kreuzotter @ 40 km/h
21.8_1.83m___73 kg____221 W___ 3.0 W/kg___ Klugschnacker@40.0km/h__20.1km
21.8_1.83m___73 kg____227 W___ 3.1W/kg____ Klugschnacker@39.8km/h__20.1km
22,0_1,79m___72,8 kg___256 W___ 3,5 W/kg___ mumuku @ 39,7 km/h garmin vector
22,1_1,70m___63,8 kg___251 W___ 3,93W/kg__ Captain Hook 41,4 kmh (Avg mehrerer Proben auf Pendelstrecke)
22,9_1,70m___66 kg____218 W___ 3,30W/kg ___Captain Hook (stages)
23,2_1,70m___67 kg____225w ___ 3,35W/kg ____Captain Hook (41,8kmh inkl Wende. Weniger Last in Position nicht fahrbar)
22,9_1,88m___81 kg____250 W___3,08 W/kg___Andreundseinkombi @ 40,1 km/h
22,9_1,88m___81 kg____244 W___3,01 W/kg___Andreundseinkombi @ 39,5 km/h
22,9_1,88m___81 kg____239 W___2,95 W/kg___Andreundseinkombi @ 40,5 km/h
23,0_1,84m___78 kg____285 W___ 3,65W/kg___ Superpimpf @ 39.5km/h
23,1_1,86m___80 kg____296 W___ 3,7 W/kg___ Tzwaen @ 41 km/h
23,1_1,80m___75 kg____277 W___ 3,7 W/kg___ Sense @ 40 km/h
23,2_1,70m___67 kg____239 W___3,56W/kg____captain hook 126km Tr.-Runde
https://www.strava.com/.../1108367777/overview 40,5kmh
23,5_1,80m___76 kg___ 255 W___ 3,35 W/kg___ Paoloest @ 41,2
23,5_1,83m___80 kg___ 280 W___ 3,5 W/kg___ Carlos @ 40,3
24,0_1,75m___75 kg___ 257 W___ 3,4 W/kg___ einzelstueck @ 39,4
24,4_1,81m___80 kg___ 221 W___2,76 W/kg___Kido @ 39,6
25,9_1,77m___81 kg___ 320 W___ 3,95 W/kg__ bubueye @ 39,6 km/h
26,6_1,89m___95 kg___ 282 W___ 3,0 W/kg___ Dirk @ 39,8 km/h
22,1_1,78m___70 kg___ 255 W___ 3,6 W/kg___ Newcomer26 @ 40,8km/h
22,0_1,86m___76 kg___ 242 W___ 3,18W/Kg___Sabine-g @ 40,1km/h Pendelstrecke 2 x 5,8km x 6 vorne 56mm, hinten citec Scheibe, Einteiler, normaler Helm kein 30 Tage Bart
22,0_1,86m___76 kg___ 228 W___ 2,96W/Kg___Sabine-g @ 40km/h (39,98) Pendelstrecke 2x12km vorne 56mm, hinten 80mm, Einteiler, normaler Helm 30 Tage Bart
22,0_1,86m___77 kg___ 258 W___ 3,35W/Kg___Sabine-g @ 40,2km/h
22,0_1,86m___77 kg___ 248 W___ 3,25W/Kg___Sabine-g @ 40,1km/h https://connect.garmin.com/.../activity/1739088190
22,0_1,86m___77 kg___ 231 W___ 3,00W/Kg___Sabine-g @ 40,2km/h (16°C) https://www.strava.com/activities/2297148171
Pendelstrecke 5,4km vorne 80mm, hinten Scheibe, Einteiler, AeroHelm
22,0_1,72m___65 kg___295 W____4,5 W/kg____ triduma @ 38,4km/h
27,0_1,72m___82 kg___256 W____3,1 W/kg____Mirko @39,6km/h
28,7_1,72m___85 kg___251 W____2,94 W/kg___Mirko @39,9 km/h
??,0_1,79m___74 kg___250 W____3,4 W/kg___ Eber @40 km/h Pendelstrecke 2x11km
??,0_1,79m___74 kg___255 W____ 3,4 W/kg___ Eber @40,5 km/h Pendelstrecke 2x11km
24,0_1,87m___84 kg___270 W____3.21w/kg___ Microsash@40,2kmh/h 10km
24,3_1,86m___84 kg___302 W____3.60W/kg___ MarcoZH @40,5km/h (Scheibe/800)
24,3_1,86m___84 kg___296 W____3.52W/kg___ MarcoZH @40,3km/h (Scheibe/485)
24,3_1,86m___84 kg___311 W____3.70W/kg___ MarcoZH @39,8km/h (625/485)
24,6_1,86m___85 kg___261 W____3.07W/kg___ MarcoZH @39,4km/h (Scheibe und 485/800)
20,0_1,79m___64 kg___229 W____3,58W/kg___ Joesoletti @39,72km/h 6,7km
24,4_1,90m___88 kg___321 W____3,65W/kg___ Steppison @40,7km/h auf 24km (60/Disc)
25,3_1,80m___82 kg___272 W____3,32W/kg___ skyfox @41,0km/h_26°C (Rundstr.)
23,8_1,90m___86 kg___358 W____4,16W/kg___ veloholic @41,5km/h_10° (625/625, 2km Strecke)
23,4_1,78m___74 kg___248 W____3.35W/kg___ Kruemel @41,5km/h
21,8_2,02m___89 kg___265 W____2,98W/kg___ deirflu @39,9km/h
24,0_1,86m___83 kg___261 W____3.14W/kg___ 365d @40.5km/h (Super9/808)
24,0_1,86m___83 kg___273 W____3.29W/kg___ 365d @40.7km/h (ARC1100_80/62)
22,4_1,83m___75 kg___262 W____3,43W/kg___ robaat @40,2km/h 30°C
22,1_1,83m___74 kg___280 W____3,78W/kg___ amarkov @40,0km/h 26°C (26,7 km Strecke, flach)
26,8_1,78m___85 kg___240 W____2,82W/kg___ Mr. Brot@40,1km/h (16,3°C Luftdichte 1,24__ 2x 5km Pendelstrecke =20km)

You can study yourself how you do amongst those people, at first glance you fall into the average.

Furthermore, generally one hears from testing outside that a disc is 0,5 km/h faster than a fast spoke wheel, which is about a minute over 40 km.

There’s so many variables that it’s impossible to know unless you do it in an indoor velodrome. My best 20k was 42.5kph on 266w at 62kg with 4 dead stop 180 turns. But then on a local 4k strava segment that is fairly flat I’m slower than that doing 315w, shit road, not running all the go fast gear, no draft from overtaking other cyclists.

For maximal speed i think you want a slight tailwind on the section of out and back that has the most elevation gain.

The best advice I got on ST recently about this was to choose a loop or course you personally do very often. Then you can get a pile of data on the same route with notes about wind.

Your weight (and likely body size) are pretty small. That speed at that power sounds about right. Not sure how flat it was. Just too many variables to say for sure.

I would't worry too much about "absolutes" as I would about optimization. Meaning, if you keep doing that same lap course over and over again you should be able to improve your times. Or try things and see what happens.

Thanks for sharing this, very interesting data, as an engineer I love hard numbers and data of course. I thought I was fairly aero and efficient managing 40 kph on 215 w, @ 63 kg, but saw a guy or girl doing it on 202 w @ 63 kg, would love to see his/her setup and position.

Do you have race files to look at? Here's a 70.3 race file for me at a simar speed, 24.5 mph. I weigh 158, 5'9.5.

http://tpks.ws/...HAHHDS5TI4FEYTRMETSU

In addition to position, things like tire/wheel combo and other gear choices chan make a big difference.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

aims is a guy, but he added in that line "10 m hinter Feld" which means something like "10m behind group" so forget that line.

A Crr of .003 would be a very good road and very good tires.

Shammad10, you can probably go quite a bit faster with some easy mods, but we need to know the details of your setup and position. Most likely you have much lower hanging fruit than a disc wheel. You could put a cover on your current wheel and get most of the benefits anyway.