If you want a productive way to spend a few hours, maintenance knowledge, and/or have a bunch of bicycle parts lying around, there is no reason to shy away from building your own mountain bike.
In general, you should at least have some maintenance knowledge of your bicycle, such as adjusting your derailleurs and changing your tires or tubes. If you don't have these skills, you can practice these tasks on your bike or a friends bike, or just start this project anyway.
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Step 1: Parts
You will need the following parts to assemble a mountain bike:
- Generally, you should choose the frame you want before deciding on other components.
- Choose 26" wheels for downhill/jumping, 27.5"/650b for all-around riding, or 29" for cross country riding.
- Disc brakes offer more modulation and are the more current standard.
- Front and rear wheel (26", 27.5"/650b, or 29")
These should match your frame's wheel size specification as well as your frame's brake specification (disc vs v-brake). For disc brakes, maximum rotor size does not affect wheel choice.
- Your tire size must match your wheel size in diameter (26",27.5"/650b, or 29")
- Maximum tire width is often given by the manufacturer, but 2.1"-2.2" widths will fit most frames
- Tubes should approximately match your tire size. Tubes that are exceedingly large or small will lead to premature flat tires.
- Almost all stems are compatible. The standard for threadless stems is a 1 1/8" (28.5mm) clamp for the steerer tube and a 31.8mm clamp for the handlebars.
- Most handlebars fit the 31.8mm standard. Choose the one that best fits your budget. More expensive handlebars generally save more weight. Carbon handlebars dull vibrations and can decrease fatigue.
- Grips are interchangeable as well. For added safety, you can get lock-on grips.
- Derailleur/Derailleurs - the mechanisms that move the chain to select the gear that you are in.
- If you want a 1x10/11 mountain bike, you only need a rear derailleur. For a 1x setup, you should get a derailleur with a clutch built in. For a 2x or 3x setup, you need a front derailleur as well.
- Shifters must be compatible with your derailleurs for optimal performance. In general, a brand's offerings for a given speed are all compatible within the mountain or road lineup. For example, a 10 speed Shimano mountain bike shifter is compatible with all 10 speed Shimano mountain bike derailleurs. Furthermore, SRAM road and mountain lines that are 10 speed and earlier are cross compatible.
- Cassette - the gears that attach to your rear wheel
- Your cassette should match your drivetrain. For example, an 11 speed rear derailleur corresponds to a 11 speed cassette.
- The crank should be the same brand as your shifters and derailleurs for best shifting performance.
- Bottom Bracket - the bearings that interface between your crank and your frame.
- Sometimes comes with your crank. Should match the specification of your frame (often BSA/English) and your crank (gxp, hollowtech, square taper and others)
Your chain should correspond to the size of your cassette. There are chains for 7-9 speed, 10 speed and 11 speed cassettes. For best performance, your chain should correspond to the brand of the rest of your drivetrain.
- Most pedals are compatible with most cranks. There are two kinds of pedals to chose from, platform pedals and clipless pedals. Clipless pedals require cycling-specific shoes that can lock into to the pedal. Some pedals offer a clipless pedal on one side and a platform on the other.
- Headset - the bearings that interface with your frame and fork.
- Headset choice is based on the frame's specifications. If a specification is not directly given, you can use this site to deduce which headset standard will fit your frame.
- For mountain bikes, forks are generally 1 1/8" straight or 1 1/8" to 1 1/2" tapered. If your frame can fit tapered forks, it can also fit 1 1/8" straight forks with a crown race adapter that is specific to the headset you chose.
- Cantilever brakes (v-brakes) are a common of brakes for mountain bikes. Most cantilever brakes work with most frames.
- Disc brakes are a newer but very popular type of bicycle brake.
- Your seatpost must match your frame's specification for seatposts. Some common sizes are 25.4mm, 27.2mm, and 31.6mm.
- Seatpost clamp
- This should also match with your frame's specification.
- Saddles are compatible between all seatposts. You should try to demo some saddles to find one that comfortable to prevent injury.
Step 2: Tools
- Cassette lockring tool
- Bottom bracket tool - must match with your bottom bracket
- Press fitting tool (For press fit bottom brackets or headsets)
- Chain tool - should match with your chain (11 speed chains need an 11 speed chain tool) (not needed for SRAM chains)
- Crown race setting tool - this can be improvised with a PVC pipe and a PVC fitting
- Saw guide (for cutting the steerer tube)
- Hex wrenches (various sizes)
- Torque wrench (optional, recommended)
Step 3: Attach Tires to the Wheels
Before attaching your tires to your wheels, check that you have rim tape on your wheels. If you can see the ends of your spokes on the rim, you need to apply rim tape. There are two kinds of rim tapes, a tape kind and a continuous loop that is sometimes called a rim strip. To install rim tape, stick the tape to the rim, making sure that the tape is applied symmetrically to the rim. Cut off the excess tape. To install a rim strip, use a screwdriver to line up the hole in the rim for the valve stem with the hole in the rim strip. Pry the rim strip over the rim symmetrically until you get to the other side. Use another screwdriver or similar object to put the last part of the rim strip onto the wheel. Check to make sure that the strip is applied symmetrically, using your fingers to correct the allginment if necessary.
To attach the tires to the wheels, first put the tire halfway on the rim. Next, slightly inflate the tube. This will help prevent the tube from being pinched and breaking. You can then insert the tube into the tire. Make sure that the valve stem goes through the hole in the rim. After the tube is inside the tire, push the other side of the tire onto the rim. Finally, inflate the tube to your desired pressure.
Step 4: Attach the Cassette
To attach the cassette to the rear wheel, put the cogs onto the wheel in the order that they came from the box (largest first, smallest last). Then, take the lockring and tighten it by hand onto the wheel before using the cassette lockring tool and a wrench to finish tightening the cassette to the wheel.
Step 5: Attach the Brake Discs (Rotors)
If you are using disc brakes, now is a good time to attach the rotors. Take care not to touch the braking surface as any oil on the brake permanently decreases its performance. Make sure that the rotor is attached in the correct direction. There are normally arrows indicating the direction the rotor will spin when your bike is rolling forward.
Six Bolt Discs
Place the disc brake over the corresponding holes on the rim. Taking your screwdriver, tighten each bolt in a star pattern.
Place the brake disc onto the hub where the rotors attach. Hand thread the lockring onto the hub. Use the lockring tool that corresponds to your brake discs and a wrench to fully tighten the lockring onto the wheel.
Centerlock disc image source: http://www.parktool.com/blog/repair-help/rotor-disc-service-and-installation#article-section-1
Step 6: Attach Seat and Seatpost to the Frame
To attach the seat to the seatpost, loosen the clamp on the seatpost. Fit the seat's rails inside the clamps, making sure that the clamps attach to the saddle where the rails are straight.
Fit the seatpost clamp onto the frame. You may need to loosen its bolt first. If the seatpost and frame are both metal, apply grease to the seatpost. If the frame and seatpost are both carbon, apply carbon fiber assembly gel. For a carbon seatpost in a metal frame, do not apply anything. Next, insert the seatpost into the frame. The precise depth does not matter, as this will be adjusted later. Tighten the seatpost clamp bolt enough that the seatpost cannot move.
Step 7: Install Bottom Bracket
Press Fit Bottom Bracket
Note: if you do not have a press-fitting tool, you may consider getting this job done by a bike shop. These tools are fairly expensive compared to the cost of installation at a bike shop, and press fit bottom brackets are somewhat difficult to work with.
First, for a press fit bottom bracket in an aluminum frame, prepare the frame by applying grease to the bottom bracket area. Then, one assembles the bottom bracket tool through the frame and around the bearings and tightens the tool until the bearings are fully inserted into the frame. After this, you can remove the bottom bracket tool. The bottom bracket is then installed.
Threaded Bottom Bracket
Before installing a threaded bottom bracket, first double check that you have the right bottom bracket for your frame. Installing the wrong bottom bracket will destroy the threads on the frame, rendering the frame unusable. If the threads are metal, begin by greasing the threads in the frame. Then, insert the right bottom bracket half into your frame. Tighten it by hand as far as you can. If screwing in the bottom bracket is immediately difficult, make sure that you are not cross threading the bottom bracket. Once the right half of the bottom bracket is touching the frame, install the left half of the bottom bracket by hand. When you cannot tighten either half of the bottom bracket by hand, use your bottom bracket tool to finish tightening both sides of the bottom bracket into the frame.
Step 8: Install Crank
Crank installation is somewhat dependent on the manufacturer of your crank. In this instruction set, I will go into detail for installing a HollowTech II crankset. Otherwise, I recommend these videos for instructions on installing your type of crankset:
Square taper, ISIS, Octalink:
Step 9: Install the Crown Race
Installing the headset is the most difficult step of assembling a bicycle. Furthermore, a proper crown race installation tool is fairly expensive. This would be a good step to get done at a bike shop.
To install the crown race, start by sliding it onto your fork. When it is stuck, slide your crown race installation tool on top of the crown race , and hammer until the crown race is properly installed on your fork. You will know this because there will be no space under the crown race. Furthermore, hammering the tool will often make a different noise once the installation is complete.
Step 10: Install the Headset
There are three common styles of headsets for modern frames: threadless, zero stack, and integrated.
If you do not have a headset press, you can either make one with some washers and a long bolt, or have this job done at a bike shop. Otherwise, assemble your headset press around your headset and frame (see photo above). Tighten the headset press until the headset is fully inserted into the frame. Slide the fork into the headtube. Place any washers included with the headset and the dust cap over the steerer tube and slide them down, flush with the top bearing of the headset.
To install an integrated headset, grease the points where the bearings contact the inside of the frame. Place the bottom bearing on top of the crown race and fork, and insert the fork into the frame. Install the top bearing, washer, and dust cap around the steerer tube and flush with the top bearing of the headset.
Bearing press photo source: http://www.parktool.com/blog/repair-help/threadless-headset-service#article-section-4
Step 11: Cut the Steerer Tube
Before cutting the steerer tube, decide where to cut it by attaching the stem and any spacers you want to achieve your desired handlebar position. I suggest putting more spacers rather than less so that, as you adjust your position on your bike, you have greater room to make adjustments. Once you have decided on a position for your stem and handlebars, mark where you will cut with a marker or screwdriver. Remove the fork from the frame. Make a second line 3mm below the line you just marked. This second line is the line that you will actually cut. Place the fork in your saw guide and clamp it. If you have a vice, you can lock the saw guide into the vice to facilitate cutting. Using a hacksaw, saw through the steerer tube. Take the fork out of the saw guide. If the cut edges are rough, sand them down. Reinstall the fork to the frame and reattach the stem and handlebars.
Step 12: Attach the Stem
To attach the stem to the fork, slide it onto the steerer tube as you did when sizing the fork to be cut. You can tighten the stem now, alternating between the top and bottom bolts to ensure even tightness, or wait until the handlebars are attached, which usually makes aligning the stem easier.
Step 13: Attach the Handlebars
To attach the handlebars, slide them through the stem. Make sure that they are even and at a comfortable angle. Tighten the bolts in any Z pattern so that they are at approximately even tightness.
Step 14: Install the Shift Levers
To install the shift levers, simply slide them onto the handlebars, and tighten them just enough so that they can be easily adjusted later.
Size the cable housing before cutting it with a wire cutter, put a ferrule (small metal end cap) on the end, then thread the cable through it. attach the cable to the frame using zip ties or clips, and attach the end of the cable to the derailleur. You can also cut the cable and crimp an end cap to the end of the cable.
Step 15: Install the Grips
Before installing the grips, make sure that you have attached the brake and shift levers. To install the grips, slide them onto the handlebars. If they are locking grips, they should be easy to slide onto the handlebars. Make sure to tighten them. If installing the grips is difficult, you can put alcohol on the handlebars and inside the grips to make them slide together easier. The alcohol evaporates and does not compromise the safety of the grips. Make sure to put on the end caps to prevent injuries!
Step 16: Install the Wheels
Installing the wheels is fairly straightforward. If your wheel is a quick release, attach the quick release skewer to the hub. This is accomplished by unscrewing the removable side of the skewer, taking care not to lose the springs, taking off one spring, and pushing the skewer through the hub before attaching the spring and then the nut. For both the front and rear wheel, line up the axle with the dropouts (the slot where the wheels attach to the frame). At this point, one can tighten a quick release skewer before using the lever to fully attach the wheel to the frame. There are a few different styles of thru-axles, but in general you must insert the axle through the hub and then screw it into the frame.
Step 17: Install the Brakes
First, slide the brake levers onto the handlebars.
To install cantilever brakes, simply screw each arm into one of the post mounts. Make sure that the brakes are aligned symmetrically. Position the brake pads so that the align with the braking surface on the wheels. Run the brake cable through the housing and into the clamp for the brakes, cutting off excess housing and cable.
Disc brakes normally come preassembled. This makes installations somewhat easier. To install disc brakes, loosely screw in the disc brakes onto the frame. With the wheels attached, and the frame right side up, squeeze the brake levers. This aligns the brake calipers. While holding the brake levers, fully tighten the bolts for the brake calipers.
If your brake lines are too long, you will have to cut them and bleed the brakes. This process depends on your brake manufacturer, so consult your user manuals on how to accomplish this process.
Step 18: Attach Chain
There are two methods of chain attachment: power links and chain breakers.
Using a Chain Breaker:
If your chain comes unbroken, you need a chain breaker to separate the chain. Using the chain breaker, line up a pin and use the chain breaker to partially remove the pin so that you can separate the chain. At this point, you can elect to use a quick link, or thread the chain through the derailleur(s), choose a chain size that allows you to have your chain around the biggest gears, and then break that part of the chain, then rejoin the chain using the chain breaker to push the pin back into the chain.
Using a Power Link:
Using a power link (an extra chain link that clips the chain together) is much easier than using a chain breaker. Many SRAM chains come pre-sized with a quick link, allowing you to attach a chain without tools. To install the quick link, first route your chain through the derailleur(s) and bring them together under the chainstay. attach one half of the power link to one side of the chain and the other half of the power link to the other side. bring the two ends of the chain together and link them with the power link. Rotate the cranks backwards so that the power link is now above the chainstay. Give the crank a quick yank forward to lock the power link in place.
Step 19: Adjust Derailleur(s)
To adjust the derailleurs, you generally need to adjust the upper limit screw, lower limit screw, and the barrel adjuster. First, shift your derailleur into its lowest setting. Use the lower limit screw to adjust the location of the derailleur so that it lines up with the lowest cog. repeat the same process with the upper limit screw and the highest cog. Make sure that your derailleur can shift into the highest and lowest gears. Next, screw the barrel adjuster in and out until you reach a point where the derailleur shifts smoothly between all gears. Shift through all of the gears, up and down, to make sure that your bike shifts smoothly through the full range of gears.
Step 20: Final Check
Go over each bolt you installed and make sure that everything is tight. You should consider taking your bike to a bike shop to have them make sure you assembled your bike correctly. Finally, you should be ready to ride! Make sure to wear a helmet!