You can spend a lot of money on an electric mountain bike, and there are some great bikes out there if you have deep pockets. But don’t worry: the Rockrider E-ST900 from sporting retail giants Decathlon has you covered on a budget. It’s fun to ride, well-specced and unbeatable value.

Buy the Rockrider E-ST900 here

Decathlon Rockrider eST-900-3.jpg, by dave atkinson

Built around a sturdy 6061 Aluminium frame, the Rockrider looks the real deal. There’s a 120mm travel Rock Shox Judy fork up front, Boost-spec wheels, big-chamber 2.8” tyres and a Shimano Deore 10-speed transmission. All that and the bike gets a proper mid motor courtesy of Brose, and a 500Wh battery for full-day exploring… all for £1,599. 

I’d describe the geometry of the E-ST900 as fairly traditional in mountain biking terms. It’s not especially long in the front, and the head tube isn’t too slack, so if you’re used to pointing something like a Mondraker or a Nicolai down your local trails then this bike will certainly feel a bit old-fashioned. The reality though is that it’s not a bike for that type of rider: it’s a bike for riders like me, who are reasonably competent off road but aren’t flat-out gravity chasers.

Decathlon Rockrider eST-900-4.jpg, by dave atkinson

I spend most of my off-road time riding local trails and bridleways, which mostly aren’t that technical and require stints on the tarmac to link them up; and this bike is just the job for that sort of riding. It’s happy enough rolling along on the blacktop on its shallow-tread Hutchinson Taipan tyres, and when you leave the tarmac you can throw it around without feeling like it’s not the right tool for the job. There are faster and more capable bikes off-road, sure, but the 120mm Rock Shox Judy fork can take some fairly big hits. The E-ST900 also has poise enough that you can get it down some pretty technical stuff. I don’t live in the Alps, but there’s plenty of slippery, rocky riding in the bridleways around Bath that the Rockrider took in its stride. It’s capable enough to cope with the blue runs at a bike park, or the reds if you take a bit of care. That’s as deep as I like to go anyway!

Decathlon Rockrider eST-900-14.jpg, by dave atkinson

Once you’re at the bottom, getting back up is a joy thanks to the Brose motor. It’s a specific build for Decathlon which the company says is rated at 90Nm. Like all Brose motors it’s very quiet, and the way that it applies the assistance to the rear wheel feels very natural. Control is from a bar-mounted remote that offers four levels of assistance: 40%, 80%, 160% and 320% of what you’re putting through the pedals. There’s an LCD display which gives you your speed and all your other metrics, as well as a human power reading that tells you how hard you’re working.

Decathlon Rockrider eST-900-10.jpg, by dave atkinson

The remote isn’t the easiest to use that I’ve ever tried – the buttons are flat against the surface of the unit and not always easy to locate in gloves – but it’s decent enough. The battery reading shows four bars but they get eaten away gradually, so it’s more granular than you expect. The battery depletion is pleasingly linear, with the last bar of the battery pushing you a similar distance to the first.

Decathlon Rockrider eST-900-5.jpg, by dave atkinson

In terms of absolute power the motor isn’t as punchy as some. It doesn’t feel like a match for a Bosch Performance Line CX or a Shimano STEPS E8000 motor but it’s only really one rung down, and it’s exceptional given the price tag. To get a comparable motor – a Performance Line, or an E7000 – from most other brands you’d be looking at something north of £2,000, and quite a long way north in many cases.

The Rockrider’s motor took me up everything I pointed it at without missing a beat. There were times when my technical ability was found wanting on steeper, more technical stuff, but the motor never was. Assuming that I could keep my wheels pointed in the right direction, the bike got me to the top. It’s never a free ride: you need to add some oomph of your own, and there’s the hauling of a 22kg bike about to find the right lines, but it made riding possible that I wouldn’t have managed without a motor… or would have damn near killed me, anyway!

Decathlon Rockrider eST-900-9.jpg, by dave atkinson

Range is a very moveable feast with an electric mountain bike, but with a motor that has a wide range of assistance levels and a 500Wh battery you should be able to get a proper long ride out of the Rockrider. I found that a 25km, 1h30m ride that was a mixture of on- and off-road was eating through about half of the battery. It’s fairly hilly round here, so that’s about 500m of climbing, and I wasn’t being particularly frugal with the mode selection. Once you have run the battery down it’s a simple job to plug in and recharge, although it’s certainly not a speedy affair. This isn’t a bike you can get meaningful charge into over an hour’s break for lunch, you really need to have it plugged in all night to be sure of a full tank for the next outing.

Decathlon Rockrider eST-900-2.jpg, by dave atkinson

Anything that wasn’t up to scratch? Well, it’s great that Decathlon has specced tubeless-ready tyres and rims – the 36mm Sun Ringle rims are excellent – but the Hutchinson Taipan tyres didn’t really do it for me. They’re a shallow tread and quite a hard compound, so they roll okay on tarmac but they’re pretty squirrelly in the corners. Off-road they’re okay on hardpack, but on mud and rocks they just feel a bit vague and don’t bite. It’s difficult to spec a tyre on a bike like this that will cover all conditions, but the Taipans don’t really feel like they do anything that well. I’d definitely be tempted to swap them out for something a bit more aggressive.

Decathlon Rockrider eST-900-8.jpg, by dave atkinson

The tyres are a fairly minor gripe, and easily remedied if you feel the same way, so let’s not lose sight of the bigger picture: for £1,600 you’re getting a Brose motor, full-fat 500Wh battery, tubeless Boost-standard wheels, Shimano Deore transmission, a Rock Shox fork and serviceable finishing kit. Whatever else the E-ST900 might be, it’s astonishing value for money. There literally isn’t a single other electric mountain bike I can think of that can match it step-for-step. Add to that the fact that it’s fun to ride and capable enough over fairly technical terrain and what you have here is a real winner. If you enjoy getting out and about off-road and you’re happy enough with a more traditional geometry, you really don’t need to look any further.

decathlon.co.uk