Elliptical chainrings are the flared trousers of cycling. Every 20 years or so they come into fashion and then disappear again. But with top professionals such as Thor Hushovd and Emma Pooley fitting them to their bikes, maybe this time they’ll be more than a trend. We’ve been testing Rotor’s 3D Aero TT crankset (£258), fitted with its 53/39 Aero Q-rings (£169) and BB1 ceramic bottom bracket (£88) to find out.
A total weight of 849g is respectable for an aero chainset, but low weight isn’t the reason for choosing the Rotors. What’s clever is the way the elliptical Q-rings alter the gearing as you turn the pedals. The 53-tooth big ring is effectively a monster 56-tooth when your legs are really pumping, and a 51-tooth at the dead spots.
Fitting is straightforward, although we had to raise the front derailleur slightly to allow for the shape of the chainrings. We set up the rings in the middle of Rotor’s recommended range of positions and found the pedalling action smooth, as if we’d spent a couple of months riding fixed and had gone back to a geared bike with supple legs and an efficient technique. Gearshifts did feel more hesitant than with standard round rings though. The Rotors were benchmarked against circular chainrings in a couple of tests. First, we held a set power output on a turbo trainer for 20 minutes and recorded our average heart-rate to see if we could achieve the same level with less effort. This test showed no benefit – the heart-rate was identical each time.
Next, we compared the round and elliptical rings while riding flat out on a favourite training loop. The Rotor’s aluminium cranks were impressively stiff, and holding a high gear uphill felt less laboured. What’s more, we improved our average speed by 0.3mph compared with our previous best. There are so many variables in on-road testing that we wouldn’t claim this is conclusive, but the Rotors certainly feel quick. Put it this way: they won’t be coming off our TT bike until Rotor makes us give them back.