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Condensed answer:

The difference between a 54cm and a 56cm road bike frame isn’t as massive as it may sound, especially after counting for size variation between brands.

In most cases, an individual who fits well on one does well with the smaller or larger size too.

Nonetheless, the classic way of determining frame size should still be followed for optimal results.

Height vs. Inseam

Many people wrongfully conclude that height is the only important factor when choosing the correct frame size. Height matters but so do bodily proportions.

Two men can be the same height but one may have a short torso and long legs while the other has a long torso and short legs.

For that reason, bike size is determined by measuring the rider’s inseam.

The inseam is the distance between the rider’s crotch and the floor.

One of the classic ways to measure your inseam is to place a book between your legs and put in slight contact with the groin area. Then, measure the distance between the book’s edge that’s touching your body and the floor with a tape measure.

The measurement should be done on a leveled surface and without shoes or socks. Consult the video below for more information.

Once you have your inseam, you can use a frame size calculator or consult the table below to find out what size frame you need.

Conclusion: A 54cm frame works fine when the inseam of the rider is about 82cm. A 56-frame requires an inseam of about 84-85cm.

If your inseam is closer to 82cm go for a 54cm frame; if it’s closer to 85cm, then a 56-frame would probably work fine too.

The Difference Between a 54cm and 56cm Frame Is Not Massive

A 2cm difference is not enough to make a frame too small or too big. In fact, the contrast is so slim that in most cases it comes down to personal preference.

For example, a smaller makes the bike snapper. For that reason, professionals ride smaller frames than what one might expect.

A larger frame, however, makes the bike more stable via its longer wheelbase (the distance between the two axles) and is more comfortable to pedal for long distances.

Variations Between Brands and Models

Size varies from one manufacturer to another. In some cases, there are also size differences between models made by the same company.

It’s important to find information about the frames you are analyzing. Ideally, visit a local bike shop that has the frame/bike you plan on riding and see how it fits you.

Arm Length Is Important Too

Even though the inseam is the go-to measurement for selecting a frame, the arm length of a rider influences the decision too.

For example, someone with a long inseam but fairly short arms could experience back discomfort due to the stretched position when put on a maximally large frame based on the inseam data.

That said, this particular issue can be fixed by getting a shorter stem and/or moving the saddle forward so that the rider gets closer to the handlebars.

FAQ: Should I get a frame that’s slightly smaller for me or slightly bigger?

If the frame is vaguely in the size range that fits you, then it comes down to personal preference and performance goals.

Professionals today ride much smaller frames than expected because they like the snappy/sporty feeling of a smaller bike. However, if you want maximal pedaling efficiency for long-distance riding, then a large frame makes sense too as it increases comfort.

Don’t forget that within a certain range, it’s possible to make a frame feel smaller or bigger via the stem, handlebars, seat post, and saddle.