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The Rockrider ST 120 Mountain Bike - worth the money?

B'Twin Rockrider 27.5" ST 120 Alloy Hardtail Mountain Bike S,M,L,XL, Black, Blue, Alloy Frame, 27.5" Wheels, 15.1kg, 9 Speed, Disc Brakes, Single Chainring

Available in S, M, L & XL in Black & Blue.

just £300!

View the B’Twin Rockrider 27.5″ ST 120 Alloy Hardtail Mountain Bike

The ST 120 is currently the cheapest bike in the Rockrider line up which includes disc brakes (it's cheaper sibling, the Rockrider ST 100 only has V-Brakes).

In addition the ST 120 also features a single chainring setup, with 9 gears rather than the 7 speed triple setup of the ST100. In short, the ST 120 will both feel and perform more like a real mountain bike, with simple shifting and superior stopping power.

The frame is 6061 straight gauge lightweight alloy, in order to reduce overall weight to a minimum.

Taking of weight, as a result of the single chainring, the ST 120 doesn't require a front shifter nor derailleur, and this results in a bike which saves around 1/2 a pound over the ST 100. There's also a ladies version of the ST 120, with female specific geometry and saddle.

So is the ST 120 worth buying? Or should you be looking at the ST 520? Read on to find out.

The ST 120 Frame and Forks

ST 120 Frame and Forks

The Rockrider designed frame is pretty similar throughout the lower ST (Sports Trail) series, all of which feature the "CGF" philosophy.

"Comfort Geometry", as Rockrider have coined it, is achieved by slacking the head angle and reducing the length of the rear of the frame. This leaves the rider more upright, yet helps keep the steering agile.

The ST 120's frame features the distinctive inward bends on both the seat stays and downtube to lend an extra layer of comfort to the rider. As per most bikes of this price range, cables are externally routed and the bike comes with 27.5" wheels.

The black forks are Rockrider's own brand, providing 80mm of travel, which is adjustable. Simply dial in your weight on the right hand of the crown, and the U-Fit system will help tailor the travel for your riding.

Obviously these forks won't be as plush as high end models, but to have adjustable suspension at this price point is pretty impressive.

Mid Size 27.5" wheels

ST 120 27.5 inch Wheels

The 27.5" wheels comprise of 19mm double walled alloy rims, with 28 spokes front and rear. In an upgrade over the ST 100, both wheels utilise quick release levers, making removing the wheels for transportation or fixing punctures much easier.

The tyres supplied are the all rounder Rockrider Dry MTB models, 2.0" in width and featuring a relatively fast rolling tread. These can easily be changed at a later date if you fancy something wider or more suited to riding on the road.

Rockrider Bars, Stem, Headset and Grips

Handlebars and Stem

The bars on the ST 120 are 20mm wider than that of the ST 100's, being 640mm in total. Again, they are made from steel, so there's potential to save weight here if you swapped them out for an inexpensive alloy set.

The alloy stem is 90mm long, with a 10 degree angle, and the grips are the soft Rockrider lamellar models. Finishing off the steering is a generic Rockrider headset, in black as per the rest of the controls.

Simple 9 speed Setup

9 Speed Microshift Drivetrain

The ST 120 has a single 9 speed drivetrain, meaning there is no front derailleur nor front shifter, with just a single chainring up front and 9 cogs on the rear cassette. This saves a little weight and make shifting a lot simpler.

Rear shifting is operated via the Microshift SL-759 shifter, which controls the RD-M46-L rear mech. KMC supply the Z9 steel chain, which rotates the 11-36 Microshift H092 cassette.

The 9 speed Rockrider ATB 100 chainset features a single 32 tooth ring with chainguards to prevent damage to the chainring's teeth and stop your legs from getting mucky.

All in all, a simple yet reliable drivetrain, which should be easy to maintain given the single derailleur and shifter.

Mechanical Braking

Tektro TKD 68 mechanical disc brakes

The ST 120 features Tektro TKD 68 disc brakes, which are mechanical (cable operated) rather than hydraulic. This will result in a touch less power and slightly more maintenance, but they will still be far more effective than V Brakes.

The rotors are 160mm in diameter, which you should be able to upgrade to 180mm if you require more stopping power; you'll just need a new rotor and adapter.

Stealthy finishing kit

Saddle and Seatpost

The rest of the bike is finished in a matte black colour; the Flex seatpost is 27.2mm in diameter and either 350mm or 400mm long. Weight savings can be made here, as this model is made from steel, and a cheap alloy replacement will save you a bit of mass.

The saddle is Rockrider's Ergofit model, which is designed for men, but a female specific version is available on the ladies ST 120.

Lastly, the resin pedals are Rockrider's cheap yet effective platform mountain bike models. They won't be as grippy as alloy models, but equally they shouldn't scratch you as badly should your foot slip off the pedal.

The Rockrider ST 120 - good value entry level biking?

Rockrider ST 120 Conclusion

The ST 120 is the second model up in the Rockrider ST series, costing slightly more than the popular Rockrider ST 100. So what differentiates the ST 120 from it's cheaper sibling?

On first glance the obvious upgrade is disc brakes. Tektro's TKD 68 provide superior stopping power, and despite their mechanical (cable based) nature will offer better performance than V Brakes. These can easily be upgraded to a hydraulic system at a later date if you so wish.

The second difference is the single chainring setup, complete with 9 speed cassette. This will help reduce overall bike weight due to the absence of a front mech, shifter and two chainrings compared to a triple setup. As per many lower end bikes, Microshift provide the majority of the drivetrain, with the exception of a 9 speed KMC chain.

The ST 120 comes with an 80mm suspension fork and 27.5" wheelset, both of which will be reasonably heavy; however given the cost we can't complain.

Please note: it will be worth upgrading the handlebar from the stock narrow 640mm steel component to a wider alloy set; the bike will be more fun to ride and weigh slightly less.

In terms of weight, the Rockrider ST 120 Mountain Bike weighs approximately 250g / 1/2 lb less than the cheaper ST100 model, with measurements ranging from 15.1kg (S) to 15.5kg (XL).

So is it worth buying? In our opinion yes; it's a cost effective beginners mountain bike which can easily be upgraded as your skills progress.

The official manufacturer's info

Here's what Rockrider / Decathlon have to say about the ST 120

This 27.5" mountain bike is designed for getting started with MTB touring in dry weather, for rides up to 1.5 hours.

An efficient, easy-to-handle MTB! Riding the ST 120 MTB you will feel the precision and light weight provided by the single chainring (1x9 speeds) and mechanical disc brakes.

Change speeds easily! Cycling comfort: Enjoy touring: raised position, 80 mm suspension, hammock saddle, FLEX seat post.

Ease of use: Adjust your speed without thinking: 9-speed single-chainring drivetrain.

Directional control: Control your trajectory: cable disc brakes, tyres with side knobs.

Efficiency: Pedal efficiently: light aluminium frame, 9 speeds and fast tyres.

Robustness: An ultra-strong MTB: welded saddle, double-wall rims.

The 100% aluminium CGF frame (Comfort Geometry Frame) is both comfortable and easy to handle. The slope angle has been designed to keep your back straight, while the rear bases were shortened to make the bike very agile in turns.

Front suspension: The 80 mm front suspension helps you get started with overcoming obstacles on slightly uneven trails easily.

Easily adjust the hardness using U-Fit technology (weight adjuster). Simply set the number to your weight (55 kg to 105 kg) using the dial on the fork.

REAR SUSPENSION: None: This mountain bike has no rear suspension.

It is a "semi-stiff" mountain bike: perfect for beginners launching themselves into their first mountain bike touring rides.

Compared to a full suspension mountain bike (with rear suspension), the advantages are clear: the mountain bike is lighter; you spend less energy on flat ground.

DERAILLEUR & DRIVETRAIN: A SINGLE CHAINRING LIKE THE PROS!: The single chainring is easy and efficient to use:.

1 chainring and 9 speeds. Accelerate on the flats and easily tackle the climbs. With a single lever on the handlebar, you can change gears while hardly thinking! ROCKRIDER FC ATB 100 - 32-tooth single chainring equipped with 2 chain guides (anti-derailment).

MICROSHIFT RD-M46-L rear derailleur. MICROSHIFT SL-759 right shifter. MICROSHIFT H092 9-cog cassette (11-36 teeth).

Wide, sturdy KMC Z9 chain HANDLEBARS, STEM, GRIPS: With a stem that tilts 10 degrees upwards, the riding position of the ST 120 is raised, accessible, and comfortable. In detail:. 90mm aluminium stem with an angle of 10 degrees for maximum comfort.

640mm wide steel handlebar for stability and control. "Soft touch" lamellar grips for a firm yet soft and pleasant grasp.

Saddle: The saddle of the ST 120 is welded to prevent any movement of the saddle.

And because your comfort is our priority after your safety, we've added an exclusive wider Ergofit saddle with a hammock shape. Easily adjust the height of your saddle with the Flex steel seat post (350mm or 400mm long depending on the bike size). Its smaller 27.2mm diameter provides your seat with natural flexibility, 30% more than a standard solution.

MECHANICAL DISC BRAKES: The Tektro TKD 68 160 mm double disc brakes provide powerful, progressive braking at the front and rear. The aluminium Tektro brake levers are precise, and easy to hold. The brakes can be applied using only two fingers.

3 or 4 sets of 10 dry, intermittent stops are enough to break in your pads. We recommend that you have your brakes checked at least once a year.

27.5" WHEELS & TYRES FOR DRY TERRAIN: The 27.5" wheels of the ST 120 are tolerant and sturdy, with 19 mm double-walled rims with 28 spokes.

Start overcoming obstacles fearlessly, including small rocks, cracks, holes and bumps! Because your first rides will be on dry ground, the Dry 27.5 x 2.0 tyres are most suitable. The central section has low rolling resistance (faster), while the side lugs provide good grip on turns.

Platform pedals: The Rockrider ST 120 mountain bike comes with resin mountain bike platform pedals for lower weight and increased safety.

If your foot can slip off the pedal, you're less likely to injure yourself. The ST 120 mountain bike comes with a bell, lights, wheel reflectors, and pedals.

Weight: Small: 150-164cm - 15.1 kg.

Medium: 165-174cm - 15.2 kg.

Large: 175-184cm - 15.3 kg.

X-Large: 185-200cm - 15.5 kg.

ST 120 pics
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Full MTB Spec

Here you'll find the current specification of the ST 120.

Frame & Fork
FrameAluminium CGF hardtail frame
Forks80 mm front suspension with U-Fit technology (set your weight)
Frame MaterialAlloy
Frame TypeHardtail
Fork TypeSuspension Fork
Wheels27.5" wheels, 19mm double-walled rims with 28 spokes
TyresDry 27.5 x 2.0 tyres
Wheel Diameter27.5"
Handlebars640mm wide steel handlebar
Stem90mm aluminium stem with 10 degrees angle
HeadsetOwn Brand
GripsSoft touch lamellar grips
Finishing Kit
SeatpostFlex steel seat post (350mm or 400mm long and 27.2mm diameter)
SaddleErgofit saddle
PedalsResin mountain bike platform pedals
BrakesTektro TKD 68 160mm disc brakes with 2 finger aluminium levers
Brakes TypeDisc Brakes
Chainset1 x 9 speed Rockrider FC ATB 100 chainset - 32-tooth single chainring equipped with 2 chain guides
Front Derailleurn/a
Rear DerailleurMicroshift RD-M46-L rear derailleur
ShiftersMicroshift SL-759 right shifter
ChainKMC Z9 chain
CassetteMicroshift H092 9-cog cassette (11-36 teeth)
Number of Gears9 Speed
ChainringsSingle Chainring
Cassette9 Speed
General Details
Other InfoComes with a bell, lights, wheel reflectors, and pedals
Bike TypeMountain Bikes
Designed forMTB
ColourBlack & Blue
SizeS, M, L & XL
Lowest Price£299.99
What size Rockrider mountain bike will fit me?

The Rockrider ST 120 MTB is available in S, M, L & XL in Black & Blue.

Below is a Rockrider MTB size chart, so you can see which ST 120 fits you.

Your height (cm)Your height (ft)Bike size
135 - 150cm4'5'' - 4'11''XS
150 - 165cm4'11'' - 5'5''S
165 - 176cm5'5'' - 5'8''M
176 - 184cm5'9'' - 6'1''L
184 - 195cm6' - 6'5''XL
ST 120 Frequently Asked Questions
  • What kind of brakes does the ST 120 have?

    The ST 120 features Tektro TKD 68 disc brakes - these are mechanical, and not hydraulic.

    This means they'll have a little less power, and a bit more maintenance than their hydraulic counterparts.

    This will largely involve making sure the brake cable is lubricated and in good shape - not a costly nor complex procedure.

    The rotors are 160mm in diameter and manufactured from steel.

  • How much does the Rockrider ST 120 cost?

    The ST 100 is now on sale for £300 (RRP is £300).

  • How many gears does it have?

    The ST 120 has a 1x9 groupset. This means it has 9 gears on the rear cassette (the Microshift H092, with an 11-36 ratio), and a single 32 tooth chainring mounted on the Rockrider FC ATB 100 chainset.

    As a result there is no front derailleur nor front shifter required - just a Microshift RD-M46-L rear derailleur and Microshift SL-759 right shifter.