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Want to go faster? Get a motorbike to follow 10 inches behind you say researchersFuji Norcom Straight time trial bike in wind tunnel

Want to go faster? Get a motorbike to follow 10 inches behind you say researchers

Following motorbike reduces air resistance even if it’s a number of metres away
by Alex Bowden
Wed, May 04, 2016 10:55
9

Aside from the obvious motivation of not wanting to be flattened by a clearly deranged motorcyclist, it seems there are aerodynamic benefits too. Research at TU Eindhoven, KU Leuven and the University of Liege has shown that a motorbike travelling right behind a racing cyclist can reduce the air resistance for that cyclist by almost nine per cent.

Phys.org reports that as well as computer models, researchers deployed scale models of a time trial rider and a motorcyclist in a wind tunnel to make their calculations.

They found that a motorcycle 25cm behind the cyclist would cut air resistance by almost nine per cent and that if there were three motorcycles, the reduction could be as much as 14 per cent. (They don’t explain what the cyclist in question might have done to justify having such a squadron bearing down on them.)

The study also modelled some slightly less terrifying gaps and found that a motorbike riding as much as five metres behind the cyclist would still have an impact. In fact, over 60km the benefit would amount to around nine seconds – a significant amount considering the tight margins in professional racing.

Although the benefits of riding behind someone else are far more significant, it has long been known that having someone in your wake can be beneficial too. The researchers say that the new evidence suggests the effect is much greater than previously thought and they have therefore advised the UCI (International Cycling Union) to extend the minimum distance between motorcycle and cyclist during a time trial from 10m to 30m. Researchers did however note that compliance with recommended distances is something that almost never happens in reality.

The recommendation also comes amid calls for greater safety measures to regulate the presence of motorbikes in bike races. A number of riders have been involved in collisions with race motorbikes in recent times, most notably Antoine Demoitié who died in hospital following a crash during this year’s Gent-Wevelgem.

Time Trial
motorbikes
aerodynamics
Alex Bowden

Alex has written for more cricket publications than the rest of the road.cc team combined. Despite the apparent evidence of this picture, he doesn't especially like cake.

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9 comments

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Bert Blocken | 7 years ago
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Rider behind other rider is indeed about 2-3% benefit.

Effect of car is largest.

see:

http://www.urbanphysics.net/2015_JWEIA__BB_YT__Car_Cyclist.pdf

http://www.urbanphysics.net/2013_CAF_BB_TD_EK_JC_PH__Preprint.pdf

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Bert Blocken | 7 years ago
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Gentlemen, I am the lead researcher that coordinated and published this research work.

I thank the writer for reporting about our work. The writer states: "They don’t explain what the cyclist in question might have done to justify having such a squadron bearing down on them". 

Actually, we did not find it necessary to explain, because this is quite common. If you watch the large tours, you will see that riders are often followed by multiple motorcycles and multiple cars. Certainly those that are in a position to win the tour. The most extreme case I know is Laurent Fignon (who very unfortunately left us much too soon) and Greg LeMond in the Tour of 1989. They were followed by 8 (!) motorcycles and several cars and an ambulance. You can see that on many photographs, also on You Tube: see around minute 8 at: https://www.youtube.com/watch?v=AyvwtOQYQ-E

Further: see figure 1 in our publication: http://www.urbanphysics.net/2016_JWEIA__BB_YT_TA_Cyclist_Motorcycle__PRE...

Free to download.

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Guerch to Church | 7 years ago
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Must be a forced air pocket between the two and the motor bike pushes the bikes wake back to the cyclists, to form a bit of a tail wind.

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ron611087 | 7 years ago
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The biggest impedance to cycling isn't air, it's UCI. In it's attempt to standardise the racing bicycle it also impedes it's development. In 1934 UCI banned recumbent bicycles because of the competitive advantage that the bike gave to the rider. And the racing bike still provides the template for the bicycle as we know it.

The biggest resistance a rider faces is air. A cyclist is probably the most un-aerodynamic vehicle on the road. Lowering air resistance is where the biggest gains in cycling performance can be made, but it won't happen. Not as long as UCI calls the shots.

IMO only two (non-chemical) rules to cycle racing should apply, and that is the bike should have two wheels (or it's not a bike), and it should be human powered. Then let design take it's course.

If UCI were around in 1880 we would still be riding penny farthings.

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brooksby | 7 years ago
4 likes

To be honest, I think this happens to me on every commute. Haven't noticed any real improvement

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JeevesBath replied to brooksby | 7 years ago
5 likes

brooksby wrote:

To be honest, I think this happens to me on every commute. Haven't noticed any real improvement

Having a car ten inches off my rear wheel regularly makes me go as fast as I can.....

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Boss Hogg replied to JeevesBath | 7 years ago
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JeevesBath wrote:

brooksby wrote:

To be honest, I think this happens to me on every commute. Haven't noticed any real improvement

Having a car ten inches off my rear wheel regularly makes me go as fast as I can.....

lol 

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KnightBiker | 7 years ago
1 like

Pro's ride faster partly because of reasons like these:

Drafting behind cars and motors (for short amounts of time) + creating a greater draft bubble when they cars motor's or cyclists are behind you + clear roads whithout any head on traffic.

- But Psychologically Having a goal to focus on also helps and maybe even more: Focussing on catching the motorbike in front of you (the rabbit-carrot incentive) keep riding in front of you.

- Similarly being the last in a group also takes more energy then being the second to last because you are carrying the most drag while closing the aero bubble.

- The Psychology of racing and taking advantage of chasing a carrot are not to be underestimated advantage the pro's have compaired to mere mortals on a sunday morning ride.

(Francesco Moser once said that time trialing is contieunesly sprinting to the next corner)

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nedcase | 7 years ago
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I've also heard separately that having a following bike helps by 2% and this percentage increases the more bikes are in the following peleton. Never feels like it though when you're out in front!

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