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How to Build a Mountain Bike From Scratch

building a new mountain bike from scratch

Having a bike is great, and the feeling of escaping into nature on your own pedal power is like nothing else. There’s one thing doing it on a mountain bike that you have bought from a shop, and it’s a new level of fun mountain biking on a bike you have built yourself.

Building a mountain bike from scratch is easier than you might think, and it is a fantastic project you can undertake for not a vast amount of money. Where do you start, and what will you need? In this article, were going to tell you how to build a mountain bike from scratch.

What Will You Need?

When it comes to making a list of parts, we need to break it down into sections to ensure we are getting everything we need and ready to build your new mountain bike.

Frame and forks

  • Mountain bike frame
  • Mountain bike suspension or rigid forks
  • Mountain bike rear shock (Required on full suspension, not hardtail)
  • Mountain bike headset to suit
  • Bottom bracket
  • Star nut or compression bung

Gearing

  • Mountain bike chainset
  • Cassette
  • Front derailleur (Optional)
  • Rear derailleur
  • Chainring or chainrings
  • Cables and outers
  • Shifters
  • Chain

Brakes and parts

  • Brake calipers
  • Brake levers
  • Hoses
  • Rotors

Wheels

  • Mountain Bike Wheelset
  • Inner Tubes
  • Mountain Bike Tires
  • Skewers or Thru Axle (Modern mountain bikes use Thru axles)

Finishing kit

  • Mountain Bike Handlebars
  • Mountain Bike Stem
  • Spacers and top cap
  • Seat post
  • Seat post clamp
  • Saddle
  • Grips

Tools

  • Torque Wrench
  • Allen Key Set
  • Bottom Bracket Tool
  • Bike Stand
  • Cable Snippers

Now you have your parts list, and we need to start putting it together. This can be a challenging task. If you are unsure how to do anything on mountain bikes, either seek advice from a professional or watch a few Youtube videos to ensure you’re getting it correct. We also recommend taking it to a bike shop to be checked before you ride it.

Find a safe place to work, and we highly recommend using personal protective equipment. Now let’s get the bike frame in the stand and start building your own mountain bike.

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Step One: Frame and Forks

assembling frame and forks
CTTO

Mountain bike frames come in a variety of shapes and sizes so make sure you read any instructions that come with your frame for any unique advice for your own bike or specialist mountain bike frames. You will need to put the headset bearings into the frame as the manufacturer recommends and pull the fork into the steerer tube. At this point, it will be loose, so you will need to put some spaces on the top and attach the stem and pinch the bolts up.

You will want to roughly work out how many spacers you want, and with the stem attached, mark the fork tube where it needs cutting. Once you have marked it, cut it and insert the stardrive or the compression bung. Now put the fork back into the head tube after applying grease to the crown race.

If you have a rear shock and are building a full suspension bike, you will need to put this in now and tighten up the pivot bolts to the correct torque. Rear shocks come in many different shapes and sizes, so you will need to follow the manufactures instructions.

Now we have our frame and forks together, and we have to attach the bottom bracket. Make sure the shell is immaculate, and you apply the bottom bracket shell anti-seize so you can take it out at a later date. Make sure you torque this up correctly and get the left and right correct. If you don’t, you will need to buy a new frame.

I would now recommend attaching the seat post in the seat tube with the saddle on, and also the handlebars onto the stem. It’s now starting to look like a proper bike build.

Step Two: Add the Groupset and Disc Brakes

adding wheels and tires
CTTO

Add the brake calipers to the forks and the frame. Then add the levers to the handlebars and plum in the hoses where required. I would recommend bleeding the groupset now, or if you bought a groupset that is already bled, just attach the parts.

Now you will want to get your chainset and attach the chainrings at the correct torque. Grease the axle of the chainset and pop it onto the frame through the bottom bracket. Attach the chainset to the frame via the manufacturer’s instructions. Depending on your chainset, they will all attach differently.

We will now attach the derailleurs. If you have gone for a 1X, just the rear, and if you have gone 2X, derailleurs will need attaching on the front and rear. Don’t worry about the cables just yet. We will come to that later, and it’s now time to get the wheels set up.

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Step Three: Wheels and Tires

wheels and tires
Photo by Caleb Woods on Unsplash

You have your set of wheels, the first thing to do with them is to make sure that they are the correct size for the frame. They should have rim tape with them, and you will need to attach this to the front wheel and rear wheel. After doing this, you will need to fit your rotors on the front and rear wheel. They will either attach with six small bolts or one big nut, ensuring that it is the correct torque again.

Now we need to pop the tires on and the inner tubes in. Getting the correct pressure is important. Also, you are going to want to make sure the tires are correctly seated and spin round evenly. Next, attach the cassette to the freewheel, making sure the cogs are in the proper order, and you get it to the correct torque when attaching the nut. Your wheels are ready to go in the frame now using the skewers or thru-axle.

Step Four: Shifters and Gearing

adding ters and gearing
CTTO

So by now, your bike is probably looking very cool and getting excited, but unfortunately, it’s still not ready. We now have the majority of the parts on, and the final steps are getting close. You will now connect the shifters to the handlebars. Don’t worry too much if they are in the right place, we will adjust them later.

Depending on if your frame is internally routed or the cables sit on the outside, you’re going to want to plumb these in here. Get all the outers cut correctly and run the cable through to the rear derailleur. Once the cable hits the rear derailleur, you will want to pull the cable finger tight and nip the cable pinch bolt up. Do the same with the front derailleur if you have one making sure the cable run is correct.

Attach the chain to the bike, making sure it runs correctly through all the derailleurs and the drivetrain. Remove the links, so it is the correct length and use a connecting link to pull it together. Now we need to get the gearing working correctly and start at the rear derailleur. Set your high limit by adjusting the H Screw and ensuring the chain drops to the lowest cog without going too far. Now the low limit screw, adjust the L screw until it will go to the largest cog without it going past and the derailleur hitting the wheel spokes or the chain falling off.

Now you will need to index your gears. Put your shifter into the highest gear. Release the cable tension, pull it finger tight, and nip the bolt up again. Now spin the pedals and shift once up the cog, and it probably won’t move. You will need to turn the barrel adjuster anti-clockwise until it jumps. Click the shifter up again, and if it doesn’t jump up, adjust the barrel further. You will find eventually, the gearing should be indexed by the end of the cassette. Check it to make sure it is ok and the gears smoothly, and once completed, cut the cable an inch past the derailleur and pop a ferrule on it.

Now the front derailleur, if you have one. You will need to adjust the height to make sure the cage sits 1mm above the chain and the angle it runs the chain through it parallel to the sides of the cage, looking at it from above. Then adjust your height screw, ensuring it doesn’t fall off the front chainring when in your highest gears. Do the same with the low limit screw making sure it doesn’t fall off in the lowest gear. Once completed, cut the cable an inch after leaving the derailleur and add a ferrule.

Step Five: Finishing Kit

adjusting the saddle to a level height
CTTO

Although we currently have the mountain bike working, it’s not finished. Let’s get your shifters and brake levers adjusted and tighten them up. Then you’re going to want to add your grips to the handlebars. Adjust your seat to the correct height via the post in the seat tube,  and tighten up the bolt to the correct torque. Then adjust the saddle to a level height, and you’re good to go.

Now come to the stem, loosen the rear pinch bolts, insert the top cap, and nip up the top cap bolt until the headset is tight so there’s no play in the forks. After completing this, straighten the stem in line with the wheel and tighten up the pinch bolts to the recommended torque.

Step Six: Safety Checks

Now, you will want to start doing some safety checks on your mountain bike. Make sure every bolt is tight, and if a torque setting is recommended, I would highly advise abiding by that.

After doing this, make sure you have no nasty knocks and bangs, and nothing is loose. I would highly recommend going to a bike shop and paying them an hour of labor to check the bike is built correctly for peace of mind.

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Frequently Asked Questions

How to build a mountain bike from scratch?

Depends really on who is building the mountain bike, if all goes well a day is a good amount of time to allow, it does depend on how easy the mountain bike parts are to fit together.

Are mountain bikes hard to ride?

It all depends on your riding style, if you off road on technical trails yes, if you are on nice smooth surfaces mountain bikes are easy to ride.

Are mountain bike parts expensive?

Basic parts are not, but very high tech parts can be yes. Downhill bikes have very expensive bike parts, and building your dream bike could cost $10000+.

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Is building a bike cheaper than a shop bike build?

It depends on the bike build, you might find buying the bike build to be cheaper and it will save you time and money.

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Conclusion

You have just built your own bike and you’re ready to go mountain biking. There’s nothing like riding mountain bikes that you have built yourself. It feels fantastic knowing you put it together, and it is the fruit of your hard labor. Building a bike is an enjoyable process and will teach you a lot about building a mountain bike from scratch and how to repair one.

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Robbie Ferri

Robbie Ferri

Robbie Ferri is a cyclist living in Norfolk in the UK. From breaking World Records to competing in some of the hardest Bikepacking races in the world he is not shy of riding the miles. He has been lucky enough to work at some amazing shops and with some big cycling brands. Alongside this he even had input in designing bikes and has also been a tester for unreleased products. He absolutely loves cycling and believes everyone should have a bike.