3T Discus 45 40 LTD wheels
£2,175, 3t.bike
In the world of aerodynamics, the ‘Rule of 105’ is a commonly accepted guideline to optimise airflow over a wheel/tyre system. The rule suggests that the rim must be at least 105% the width of the tyre if there is to be a chance of it recapturing the airflow from the tyre and smoothing it out. It is believed that the disruption caused by a wide tyre on a narrow rim almost completely undermines the dragreducing effect of deep rims.
Based on this rule, there are only a couple of wheel designs on the market wide enough to optimise the wheel/tyre system for a gravel bike, considering 700c tyres are commonly in the 37-42mm range. In the Discus 45 40 LTD wheel, 3T has ostensibly released the most appropriate example to date.
The wheels match a 45mm rim depth to a staggering 29mm internal rim width and equally surprising 40mm external width, shaping wide gravel tyres in a way to best promote what aerodynamic gains there are to be had.
Aligning with modern road wheel design, the wider rim should also make the tyre more stable, reducing the chance of squirm to improve handling while retaining the advantages in comfort and grip lower pressure tyres provide. Carbon-ti hubs help keep the wheelset weight down to a claimed 1,665g, so despite their extra girth the wheels are impressive on the scales too.