Transition Regulator SX and CX Review

Transition Bikes is based in Bellingham, Washington, a mountain biking hub nestled near the Pacific Northwest’s epic trails in the US. Transition’s ethos is all about having fun on bikes – and as a result their bikes prioritise playfulness, progression, and community over race results. 

The recently released Transition Regulator breaks from the e-bike norm. While most brands separate mid-powered and full-powered models, the Regulator offers both options in a single platform. Using Bosch’s Performance Line CX and SX systems, riders can choose the level of motor support that best suits their style  – whether it’s all-day efficiency or hard-charging descents. Transition has built the Regulator to deliver performance, whichever way you lean.

We had a rare opportunity to conduct a direct comparison between two nearly identical e-bikes from the same brand – one full-powered, the other mid-powered. Ryan Walsch (178cm, 75kg) and Josh Kluth (183cm, 71kg) will be testing the bikes back-to-back. A large frame comfortably accommodates both riders for consistent results.

Both bikes share Transition’s proven geometry, modern suspension kinematics,  full carbon frames and are exclusively mullet or mixed wheel configurations (29” front and 27.5” rear). The Regulator series are equipped with an efficient yet capable 160mm/150mm suspension travel. 

The Bosch Performance Line CX and SX differ significantly in motor systems, battery capacity and weight, allowing the rider to select the power and handling characteristics that’s best for them. Below, we break down the key differences to help you decide which Repeater is right for your terrain, pace, and ride style.

Initial Impressions

Transition Regulator CX

Transition has done a fine job of squeezing a full 600Wh battery and Bosch Performance Line CX into a silhouette not dissimilar to their Sentinel model. The overall weight of the Regulator CX is a very reasonable 22kgs with pedals. Smooth lines and bang-on geometry with the playful characteristics of  the mullet chassis means that the Regulator is set to be a sporty all-rounder with a burly specification sheet to back it up. 

The frame is packed with thoughtful design details that are easy to overlook at first glance available in Glacier White (tested) as well as Salish Sea Blue. You’ll find clean cable routing options on both sides of the frame, with high-quality ports that hold cables securely in place. There’s robust integrated chain slap protection, a main pivot guard and chain guide, plus a dual magnetic closure on the charge port to keep out moisture and debris. 

The Regulator CX also features adjustable geometry via a flip chip, and all models come equipped with sturdy mounts for a Bosch PowerMore Range Extender  – boosting capacity from 600Wh to 850Wh for even bigger days on the bike. Transition has opted for a 600Wh battery across all sizes favouring the highly efficient Bosch system and handling on the trail and it does show. 

While the Bosch Performance Line CX comes standard with 85Nm torque, 340% maximum assistance and 600W peak power, Bosch are rolling out a free system update via the Flow app that brings the system up to 100NM torque, 400% maximum assistance and 750W peak power.

Setup is always a breeze on RockShox forks with a neat rider weight and pressure guide on the back of the fork leg. We have the RockShox ZEB Ultimate set at 83psi and 3 tokens and the Super Deluxe Ultimate sitting on 30% sag and 205psi which is right within Transitions preferred range of 27% to 33% sag

DT Swiss’s H1900 wheels set up tubeless super easily, however there were no valves provided with our test bikes. If you’re considering the Transition Regulator, be sure to use valves long enough to accommodate the valve stem-mounted rear wheel magnet for the Bosch system, 45mm or longer. 

It is nice to see the addition of Schwalbe’s Albert Trail Evo Ultra Soft and Soft tyres, however we think the trail casing may be a little light on for a capable brawler of an e-bike, we will be running these a little firmer than we’d hope to fend off any accidental rim dings.

Transition Regulator SX

A near carbon copy of the Regulator CX with lighter trail bike feel, the Transition Regulator SX uses a quality handbuilt trail wheelset from DT Swiss, lightweight Raceface Era Carbon cranks, RockShox Lyrik Ultimate, and the Bosch Performance Line SX drive unit featuring 55Nm of torque with a 400Wh battery. This lighter trail package has resulted in a huge weight reduction and more refined presence on the trail – with the Regulator SX weighing a feathery 19.6kgs with pedals.

The Transition Regulator is aesthetically pleasing, with a minimal but vibrant paint job on the Madrone Gold test bike (also available in the less exciting Stormshadow Grey), the matching fork decals are a nice touch. The RockShox suspension is very easy to ensure a solid trail riding setup out of the box, and I had no issues when building the bike. 

Before hitting the trails, I did have some concerns about the performance of the lighter-weight Bosch SX motor and the smaller battery – will their performance be enough to be worth the saved weight? 

There is also no screen for the motor and battery on the bike as delivered, just the controller and the LED Bosch System Controller which is a unique feature that not all e-bikes have which gives a cleaner aesthetic I personally prefer. The new Bosch KIOX 400C is available as an aftermarket upgrade for both Performance Line SX and CX bikes if you do prefer a screen-based interface – chat to your local Bosch dealer for price and availability.

On The Trail

Transition offers four frame sizes for the Regulator, with reach starting as short as 420mm in size small, up to 510mm reach with an overall wheel base of 1307mm in size extra large for the lanky lads and ladies. Our test Regulator CX and SX rigs are both large with a 480mm reach, and on paper and trail this is bang on the money for a large frame in 2025. 

As always, I find myself between medium and large sizes. But with the Regulator’s playful character, mixed wheel setup, and taller 125mm stack and headtube, I prefer the more upright, stable feel of the large at my average 178cm height. For Josh, with longer limbs and an extra 5cm of height, the large is the clear choice. That said, riders my size chasing a more agile, flickable ride might lean toward the medium, which offers a 460mm reach and still provides plenty of room to move and stay comfortable.

Transition uses their patented Speed Balanced Geometry (SBG), a holistic approach to optimising ride dynamics by tweaking five key factors: frame reach, head-tube angle, seat-tube angle, stem length, and fork offset. By combining a slacker 65.4º head-tube with reduced fork offset and a shorter stem, SBG shifts the front wheel closer under the rider to enhance front-wheel traction and balance. In effect, SBG maintains high-speed stability while preserving manoeuvrability at low speeds. 

As a result, the Transition Regulator is a confidence-inspiring ride, while delivering sharper handling on technical terrain and improved braking control. All together this results in boosting rider confidence across all speeds and skill levels. 

With a very steep actual seat tube angle of 75º, the seat tube is nearly straight, which allows a full length dropper to be slammed – for example the 210mm OneUp dropper post would happily slide in until the collar touched the seat post clamp. Another cool feature is that the OneUp dropper post is travel adjustable so riders can basically slam that thing and adjust the travel back to their desired seat height.

We are fortunate to be let loose on the higher of two build levels the Regulator models are available in, which is equipped with Shimano’s Deore XT 12-speed mechanical drivetrain, TRP DH EVO Pro brakes and DT Swiss Hybrid H1900 wheels – which include industry leading solid ratchet internals. The Regulator SX is adorned with DT Swiss XM481 rims laced onto DT Swiss 350 DEG hubs. Both bikes feature OneUp dropper and carbon riser handle bars. 

As a complete build, both bikes feature a well thought out selection of top performing components known for their durability and trail feel, but standout components include OneUp’s trail chatter-reducing carbon bar and Schwalbe’s tyres with the new Radial casing. Both of these products really help dampen harsh bumps and tame feedback to the rider, which results in more grip and control when the going gets rough.

Out on the trails the Regulator holds its own, their GiddyUp suspension platform feels near bottomless – despite being a sensible 150mm. It also pedals efficiently, features midstroke support and ramps up superbly in deep compressions. GiddyUp features a consistent 27% progression, with anti-squat tuned to boost pedalling efficiency and acceleration around the sag point. Beyond that, anti-squat is reduced, allowing the suspension to remain active deeper in the travel without being hindered by chain tension.

With the Regulator’s near bottomless feel, we found the bike gave us oodles of confidence on the trail in both rough technical terrain and fast-paced flow trails, with Transition cleverly leaving some travel in the tank. Using a trunnion mounted 205mm x 60mm stroke shock, the Regulator’s travel can easily be increased to 205mm x 65mm for an additional 10mm of rear wheel travel for a total of 160mm. 

Both Regulators responded well to being pushed, having the required support for zealous manoeuvres at speed. The Regulator CX is equipped with super short SRAM 150mm cranks, and the Regulator SX is equipped with 160mm RaceFace Carbon Era cranks that give riders a bit more access to torque on climbs. The steep 75º seat tube angle, high stack, and shorter cranks make both of these bikes capable mountain goats with plenty of traction and clearance.

The new TRP DH EVO Pro brakes are a true standout. With heaps of power and adjustable lever position and pad contact, they proved consistent on long and arduous descents. Equipped with solid 2.3mm rotors in 200mm diameter both front and rear, these brakes never left us wanting more.

Both bikes are equipped with the latest Bosch offerings and we have detailed reviews on both the recently released Bosch Performance Line CX and its updates, along with the Performance Line SX. As we are used to, the hardware from Bosch is top notch and we had faultless encounters with both bikes. Choosing between the CX vs the SX model will come down to the type of rider you are and how you are going to ride your e-bike.

Our Take

The Regulator CX is a bit of a brawler with its burlier components, beefed up suspension, more powerful motor and larger battery. We even found we got more range and climbing out of the Regulator CX as the system wasn’t working as hard to propel us along. This does come with a 2.5kg penalty so keep that in mind – it is noticeable both on and off the trail when compared to the Regulator SX, but it remains much lighter than many full powered e-bikes we have recently reviewed. 

On the other hand, the Regulator SX is agile, manoeuvrable and could just be the best riding SL e-bike we’ve ridden to date. With thoughtfully selected components to shave weight without compromise, the Regulator SX manages to retain a planted feel while maintaining the ability to send down super technical trails, more for the rider that wants to retain the analogue bike ride quality with enough support to get you to the backcountry. A capable trail bike with some extra punch.

Overall, both bikes rode exceptionally well – the key question to ask yourself is what kind of ride support do you yearn for?

Learn more about the Transition Regulator here.