3T launches Exploro RaceMax Boost e-gravel bike

3T’s brilliant aero gravel rocket gets (e)boost to make it the world’s lightest e-gravel bike

3T Exploro Boost

When 3T launched the Exploro RaceMax last June it claimed the bike marked the next evolution in gravel.

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The idea of blending big tyre clearance and aerodynamic efficiency was taken to the max, and made for the most versatile Exploro to date, with 3T claiming it was capable of both keeping up with the road chaingang, and hitting gravel at speed.

The basis of the design was having aerodynamics to beat a headwind when pushing across an exposed gravel road or plain – something Cervélo has fully embraced with its new Áspero 5.

However, 3T hasn’t stopped there, and is now adding e-power to the mix with the launch of the Exploro RaceMax Boost, with flat-bar and drop-bar options.

Mahle’s lightweight ebikemotion motor and battery

3T Exploro Boost
The Racemax Boost looks great in the flesh, and it’s hard to tell it’s even an ebike at first glance.
Warren Rossiter / Immediate Media

The slick aerodynamic design remains but performance is bolstered with the addition of Mahle’s ebikemotion X35 rear hub-mounted motor and internally mounted 250Wh battery system.

Mahle’s system falls very much on the side of subtle assistance with the rear X35 hub motor providing its powerful 250W boost over three different profiles, controlled via the top tube-mounted iWOC button.

The idea is the system provides just enough assistance when you need it, more a gentle push in the back than a bunch of torque-laden power like you’d get from a bottom bracket-mounted system, such as from Bosch.

3T Exploro Boost
Mahle’s ebikemotion X35 rear hub motor provides the assistance.
Warren Rossiter / Immediate Media

Mahle’s system is lightweight and has helped to create some of the lightest performance ebikes around, such as Scott’s Addict eRIDE and plenty of the best performance e-road bikes available right now. I have a 3T Exploro RaceMax Boost in for testing and my complete 56cm bike weighs in at just 12.5kg with 35mm gravel tyres and a build designed to handle off-road knocks and terrain.

Control of the motor system is simple, with colour-coded lights on the control button denoting both power level and battery reserves. Press the top tube-mounted iWOC button to turn it on and the ring LED shines white, press and hold and it turns green for low assistance, orange for medium, and red for full assistance.

This is also the battery level indicator: white is 75 to 100 per cent battery remaining, green 75 to 50 per cent, orange 50 to 25 per cent, red less than 25 per cent, and flashing red less than 10 per cent.

3T Exploro Boost
ebikemotion’s iWoc controller is flush-mounted into the top tube.
Warren Rossiter / Immediate Media

The slim integrated 250Wh battery sits inside the down tube and while the battery is removable, it’s only really recommended that you do so for servicing purposes because it involves removal of the bottom bracket, too.

Unlike most of its rivals, which mount the charge port in the cradle between down and seat tube just above the bottom bracket, 3T has chosen to mount the charge port facing forwards on the underside of the bottom bracket.

This all adds up to one of the stealthiest looking ebikes around, with no obvious port on the bottom bracket and the flush-fitting iWoc controller that’s only really noticeable if you know where to look.

However, despite 3T’s waterproof claims, I do have reservations about a forward-facing ebike charger connection, given the UK’s inclement weather. I haven’t had a chance to try it yet, but with a couple of gravel routes planned with ford crossings, it’s sure to get a good testing.

3T Exploro RaceMax Boost geometry

3T Exploro Boost
Flat-bar gravel, surely that’s all about ride to work fun?
3T

3T’s Exploro RaceMax Boost is available in sizes from XXS up to a huge 61cm and the geometry is the same as the super-sporty, non-e-assisted RaceMax, which is impressive given the inclusion of an ebike drivetrain.

While the bike is compatible with both 650b and 700c wheel sizes, having that choice to swap kind of goes out of the window on an e-gravel bike that features a rear hub-based motor – you’re likely to stick with what’s specced.

Of course, if your pockets are deep enough you could get both a 700c and 650b X35 rear-hub wheel, but that’s going to be a serious extra outlay of cash. If the bike does well, though, it’s very likely we’ll see a 2× road/gravel version and a big tyred 650b bike.

XXS5154565861
Seat angle (degrees)74.57473.57372.572.5
Head angle (degrees)6969.571727272
Chainstay (cm)41.541.541.541.541.541.5
Seat tube (cm)43.646.34951.854.557.2
Top tube (cm)50.652.654.656.658.660.6
Bottom bracket drop (cm)7.97.97.77.77.57.5
Wheelbase (mm)9981,0081,0081,0141,0241,044
Stack (cm)5254.256.458.460.463.2
Reach (cm)35.536.637.738.539.340.4

Ultralight 3T Exploro Racemax Boost

3T Exploro Boost
Can you tell it’s an ebike yet?
3T

3T’s design guru, Gerard Vroomen, was at the forefront of Cervélo’s superlight road bike designs and his own Open brand makes some astonishingly light mountain and gravel designs, so it’s perhaps not that surprising that the Exploro RaceMax Boost is also available in a very limited and lighter weight offering.

The Exploro Racemax Boost Ultralight build comprises parts from Carbon-Ti, 3T, THM and more to create a gravel bike that weighs just 10.89kg with proper 38mm Panaracer Gravel tyres.

Remember, that’s with a full ebike system and 250Wh battery – the ebikemotion system alone weighs in excess of 3kg.

3T Exploro Boost
A claimed 10.89kg for a fat-tyred gravel bike is pretty decent, especially with a motor and battery fitted.
3T

At £10,299 / $9,999/ €10,199, 3T’s RaceMax Boost Ultralight doesn’t come cheap, but it just goes to show that e-assistance doesn’t have to mean e-hindrance, and is an indication of what the future could hold for e-road and e-gravel bikes.

3T Exploro RaceMax Boost first ride impressions

The Exploro RaceMax Boost feels every inch as good as the brilliant non-e-assisted RaceMax with one simple difference; when the dirt road heads upwards I can add a bit of extra boost for extra traction, to keep me pedalling up trails I have no right to be pedalling on.

That means with the 1× GRX 40/42 gear combo, 20 per cent plus gradients on surfaces that a 35mm tyre has no business keeping grip on are doable.

I have to admit to being a big fan of e-gravel for the simple reason that it overcomes the limitations of slender (by mountain bike standards) levels of grip. The welcome 250W e-assistance means you can remain seated on steep inclines and the rear tyre holds grip whereas on a standard (non-ebike) gravel bike you’d need to stand and risk losing rear wheel traction.

3T Exploro Boost
Shimano’s 1× GRX handles drivetrain duties.
Warren Rossiter / Immediate Media

This is a rapid bike. It’s easy to hold pace on the road beyond the top assistance speed of 25kph (the legal limit in the UK), which maximises the bike’s range with the motor only kicking in when you need true assistance on steep road climbs or steep, loose gravel ascents.

So far, it has handled superbly on the limited amount of testing I’ve undertaken and the geometry feels so sorted both on-road and off. The 3T bar and Selle Italia saddle are proving comfortable too.

3T Exploro Boost
3T’s new super-wide gravel rims are shod with Pirelli’s excellent Cinturato gravel tyres.
Warren Rossiter / Immediate Media

When it comes to performance drop-bar ebikes, the 3T Exploro RaceMax Boost is proving to be one of the best around and has been putting a massive smile on my face all day – but it’s not a cheap ride.

Look out for my full review soon.

Exploro RaceMax Boost spec and pricing

The Boost range is compact with just three models currently available; both the drop-bar and flat-bar versions are priced at £7,299 / $6,999 / €6,999, while the Racemax Boost Ultralight costs £10,299 / $9,999/ €10,199.

3T Exploro Racemax Boost GRX

3T Exploro Boost
The Racemax Boost is fitted with a 3T Apto Stealth stem and Superergo PRO alloy bar.
3T
  • Frame: Exploro RaceMax – BOOST
  • Motor: Mahle ebikemotion X35 System
  • Frame material: Unidirectional pre-preg carbon, high-modulus/high-strength performance blend layup
  • Fork: Fango RaceMax with compact crown
  • Headset: 3T MinMax custom by Cane Creek IS42/28.6 + IS 47/38
  • Handlebar: Superergo PRO alloy (XXS: 38cm / 51: 40cm / 54 & 56: 42cm / 58 & 61: 44cm)
  • Stem: 3T Apto Stealth (XXS: 70mm / 51: 80mm / 54: 90mm / 56: 100mm / 58: 110mm / 61: 120mm)
  • Rear derailleur: Shimano GRX – long cage mechanical (RX-812)
  • Shift/brake levers: Shimano GRX
  • Brakes: Shimano GRX flat-mount hydraulic disc with Shimano 160mm six-bolt rotor
  • Crankset: Shimano GRX, 40t chainring (XXS: 165mm / 51: 170mm / 54 & 56: 172.5mm / 58 & 61: 175mm)
  • Cassette: 11-speed Powerglide, 11-42
  • Wheelset: 3T Discus 45 / 40, tubeless-ready – Fulcrum E-Racing 900 DB alloy wheels available B2B only
  • Tyres: Pirelli Cinturato Gravel M, 700c, 35mm labelled width
  • Seatpost: New 3T Charlie Sqaero Team with Ritchey WCS Clamp
  • Saddle: Selle Italia Novus Evo Boost Superflow
  • Buy direct from 3T

3T Exploro Racemax Flatbar

3T Exploro Boost
The carbon Flatbar version looks set to be our new favourite commuter.
3T
  • Frame: Exploro RaceMax – BOOST
  • Motor: Mahle ebikemotion X35 System
  • Frame material: Unidirectional pre-preg carbon, high-modulus/high-strength performance blend layup
  • Fork: Fango RaceMax with compact crown
  • Headset: 3T MinMax custom by Cane Creek IS42/28.6 + IS 47/38
  • Handlebar: 3T carbon Flatbar LTD
  • Stem: 3T Apto Stealth (XXS: 70mm / 51: 80mm / 54: 90mm / 56: 100mm / 58: 110mm / 61: 120mm)
  • Rear derailleur: Shimano BL-RS600
  • Shift/brake levers: Shimano GRX
  • Brakes: Shimano BR-RS_405 flat-mount hydraulic disc with Shimano 160mm six-bolt rotor
  • Crankset: Shimano GRX, 40t chainring (XXS: 165mm / 51: 170mm / 54 & 56: 172.5mm / 58 & 61: 175mm)
  • Cassette: 11-speed Powerglide, 11-42t
  • Wheelset: 3T Discus 45 / 40, tubeless-ready – Fulcrum E-Racing 900 DB alloy wheels available B2B only
  • Tyres: Pirelli Cinturato Gravel M, 700c, 35mm labelled width
  • Seatpost: New 3T Charlie Sqaero Team with Ritchey WCS Clamp
  • Saddle: Selle Italia Novus Evo Boost Superflow
  • Buy direct from 3T

3T Exploro Racemax specification as tested

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  • Weight: 12.5kg (56cm)
  • Frame: Carbon
  • Fork: Carbon
  • Gears: Shimano GRX 600 (40/11-42)
  • Brakes: Shimano GRX RX400
  • Wheels: 3T Discus 45/40 with ebikemotion X35 rear hub
  • E-motor: Mahle ebikemotion X35 250W, 250Wh internal battery, iWOC controller
  • Finishing kit: 3T Apto Stealth stem, 3T Superergo pro bar, Pirelli Cintauro Gravel M 35c tyres, 3T Charlie Sqaero Team seatpost, Selle Italia SLR Boost saddle.