Different configurations for lenticular wheels

Question

I have a question about lenticular wheels for track bikes, originated by watching the last World Championships in 2022. In many situations, bikes have a pair of lenticular wheels, like this case:

(from GettyImages: British team riders Neah Evans, Katie Archibald, Megan Barker and Josie Knight compete in the Women's Team Pursuit qualifying during the UCI Track Cycling World Championships at the Velodrome of Saint-Quentin-en-Yvelines, southwest of Paris, on October 12, 2022)

In other situations, the lenticular wheel is just at the back:

(from GettyImages: Cyclists compete in the Women's 10 km Scratch Race final during the UCI Track Cycling World Championships at the Velodrome of Saint-Quentin-en-Yvelines, southwest of Paris, on October 12, 2022)

But what surprised me, is another, rarest case, in which the lenticular wheel is at the front:

(from GettyImages: Cyclists of the Endurance French team take part in a training session ahead of the Cycling indoor UCI Track World Championship in Montigny-le-Bretonneux on October 4, 2022. - The World Championship will take place from October 12 to 16, at the Velodrome of Saint-Quentin-en-Yvelines, in Montigny-le-Bretonneux, outside Paris)

So, I'm asking: what are the main benefits of mounting a lenticular wheel just at the front? I suspected that the overall stability of the bike would be compromised, even on track.

Answer 1

A few things worth noting.

1. A front disc wheel (lenticular or paracular) is almost always aerodynamically faster than a non-disc wheel, all other things being equal (e.g. tyre, pressures, etc.). So it's typically 'faster' than a spoked wheel.

2. A front disc wheel is noticeably harder to control than a spoked wheel; even in the absence of other riders creating 'dirty air'. The wheel will catch any 'dirty air' and also has different handling characteristics (harder to turn in).

[Note that rear disc wheels don't exhibit these types of control issues, so you'll see rear discs being used in pretty much all competition on the track.]

That said - where a trackie is riding pursuit (individual or team), the choice is 100% a front disc (at least at the upper ends of the sport). Despite the decrease in controllability, in team pursuit, riders are entirely predictable, and each member of the team has (usually!) practiced extensively with the rest of the team, so each knows how the others ride, and what to expect. You don't have other riders suddenly moving around the track generating unpredictable air flows.

For bunch racing (scratch, points, maddison, etc.), things are very different. Riders need to be able to change direction (sometimes suddenly!), and there is a lot of 'dirty air' as riders go past each other. Using a front disc would make racing in bunches not just difficult, but dangerous given the reduced level of control a rider would have. For this reason, you'll pretty much never see a rider in a bunch race using a front disc wheel.

Finally, when it comes to training, it's quite coming (although it looks a bit weird) to see pursuit riders practicing with a front disc and a regular spoked rear 'training' wheel. There are two reasons for this:

1. Using a front disc in training allows the rider to practice gaining more experience in controlling the bike - even in individual pursuit, where the air is 'clean', the front disc makes turning into each bend just a little bit trickier, and a good, smooth path round the track can make the difference between winning and losing!.

2. Why use your expensive rear disc wheel (wearing the tyre) when you're not competing? Hence, riders will use a regular spoked training wheel on the rear.

There's also a school of thought that 'building' towards race pace can/should include:

• start training on regular spoked wheels
• progress to the front disc and spoked rear
• finally, just before race day, full dress rehearsals with 'double discs' and full aero gear to feel the benefits gained from your top-end equipment.

Hopefully, this helps to explain the pictures above, and what you're seeing on the TV and at the track!

Answer 2

The rear wheel sits in an area of turbulent flow; the air around the front wheel is "clean" (perhaps not as clean in a team time trial). Aerodynamic improvements in the front have more benefit than those in the back.

The problem is that front disks are hard to handle due to their inertia and sail effect; even on an indoor track, air conditioning could blow you around. I'm guessing different teams weigh the pros and cons differently and come up with different conclusions.