To ensure you acquire a bike that suits you and is appropriate for the sort of riding you want, it’s crucial to grasp the basic measures that characterize your bike frame if you’re considering purchasing a new or first bike.
Additionally, if you rent a bike, knowing your frame’s essential dimensions can help ensure that the hire will be pleasant to ride and that it can be altered to fit you. You want to appear at a few basic metrics to guarantee you’re likening like with like since not all constructors measure frame sizes likewise.
What is required to measure a bicycle frame
- A measuring tape
- A clinometer for calculating angles
- Lengthened spirit level
- The plumb line
Although most manufacturers now size both road and mountain bikes in metric measurements, you may still come across those that do so. Some companies, like Moots, even combine the two!
To maintain consistency, we strongly advise that you stick with metric measurements. If you absolutely must, you can convert centimeters to inches by multiplying them by 2.54. On a maker’s website, you can often discover a geometry diagram for every size of an existing frameset. It is worthwhile to duplicate this if your bike is still in production because it will be more exact than your measurements and probably come in useful in the future.
How to gauge the length of a top tube
Back then, all bicycles had horizontal top tubes. Now, the upper lines of many bicycles will be slanted. The actual top-tube length will often be listed in a bike geometry table. The horizontal top resulting in a total, also known as the operative top tube distance or virtual fully equipped in many geo diagrams, must be measured for a reliable measurement independent of the maximum tube angle.
That is the horizontal separation between the Seatpost centerline and the head tube centerline. You must use your graduated cylinder or the clinometer app to confirm that your measurement is flat.
Road bikes are frequently sized by top tube length. With mountain bikes, the frame size is often indicated with S, M, L, etc. Several road bikes employ the same system: The road bikes from Merida pass through S, S/M, M/L, and L.
Of course, each manufacturer will interpret this dimension differently. For example, Ridley’s size S frames feature a top tube around 54 cm long, the same as many companies’ size medium frames.
How to gauge the length of a seat tube
The seat tube distance is measured in a conventional line from the bottom bracket’s center to its top. It’s challenging to evaluate the measurements of one bike to those of an alternative since specific bikes, like the Trek Madone, have a significant expansion of the seat cylinder just overhead the highest tube connection, whereas others have a seat mast.
Additionally, the seat tube on mountain bikes, in specific, frequently has a bend, so you don’t need to track that line because it will be longer. If you’re unsure whether you’re following the appropriate path, align your straight razor with the bottom support midpoint, and the bottom of the seat stays and measurements along this.
Calculating wheelbase
The length that separates the front and rear axles of your frame is its wheelbase. It affects the ride comfort of a frame significantly and varies with the body frame. It’s not too difficult to measure, but you must place the fork directly ahead for an accurate reading.
Similar to range and stack, it is essential to do the dimension numerous periods to ensure that you have the same result. Additionally, accurateness will improve if you estimate the wheelbase along the sides of the bike and aggregate them because this will account for any divided slant.
Chainstay length measurement
The length of your chain stays, one of the two parts that make up your wheelbase, dramatically affects how your frame handles. Generally speaking, a bike with lower chain stays will feel less lively than one with more extended stays.
The chainstay length may be measured with a ruler since it is the straight line length between the middle of the bottom bracket spindle and the center of the front dropouts.
Angle measurements for the seat and head tubes
Two of the most crucial elements in riding are the seat pipe and cap tube viewpoints, with higher upright tube viewpoints often resulting in more responsive riding. It is when your clinometer app will be helpful.
By aligning your smartphone and using the clinometer app, you can determine the seat tubing angle if your saddle tube is straight. Make certain your bike is upright and on a level superficial for precise estimation. If your seating tube is kinked, you must align the phone with the line drawn with a sharp edge between the base of the seat stays and the bottom bracket shells.
The front of the cylinder block won’t be at the same angle as the centerline of most modern bikes since they have tapering head tubes. Placing your phone at the centerline angle or employing a straightforward edge to align with the centroid of the highest and bottom of the cylinder block can help you come near to the latter.
If your fork legs are straight and do not have an angle at the summit, the inclination of the legs and the head tube may be measured. Once more, it’s crucial to have the bike upright. Additionally, you may gauge the cranium tube angle by aligning the clinometer with the handlebar stem extension previously mentioned.
Measurement of the bottom bracket drop
The distance between the cranks axle’s centerline and the wheels axles’ elevation is known as the bottom bracket drop. To calculate it, compare the height of the bottom bracket and the rear suspension, then deduct one from the other. It’s yet another significant metric that bike companies include in their geo-maps.
Size of children’s bikes
It’s crucial to get a kid the proper bike size. It not only makes the ride more comfortable but also makes the bike safer. You may be wondering how one determines a child’s bike size.
It is advised, if at all feasible, to take children to a nearby shop where they may check out a range of bikes. They will be able to develop a sense of what is appropriate, cozy, and secure. The procedure is much more straightforward with hands-on expertise, allowing you to prioritize your child’s safety.
However, assessing your child’s height is advised before making an online bike purchase. Children’s bikes are sized based on wheel diameter, unlike adult bicycles, which are sized by frame.
To ensure a proper fit and safety, you must measure the child’s height and compare it to the appropriate wheel diameter. Only then can you rest comfortably. Invest in a high-quality helmet to match the new bike; a wide selection is available, so you’re likely to find one they like.
Measure the size of the bottom bracket
The height from the floor to the middle of the bottommost bracket canister is known as the bottom bracket height. That makes it very simple to measure, but make certain your bike is vertical straight up for an accurate measurement.
Contrary to bottom bracket droplets, it will also be (somewhat) impacted by your tires, so ensure they are inflated to your normal running pressure. You now have all the information necessary to size up your frames. You don’t want to go through the process again, so save your numbers somewhere secure.