How To Measure A Bike Frame

How To Measure A Bike Frame

If you are thinking about buying a new bike, whether it is for yourself or for someone else, it is very important to understand which aspects and measurements are the most important in order to make the perfect choice. A key detail relies on knowing how to measure a bike frame.

The frame of a bike is definitely going to be among the most crucial measurements to consider, as this will ensure that it fits the rider’s body and riding style effectively.

We will discuss exactly how to measure a bike frame, as well as how to choose the right bicycle size for a variety of different riding styles.

How To Measure A Bike Frame Properly

How To Properly Measure A Bike Frame

Understanding how to properly measure a bike frame in order to determine the perfect sizing for a rider is of utmost importance. Whether you are buying or selling, the bike’s frame measurements should be one of your main concerns.

Here is a detailed step-by-step guide for measuring a bike frame:

  • Start by checking for a size label on the bottom of the saddle tube. This is the tube that connects to the bike saddle post. Some bikes will not have this size label, but it will save time if your bike does.
  • If there is no size label on the saddle or seat tube, measure this by starting from the center of the gear crank and ending at the top of the seat tube. It helps to remove the seat if possible so it does not get in the way.
  • Place one end of the tape measure at the center point of the gear crank, and then place the other end up to the very top of the saddle tube, where the seat post connects. Take this measurement in either centimeters or inches, but make sure to stick to this unit for the entire frame measurement process moving forward.
  • Next, use your tape measure and find the length of the vertical head tube, which is the part that connects the handlebars to the top of the fork. The fork is the split piece of metal that connects to the center of the front wheel. This part is always the shortest of all main bike tube measurements.
  • Be sure not to accidentally include the base of the handlebar post in this measurement.
  • Now it is time to measure the slanted top tube, which can be a little bit tricky. This tube runs roughly parallel to the ground, between the seat post and head tube. In order to measure the length of this slanted tube, you will actually be measuring what is known as the effective top tube.
  • In order to do this properly, but hold a level perfectly flat, starting from the point where the top tube connects with the head tube. Noten where this plane intersects with the seat tube, and take your measurement accordingly.
  • Most bikes, especially road bikes, will be designed with a slanted top tube. In the case that your top tube is flat instead of slanted, simply use your tape measure and run it directly along the tube to get your number.
  • Take these measurements and cross-reference them with your lower body’s relative measurements. Use your inseam measurement (ground to your crotch) in order to ensure that you are choosing a bike frame size that will fit your body’s proportions correctly.

How To Pick The Right Bicycle Size

In this section we will discuss how to pick the right bicycle size for a variety of different styles of bikes.

Road Bike

Road Bike

One of the most important measurements to consider for determining the proper road bike size is your saddle height. This measurement can be roughly calculated by using what is known as the LeMond formula.

This formula is executed by taking the length of the inside of your leg (your inseam essentially) and multiplying it by 0.855.

You may also take the more simple route by following the bicycle manufacturers sizing guidelines, which will usually correlate a number of different height ranges with recommended bike sizes.

Mountain Bike

Mountain Bike

Mountain bikes will typically come in three standard sizes; small, medium and large. These general sizing guidelines are meant to correspond to the prospective rider’s height.

Many bike manufacturers will include size charts with their products that list a height range for each bike size. In the event that the rider falls somewhere in between size ranges, it is a rule of thumb that you should opt for the smaller size rather than the larger one.

This is because there is more potential to make the necessary adjustments needed to fit the bike to the rider’s body when you are working with a bike that is slightly small, rather than one that is slightly too large.

Having a basic understanding of general bike geometry and how it affects fitting can also be helpful when comparing one bike to another, or dealing with a fitting situation.

There are a number of important indicators, some of which include:

  • Effective Top Tube Length
  • Reach (distance from center of bottom bracket to center of head tube)
  • Standover Height & Clearance
  • Saddle Height

Adult Tricycle

Adult Tricycle

Choosing the right size of adult tricycle will largely depend on the size of the wheels that each model comes designed with.

Wheel diameters on adult tricycles currently found on the market range anywhere from 16 inches in smaller models, to 24 and even 26 inches on larger, more heavy duty models.

Rider height is not as restrictive for finding the right bicycle simply because of the unique design and intended purpose of adult tricycles. These trikes are meant to accommodate a variety of rider sizes, skill levels and age ranges.

Typically, tricycles with 20 – 24 inch wheels are best suited for riders between 4 feet 8 inches and 5 feet 5 inches in height. The tricycles with 26 inch wheels are usually larger, and are therefore more suited for riders between 5 feet 4 inches and 6 feet 2 inches tall.

It is obviously still important to pay attention to the saddle height and overall frame size when purchasing the right size of adult tricycle.

However, a lot of these models are made with very low, accommodating seats that are not meant for precision and specificity.

BMX

BMX

BMX bikes are known for coming in a wide variety of wheel sizes, ranging anywhere from 12 inches to 24 inches and in some cases more. The most common, and the true wheel size for BMX bikes is 20 inches.

The top tube on BMXs is the most important measurement to consider when choosing the proper bike size for a rider. Even more important than the wheel size.

Different sizes are meant to suit different sized riders. Here is an approximate guide:

  • Under 3’3”: 12” Wheel SIze
  • 3’3” – 4’: 12” – 16” Wheel Size
  • 4’ – 4’6”: 16”- 18” Wheel Size &
  • 4’6” – 4’10”: – 18” – 20” Wheel Size & Small Top Tube Size
  • 4’8” – 5’4”: 20” Wheel Size & 19.5” – 20.4” Top Tube Length
  • 5’4” – 5’10”: 20” Wheel Size & 20.25” – 21” Top Tube Length
  • 5’8” – 6’: 20” Wheel Size & 20.5” – 21.5” Top Tube Length
  • 6’ +: 20” + Wheel Size & 21” – 22” Top Tube Length

Hybrid Bike

Hybrid Bike

Like most other styles of bicycles, finding the right size depends largely on ensuring that the frame is the right size for your height and weight, as well as the relative length of your limbs.

Here is a brief sizing guide:

  • 4’11” – 5’3”: Bike Frame: 13 – 15 inches
  • 5’3” – 5’7”: Bike Frame: 15 – 17 inches
  • 5’7” – 5’11”: Bike Frame: 17 – 19 inches
  • 5’11” – 6’2”: Bike Frame: 19 – 21 inches
  • 6’2” – 6’4”: Bike Frame: 21 – 23 inches
  • 6’4” +: Bike Frame: 23 inches +

Conclusion

Learning how to properly measure a bike frame is an important part of being able to effectively choose the right size bike for any rider. In this article, we provided a detailed, step-by-step guide for how to properly measure a bike frame.

We also discussed how to pick the right size of bike, more specifically for a number of popular styles including BMXs, road bikes and mountain bikes.

Consider what we have talked about and apply this information to your search for the best possible size of bike. Thanks for reading and happy riding!

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Last Updated on February 18, 2022 by Matthew Carpenter

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