Sprockets

BMX Sprocket Buyer’s Guide

This particular component goes by many names, including sprocket, chainring, chainwheel, and front cog. Regardless of the title, the sprocket is an important component on a bike. The type of sprocket that a rider chooses should reflect their style of riding, and how much stress they place on their drivetrain. This article will cover some of the options available when purchasing a new sprocket.

Sizes

Sprockets are available in many sizes ranging anywhere from 45 teeth down to the micro 16 to 20 tooth range.

As a general rule, you should pick a sprocket that fits into the standard 2.75 gear ratio (the number of front sprocket teeth divided by the number of teeth on the rear driver). Common gear combinations are: 23/8, 25/9, 28/10, 30/11, 33/12, 36/13, 39/14, and 44/16.

Machining

Most aftermarket sprockets are machined with various cutouts and patterns. This affects the aesthetic look of the sprocket more than strength, but sprockets with more machining will generally be weaker.

Materials

Sprockets are manufactured out of several variations of aluminum and steel. Aluminum is most commonly used due to the material’s high strength to weight ratio. Steel sprockets generally fit into the lower price category due to less complicated manufacturing processes. While steel is stronger then aluminum, it is considerably heavier, meaning most steel sprockets are thinner then their aluminum counterparts, negating some of the strength benefits.

Types

Spline Drive – Like the name suggests, spline drive sprockets attach to the crank arm through a crankset’s splined spindle. It is important to note that spline drive sprockets are designed to work with a specific spindle, so choose a version that will fit your crankset. Both the number of splines and the diameter of the inner hole on the sprocket must match the number of splines and diameter of the spindle on your crankset.

Bolt Drive – This is the most common type and comes on almost every stock bike. Looking at the back of the drive side crank can identify this style - there should be a bolt that goes through the sprocket and threads into the crank. Some low-end complete bikes use a 1-piece crank which won’t have an actual bolt threading in, but rather just a pin sticking out of the arm and through the sprocket. The diameter of the inner hole on the sprocket must match the diameter of the spindle on your crankset.

Guards – Some sprockets offer bash guards that are designed to protect the sprocket’s teeth and the chain. Sprocket guards are available in two options - either as a one-piece design, fixed to the sprocket, or as an additional attachment that bolts on to the sprocket.

How Much To Spend

You should be looking to spend between $20 and $70. The less expensive sprockets in the $20-$40 range will use less durable materials and less complicated machining patterns, making them more prone to bending. The more expensive sprockets will use higher quality materials machined in a way that will create a strong, durable component.

What To Look For

First, you should decide on the gear ratio you want to run. As mentioned before, the common gear combinations are: 23/8, 25/9, 28/10, 30/11, 33/12, 36/13, 39/14, and 44/16 (front chainring/rear driver size). These all have the standard 2.75 gear ratio. A combination that has a smaller gear ratio will be easier to pedal at first, but you will “max out” faster, meaning you won’t be able to pedal anymore once you reach a certain speed. The opposite goes for a larger gear ratio. It will take more force when you start pedaling, but once you are moving at a higher speed you will still be able to pedal. For most riders, the standard gear ratio of 2.75 will function just fine for everyday riding, so choosing a non-standard ratio should only be for the riders that need a special setup for their style of riding.

When picking a material and machining pattern, a rider should consider how much abuse they put on their drivetrain. If you’re a street rider that is harsh on your bike and often breaks chains, you will want a thicker sprocket with a machining pattern that emphasizes strength over weight savings. If you’re a light rider that doesn’t put as much stress on a bike, the opposite can be considered for maximum weight savings. It is always important to pick a component that will last on your bike. The last thing you want is to be constantly replacing sprockets and drivetrain components.

Product Reviews

Before buying, be sure to do your research and read product reviews. Reviews are a great way to find out specifics about a particular model, user impressions, and things to watch out for. After you’ve purchased a product and had enough time to thoroughly test it, we encourage you to leave a review for other people to see when they are researching bikes and parts on the web.

We hope you’ve found this information to be helpful. If you have a question that isn’t answered in this guide, our BMX forums are a great place to get advice from knowledgeable riders. Your local bike shop is also a great resource.