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This post compares the advantages and disadvantages of 53/39 and 50/34 road chainrings.

The Advantages of 53/39 Chainrings

• High Gearing

The apparent advantage of a 53/39 setup is the extra high gearing that could prevent the bike from “spinning out” on descents.

“Spinning out” occurs when the wheels are rotating faster than the speed that the rider can generate via the pedals. In that case, it’s pointless to pedal because the motion does not contribute to forward movement.

Higher gears increase the top speed that can be reached via pedaling and make it less likely to spin out.

Understanding Gear Ratios

Gear ratios indicate the number of rotations that the rear cog and wheel make per 1 full revolution of the cranks/chainrings. The larger the chainring, the larger the gear ratio.

For example, if a chainring with 53 teeth is combined with a rear cog with 12 teeth, the gear ratio is 53:12 = 4.41. In this case, the rear wheel will rotate 4.41 times per 1 spin of the cranks.

One can increase the gear ratio by getting a larger chainring and/or using a smaller cog. When all other parameters are equal (wheel circumference, cadence), a bike with higher gear ratios is faster.

The next table compares the maximum pedaling speed of two bikes with identical wheels but different chainring combinations:

Conclusions:

• A 53T chainring offers a 6% higher top speed than a 50T one.
• A 39T chainring offers a 14.7% higher top speed than a 34T one.

Note: The above applies only when all other parameters are the same. Different cassettes result in different gear ratios. Also, wheels with a larger circumference offer greater speed because each revolution of the rear wheel propels the bike further. Greater distance covered in the same time frame equals higher speed.

• Classic Appearance

53/39 ratios are a classic that some people continue to find appealing.

The Downsides of 53/39 Chainrings

• The 53T Ring is Of Questionable Value

The extra speed that a 53T chainring offers is of questionable value to the average modern rider. In the past, a 53T chainring was beneficial because the smallest cog on most cassettes was a 13T. Currently, 11T is the norm.

A 53/13 gives us a 4.07 gear ratio. Meanwhile, a 50/11 offers a 4.54 gear ratio. In other words, a 50T ring combined with an 11T cog offers a greater top speed than a 53T chainring did back in the day. For most people, the top speed that a 50T can generate is plenty.

If you combine the 53T chainring with an 11T cog, you will acquire a very high gear, but it will have usability only during extreme descents.

• Climbing is Harder

Unless you couple the chainrings with an appropriate cassette, 53/39 will make climbing harder.

If you live in a particularly hilly area and have a long commute, you will benefit from smaller chainrings or a larger cassette at the back. This is especially true for riders who don’t care much about improving their strength and stamina and see their bikes simply as commuting machines.

If you are more serious about riding, then 53/39 coupled with a standard 11-28 cassette will offer plenty of low gearing once you’re in shape.

The Advantages of 50/34 Chainrings

• Low Gears for the Win

The 34T chainring offers very low gear ratios. For example, a 34/28 combo results in a 1.2 gear ratio. Meanwhile, a 39/28 gives us a 1.39 gear ratio. The lower the gear ratio, the easier it is to spin the rear wheel.

If you plan to use your bike for long ascents and/or you’re not particularly strong at the moment, the low gears will be highly beneficial.

• Lower Joint Stress

The low gears allow high cadence (RPM) and reduce the torque that the rider has to generate to conquer the terrain. People who are currently suffering from joint issues will find the reduced strength requirements beneficial.

The Downsides of 50/34 Chainrings

• Large Gap

The jump from 34 to 50 and back down is quite large. Consequently, it’s often necessary to make a few upshifts or downshifts at the back of the cassette when switching between the rings to get in a gear that allows you to continue pedaling smoothly. Some people will find the extra shifting annoying, but ultimately, it’s not a big deal and most riders get used to it fairly quickly.

Summary: What You Need To Know

• 53/39 can offer an extremely high gear (e.g., 53/11), but it’s an “overkill” for most people.

• 53/39 is a good choice for people who are already in decent shape and/or plan on riding primarily on flat terrain.

• Even though 53/39 offers higher gearing, a very low gear can be acquired by using a wide-range cassette (e.g., 11-34).

• If you live in a hilly area and care more about comfort and ease of use than developing pedaling strength, 53/39 will be needlessly high.

• 50/34 is a more universal choice because it offers usable high gears and very low gears as well. It allows you to go fast and climb hard too. For most people, this is the safer choice.

• 50/34 comes with a large gap and requires extra shifts at the back upon switching between chainrings.