Transition Regulator SX

The Transition Regulator SX is for riders who still want to feel as though they are riding a mountain bike, just with useful help on the climbs. It is a carbon full-suspension electric trail bike with Bosch's compact Performance Line SX motor - up to 60 Nm and 600 W peak - a fixed CompactTube 400 Wh battery, and 160 mm of fork travel over 150 mm at the rear. UK bikes start at £6,999.

You get mixed 29 in and 27.5 in wheels, four-piston brakes and aggressive Maxxis tyres rather than skinny e-bike rubber. Against the higher-powered Regulator CX, the SX is the lighter, more conventional-feeling option in the pairing. The motor rewards cadence and rider input, which suits trail riders who have stayed away from full-power eMTBs because they felt too heavy and detached.

The first Regulator generation

This first-generation Regulator platform launched in 2025 and is the current UK model. Deore and XT complete bikes share the carbon frame, Bosch SX system, battery and travel, so the buying choice is equipment rather than a different chassis.

Carbon frame, mixed wheels and GiddyUp suspension

Transition uses a carbon GiddyUp full-suspension frame in SM, MD, LG and XL, with reach from 425 mm on SM to 510 mm on XL. Every size is a dedicated mixed-wheel bike: 29 in at the front and 27.5 in at the rear. A 29 in rear wheel is not compatible, so this is a format you choose rather than a setup you convert later. Maximum published rear tyre size is 27.5 in x 2.6 in, subject to the tyre, rim and mud you actually run.

Stock travel is 160 mm up front and 150 mm behind, with a 205 mm x 60 mm trunnion shock on both UK builds. Transition publishes a 27% progressive leverage curve and says the frame can take air or coil shocks. A compatible 205 mm x 65 mm shock can lift rear travel to 160 mm if you want extra descending margin, but that is an aftermarket change, not the factory setup. The stock 150 mm figure better matches the bike's lighter, livelier brief.

A 64.5-degree head angle is slack enough for steep descents without making the steering slow. Stems are 40 mm, and chainstays step from 442 mm on SM and MD to 448 mm on LG and XL so larger riders keep some length behind the bottom bracket. Steep effective seat angles and 160 mm cranks support technical climbing, while dropper travel steps up with size so bigger frames are not left with a short post. If you sit between two reaches, those longer rear centres on LG and XL are part of the decision.

You charge the 400 Wh battery on the bike, because it is fixed inside the down tube and not designed for daily removal. That is straightforward if the bike lives near a socket, and awkward in a hallway or lock-up without power. For longer days the frame is prepared for Bosch's PowerMore 250 Wh range extender, taking combined capacity to 650 Wh once you add the mounting kit and 150 mm cable. The extender cannot run the bike on its own, and there is no official mileage figure to hang a ride on - plan around those watt-hour numbers, because mode, climbing, temperature and how hard you ride will move the real distance around.

Transition Regulator SX Deore vs XT

The extra XT money does not buy more torque, a bigger main battery or extra factory travel. Both bikes share the carbon chassis, Bosch Performance Line SX system, CompactTube 400 Wh battery, mixed wheels and 160/150 mm travel. What you pay for is the finishing kit.

Regulator SX Deore is the £6,999 build, with Shimano Deore M6100 12-speed gearing, a RockShox Lyrik Base fork, Super Deluxe Select shock, Deore M6120 four-piston brakes, WTB ST i30 rims on Novatec hubs and an SDG Tellis dropper. No complete-bike weight is published. Bars are 780 mm Race Face Chesters, and dropper travel grows with frame size.

Regulator SX XT is the £8,499 build: Shimano XT M8100, Lyrik Ultimate and Super Deluxe Ultimate, TRP EVO PRO brakes, DT Swiss XM 481 rims with 350 Classic DEG hubs, a OneUp carbon bar and OneUp droppers with more travel than the Deore at most sizes. Claimed weight is 18.67 kg in size MD. Tyres use Maxxis 3C EXO+ casings rather than EXO.

Choose Deore if the shared chassis and Bosch system matter more than extra suspension adjustment and a lighter wheelset. XT makes sense when the more tunable RockShox kit, carbon cockpit and published weight are worth the jump. Match the components on the displayed offer rather than assuming a price point always equals one named build, because substitutions do happen and cockpit details change with size.

Wet weather, charging access and warranty

UK mud will wear pads, chains and pivots on any trail bike, and the charge-port door is worth a wipe when it is caked. That is ordinary care, not a Regulator-specific flaw. Firmware and diagnostics sit with Bosch-certified support, so factor in access to that network. Transition states a lifetime warranty message on the frame, and Bosch Smart System components are stated to have two years of cover from purchase.

BikeMag tester Deven McCoy wanted more substantial down-tube protection after hearing debris hit the frame, and he questioned how well the charge-port door kept muck out. Take both as one rider's notes rather than a known failure pattern. Protective film or a suitable guard is a sensible extra on rocky local trails, and a quick clean of the port after wet rides is cheap insurance.

Pick the Regulator SX when you want assistance that extends a mountain-bike ride rather than taking it over. Deore at £6,999 already has the carbon frame, Bosch SX system, mixed wheels and the brakes and tyres that define the bike. XT at £8,499 is the move if Ultimate-level RockShox, a carbon bar and the 18.67 kg figure in MD are worth the jump. Either way you get a trail bike that can add a climb, cover the ride from home and still ask you to ride it.