Decreasing Marginal Aero Gains – PART TWO

Olly Words By The Velo House | 21/04/2017 12:13:44

Once you have got your position, clothing and helmet sorted there are smaller gains to be made with aero wheels, frames and accessories. That said aerodynamics are the biggest obstacle on a flat TT where you will be travelling at 40-50kph on faster stretches and a 1 watt saving in drag can mean 5 seconds over a 40km TT at 40kph. Testing by some of the big bike manufacturers indicates that the difference between a fairly standard road bike with shallow wheels and a fully aero TT bike with aero wheels and an aero helmet is 5-6 minutes over 40km travelling at 40kph, a saving of 10%.

For aero wheels the front wheel makes more difference than the rear and generally deeper and wider rims are better. Matching the tyre width to the rim to create a smooth transition from the front edge of the wheel is important. Generally a disc wheel is quicker at the rear (not allowed on the front due to cross winds) but they are heavier and can be difficult to handle in very windy conditions. Tubular tyres are generally favoured by experienced TT riders although there is now lots of research to indicate that modern clincher tyres offer less rolling resistance than tubulars and tubeless set ups are now the fastest.

A good aero frame will make you faster in 2 ways. The tubing is normally optimized to move air around it and the wheels as smoothly as possible. Drinks and storage systems are now being added not just for convenience but also to help with the aerodynamics. These are often banned in professional UCI races but not in most local and national TT events. The new Scott Plasma has a clip on aero drinks bottle that makes the frame more aero than without it.

scott plasma pair

Brakes are often integrated into the frame or hidden by covers to aid air flow over the frame although this can make them more difficult to adjust and much more fiddly to put back together if you are travelling with your bike.

Secondly an aero frame is designed to get the rider into an aero and efficient position and as you are the biggest drag in the air. With a steeper seat angle to move you over the bottom bracket and a lower front end to reduce frontal drag an aero frame can help you find a comfortable position as a steady body is key to cutting through the air.

Keeping you head still is another good way to stay aero. Moving your Garmin or Wahoo computer to the front of your aero bars so you can see it without drop your head is important for pacing and aerodynamics. Another trick is the “shrug”, drop your shoulders and lower your head into you neck to narrow and lower your frontal area. This takes quite a bit of practice and is difficult to hold for long periods so save it for the fastest stretches when drag is at its highest.

More to come on pacing and the mental side of Time Trialling in the final parts of this series.