One of the first questions new bike buyers ask is, "What size road bike do I need?" When new cyclists walk into a bike shop, they come with a few burning questions. Some cyclists know what kind of bike they want, the color, and all the accessories they want to add.
But few cyclists know precisely what size road bike they need. Different manufacturers may run big or small, and some are labeled as "Small, Medium, Large" rather than "52cm, 54cm, or 56cm." Even experienced cyclists may need to test a few sizes before finding a perfect match.
Beginner's Guide to Road Bike Sizing
In this post, we'll help you answer the question, "What size road bike do I need?" First, we will run through different bike sizes and bike size charts. Then, we will discuss frame geometry and the essential measurements you need to know.
We'll also discuss the similarities and differences between road bike sizing, mountain bike sizing, and triathlon or time trial bike sizing. Finally, we'll wrap it all up with our bike size guide, which will help you determine what size road bike is best for you.
Here is a list of everything we're going to cover in this article:
Bike Size Basics
- Different Bike Size Measurements
- Bike Size Charts
Frame Geometry for Beginners
- Top Tube Length
- Effective Top Tube
- Seat Tube
- Head Tube
- Contact Points
Sizing for Different Bikes
- Women's Bikes
- Road Bikes
- Mountain Bikes
- Triathlon or Time Trial Bikes
Complete Bike Size Guide for Beginners
- Step 1: Finding a Bike That Fits
- Step 2: Basic Bike Fit
- Step 3: Test Ride
- Step 4: Professional Bike Fit
Answering "What Size Road Bike Do I Need?"
- Perfecting Your Riding Position
Bike Size Basics
There are three types of bike shapes: traditional, compact, and semi compact. These shapes are different from the actual size of the bike, which is either S/M/L or a certain number of centimeters.
Because of the three different shapes, you could have vastly different bikes labeled as "Medium," for example. Thus, it's essential to take a close look at the details of a prospective bike before making the final purchase.
Below, we'll get into the specific bike size measurements you should look for when shopping for a new bike.
Different Bike Size Measurements
Traditional bike frames look like a triangle. They have a top tube parallel to the ground and tubing that connects like basic puzzle pieces. There are no significant bends or curves in the frame, which makes these types of bikes a bike stiff and unforgiving. Most modern road bikes are compact or semi compact frames.
First, we have compact frames with a sloping top tube, a relatively short wheelbase, and a small rear triangle. As the name suggests, these frames look smaller to the naked eye, but most have a longer seat post to make up the difference. You will have more standover on a compact frame and a stiffer ride that is ideal for sprinting and racing.
Most bike racers use compact or semi compact frames which are better for handling, sprinting, and ripping through corners. Semi compact frames are, quite obviously, right in the middle of traditional and compact frames. They have a slightly sloping top tube and a smaller rear triangle. Still, the fit differences will not be as pronounced as in compact bicycle frames.
Bike Size Charts
Most bike manufacturers use a basic bike size chart that sorts frame sizes by rider height. However, every manufacturer is different, so their size chart measurements may vary slightly.
Here's an example bike size chart for road bikes:
Frame Geometry for Beginners
The bike size guide should only serve as your starting point. There are a few more measurements to consider when searching for the best bike fit.
In this section, we'll dive a bit deeper into a bike's geometry. We won't get too lost in the technical terms, and we're only going to focus on the measurements that matter for your bike fit. First, let's start with standover.
One of the most basic bike frame measurements is the standover, which is the amount of space between your butt and the top tube when standing directly over the frame. You might adopt this position at the start of a ride when both feet are still unclipped.
Your standover should allow you to place both feet flat on the ground with 1-2cm of space between your bottom and the top tube.
Your frame may be too big if you are effectively sitting on the top tube with both feet on the ground. But if you have 6+ centimeters between your bottom and the top tube with both feet flat on the ground, your frame may be too small.
Top Tube Length
The top tube is the tube at the top of the bike, which sits between your thighs as you pedal.
Top tube length is crucial for determining overall bike fit – while seat tube length may help you find the right height, the top tube length can help ensure comfort and control over the frame.
Effective Top Tube
Effective top tube refers to the distance between the seat post and head post on a sloping head tube. This is crucial because some bikes have a sloping top tube, so measuring the top tube length alone won't tell you much about the bike's potential fit. After all, your reach is determined by the effective top tube length more than just the top tube length.
Once your feet are in the pedals and your saddle height is adjusted correctly, the next most important measurement of bike fit is your effective top tube length.
A neutral fit is best for beginner cyclists, and a professional bike fitter can help you find your ideal reach. As you increase your effective top tube length and reach, you will stretch out your position, making it more aggressive and aerodynamic.
You can shorten your reach with a shorter effective top tube for a less aggressive, more comfortable, and more upright position.
The seat tube is the tube that extends down from the seat post to the bottom bracket, forming the back end of the bike's triangle. Many bike manufacturers use the seat tube length to size their bikes. When bikes are sized as 52cm, 54cm, etc., this typically refers to the frame's seat tube length.
In some cases, the centimeter sizing describes the top tube instead of the seat tube, but this is much less common.
However, the seat tube measurement (and many other bike frame measurements) do not account for frame angles. Thus, two frames with the same seat tube length could have vastly different fits if one has extreme angles while the other has traditional angles.
The head tube is the small piece of tubing that connects the stem to the frame and the frame to the front fork.
Typically, you can't adjust the height or length of a head tube, but it still plays a big role in determining your bike fit. Larger frame sizes will have a larger headtube. And if it's too large, your reach will be uncomfortable or unsustainable.
It is difficult to determine the best head tube without a proper test ride, so head to your local shop to try a few different sizes.
In addition to the size and shape of the frame, you need to pay attention to your contact points on the bike:
Your contact points will help determine your riding position, which can be adjusted and optimized with a professional bike fit. In other words, your contact points are moveable, whereas the bike's frame is not.
The first step in bike sizing is to find the correct size frame, and the next is to optimize your contact points. We'll dive deeper into this topic below in Complete Bike Sizing Guide for Beginners.
Sizing for Different Bikes
We already know that not all road bikes are made the same, but neither are other types of bikes. Mountain bikes, triathlon bikes, and time trial bikes come in all different shapes and sizes, and you could say they are vastly different from road bike sizes. Gravel bikes, for one, are very similar in size to road bikes, so you can use the same road bike sizing guidelines when shopping for a gravel bike.
Below, we highlight some of the significant differences between road bikes and other types of bikes.
One of the most interesting debates in bike sizing is, "What is a women's bike?" Multiple manufacturers build "women's bikes," but few include frame anatomy or features unique to women. Most women's bikes are identical to men's but come in different color schemes.
A few women's bikes feature unique geometry, but most women still ride unisex bikes. Regarding bike sizing, there are many more differences between individual female anatomies than between males and females in general.
In this article, we've focused on road bike sizing. But that doesn't mean that all bike sizing is the same. Your bike size could differ between a road bike, hybrid, cruiser, mountain bike, or time trial rig. It all depends on your riding position and unique physiology.
Below, we're going to point out a few differences between a road bike and mountain bike sizing, as well as a road bike and triathlon or time trial bike sizing. Each bike is built for a different cycling style, with a few main differences between frame shapes and sizes.
Don't swap out your road bike for a mountain bike of the same size, at least not automatically. Read over our bike size guidelines first, and then try and test-ride a new frame before making the final purchase.
Mountain bikes have significantly different frame shapes and sizes than road bikes because of their desired terrain. Simply put, mountain bikes are built for off-road riding. Road bikes are the opposite, designed for pavement.
With an upright riding position and flat handlebars, mountain bikes are designed for technical climbing, single-track trails, and gnarly descents. They are not intended for high-speed corners, time trials, or sprinting.
Most mountain bikes are sized using Small, Medium, Large, etc. descriptions rather than centimeter-measured lengths of the seat tube or top tube.
Triathlon or Time Trial Bikes
Triathlon or time trial bikes differ significantly from road bikes in their shapes and size. A triathlon or TT bike is designed to be fast in a straight line. Thus, it has long aerodynamic handlebars extending above the front wheel and a steep seat tube angle that pushes the rider's position over the bottom bracket.
This helps triathlon or TT riders go fast in the aero position with their forearms nestled into the aero bars. Triathlon or TT bikes are built with thicker, aerodynamic frames that use slightly different shapes than road bikes. The latter is designed for all kinds of road riding and racing. This includes corners, descents, sprints, and climbs.
Road bikes are much more versatile than triathlon or TT bikes. Their frame reflects these features, as road bike frames are not optimized for just one thing. Instead, they are powerful all-rounders with balanced riding positions.
Most triathlon or TT bikes are sized the same way as road bikes, referring to the effective top tube length in centimeters. However, the riding positions are so vastly different that it's crucial to fit in a test ride before committing to a new triathlon or TT bike size.
Complete Bike Size Guide for Beginners
When you're looking at buying a bike, you need to make sure you have the right size frame. That's the whole point of this article!
You need a bike that fits and one that fits you properly. You shouldn't just choose a bike based on height, as this is much too oversimplified. Here, we'll give you a checklist for bike-buying, everything you need to know to find a bike that fits.
Step 1: Finding a Bike That Fits
There is more to bike fitting than finding the right frame size. While the correct frame size may put you in a comfortable position on the trainer, there is more to cycling than stationary pedaling.
A proper bike fit will help increase your comfort on the bike, as well as dial in your bike handling. This includes cornering, climbing, descending, sprinting, and more. When you find a bike that fits, you have found your starting point.
Use our road bike sizing chart as your starting point:
It won't be hard to find a bike that generally fits, but then you'll want to dial in your fit with a test ride. The correct frame size will set you up for success. Still, there are a few additional steps to completely dialing in your position.
Step 2: Basic Bike Fit
Finding the right bike size takes more than just plugging in the numbers. You should also get a basic bike fit to fully dial in your position ahead of your first few rides.
You can start by heading to your local bike shop and asking them for sizing recommendations based on your physiology and the kind of bike that you're looking for.
Following the numbers and bike fit measurements, you can narrow down your choices to the bike frame's specific size and shape. If possible, we recommend a test ride on a few prospects to get a feel for each bike. One manufacturer's frame may feel very different from another's, even with the same frame shape and size.
Step 3: Test Ride
Once you gathered enough information from our sizing chart and recommendations from your local shop, it's time to test out a bike. At this point, you should have one or two different sizes in mind.
If possible, test ride the specific bike in the specific size that you are looking at. The right size bike should feel comfortable right from the start. Once you've found a comfortable bike, it's time to dial in your fit.
Step 4: Get a Professional Bike Fit
Once you've found a bike size that you know and love, it's time to make the final purchase. Some bike shops offer a professional bike fit in-house. You can have your bike fit done right there in the shop, and you don't even need to make a second trip.
A professional bike fitter will help adjust your handlebars, saddle, and riding position so that is ideal for your physiology and your riding goals. Road racers may have an aerodynamically-optimized position, while a casual road rider will have a more upright position, for example.
Bike fitting is a crucial part of the bike buying process, not only for performance but also for injury prevention. Having a proper bike fit can help you avoid chronic pain and injuries, especially after spending hours in the saddle. You will also be more comfortable and powerful on the bike with a proper fit. And who doesn't want to go faster?
Answering "What Size Road Bike Do I Need?"
Start with the bike sizing chart as a rough guide to finding the best road bike size. Consider your height and your anatomy. Are you someone with long legs or long arms, or are you average-sized? If you are average, congratulations, your bike buying process just got a little bit easier.
Riders with tall or long dimensions may have a harder time finding the perfect fit, but that doesn't mean it will be hard at all. If you have longer arms, then you know you need a road bike with a longer effective top tube. If you have longer legs, then you probably need a larger bike size so that you have plenty of standover and a longer seat tube.
Remember: don't overthink it. And if you're unsure, head to a local bike shop and ask lots of questions. They will be happy to help, and they'll probably let you test ride a few bikes to see what size is best for you. With a few test rides under your belt, you will feel the difference between each size and you'll know which frame size is best for you – maximizing comfort, efficiency, and handling, all in one.
Perfecting Your Riding Position
Having the perfect frame doesn't do any good if your saddle, shoes, and handlebars are all in the wrong place. Thus, it's important to dial in more than just your frame size for the fastest, most efficient, and most comfortable bike fit.
First, take a look at adjusting your saddle fore aft, or even try tilting it up or down. If you've tried every position and it's still uncomfortable, it might be time for a new saddle.
Next, try adjusting your cleats if need be. It's always best to start with them in the neutral position, centered fore aft and left to right. Try that out for a few rides and see if you have any pain or discomfort. Make small adjustments to your cleats and you should notice the difference right away.
Finally, dial in your reach by adjusting your handlebar position. This can be done with small tweaks such as tilting your bars up or down. Or you can make a bigger adjustment like swapping out your stem. A professional bike fitter can give you the best guidance, but you can also try some smaller tweaks on your own.
When it comes to finding the perfect bike fit, it's not something that happens overnight. But with a little bit of research and a few test rides, you can find the road bike size that is perfect for you. From there, do a few rides and some testing to completely dial in your position with cleat, saddle, and handlebar adjustments. If you can tick off all those boxes, I can almost guarantee that you'll never have felt better on the bike.