What you need before you start

Building a bicycle from parts means assembling a frame, wheels, drivetrain, brakes, and handlebars into a working bike. You will need the frame itself, two wheels with tires and tubes, a crankset and pedals, a chain, front and rear derailleurs (or a single-speed setup), brake levers and brake calipers, handlebars and stem, a seat and seatpost, and cables for shifting and braking. Most of these come as complete groupsets — matched sets of drivetrain parts made by Shimano, SRAM, or Microshift — which simplifies compatibility.

You will also need tools: a bottom bracket tool, crank puller, chain tool, cable cutters, Allen wrenches (2mm through 6mm), a Phillips and flathead screwdriver, a torque wrench, and a bike stand to hold the frame while you work. A headset press is necessary if you are installing a new headset into the frame. Many bike shops will lend or rent tools if you do not own them, and some offer workshop space by the hour.

Key Takeaways

  • Start by installing the bottom bracket, headset, and seatpost into the frame before attaching any wheels or drivetrain parts.
  • The crankset, chain, and derailleurs must match in speed — a 10-speed chain will not work with an 11-speed cassette — so buy them as a grouped set.
  • Wheels go on last, after the frame is complete, because they are the easiest parts to remove if something else needs adjustment.
  • Cable routing and brake adjustment take longer than frame assembly, so set aside time to test and fine-tune before your first ride.

Installing the bottom bracket and crankset

The bottom bracket is the bearing assembly that holds the crank axle. Place the frame in your bike stand and locate the bottom bracket shell — the cylindrical opening where the frame tubes meet. Use your bottom bracket tool to remove the old bracket if one exists, or to install the new one if the frame is bare. Most modern frames use a threaded or press-fit bottom bracket; check your frame's manual to know which type you have.

Once the bottom bracket is seated, insert the crank axle through it. The right crank (the one on the chain side) slides in first, then the left crank. Tighten the crank bolts with an Allen wrench to the torque specification listed in your crankset manual — usually between 12 and 15 newton-meters. Over-tightening can crack the crank; under-tightening will cause it to slip during pedaling. Install the pedals by threading them into the crank arms by hand first, then tightening with a pedal wrench or Allen wrench.

Assembling the headset and steering

The headset is the bearing assembly at the front of the frame where the fork and handlebars meet. If your frame came with a headset already installed, skip to the stem and handlebars. If not, you will need a headset press to install the cups into the frame's head tube. This is a specialized tool; most bike shops will press a headset for under $20 rather than sell you a $100 tool for a one-time job.

Once the headset is in place, insert the fork into the head tube. Install the headset spacers and top cap according to your headset manual — the order matters. Slide the stem onto the fork's steerer tube and tighten the stem bolts to find it. The stem should be tight enough that you cannot twist the handlebars relative to the wheel, but loose enough that you can turn the fork smoothly by hand. Attach your handlebars to the stem and adjust them to a comfortable height and angle before tightening the bar clamp bolts.

Mounting the drivetrain and chain

The drivetrain consists of the chainrings (front gears), cassette (rear gears), derailleurs, and chain. Start by installing the cassette onto the rear wheel's freehub using a cassette lockring tool. The smallest cog goes on the outside (toward the rim); the largest goes on the inside (toward the hub). Tighten the lockring firmly so the cassette cannot slip under load.

Next, install the front derailleur on the seat tube — the vertical tube running from the bottom bracket to the seat. Position it so the outer cage plate is about 2 millimeters above the largest chainring. Install the rear derailleur by bolting it to the derailleur hanger on the right side of the frame. Thread the chain through the front derailleur cage, then through the rear derailleur cage, and connect the ends using a chain tool. The chain should be long enough that the rear derailleur has slight tension when the chain is on the smallest cog in front and the smallest cog in back, but not so long that it sags when on the largest cog in front and largest cog in back.

Installing brakes and cables

Rim brakes mount directly to the frame and fork; disc brakes bolt to adapters on the frame and fork. For rim brakes, position the brake calipers so the brake pads sit centered on the rim's braking surface, then tighten the mounting bolts. For disc brakes, mount the caliper to the adapter and may support the rotor spins freely without rubbing the pads.

Run the brake cables from the brake levers on the handlebars down the frame tubes to the brake calipers. Use cable housing to protect the cables where they run along the frame. Thread the cable through the caliper's cable anchor bolt and tighten it firmly. Adjust the brake lever reach — the distance from the lever to the handlebars — using the reach adjustment screw on the lever itself. Squeeze the brakes and spin the wheel; the pads should contact the rim or rotor evenly and release completely when you let go of the lever.

Shift cables follow a similar path from the shifters on the handlebars to the derailleurs. Route them through cable housing along the frame, then thread them through the derailleur's cable anchor bolts. Tighten the anchor bolts and test the shifting by moving through all the gears. The chain should move smoothly between cogs without hesitation or cross-chaining (running the chain at extreme angles).

Attaching wheels and final adjustments

Install the front wheel by opening the quick-release lever or unscrewing the axle nuts, sliding the wheel into the fork's dropouts, and securing it. The wheel should sit centered in the fork with no side-to-side movement. Install the rear wheel the same way, making sure the chain sits on the smallest cog in back and the smallest chainring in front before you tighten anything. Spin both wheels to confirm they do not rub the frame or brakes.

Once the wheels are on, test the brakes again by squeezing each lever hard and confirming the wheel does not turn. Test the shifting by pedaling gently and moving through all the gears on both the front and rear derailleurs. Make small adjustments to the derailleur limit screws if the chain struggles to move to the smallest or largest cog. Install the seat and seatpost at a height where your leg is nearly straight when the pedal is at its lowest point.

Check all bolts one more time with your Allen wrenches and torque wrench. Loose bolts are the most common reason a new build feels wrong or makes noise. Spin the wheels, squeeze the brakes, and shift through the gears one final time before taking the bike out for a short test ride on flat ground.

Common mistakes to avoid

Mixing drivetrain speeds is the most expensive mistake — a 10-speed chain will not shift cleanly on an 11-speed cassette, and vice versa. Buy your crankset, derailleurs, cassette, and chain as a matched groupset to avoid this. Under-tightening the bottom bracket or headset will cause creaking and loose feeling in the pedals or steering; use your torque wrench and follow the manual's specifications exactly.

Routing cables incorrectly can cause sluggish shifting or brake drag. Keep cables as straight as possible and avoid sharp bends. If a cable housing is kinked, replace it rather than trying to straighten it. Forgetting to adjust the derailleur limit screws after installation is also common — the limit screws prevent the chain from falling off the smallest or largest cog, and skipping this step can result in a dropped chain during your first ride.

Frequently Asked Questions

Do I need a bike stand to build a bicycle?

A stand makes the work much easier because it holds the frame steady while you use both hands on tools. You can clamp the frame in a workbench vise or have someone hold it, but a stand costs $30 to $60 and is worth the investment if you plan to build more than one bike or do regular maintenance.

What is the difference between rim brakes and disc brakes?

Rim brakes squeeze the wheel's rim to slow it down; disc brakes use a rotor bolted to the hub. Disc brakes work better in wet or muddy conditions and offer more stopping power, but they cost more and require a frame designed for them. Rim brakes are lighter and cheaper but wear out the rim over time.

How tight should the crank bolts be?

Crank bolts should be tightened to 12 to 15 newton-meters, which you can measure with a torque wrench. If you do not have a torque wrench, tighten them firmly with an Allen wrench until they stop, then give them a quarter turn more. They should be tight enough that the crank does not move relative to the axle, but not so tight that you crack the crank arm.

Can I use any chain with any cassette?

No. A 10-speed chain is narrower than an 11-speed chain and will not shift cleanly between 11 cogs. Always match your chain, cassette, and derailleurs to the same speed — all 10-speed, all 11-speed, or all 12-speed. This information is printed on the packaging of each part.

What should I do if the brakes rub after I install the wheels?

Spin the wheel and watch where the pads contact the rim or rotor. If the wheel is bent, it may need to be trued at a bike shop. If the brake calipers are misaligned, loosen the mounting bolts slightly, center the pads, and retighten. For disc brakes, you may need to adjust the caliper position relative to the rotor using the adjustment bolts on the caliper itself.