2026 Transition Regulator SX Review

Technical Details

I tested the Regulator SX, the new lightweight all mountain e-MTB from Transition, in their hometown of Bellingham, WA. They're no stranger to the e-MTB landscape, having three previous platforms with different drive system manufacturers. The big story here is the new use of Bosch’s reliable ebike systems. The PNW mountain bike staple is known for real-world durability, and Transition wants their e-MTBs to deliver on that promise. But my biggest takeaway is how well the lightweight Regulator SX model handles. It's one of the most fun bikes I've ridden, electric or not.

There are two different Regulator models using drives and batteries from the large German technology company. The Regulator CX is the full power option, employing a fifth-generation Bosch CX drive alongside a PowerTube 600 battery. With all its output, it’s still impressively light at under 50 lbs. But with the SX model, Transition’s “light-enough” approach and versatile riding characteristics create a combination that blurs the lines. It’s what I’ve hoped emtbs would become, and it’s addictive.

Bosch's SX drive is the lightest they've made, and uses a unique CompactTube 400 battery. Combined with a sleek carbon frame and thoughtful parts, Transition has found a power-to-weight ratio that’s truly impressive in a bike that “feels” overbuilt. The stock SX drive unit provides 55nm of max torque and up to 600 watts peaks of power. The integrated battery can be combined with a PowerMore 250 range extender - in place of a water bottle - for up to 650 watt hours of range on long rides.

The extender is widely available, which is great, but it's an additional $499, which is spendy. For reference, I'm over 200lbs and would expect to only need the extender on rides longer than 3 hours, or with more than 3000’ of gain. Of note though, the extender drains alongside the battery, extending its life, and can't help once your main battery is drained. And while it's a similar size to a bottle, it's heavier, so the extender uses its own dedicated mount. You need to install that, but it feels stout and has a thoughtful cable guide. If you run out of juice, the Regulator pedals just fine when “off”. And you're not able to remove the battery on these bikes like you can with the Transition Relay.

For full-day missions to the far reaches using assistance, the smaller SX system, even with its extender, presents some range anxiety. But in reality, I personally want the ability to get the most out of my normal 2-3 hour rides. With that, the plain benefit is that the smaller system is over 4 lbs lighter than bigger drive and battery found in the full power Regulator CX. That’s enough to have a meaningful effect on handling and change the needs of the build kit.

On the XT model, weight is saved where it makes sense, like using the very capable Rock Shox Lyric Ultimate fork and Maxxis Exo+ casing tires. The result: an impressive 42 lbs of easy-to-control power. 

Build Kits

There are currently just two build options: Deore and XT. The Regulator SX Deore build isn’t quite as light as the XT, but still gives you all the same benefits of the carbon frame and SX system. Transition's component choices for this build are designed maximize value without compromising performance.

The Regulator SX XT build comes with really cool part choices across the board. They not only suit the bike's intentions to a tee, but demonstrate how Transition remains at the forefront of understanding trends and rider's preferences.
 

Ride Impressions

Test Bike Setup
My test ride was quick and easy to get along with. I had to find a size XL for my 6’4 height but it felt expectedly at home. The 510 mm reach and moderate stack height above the 64.5 degree head angle felt like a modern recipe and there were no surprises as I found my balance. The XL and L sizes share 448mm chainstays, which paired with the dedicated 27.5” rear wheel felt snappy but stable. I normally ride the Transition Sentinel in the same size and I was happy to settle into a supercharged version of my familiar bike.

It would be cool to see some added adjustability on the Regulator SX, as the CX model comes with the choice of a high or low frame setting. However, there's a nice simplicity to fewer options. I set up 30% sag in the suspension and that was it, the bike was ready to go. The RockShox Ultimate suspension felt great throughout my time on the bike. I rode familiar trails at Galbraith mountain. With a good amount of variety thrown in, I can say I wouldn't have reached for a flip chip even if it was available. 

Climbing / Uphill
Climbing was comfortable; immediately noticeable and welcome were the short cranks and long dropper post. The Bosch interface is intuitive and mostly goes unnoticed as you find your settings via the controller, which can be tailored in your phone app. Next thing I knew I was up to speed in short bursts and became grateful for the bike's powerful but sensitive brakes. In this case, TRP’s reworked DHR EVO Pros feel like they could stop a train, without derailing it. You now have more control over the levers, and I found them more comfortable.

At each step, the Regulator SX felt intuitive. The angle of the massive OneUp seatpost put me into a comfortable and planted climbing position. The drive’s assistance never felt like it was trying to wheelie away from me in corners, or break free from traction in loose dirt. I’d love to spend more time getting a feel for this level of control. It's an ego boost to tackle sections of climbs that would otherwise be laughable. Shifting via the trusty mechanical Shimano XT drivetrain was quick and the short Race Face Era cranks left plenty of pedal clearance over roots and rocks. All of this combines to make for fun and fast climbing. This gets amplified when the SX drive senses a high cadence and increases the motor power to an above-normal peak. It’s a clever tune of the system to get you the most out of the battery while matching the needs of the climb. 

Descending / Downhill
When gravity starts to pull, the blend of emtb characteristics and trail bike manners starts to get blurry. There’s extra weight, yes? But it hardly feels like a detriment with all the added cornering control. And coming quickly out of turns, the Regulator SX feels ready for anything. Slung comfortably into Transition’s trademark suspension, the low mass remains easy to unweight. And after popping up or jumping, the bike falls back into the trail without hanging up. Adjusting to the mixed-wheel setup felt seamless, with the bike promoting a carving sensation that left me head-shaking and hollering.

Bellingham’s berms are long enough to have complete thoughts, like “this could happily be my only bike, even though it’s an emtb?”. The next long berm then just confirms the previous. Like other Transition trail bikes I've ridden, there seems to be magic amount of lateral flex in the frame. It allows you to both sneak though corners, and remain stable at speed pushing into your feet. From fast and flowing jumps to tight and rocky tech, the Regulator SX remained composed. Only when creeping up on new-to-me features did I remember I was on an ebike. The slowest speeds remind you that you're managing the momentum of that bit of extra weight. Luckily, the motor is there to help you find speed wherever you need it.  

How Does it Compare?

There is currently no alloy version of the Regulator SX. If that's what you're looking for, something like the Devinci Troy E Lite could be comparable, as it shares the Bosch SX drive and CompactTube 400 battery. So too does the Norco Fluid VLT, which has slightly less travel in a mixed-material frame. But for the relative extra cost, I think Transition's offering is the most refined of the three. It has an attention to detail and design priorities that won't go unnoticed by the rider, especially if steep and technical trails are on offer.

While Transition's Relay and Repeater models are designed to handle enduro duties outright, the Regulator can be modified into a mini enduro bike by swapping shocks for a 10mm increase in rear travel. They also say the frames are plenty strong to accommodate a bigger fork, if you're interested in the ability to increase front travel and slightly slacken the head angle.