Sharing the work.

Because you require approximately 20-30% less power to ride in someone's slipstream - this means when you get to the front you can put in a harder effort than you could if you were riding at a constant speed on your own, and when you've done your turn you swing to the back and have time to recover before you hit the front again. You are effectively riding short intervals with recovery time between each effort.

I remember reading this on an Aussie site http://www.bikeon.com.au/ride_mag5.html (am going to Aus in the new year and definitely taking the bike!) and they quoted this table which I suppose may answer your question. I dont know who provided the figures though.

The effect of drafting

Wheel gap in cm            decrease in resistance

150                                      44%

300                                      42%
 
600                                      38%

900                                      34%

I believe that sitting 3rd or 4th in a line or further back makes no difference, although there is a difference between 2nd and 3rd. Of course it also makes a difference to the recovery time you get while drafting, the more people the longer the break while others take the lead.

felgen wrote:

I remember reading this on an Aussie site http://www.bikeon.com.au/ride_mag5.html (am going to Aus in the new year and definitely taking the bike!) and they quoted this table which I suppose may answer your question. I dont know who provided the figures though.

The effect of drafting

Wheel gap in cm            decrease in resistance

150                                      44%

300                                      42%
 
600                                      38%

900                                      34%

Are you sure these figures aren't out by a factor of ten? 900cm is about thirty feet, I suspect you'll get bu**er all drafting effect at that distance! In the few duathlons I've done, I think the minimum gap you must maintain between bikes is seven metres. According to these figures you'd still be getting about 36% drafting effect.

mech_daddy wrote:

Wow i didn't know aerodynamics would have such an effect.

You should draft behind one of those new fast tractors that were out recently harvesting the crops I managed 37mph for a few miles behind one coupe of weeks ago on nice clear stretch.
Not advisable if you are on windy narrow roads tho Better still and much safer as long as you can ride a fixed fast, go to a track and do a derny session
Think they are still on at Newport but not sure if the track league starts next week so it may finish this week!

I may be wrong but I haven't seen a derny on the Thursdays, I have been on a Thhursdy as several times. Seen it for the sprinters after the vets sessions on Fridays and also on Tuesdays.
Not managed to get there for training when its there yet

guv001 wrote:

I'm talking about Maindy not Newport OWM

I should have read your last post more closely
I think they are now doing road bike racing for a few thursdays on Maindy Track?

Raises an interesting question about 'draughting ettiquete'!

If you are out on a solo ride, doing your own thing and trying to avoid cheating in a tow, how do you feel about someone sucking on your wheel without so much of a kindly word or a polite request? I suppose this happens more on a shortish training loop with people whizzing around trying to beat PB's. Happens a lot on my local loop. I did it myself a bit to begin with but then realised I wasn't getting good comparitive data from each ride, and deceiving myself some days that I had rode a great session, so now I avoid sucking wheels.

Also, I notice nobody talks about the benefit to the rider in front as well if you have a long line of riders draughting. May be small, but you do get some benefit with other people draughting you, because they alter the drag profile coming off your bike and also reduce resistance... Never seen any figures for that though.

Alex_Simmons/RST wrote:

[I think we are talking about drafting and not draughting. Unless you are planning on doing some engineering design work while riding your bike. As for riders behind reducing your aero drag, I'm not aware of data but it would be very very small if at all and is probably an old coach's trick to get a rider to hang on in team time trials

Bu**er! Err, no I was indeed talking about draughting. Do you think it's ok for someone to ride along in your wake with a sheet of A4 taped across their aero bars, whilst taking precise measurements of their seat tube / top tube, without paying due attention to the rider in front... Do you think it's dangerous? But Anyway, regards the aero effect of having another rider behind you, I have seen no data relating to cycling (which doesn't surprise me), but its quite well documented in other sports with engines... If you look on high speed ovals in the USA, a pair of NASCAR race cars 'drafting' will lap quicker, on circuits where it's just foot flat to the floor all the way around. A line of them will lap quicker still, if you are looking at pure aero effects. Five riders in line will effectively act as one long aerodynamic body, with a totally different form factor than a single rider, so it should make a small difference, though perhaps not as graphically illustrated as with a race car. After all, it's the turbulence, vortices, eddy currents etc that are shed behind you that creates the 'work' in overcoming aerodynalic resistance...

derekwatts wrote:

Raises an interesting question about 'draughting ettiquete'!

If you are out on a solo ride, doing your own thing and trying to avoid cheating in a tow, how do you feel about someone sucking on your wheel without so much of a kindly word or a polite request? I suppose this happens more on a shortish training loop with people whizzing around trying to beat PB's. Happens a lot on my local loop. I did it myself a bit to begin with but then realised I wasn't getting good comparitive data from each ride, and deceiving myself some days that I had rode a great session, so now I avoid sucking wheels.

Also, I notice nobody talks about the benefit to the rider in front as well if you have a long line of riders draughting. May be small, but you do get some benefit with other people draughting you, because they alter the drag profile coming off your bike and also reduce resistance... Never seen any figures for that though.

Yes, apparently drafting does marginally benefit the rider in front - something to do with "filling in their eddy" - (only briefly read that though, not seen any data). Regards drafting on solo training rides - don't see a huge problem with it myself - typically you'll only be with someone (or them with you) for one or two miles at most (before someone turns off) - also, if you've already got 30-40 hilly miles in your legs (for example) and you close up behind another roadie doing 23 mph on the flat (on a decent route), it's not as if your going to move up to 25/26mph and sustain that for 3 or 4 miles (some could obviously - but on a "moderate" Sunday...), rather, you might just tuck in and have a rest for a mile or two - and there's the cameradary (spelling?) angle aswell. In the grand scheme of things, it's not a huge issue (all imho). Obviously there's nothing stoping somebody saying hello before tucking in etc,etc, and if your on fresher legs, nipping past and droping someone.

guv001 wrote:

So how do a team eg CSC drop everyone by riding on the front surely they as a team are expending more energy than the other teams behind. Does this just come down to fitter stronger riders or is there another tactic I'm missing?

Are you talking flat land or hills?

On hills it's mostly about power to weight ratio, so if you have more good climbers on your squad, then chances are you'll have the numbers to keep the pressure on. While reduced, there is still a drafting advantage to following a wheel up hill. So what happens often in these type of teams is the team leader's helpers will sacrifice themselves without necessarily the expectation themselves of being able to go the full distance at that pace.

But it is more often about tactics and it depends on the type of rider. Some cope better with accelerations and variable paced efforts (e.g. Pantani), others prefer a more consistent effort level (e.g. Leipheimer, Evans), so often the attacks are made by a leader's team mates, knowing that the opposition rider who is outnumbered must respond (since the team mates are still a threat in their own right), even though it is not his preferred means of climbing.

On flat lands, the team on the front shares the work and drives it hard. Especially effective in strong cross winds at breaking up the peleton since not everyone can fit into the echelon and gain the benefit of a draft, meaning that the riders behind effectively are forced to put in as much effort as the riders driving the pace. Any weakness on that day, and you are in big trouble.

Really good teams know exactly how wide to make the echelon, so that only their team mates get the most benefit from the draft. It is brutal at times and requires one to get good at riding in the gutter. Then the punctures come and so on.

guv001 wrote:

Also how is it harder pulling another rider uphill (except for the draughting effect which must be reduced at such low speeds) is this purely pyscological?

It isn't. It's more to do with tactics.

The rider behind is still getting some assistance, so by towing them you are using more energy and setting them up to overtake you for the win. That determines your tactics. In some cases, the lead rider will do that because they are more interested in establishing a time gap over dropped riders and will sacrifice a win in the process as it is faster overall to ride at a constant effort than play tactical games on the way up.