ROCKRIDER ST 520 MTB - BLACK/BLUE

The recommended average pressure is 1.8 bar.If you want a bit more grip and comfort, AND/OR if you weigh less than 70 kg, you can reduce the pressure by 10%, although this will increase the risk of getting a puncture on rough ground. Whatever you do, never go below 1.6 bar (the minimum recommended pressure).Remember to regularly check your tyre pressure.

Your handlebar comes in the highest setting (the most upright and therefore the most comfortable position). For better aerodynamics and more efficient pedalling, you can drop your handlebar to extend your upper body (your back will be at more of an angle for a sportier ride). Do this by simply removing the spacers that sit under the stem, as shown in this video.

Your ST 540 bike's frame comes with a quick release system. Stand astride your bike. Undo the clamp by pulling its lever. Pull or push the saddle until it is at hip height. Tighten the clamp by pushing its lever back into place. For more precision, take a look at our video tutorial.

The BTWIN U-Fit fork has been designed to be as easy as possible to adjust. It features a real innovation: turn the dial until your weight appears on the top of your fork. As you turn the dial, the spring will be compressed or released to adjust it to your weight.

When your bike leaves the shop with its shiny new brake pads and discs, their braking power is weak.Continuous harsh braking (for example, going downhill) can overheat the brakes and lead to "glazing".This can make your brakes completely unusable, so to stop it happening, we recommend bedding in your brakes.Bedding in takes just 10 decelerations per brake. By deceleration, we mean going quickly from 25 to 5 km/h, but without stopping the wheel from spinning, and using just one brake at a time.

When you start using your new bike, lots of its parts are going to wriggle around as they settle into place.This includes your spokes, which might sound as if they're cracking due to the residual torsion from assembly.Your bike is equipped with double-walled rims (inside the wheels), which are sturdier than single-walled rims. Your wheels therefore shouldn't buckle.If they do, then please contact one of our Decathlon workshops to get them adjusted free of charge:1- As part of the free service we offer 6 months after buying your bike 2- If you have taken out the €1 breakdown insurance (valid for 2 years)Message for parents:Certain mountain bike tricks that are popular with kids (wheelies, skids, bunny hops, etc.) can lead to play in the rear hub and buckling in the wheels if they are repeated over and over. If your kids are doing these tricks often, it's important to make them aware of this problem.

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.  

There are several things you can do to soften your fork:1- Check the stiffness setting: see ADJUSTING YOUR FORK'S STIFFNESS2- Do some basic maintenance: your fork needs a regular dose of oil. Place several drops on the fork's steerer tube and move it around to work the oil into the blades.3- Take it to the workshop for a full service.

There could be several reasons why your gears (chainring) aren't shifting smoothly.1- Check the position of the cable end caps.Incorrectly positioned end caps can disrupt the pulling action on the derailleur cable and cause the shifting of the gears to be off. If either cable end cap is incorrectly positioned, put it back in place.2- Your cable and housing might be jammedIf you can't get down into the smallest gear on your chainring, and the derailleur doesn't shift even when you move the gear shifter, then the cable and housing must be jammed. In this case, the cable and housing need to be replaced. Your local Decathlon workshop can assist you with this. Alternatively, watch this video to learn how to replace them yourself.NB: If you regularly ride your mountain bike in wet or muddy conditions, or if you regularly wash your bike with lots of water, then your cables and housing will need to be replaced more frequently. We strongly recommend against washing your bike with a power washer as this can push dirt inside the housing.

There could be several reasons why your gears (sprockets) aren't shifting smoothly.1- Check the position of the cable end caps.Incorrectly positioned end caps can disrupt the pulling action on the derailleur cable and cause the shifting of the gears to be off. If either cable end cap is incorrectly positioned, put it back in its place.2- Your cable and housing might be jammedIf you can't get down into the smallest year on your cogs, and the derailleur doesn't shift even when you move the gear shifter, then the cable and housing must be jammed. In this case, the cable and housing need to be replaced. Your local Decathlon workshop can assist you with this. Alternatively, watch this video to learn how to replace them yourself.3- Take your bike to a Decathlon workshop to get the derailleur adjusted 4- You might also want to check that the derailleur hanger isn't twisted. If it is, see "YOU'VE BROKEN YOUR DERAILLEUR HANGER"   NB: If you regularly ride your mountain bike in wet or muddy conditions, or if you regularly wash your bike with lots of water, then your cables and housing will need to be replaced more frequently. We strongly advise against washing your bike with a power washer as this can push dirt inside the housing. 

If your brake lever feels spongy and/or touches the handlebar before your bike starts to slow down:Adjust the brake cable tension using the barrel inside the brake lever Unscrew the barrel and the locknut until the cable is sufficiently tight and the brake lever is firm but not too hard.Once you've got the tension right, tighten the locknut firmly against the brake lever to secure the setting.

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.

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.

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 drivetrain, you'll need a degreaser spray, a suitable brush and a lubricant. The first step is to protect your disc with a clean cloth to stop any grease getting onto it. Next, apply degreaser to the entire drivetrain, and brush the cassette, chain and derailleur jockey wheels. Leave for a few minutes, then rinse from a moderate distance. Wait for the drivetrain to dry before moving on to the lubrication stage. Shake the lubricant and apply to the inside face of the chain to help it run smoothly. 

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! 

To do this, you'll need a new derailleur hanger that's compatible with your bike (please check our "SPARE PARTS") and a 5 mm Allen key. Remove the wheel and the damaged derailleur hanger. Position the new hanger on the frame.  Remove the piece of old hanger from the derailleur before putting the new one on using the 5 mm Allen key. All that remains is to put the derailleur on the new hanger and check the gears.

To do this, you'll need a chain tool, a new chain and a quick link. Position the chain on the last cog and the smallest chainring.  Use your chain tool to remove the quick link, then take the old chain off. Position the new chain on the last cog and the smallest chainring to figure out the right length. The chain should be almost grazing the derailleur's top jockey wheel. Once you've decided on the correct length, cut the chain using the chain tool. Then fit the quick link to the chain and turn the pedals to position the quick link at the top of the chain. Give the pedals a good tap to make sure the chain is fully seated.

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