BE SIZE WISE
KNOWING WHAT SIZE BIKE TO BUY CAN BE A MINEFIELD, SO HERE’S OUR GUIDE TO HELP YOU CHOOSE THE CORRECT SIZE FRAME
Riding a bike that doesn’t fit is no fun. It’s uncomfortable and you risk injury from being too cramped or too stretched out.
Getting the right fit means more than just having the right size frame though. It also means your bike fits at all the main contact points: saddle, handlebar and pedals.
Of course, we’re not all the same, so use the information here as a guide. After you get the position close using these tips make smaller adjustments based on what feels better.
You’ll be able to get fit advice in person from a bike shop, though we would recommend getting an understanding of the different elements that affect how a bike fits to ensure you end up with the right size. Also, take any bikes you are considering for a test ride to gauge how they feel in action.
Manufacturers’ guidelines
The simplest way to determine what size to go for is by using the guidelines manufacturers provide, which correlate various height ranges with different bike sizes.
There are no standard sizes between those manufacturers, and each will have its own approach to bike design, so it’s useful to have an understanding of bike geometry and how that affects the fit to ensure you get the size that suits you best.
Anatomy of the bicycle frame
Bike manufacturers will usually list the measurements for each element of a bike’s geometry, so knowing what each measurement refers to is the first step.
The diagram below helps to identify the different frame tubes. The effective top-tube concerns bikes that use a sloping top-tube, such as road bikes with a semicompact or compact geometry.
With experience you will soon find that a correctly sized bike will look in proportion when finally set up.
Manufacturers make frames in various sizes to suit the variety of riders. Getting the size right is essential, but this step is only half the story. The fine-tuning starts when you choose the length of the stem and the width of the handlebar.
There are three geometries of frame size to consider: traditional, compact and semi-compact.
Traditional
Traditional frames are characterised by a top-tube that runs parallel to the ground. There is a reduced space when standing over the bike, so sizing can be more critical.
Compact
Compact frames are meant to look more radical than conventional level top-tube frames, so expect to see an extra two to three inches of seatpost showing when compared with horizontal top-tube bikes.
Compact geometry frames are characterised by a sloping top-tube, shorter wheelbase and smaller rear triangle. The result is more standover clearance than a traditional geometry frame and a possibly stiffer but more responsive ride.
The contact points should be exactly the same, so be aware of this when buying – a compact should feel exactly like your preferred conventional road bike with respect to riding position.
Important lengths
The most important consideration to make as you decide which frame to go for is the effective top-tube length: the distance from the head-tube to the seatpost on a bike with a sloping top-tube, or simply the length of the top-tube on a road bike with traditional geometry.
Get the top-tube length too long and you’ll be overreaching to the handlebar, using a flatter riding position, akin to a racing position, which could be uncomfortable on longer rides.
If you are looking for a more comfortable riding position, you may wish to go for a shorter effective top-tube length. The chart below will be able to help as a starting point to working out the most suitable frame size.
YOU CAN FINE TUNE YOUR BIKE FIT, STARTING WITH SETTING THE HANDLEBAR AND SADDLE HEIGHTS
Tweaking the bike fit
Once you have decided on your frame size you can fine tune your bike fit, starting with setting the handlebar and saddle heights. You can find tutorials at tinyurl.com/cplussaddleheight.
You may also want to adjust or change the stem, as that can affect your reach – literally, how far you are reaching forward to the handlebar – and the handling and performance of the bike.
Further tweaks can include adjusting the fore/aft position and tilt of your saddle, the angle of your handlebar, and the distance to the brake levers. Many of these changes can be made in a good bike shop, though a professional bike fit is worth its weight in gold. As part of a bike fitting session, experts will get you riding on a fixed trainer to check your bike position and ensure everything fits you perfectly.