Pros and Cons of Replacing a Road Bike Chainring

Benefits of Replacing a Road Bike Chainring

Change the Gear Ratio Without Altering Gear Steps

The speed of a road bike is determined by the formula:
Gear Ratio × Crank Cadence × Tire Circumference.
Among these, the gear ratio is the easiest to customize.

The gear ratio is calculated by:
Number of teeth on the front chainring ÷ Number of teeth on the rear sprocket.
This means that by changing the front chainring, you modify the numerator of the gear ratio, significantly affecting the overall gearing.

While changing the rear sprocket is a common way to adjust gear ratio, swapping the chainring is more effective when you want to generally lighten or harden all your gears.

Let’s see how different the gearing becomes using an example with a 52/36T crankset and an 11-speed 11/28T rear sprocket.

Now, suppose we replace the rear sprocket with a wide-ratio 11-34T model. The gear ratios would look like this:

Although the top-end (Outer/11T) gear ratio remains the same, the lowest gear becomes lighter (1.06), and overall gearing becomes about one step easier. However, this also increases the gap between each rear gear ratio step.

Next, let’s look at the case where the front chainring is swapped from 52/36T to 50/34T.

By replacing the chainring, the overall gear ratios become lower. However, since the rear sprocket’s tooth configuration remains the same, the gap between gear steps doesn’t increase. This also means fewer new gear ratio options are added compared to widening the rear sprocket range.

Replacing a Worn Chainring Can Prevent Chain Drops

Road bikes typically have both front and rear derailleurs, but chain drops occur more frequently on the front.

While chain drops can have many causes, a worn chainring increases the likelihood that the chain will slip off the teeth, leading to drops.

If you’re experiencing frequent chain drops at the front, and your chainring is worn, replacing it may solve the issue.

Slight Weight Reduction Is Possible

When replacing a chainring, opting for a higher-grade model or a smaller size can slightly reduce overall weight.

For example, mounting a DURA-ACE chainring on an ULTEGRA crankset or switching from a 52/36T to a 50/34T setup will result in minor weight savings.

While the weight difference is small, it’s worth noting that widening the sprocket range can actually increase weight by about 50g. So for weight-conscious riders, replacing the chainring might be a better option than upgrading the sprocket.

Disadvantages of Replacing the Chainring

High Replacement Cost

While rear sprockets can be replaced for just a few thousand yen if you opt for cheaper ones, chainring sets often cost over 10,000 yen, making them more expensive to replace.

Not Easy to Replace Casually

Replacing the rear sprocket is relatively easy and quick—just remove the wheel and use a special tool. However, replacing the front chainring usually requires removing the crank from the bottom bracket due to structural constraints (though there are some cases where removal isn’t necessary). This makes the replacement process more involved.

Therefore, for hobby cyclists, chainring replacement is less about swapping rings depending on the terrain and more about adjusting the overall gear ratio to match their leg strength.

Limited Ability to Expand Gear Ratio Options

Replacing the front chainring does offer the benefit of maintaining consistent gear ratio steps between shifts, but it doesn’t significantly widen the gear range.

With a sprocket replacement, you can make your lowest gear lighter for climbing hills by effectively adding a lower gear. However, chainring replacement alone cannot achieve such a significant change in gear range.