Maintain Your Bike & Ride Smoothly with Metric Fasteners

bikeSpring is in the air, and that means a lot of people will be dusting off their bicycles and heading out for long rides. The question is, are those bikes ready for another season of two-wheel adventures? Worn or loose fasteners and bolts can turn a pleasant ride into a nightmare. Before hopping on your bike, make sure it’s up to the task.

A bicycle is made up of a surprising number of parts. All of those parts are held together by various metric bolts and washers. If any one of those metric fasteners are worn or incorrectly sized, parts can come loose and you may be at risk for injury. Here, we’ll take a look at some of the most important systems of a bicycle, and the most common metric fasteners used by those systems.

Braking System
Any engineer will tell you that stopping is more important than getting started. When you grab those brake levers, you expect them to work every time, and immediately.

The braking system starts with the levers mounted on the handlebars. Those levers put tension on cables that run down the stem to the front forks and along the tube to the rear brake bridge. Mounted on the forks and bridge are the calipers, which hold the brake pads. When the levers are pulled, the cable tightens, closing the calipers and forcing the pads against the rim. The friction between the pads and rim slows the bike.

This entire system depends on metric fasteners:

  • The levers are typically mounted to the handlebars using 5mm bolts.
  • Calipers are attached to the fork and bridge using a 5mm metric bolt and metric washer, or a T25 Torx bolt.
  • The brake pads are attached to the calipers with a 4- or 5mm metric bolt. Slack in the cables is removed using 5mm pinch bolts.

Steering System
Most people don’t think of bikes as having a “steering system.” They just have handlebars, right? The handlebars are only the top of the system. When you turn the handlebars, the stem, fork, axle, and wheel all turn together. If any of the metric bolts in the system have failed, you could find the handlebars going one way, while the wheel goes another.

The handlebars are held in the stem, usually with two or four 4- or 5mm bolts. At the other end, the stem is connected to the steering tube using two 4- or 5-mm pinch bolts. This allows the handlebars to turn the forks. In the forks, the front hub is held in place by metric bolts and metric washers from 5- to 15mm, depending on the bike model.

Seating System
The seat on your bike is actually made up of two parts—the saddle and the seat post. If you’ve ever had a seat twist while you’re leaning into a turn, or drop out from under you when you hit a bump, then something is loose with your metric fasteners.

The saddle that you actually sit on is connected to the seat post with a saddle clamp. The clamp is tightened using 4-, 5-, or 6mm metric bolts. The seat post is inserted in the seat tube, and held at the desired height using the seat binder. The seat binder is a clamp at the top of the seat tube, and is tightened using another 4-, 5-, or 6mm metric bolt.

Keeping it All Together
Of course, this doesn’t cover every metric bolt and metric washer on your bike, but without these three critical systems working and being held together properly, you and your bike could be at risk. These metric fasteners take a lot of abuse, and should be inspected and replaced regularly.

Need help with sizing your bike’s metric bolts and metric washers. Contact us to speak with one of our representatives.

About the author

Mr. Metric is the spokesperson for, an online store for metric fasteners. Get $7.50 flat shipping with no minimum orders, plus advice and best practices for using metric fasteners in any application.

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