This 27.5" mountain bike is designed for your MTB outings, all year long, lasting more than 3 hours Greater efficiency and control: 120 mm ROCKSHOX fork and lockout air shock with controls on the handlebar, single chainring, lightweight 27.5" double-walled wheels... Enjoy the light weight of this ST 900 S mountain bike!
The recommended average tyre pressure is 1.8 bar.
Your handlebar is set in the highest position to help keep your back raised, which is the most comfortable position for riding.
For improved aerodynamics and more effective pedalling, you can lower your handlebars to lower your body. This will cause you to lean forward and adopt a racing position.
Follow the steps in this video to move the headset spacers below the stem and lower the handlebars on your bike.
Your ST 540 bike frame is fitted with a quick-release lever.
Stand next to your saddle. Tilt the quick-release lever to unlock it. Pull the saddle up or push it down to bring it level with your pelvis.
Tilt the lever again to lock it.
To make sure you get it right, take a look at our tutorial video.
The BTWIN U-Fit fork has been designed to make adjusting it as easy as can be. A genuine innovation: weigh yourself and then turn the thumbwheel on the fork until your weight appears in the window. This will make the spring harder or softer, in line with your weight.
The brake pads and discs on a new bike are new themselves and don't work to their full potential.
You can avoid the risk of the inner tubes on your mountain bike getting punctured or pinched by switching to TUBELESS.
To do this you'll need to buy the following:
- A pair of TUBELESS tyres:
DECATHLON: ALL TERRAIN 9 SPEED 27.5X2.10 TUBELESS READY MOUNTAIN BIKE TYRES / ETRTO 54-584 (8386245)
- 21mm rim tape:
ALLTRICKS: NOTUBES YELLOW 21MM RIM TAPE FOR FIVE RIMS
- A pair of Schrader TUBELESS valves:
ALLTRICKS: PAIR OF NO FLATS JOE'S SCHRADER TUBELESS 36MM VALVES (AUTO)
DECATHLON: TUBELESS READY TYRE AND WHEEL SEALANT (8550735)
STEPS TO FOLLOW:
When you take your new bike out for a ride for the first time, a lot of parts move around and fall into place.
Unfortunately, anyone can get a puncture. - The ground (thorns, brambles, glass, nails, etc.)
There are one or two things you can do to make your fork "softer":
There could be several reasons why your gears (cogs) are not shifting correctly.
The lever is spongy and/or touches the handlebars before you can brake:
A bent hanger causes the derailleur to be out of alignment and therefore unable to function correctly. Stand behind your bike and examine the alignment of the derailleur.
Have you broken your chain? You've got 2 options: 1- Repair it yourself with the help of this video. You're going to need a chain tool and a quick link. 2- Visit one of our Decathlon workshops to get our technicians to repair it.
These videos show you how to perform your own repairs and replace parts.
- Fitting/removing a rear wheel - Repairing a puncture
- Changing an inner tube - Adjusting the height of the handlebar
- Repairing a chain - Replacing the derailleur hanger
Don't forget to check out our YouTube channel for even more video content.
PUTTING ON/TAKING OFF A REAR WHEEL
REPAIRING A PUNCTURE
CHANGING AN INNER TUBE
ADJUSTING THE HEIGHT OF THE HANDLEBARS
REPAIRING A CHAIN
CHANGING THE DERAILLEUR HANGER
To clean your bike, you'll need a bike cleaner, a sponge and a brush.
First, hose your bike down.
Next, use the sponge and brush to apply the cleaning products.
Leave the cleaning products time to work, then rinse the bike.
Do this from a reasonable distance so as not to damage the mechanical parts.
Lastly, dry your bike with a soft, clean, dry cloth.
To clean and lubricate your drive train, you will need a degreaser spray, a soft bristled brush and a lubricant.
The first step involves covering the brake disc with a clean cloth to prevent any lubricant from getting on to it.
Then apply the degreaser to the whole of the drive train and scrub the cassette, chain and derailleur jockey wheels with the brush.
Leave to act for a few minutes before rinsing the degreaser off from a suitable distance.
Allow the drive train to dry before applying the lubricant.
Shake the lubricant and apply to the inside of the chain, where it will work best.
Is your gear cable dirty, rusty or damaged, or are your gears hard to shift or shifting randomly?
Then your gear cable needs to be changed! To do this, you'll need some pliers, a screwdriver, a cable cutter, an Allen key and a new set of cables and housing.
First of all, you'll need to remove the cable from its housing. Start by removing the plug from the shifter. Shift the gears all the way down, then cut the cable so you can pull it all the way out of the housing.
Next, hold the housing against your bike to work out how long it needs to be. Cut it and place the end caps on. You can now install the housing.
Pass the cable through the shifter and feed it through the housing. Next, screw the plug back in and fix the cable to the derailleur. Adjust the drivetrain by tightening the cable if the gears are struggling to shift up and slackening it if they are struggling to shift down.
Once you're done, cut the cable and use the pliers to crimp the end cap onto it.
To repair a puncture, you'll need: a pump, a bowl of water, a cloth and a puncture repair kit.
Pump a little air into the inner tube. Locate the hole by submerging the tube in the water.
Once you've found the hole, dry the inner tube with the cloth and use the sandpaper in the repair kit to sand the tube.
This will enable the glue to stick better.
Apply the glue generously to the hole, and wait for 3 to 5 min.
Lastly, place the patch over the hole and press down for a few minutes.
You can then put your inner tube back into your tyre!
You will need the following: new brake pads, a flat screwdriver and a 3mm Allen key.
Remove the wheel first of all. Then use the screwdriver to move the pads apart and put the pistons back into their original position.
Take out the pin holding the pads in place and remove them from their housings. Position the counter spring between the new pads.
Insert the new pads in the brake calliper and then put the pin back in place to complete the process.
Put the wheel back on and check to make sure that the brake pads are properly in place and do not rub against the disc.
You will need a 5mm Allen key.
Unscrew the brake calliper, spin the wheel and operate the brake lever. It is important to keep the brake lever engaged before screwing the calliper back in place.
Check to see that the disc and the pads are still in contact.
You will need a new derailleur dropout that fits your bike (check the "SPARE PARTS" section) and a 5mm Allen key.
Take off the wheel and the damaged derailleur dropout.
Position the new dropout on the frame.
Remove the old dropout part from the derailleur before fitting the new one with the Allen key.
Fit the derailleur on to the new dropout and check the gears.
You will need the following: a chain tool, a new chain and a quick-release link.
Put the chain on the cog and on the smallest chainring.
Remove the quick-release link using a quick-release chain tool and then remove the chain from the drive train.
Put the new chain on the last of the cogs and on the smallest chainring. This makes it easier to determine its optimal length.
The chain should pass close to the top pulley of the upper jockey wheel on the derailleur.
Once you've determined the length of the chain, use the chain tool to cut it as required.
Then fit the quick-release link on the chain and turn the pedal to position the quick-release lever on the top part of the chain. Press it with your hand to check that it is on the right position.
Please contact one of our technicians who will be happy to help
ROCKRIDER guarantees the frame, handlebar and stem of your mountain bike for life (in normal conditions of use).
The guarantee for other parts is two years.
As soon as your child starts using the bike, some components will move slightly. It's for that reason that we offer a free check of your mountain bike six months after purchase.