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The budget Rockrider ST 100 Mountain Bike - is it any good?

B'Twin Rockrider 27.5" ST 100 Alloy Hardtail Mountain Bike XS,S,M,L,XL, Grey, Yellow, Alloy Frame, 27.5" Wheels, 15.3kg, 21 Speed, Caliper Brakes, Triple Chainring

Available in XS, S, M, L & XL in Grey & Yellow.

just £230!

View the B’Twin Rockrider 27.5″ ST 100 Alloy Hardtail Mountain Bike

The Rockrider ST 100 is a highly affordable mountain bike, for sale at pretty much the lowest you can realistically purchase a useable mountain bike for, currently priced at a shade over the £200 mark.

And you get a fair bit for your money; 80mm suspension forks, an alloy frame, 27.5" wheels and a full 21 speed Microshift groupset. There's even a female version too.

The downsides? B'Twin couldn't quite include disc brakes within this bracket, and so V-Brakes are fitted instead. Similarly on cheaper bikes, it's difficult to keep the weight down without impacting strength, and so this Rockrider mountain bike tips the scales at 15.3kg (33.7lbs for the old school riders!).

The ST 100 Frameset

Rockrider ST 100 Frame

This bike is provided with a "lightweight" (although no actual frame weight is supplied!) alloy hardtail frame which they label as "CGF" or Comfort Geometry Frame.

It's not entirely clear what they mean by this, but you can assume it refers to the relaxed geometry for comfortable riding. This has been achieved by designing a slack head angle and shorter rear end.

The suspension fork is an own brand type affair, with 80mm of adjustable mechanical travel and largely constructed from steel.

There are no real issues with either of these components other than it would have been nice for Rockrider to include a disc tab on the frame for future upgrades.

I appreciate that they couldn't include disc brakes at this price, but it would have been a handy addition to have the possibility to upgrade.

As it is, you can't ever use disc brakes on this bike and will be only able to run V Brakes. The good news is that if this is a deal breaker then you can always buy the disc equipped ST 120 instead.

Onto the wheels

ST 100 27.5 inch Wheels

The ST 100 is supplied with a set of 27.5" (650b) alloy MTB wheels. The rims are double-walled and feature 28 spokes front and rear.

Tyres, as per the forks and much of the componentry, are Rockrider own brand; the 2.0" wide Dry models.

As per the missing disc mounts, it would be nice if the bike featured quick releases front and rear, but sadly these are only supplied for the front wheel. This won't affect daily riding, but will make changing punctured inner tubes a little more complicated by the need for a wrench.

Steering the ST 100

Handlebar, Stem and Grips

The handlebars supplied are 620mm wide and made from steel. Unfortunately at this price point Rockrider were unable to provide alloy bars, so steel was their solution; just as strong but a fair bit heavier.

These are complimented by their own brand soft touch grips, and attached to the fork steerer by either a 90mm or 110mm length stem. The stem supplied depends on the bike size chosen, with larger frames featuring a longer stem. Rounding off the steering is an own brand headset finished in black.

Shifting through the 21 gears

21 Speed Drivetrain

The drivetrain is largely Microshift based, with the FD-M20 front mech shifting across the triple chainring chainset, and the RD-M25 7 speed rear derailleur carrying out shifting duties in the rear. This rear mech is protected by a steel guard to prevent damage. Equally the chainrings have a guard fitted to prevent your clothes from getting mucky.

Shimano provide the TZ500 14-28 cassette, and the chain is the KMC Z51. This 21 speed system is controlled via the Microshift MS25 grip shifters (twist operated) on the handlebars.


ST 100 V Brakes

Next to these shifters you'll find a pair of black alloy brake levers, which are designed to be operated with 2 fingers. These cable powered brake levers control the V brakes, which slow the bike by pushing the brake pads against both sides of the wheel rim. This form of braking isn't as powerful nor predictable as disc brakes, but are perfectly acceptable given the low price tag.

Rockrider Finishing Kit

The ST 100 Saddle and Seatpost

All of the finishing kit is black, and as mentioned previously, own brand kit. This isn't a massive surprise given the low cost of the the ST 100. Nor is it necessary a negative; own brand kit saves money and enables the manufacturer to pass these savings on to you.

The Rockrider Flex seatpost varies in length (as per the stem) from 350mm to 400mm depending on the bike size you choose. The hammock style saddle is a generic Ergofit model, with a reasonable amount of padding.

Finally the pedals are a plain black and grippy Rockrider platform style model made from resin. These can obviously be swapped out at a later date for alloy or SPD models should you wish.

The Rockrider ST 100 - worth the money?

My conclusion for the Rockrider ST 100

The Rockrider ST 100 Mountain Bike is a low cost hardtail MTB designed for the smallest of budgets. Featuring a 27.5" wheelset, alloy frame and 80mm of unbranded front suspension, it's a rideable hardtail mountain bike for those starting out.

In terms of value for money, it's not a terrible specification, but unfortunately (and somewhat understandably given the low price tag) doesn't include disc brakes, nor even disc mounts should you wish to upgrade at a later date.

The ST 100 has 21 gears from a mainly Microshift groupset (Shimano provide the 7 speed cassette) including a triple chainset to help get you up the steeper ascents and is available in bright yellow or understated grey colour schemes.

Shifting is via old school gripshifter style controls mounted on a pretty narrow 620mm set of steel handlebars - we'd recommend upgrading these for wider alloy models to save weight and gain control.

In short, it's not a bad starter bike for newcomers in terms of value for money, but will weigh a substantial amount (between 15.3kg to 15.8kg - 33.7lbs to 34.4lbs - depending on frame size) and in time you may wish to upgrade to a bike with disc brakes and wider bars.

If this is the case then the Rockrider ST 120 costs slightly extra, but is more future proof for upgrades and thus should last you longer.

Rockrider's supplied product info

Here's Rockrider's official blurb on the ST 100

This 27.5" mountain bike is designed for your first mountain bike rides in dry weather for up to 11/2 hours.

Effective? Strong? Both please! Easily get through your first obstacles: lightweight aluminium frame and 27.5'' tyres on double-walled rims (26" in XS).

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

Robustness: An ultra-strong MTB: double-walled rims, welded saddle, derailleur guard.

Efficiency: Light frame, 21 speeds, 27.5" wheels (XS 26"), tyres with low rolling resistance.

Directional control: Control your steering: V-Brake pads, tyres with side lugs. The ST 100 mountain bike frame is UNISEX.

The ST 100 mountain bike exists with the same frame in a WOMEN'S version: adapted seat, narrower handlebars, shorter stem, fork with a more flexible spring, and brake levers that are closer to the handlebars. As a WOMAN, if you choose the MEN'S model, we recommend purchasing the WOMEN'S SPORT 500 saddle which is adapted to women's body types.

A LIGHTWEIGHT, COMFORTABLE, FUN FRAME: It isn't always easy to get the right position on a mountain bike.

Our designers have created an entirely new frame that is easy to step over. 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 straighter whilst the rear has been shortened to ensure the bike is very agile when turning.

FRONT SUSPENSION: The 80 mm front suspension helps you overcome your first obstacles on slightly uneven trails with no worries. Its mechanical spring is a stamp of reliability. And the fork is particularly easy to maintain.

To adjust the stiffness? It's very easy using a single dial.

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

It is a "hardtail" 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 expend less energy pedaling on flat ground.

DERAILLEUR & DRIVETRAIN: 3 x 7 speed chainwheels, 21 speeds total! 2 easy-to-use grip shifters on the handlebars.

Left (chainrings): control ascents/descents.

Right (speeds): more precise control over your pedalling. In detail:. Triple-chainring chainset (22/32/42 teeth) + anti-grease protection.

Microshift FD-M20 front derailleur. Microshift RD-M25 rear derailleur. Microshift MS25 grip shifters with speed indicators.

Shimano TZ500 7 cog cassette, 14 to 28 teeth.

Large, solid KMC Z51 chain HANDLEBARS, STEM, GRIPS: With a stem that tilts 10 degrees upwards, the riding position of the ST 100 is raised, accessible, and comfortable. In detail:.

90mm (in sizes XS and S) or 110mm (in sizes M, L and XL) aluminium stem with an angle of 10 degrees for maximum comfort. 620mm-wide steel handlebar, for stability and control. "Soft touch" grips for a firm yet soft and pleasant grasp.

SADDLE: The saddle of the ST 100 is welded to prevent any movement of the saddle. And because your comfort is our next priority after 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, either 350mm or 400mm long (according to the bike size).

Its reduced diameter of 27.2mm provides your seat with natural flexibility, 30% more than a standard solution.

V-BRAKES WITH PADS: Two V-Brakes for effective braking. These brakes are composed of callipers that exert more or less pressure on the rim to slow or stop the rotation of the wheels.

Thanks to the special design of the ST 100's aluminium brake levers, you only need two fingers to brake.

27.5" WHEELS (26" in XS) & TYRES FOR DRY TERRAIN: The wheels of the ST 100 are tolerant and robust, with 27.5" double-walled 28-spoke rims (26" for the XS size).

Slow down without worrying about obstacles: small rocks, cracks, holes and bumps! Because your first rides will be on dry ground, this mountain bike is equipped with DRY 27.5 x 2.0 tyres.

Their performance has been optimised thanks to a faster central section, while their side lugs offer excellent traction in turns.

PLATFORM PEDALS: The Rockrider ST 100 mountain bike is supplied with hard resin platform mountain bike pedals for added lightness and safety. If your foot slides on the pedal, there's less risk of injury.

Your ST 100 mountain bike comes with a derailleur guard, chainring guard (to prevent your clothes from getting dirty), bell, lights, wheel reflectors, and pedals.

Weight: X-Small - 140-154cm : 15.3 kg.

Small - 155-164cm : 15.4 kg.

Medium - 165-174cm : 15.5kg.

Large - 175-184cm : 15.6kg.

X-Large - 185-200cm : 15.8kg.

ST 100 Photo Gallery
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ST100 MTB Specification

Here's the exact spec of the ST 100

Frame & Fork
FrameLightweight aluminium CGF frame
Forks80mm suspension fork with mechanical spring and adjustable using a dial
Frame MaterialAlloy
Frame TypeHardtail
Fork TypeSuspension Fork
Wheels27.5" double-walled 28-spoke rims
TyresDry 27.5 x 2.0 tyres
Wheel Diameter27.5"
Handlebars620mm wide steel handlebar
StemAlloy stem with 10 degrees rise, 90mm length for XS/S and 110mm for M,L & XL
HeadsetOwn brand headset
GripsSoft touch grips
Finishing Kit
Seatpost27.2mm Flex seat post (350mm or 400mm long)
SaddleHammock Ergofit saddle
PedalsHard resin platform MTB pedals
BrakesTwo V-Brakes front and rear, 2 finger aluminium brake levers
Brakes TypeCaliper Brakes
ChainsetTriple chainset for 7 speed system
Front DerailleurMicroshift FD-M20 front derailleur
Rear DerailleurMicroshift RD-M25 rear derailleur
ShiftersMicroshift MS25 grip shifters with speed indicators
ChainKMC Z51 chain
CassetteShimano TZ500 7 cog cassette, 14 to 28 teeth
Number of Gears21 Speed
ChainringsTriple Chainring
Cassette7 Speed
General Details
Other InfoComes with a derailleur guard, chainring guard, bell, lights, wheel reflectors, and pedals
Bike TypeMountain Bikes
Designed forMTB
ColourGrey & Yellow
SizeXS, S, M, L & XL
Lowest Price£229.99
Which size bike shall I get?

The Rockrider ST 100 MTB is available in XS, S, M, L & XL in Grey & Yellow.

Here's a size chart for Rockrider MTBs so you can make sure the ST100 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 100 FAQs
  • How much does the ST 100 weigh?

    The ST 100 weighs between 15.3kg (33.73lbs) and 15.8kg (34.83lbs) depending on the frame size.

    An Extra Small is 15.3kg (33.73lbs), Small is 15.4kg (33.95lbs), Medium is 15.5kg (34.17lbs), Large is 15.6kg (34.39lbs) and finally Extra Large is 15.8kg (34.83lbs).

  • Who manufactures the ST 100?

    Rockrider, the brand who designed the ST 100, are owned by the French superstore Decathlon.

    Decathlon used to release all of their bikes under the brand B'Twin, but in recent years decided to set up specialist brands for each different type of bicycle.

    Rockrider is their brand for all of the mountain bikes, and a few E-MTBs that Decathlon sell.

  • What's the price of the Rockrider ST 100?

    The ST 100 currently costs £230.

  • How many gears does the ST 100 have?

    The ST 100 has a 3x7 drivetrain, with 3 chainrings at the front and 7 cogs on the rear cassette, resulting in a total of 21 gears.

    The majority of the drivetrain (front mech, rear mech, shifters) is Microshift, with a Shimano cassette and KMC chain.

  • What's the frame and fork made out of?

    The ST 100's frame is made from 6061 alloy to keep it lightweight yet strong. Please note that neither the frame nor fork contain disc brake mounts, so you cannot run disc brakes on this bike.

    The fork is a mixture of materials, but is predominantly manufactured from steel, so will weigh a little extra than more costly models.