A Science Experiment and a Quiz - The True Benefit of Drafting

[morris]

You hear, read, and observe that drafting behind another rider saves you energy.  Do you know how much?  This past Saturday two handsome fellows went out for a ride.  They picked a mostly flat course for a 20-min effort and time trial.  They both weigh the same, ride the same road bike, road on their hoods but with an aggressive posture, and were both equiped with power meters.  The lead gentleman buried himseld over the course of this 20 minutes, holding back his own vomit, and produced a stunning average power of 313 watts and a normalized power of 316 watts.  The gentleman following him stayed on his wheel in his draft, shouted encouraging words, and took in the scenery.

[joe]

What's the weight of the one pushing 316 watts? A w/kg would be nice...

Thanks,
Joe

[Robert]

I'm guessing you were the most handsome one, right Morris?
Was there a tailwind or headwind? Headwind would save him more and less in a tailwind.
In calm conditions my best guess would be that the guy drafting averaged between 230 and 250.

[morris]

Scott was pulling and I was drafting.  So not so handsome after all.  There was a slight headwind, but nothing over 10 mph.  Scott and I both weigh in the 172-175 range.  That's 4 watts/kg for the effort and an FTP around 3.7-3.8 watts/kg depending on how much you discount the npower number.  Those are Cat 3 numbers.  Now we have some big expectations!!

[Robert]

I always knew Scott was strong. Man, with a TT bike and a skin suit he should be able to easily go under an hour at the state TT!
So are you going to tell us what you averaged in his draft?

300+ watts for 20 minutes, that's my goal this season! Not too far from that now.

[morris]

The answer is D: Avg power of 241 (saving 72 watts), npower of 251 (saving 65 watts).  That's a 21-23% savings.  So a tempo/low LT effort basically while he was at his limit.  It proves that you should never be on the front unless you have a gap and you can hold it to the end.  Although even on the rollers I had to match Scott's power as the draft didn't help that much.  So not a walk in the park, but not that bad of an effort either.

[phlojo]

Just for grins, LA at Tour down Under:  340 watts for 2 hours.  WOW! 

Lance Armstrong (Astana) joined 13 riders in a 90-kilometre long break away throughout the Tour Down Under's Stage three today, as the American gets back into the swing of racing. Armstrong joined a powerful break away early in the race ? which included Stuart O'Grady (Saxo Bank) and Michael Rogers (Columbia) ? and stayed away through to kilometre 101.

"I felt okay; high end intensity, I don't have that yet, I haven't worked that part of my training," he said. "Like I said you had to be strong to be in that group, if you looked around there was some horsepower in there, I've got to be happy with that."

The seven-time Tour de France winner believes the racing will help his comeback. The rider believes the only way to get competitive again after three and a half years off the bike is by racing.

"I think it's the kind of stuff I need to do, I need to get in the race and work that top end," he said. "Like I've said 100 times here, I can't get that in training so the more I can be out there... I mean, I looked down at my power metre and the average after two hours was 340 watts, you can't do that in training. You're just constantly going and going and going."