Aero! Gravel! Battery!
3T Exploro Racemax Boost £7299 3T’s quality aero gravel rocket gets an ebike booster
The 3T Exploro Racemax Boost is the stealthiest ebike I’ve come across, which is all down to the original ‘acoustic’ Racemax’s design I tested in issue 370. That bike had a hugely oversized down tube that shielded the bottles from the air, thus improving its aerodynamics. Little did 3T’s designers know – or maybe they did – that this increased volume allows room to house a 250Wh battery.
There have been modifications, the electrically assisted Racemax having a strengthened bottom bracket area to incorporate the charging port and to allow the battery to be removed. But crucially for me the bike’s geometry remains unchanged – as 3T’s Exploro Racemax is one of my all-time favourite fast gravel bikes.
The Racemax Boost feels every inch the same as the standard Racemax with one difference – when the dirt road heads upwards you can add extra boost for greater traction, this extra power keeping you pedalling up trails you’d otherwise have no right to be riding. And the 40x42 bottom gear lets you tackle gradients steeper than 20 per cent over surfaces on which a 35c tyre normally wouldn’t be able to grip.
And it’s not just fast uphill, as this Exploro feels just as slick on the tarmac between sections of dirt. On the road I spent most of my time riding above the legal assisted limit of 15.5mph (25km/h), and at just 12.5kg the weight doesn’t compromise its performance.
Power up
Mahle’s ebikemotion system is built around a powerful 250W motor in the rear hub and a slimline 250W battery in the down tube. You can remove the battery for servicing – though that does involve removing the bottom bracket. The 40Nm of assistance doesn’t sound much compared with Fazua’s claimed 60Nm or the 80Nm-plus on some Bosch and Shimano systems, but it never felt underpowered. The assistance is subtle, like a gentle push in the back rather than a full-bodied shove, but it’s ample to keep you ascending at pace.
The controls are simple, with colour-coded lighting on the top tube-mounted iWoc button denoting power level and battery reserves. Press to turn it on and the LED ring shines white, press and hold and it turns green for low assistance, orange for medium and red for full power.
It’s not just fast uphill – this Exploro feels just as slick on the tarmac between sections of dirt
The Racemax’s capability on the road means its assistance only kicks in when you really need it
The battery level indicator ranges from white, showing 75-100 per cent, down to a flashing red when there’s less than a 10 per cent charge.
The bike’s capability on the road means its assistance only kicks in when you really need it, on steep road climbs or on loose gravel ascents, maximising its range. I achieved 79km/49.16miles and 824.4m/2705ft elevation on an off-road test ride and an impressive 101km/62.88 mile on a mixed ride with 971m/3185ft of climbing.
The 1x Shimano GRX drivetrain works superbly and offers a more than ample gear range. The tubeless-ready 3T Discus wheels come with an aero-optimised 40mm deep front rim and 45mm rear, their balance of lightness, stiffness, responsiveness and shock absorption adding a lot to the ride quality. Pirelli’s Cinturato M tyres are some of my favourites and, along with the quality Selle Italia saddle and 3T bar, stem and seatpost, make it a spec I wouldn’t change anytime soon. As with the standard Exploro
Racemax, it can run 700c or 650b wheels, but as the rear hub contains the motor, running two wheel sizes won’t come cheap!
Port whine
The only thing I’m not 100 per cent keen on is the charging port – which is on the underside of the bottom bracket shell and it’s forward-facing. I’ve tested the bike in all weathers and the press-in rubber seal does its job, though I double-checked the cover was secure before every ride.
Overall, though, 3T’s Racemax Boost is a premium-quality bike. It handles superbly, it’s rapid, light and its geometry is well suited for road riding and off-road duties, so it always feels good. It’s easy to hold a pace above 15.5mph on the road, maximising its range, while excellent contact points add control and comfort, and contribute to a bike that kept me contented every moment I was riding it, from smooth tarmac to challenging gravel. When it comes to genuine drop-bar performance ebikes, 3T’s Exploro Racemax Boost is up there with the very best.