Ref: 8500762

ROCKRIDER ST 900 MTB RED/BLACK

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 with lockout controls on the handlebar, single chainring, lightweight 27.5" double-walled wheels... Enjoy the light weight of this ST 900 mountain bike!

ST 900 mountain bike

Compatible accessories

Spare parts

Assistance

Instructions

First use

INFLATING YOUR TYRES

The recommended average tyre pressure is 1.8 bar.If you're looking for more comfort and grip AND/OR if you weigh under 70kg, you can reduce the pressure by 10% but without dropping below 1.6 bar (the minimum recommended pressure). On abrasive terrain, however, this will increase the risk of punctures.You should check the pressure of your tyres regularly.

ADJUSTING THE HEIGHT OF YOUR HANDLEBARS

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.

ALIGNING YOUR HANDLEBAR

ADJUSTING THE HEIGHT OF YOUR SADDLE

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.

ADJUSTING THE TILT OF YOUR SADDLE

ADJUSTING THE STIFFNESS OF YOUR FORK

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.

BEDDING IN YOUR BRAKES

The brake pads and discs on a new bike are new themselves and don't work to their full potential.Hard, continuous braking (on descents, for example) can cause the pads to overheat and "glaze".To prevent this from happening and to ensure that your brakes slow you down effectively, we recommend that you bed them in.You need to apply each brake firmly around ten times to bed them in properly. The bedding-in process involves getting up to a speed of 25 km/h and then applying just one of the brakes firmly to reduce your speed to 5 km/h, without locking the wheel.

POSITIONING YOUR BRAKE LEVERS

CHANGING YOUR PEDALS

HOW TO CONVERT YOUR WHEELS TO TUBELESS

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)

- Sealant:

DECATHLON: TUBELESS READY TYRE AND WHEEL SEALANT (8550735)

STEPS TO FOLLOW:1. Take the wheel off.2. Remove the tyre and the inner tube from the wheel.3. Apply the tubeless rim tape.4. Insert a Schrader TUBELESS valve in the valve hole in the wheel.5. Apply the sealant.6. Fit your new TUBELESS tyre.7. You need to inflate the wheel quickly to ensure that the tyre sticks to the rim.If it seems too tricky, just visit your nearest DECATHLON workshop and ask them to do it for you.

GETTING THE RIGHT GEAR TO DEAL WITH PROBLEMS

You need to have the right equipment with you when you're out and about on your mountain bike so that you can take care of a puncture, a broken chain or any other type of setback. Here's a selection of products that can get you out of a tight spot or two.

GET THE RIGHT GEAR

HAVE A PROBLEM?

THE WHEEL IS BUCKLED

When you take your new bike out for a ride for the first time, a lot of parts move around and fall into place.You'll hear the spokes on your wheels creak because of the residual torsion in them.Your bike is fitted with double-walled rims, which help make the wheels more solid. That means they should not buckle in any way at all.If they do, then call in at one of our DECATHLON workshops to have them repaired free of charge:1. As part of a free check-up in the first six months following the date of purchase. 2. As part of our €1 damage insurance plan (valid for two years).Message for parents:Young riders like to do tricks on their bikes (wheeling, skids, jumping off kerbs, etc). If done too often, however, they can cause play in the rear hub and buckle the wheels. If your child performs these tricks on a regular basis, speak to them and let them know the problems they can cause.

wheelies and buckling of the ROCKRIDER ST 100 mountain bike's wheels

YOU'VE GOT A PUNCTURE

Unfortunately, anyone can get a puncture. - The ground (thorns, brambles, glass, nails, etc.)- And how you use your bike (taking on obstacles like rocks, steps, kerbs and potholes)are the most common cause of perforation punctures (small holes) and pinching punctures (small cracks close together), respectively.However, if you're getting a lot of punctures, it might be because of:- Incorrect wheel assembly in our factory, which has resulted in the end of a spoke piercing the inner tube- A faulty tyre or inner tube (porous)- A poorly repaired initial puncture that has left a foreign body (thorn, glass, metal splinter, etc.) in the rim or tyre.It is therefore important to correctly diagnose the puncture and remove any foreign bodies before carrying out the repair.Not sure how to remove/fit a tyre, or how to repair or change an inner tube?1- The simplest thing is to not even touch your wheel. Instead, get yourself out of trouble using a puncture repair spray: Screw the end of the tube onto your punctured tyre's valve (valve pointing down) and press and hold to inject the foam. The tyre should return to its initial shape and feel hard again so you can get yourself back home 2- If you have taken out our 1 euro breakdown insurance, you can then get your wheel fixed properly at one of our Decathlon workshops 3- To repair or change the inner tube yourself, take a look at our video tutorials below.

PUNCTURE REPAIR SPRAY

YOUR FORK IS TOO HARD

There are one or two things you can do to make your fork "softer":1. Adjust the stiffness: check the section "ADJUSTING THE STIFFNESS OF YOUR FORK"2. Do some basic maintenance: using a simple oil can. Squirt some oil on the pivots of the fork and move it around to work the oil into the blades.3. Have the bike fully serviced in a workshop.

THE REAR GEARS ARE NOT SHIFTING PROPERLY

There could be several reasons why your gears (cogs) are not shifting correctly.1. Check the position of the housing ends.Housing ends that are out of position can obstruct the derailleur cable when it is being pulled and prevent the rear gears (cogs) from shifting smoothly. If a housing end is out of position, push it back into place.2. The cable and housings may have jammed up.If the smallest gears (cogs) do not move down, if the derailleur doesn't move even when the gear shifter is operated, then the cable and the housings have jammed up. They need to be replaced. Take your mountain bike to a DECATHLON workshop or replace them yourself with the help of this video.3. Take your mountain bike to a DECATHLON workshop to have the derailleur adjusted. 4. You should also check that the derailleur dropout is not twisted. If it is, check the section "YOUR DERAILLEUR DROPOUT IS BROKEN". NB: If you regularly use your mountain bike in wet or muddy conditions or if you wash it a lot, then you will need to replace the housings and cables more often. We strongly advise you not to use a pressure hose to wash your mountain bike as it will force dirt into the housings.

YOU START PULLING THE BRAKE LEVER AND IT TOUCHES THE HANDLEBARS

The lever is spongy and/or touches the handlebars before you can brake:You need to bleed the brake system.Drop in at a DECATHLON workshop and get one of our technicians to do it.

THE DERAILLEUR DROPOUT IS BROKEN

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.If the hanger is twisted or broken, visit a Decathlon workshop to have it replaced, or use this video to help you change it yourself.

THE CHAIN IS BROKEN

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.

VIDEO TUTORIALS

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.

Personal data
Cookies