Why You Need to Worry About Road Bike Sizing and Fitting

 

Having the knowledge of bike sizing can be quite helpful in selecting the right bike for your pleasurable and comfortable ride. If the right size is chosen, the bike can run faster and will be easier to handle.

Categories and sizes

Road bikes’ frames could be made from aluminium, steel, carbon fiber and titanium. The two known categories of road bikes are “traditional (standard)” and “compact” based on their frame goemetry. Traditional/standard frames have horizontal top tube while compact frames have sloping top tube.

Road bike sizes are normally defined and measured by the length of their seat tubes; a seat tube is the part of your bike that the seat post (including saddle) slide into. And normally, the length of a bike’s seat tube is given in imperial (inches). Sometimes, this measurement may be categorized as small, medium, large or extralarge.

So, if you want to know exactly what road bike’s size you need, pay attention to these three important measurements:

  • The rider’s height (which is your height)
  • Inside leg measurement (this is your inside leg measurement)
  • The rider’s reach (this is your reach)

It is believed that your inside leg measurement will be useful in determining your stand over height, which can be defined as the distance between the top tube of the bike and your crotch when standing in front of the saddle. It may be a good idea to purchase a road bike with at least an inside leg measurement of 2 inches (2”).

Sunshine road biking

Your reach and ape index

If you are unable to settle for a particular road bike’s size because your height and inside leg measurement turn up two different bike sizes, your reach could be the last deciding factor.

To estimate whether you have a long or short reach, you need to first of all calculate your “ape index”, which is your arm span minus height.

If you have a positive ape index (which means your arm span is greater than your height), it is then advisable that you go for the larger bike’s size. But if your apex index is negative, you may then enjoy riding the bike with the smaller size.

Take for instance, 170 cm (arm span) – 162 cm (height) = -11, such a rider should go for the road bike with the smaller frame.

Measurements for standard road bikes

Height Inside Leg Frame Size
5’1”-5’3” 27”-29” 48cm
5’3”– 5’5” 28”-30” 50cm
5’5”-5’7” 29”-31” 52cm
5’7”-5’9” 30”-32” 54cm
5’9”-5’11” 31”-33” 56cm
5’11”-6’2” 32”-34” 58cm
6’1”-6’3” 33”-35” 60cm
6’3”-6’5” 34”-36” 62cm

 

Measurements for compact road bikes

Height Inside Leg Compact Frame Size
5’2”-5’4” 27”-29” XS
5’4”-5’7” 29”-31” S
5’7”-5’10” 31”-32” M
5’10”-6’0” 32”-33” M/L
6’0”-6’3” 33”-34” L
6’3”-6’6” 34”-36” XL

 

Measurements for compact road bikes (for ladies only)

Height Inside Leg Compact Frame Size
5’0”-5’2” 26”–28” 2XS
5’2”-5’4” 27”-29” XS
5’4”-5’6” 28”-30” S
5’6”-5’8” 29”-31” M
5’7”-5’10” 30”-32” L

 

Brands with different sizes

The charts above provide the general frame sizes for both the traditional/standard and compact road bikes, it is important to state that a few bike brands have different sizes as shown in the charts below.

Merckx road bikes are such a brand, and it utilizes “compact geometry”, meaning its frames have sloping top tubes instead of the horizontal one for traditional road bikes. Merckx bike frame sizes could be designated as either 42, 45, 48, 51 or 54cm.

Merckx road bike sizing

Traditional sizing Merckx sizing Rider’s height Rider’s height (cm)
51cm 42cm 5′2″–5′4″ 155–163
53cm 45cm 5′4″–5′7″ 163–175
56cm 48cm 5′7″–6′0″ 175–183
58cm 51cm 6′0″–6′3″ 183–191
60cm 54cm 6′3″–6′6″ 191–198

 

Road bike tires

Road bike tire sizes

Knowing the right road bike size is a good step towards choosing a nice bike for yourself. However, that knowledge is not enough. You also need to be aware of the appropriate tire size and type that will be able to make your cycling experience enjoyable.

If you are using your bike for daily commuting, chances are that you will soon have to change your tires. Hence, being aware of the different types of tires and their corresponding sizes for road bike are quite valuable.

Most road bike tire sizes are designated as 700 x 23, 700 x 25 or 700 x 28, with 700 as the tire’s diameter and the second number as its width in millimeters. Women’s bikes may have 650mm rims.

Wide tires (25-28 mm) have the following usefulness:

  • For training when you desire extra traction and comfort
  • As a commuter, use wide tires because they prevent pinch flats, save the rims from damage, reduce rolling resistance and guarantee smooth ride on the roads
  • To have maximum grip on the roads, use wide tires

Narrow tires (20-23 mm) have the following usefulness:

  • Good choice for any rider who wants to go fast
  • Less rolling resistance when running at higher pressure
  • For training and racing, most especially the 23mm ones
  • Fast, lightweight and maximum comfort (use 20 mm tires)

Both Performance Bike and Nashbar have a nice menu, so it’s easy to sort their tires and find the right size.

Road bike competition

Threads per inch (tpi)

The casings of road bikes’ tires are produced with cloth that consists of non-woven strands of nylon or other materials neatly arranged in piles.

Here is the secret: the more the threads per inch (tpi) for your road bike’s tires, the suppler and thinner its sidewall will be and the lighter the tire.

In the light of this, a tire with over 100 tpi is puncture resistant and good for fast-riding and can run at higher pressures. On the other hand, low-thread count tires, with tpi less than 100, are economical and durable and they are heavier with thicker sidewalls.

You should also know about the “bead types” your bike tire has. The bead is described as the portion of the tire which makes it stay stuck to the rim. This is done by a thin cord of woven steel or aramid fiber which is located around the inner circumference on both sides of the tire and holds the tire firmly to the rims.

There typically two types of bead tires: Folding bead tires and wire bed tires.

Folding bead tires are foldable, used for racing, lighter than wire beads one, more expensive and harder to mount when they are new. On the other hand, wire bead tires are usually less expensive, good for training bikes, easier to mount and maintain their shape even when not mounted.

Tread compounds are organic substances put in tires to make them firmer while running on the roads.

Examples of these tread compound include butyl rubber, carbon black compounds, silica and other synthetic compounds and other additives. All these tread compounds encourage good traction, durability and great firmness so that your bike tire can stay on the roads and not skid off.

Man standing with road bike

Bike fitting

Sometimes the term “Bike Sizing” is often confused with “Bike Fitting”. However, you need to get an appropriate bike size first before you can engage in fitting it in order to experience a maximum pleasurable ride.

For you to properly fit your bike you will be dealing with its saddle, brake levers and hoods, stem, handlebar and especially its shoes, pedals and cleats.

Why do bike fitting

Fitting your road bike is to guarantee efficiency and comfort (http://roadcyclinguk.com/how-to/technique/six-symptoms-bad-bike-fit-fix.html/7 ); this begins by paying much attention to the five points where your (the cyclist’s) body comes into contact with the bike.

These points of contact are pelvis, two hands and two feet. These five points of your body must find ideal position on your bike in order to give you enough satisfaction.

Consider these important bike fitting processes that must be undertaken on your bike:

  • Pelvis: Saddle selection, fore/aft and tilt, height and occasionally cycling shorts
  • Hands: Handle bars, hoods and brake levers which are connected through a stem
  • Feet: Cleats, cycling shoes, pedals, and sometimes crank arm length

Let’s analyze these processes one by one.

Road bikes

Pelvis

  • Saddle selection: Choose a good saddle for your bike. A saddle that is not well-position on your bike may cause you to sit awkwardly on the bike, a situation that can make you feel uncomfortable because of your tilted sitting position.
  • Saddle height: Select the right height for your saddle by sitting on it with one leg hanging free and your pelvis level is not one hip tilted higher or lower. As a road biker, you should choose a height that will comfortably allow your knee to enjoy between 27 and 37 degree of flexion from your straight leg.
  • Saddle tilt: You should tilt the saddle to the best position that will guarantee your comfort while riding on your bike.
  • Saddle fore/alt position: Knee over pedal spindle (KOPS) positioning has been used for years to explain saddle fore-aft position. This entails placing one foot forward (as in 3 o’clock) with your crank arms parallel to the ground and ensuring the forward knee cap is merely over the center of the pedal.However, road bikers that are more experienced may consider the front-to-back balance of himself/herself on the bike.

Woman on road bike

Hands

  • Handlebar positioning: Your handlebar positioning is a mixture of your road bike’s bar’s height, width, depth, brake types and position, which sometimes may include the lever’s reach.You can change the position by increasing/decreasing the length and height of the stem, the width and reach of the handlebars, and the fore/aft and inward/outward position of the brake lever hoods. Try to place your hands in the regular position you have been using in a long while.
  • Road bike handlebar width: You need a good bike handlebar width, and the best approach to getting a fitting one is to visit a bike shop and physically try your hands on the handlebar, from the drops to the tops.
  • Road handlebar reach and drop: The handlebar reach is defined as the measurement from the part of the bar that attaches to the stem to the furthermost part of the bar (the point where the bending downward occurs).While drop is said to be the measurement of the top of handlebar to the top of the lower part of the bar (which is also referred to as the “hooks”). The good rule is that to enjoy riding your road bike, you should shorten your handlebar’s reach and drop!
  • Road handlebar rotation: Try to rotate your handlebars upward until you get a more neutral position for your wrist. This will make your ride comfortable as you don’t have to worry about the pain in your wrist.
  • Handlebar height: Try to adjust your handlebar height to your comfort: some road bikers may let their handlebars be in a drop position or like riding by putting their hands on the hoods. The choice is yours.

Road bikes

Feet

  • Crank length: Most bikers prefer the crank length that comes with their bikes. But if you are uncomfortable, you may want to consider adjusting your crank length. And your crank arm length depends on you: if your inseam is under 31 inches, you may want to use a crank length that is shorter than 170mm. But if your inseam is 32 inches, you may choose to have your crank length to be more than 170mm.
  • The foot/pedal connection: Give your foot/pedal connection a good position, because if you are going to get uncomfortable while riding a bike, it comes from the pain arising from poor foot/pedal connection.
  • Cleat fore/alt position: Good cleat fore/alt position will give you a pleasurable ride experience.But in case you feel some pain in your calf or Achilles tendon, you need to change something quickly, and this could be moving the cleat back toward the heel of the shoe. But if what you feel is sore under the arch, you should move the cleat forward to the shoe.
  • Cleat side-to-side position: You must retain a good cleat side-to-side position, and the best approach to determining this is to look at the position of your knee over toe alignment, which will determine your stance width.In case you adjusted your cleat but still recognize that your bike is not fast enough, you may consider changing to a pedal that has different spindle length.
  • Cleat tilt: The tilt and angle of your forefoot on the pedal is very helpful in enjoying your ride, so pay attention to it. So, tilt your cleat until you are satisfied with the position.
  • Cleat rotation: Do not hesitate to rotate your cleat until you get a firm, good position on the pedals. Your shoe should be in a good position to make the pedaling easier.
  • Leg length issues: If you are having some leg length issues, consult your local bike shop and try out the different road bikes in order to select the best bike that matches your leg length.

2 replies on “Why You Need to Worry About Road Bike Sizing and Fitting

  • Sofia

    ***”If you have a positive ape index (which means your arm span is greater than your height), it is then advisable that you go for the larger bike’s size. But if your apex index is negative, you may then enjoy riding the bike with the smaller size.

    Take for instance, 170 cm (arm span) – 162 cm (height) = -11, such a rider should go for the road bike with the smaller frame.”***

    These statements contradict one another. First you say if your arm span is greater than height you choose the larger size, but in the example with the 170cm arm span larger than the 162cm height, you advise the rider to choose the smaller frame. I was wondering which one it is.

    Reply
  • Michael

    Hi, just a note. Two paragraphs in your Ape Index section seem to contradict each other. One paragraph says that if the arm lengh is greater than height, you should buy a larger bike. But, in the example, the arm length is greater (170) than the height (162), but you’ve given a -11 score, and said it should be smaller. Sorry, but the math doesn’t seem to add up. Could you clarify? Thanks.

    Reply

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