Choosing a bike size 101
First let’s dispense with a few less relevant pieces of info that many people think about when sizing a bike:
Wheel size is not a factor with adult Cannondale bikes
Mass market, department store bikes come in a variety of wheel sizes, from 12” - 20” for kids, up to 24” and 26” for older kids and some adults, to 29” wheel bikes for adults. Each of these mass market bikes are typically made in only one frame size. So as a customer shops in the mass market, one picks a wheel size that drives a reasonably proper bike fit for the rider. So, when you hear of a 20” bike, that references wheel size.
Riders overall height is not the driver in fitting the bike
People with the same height often have different leg lengths. Overall height is less important than what we call “stand over height”.
Below are some steps to help you choose the right size Cannondale.
Measure stand over height
Measure approximately from rider’s crotch to floor in sneakers or running shoes, feet flat on the ground. You are after a dimension is called “stand over height”. It’s a bit like the inseam of your pants, plus shoes.
Measure in centimeters or convert to centimeters (CM). (Multiply inches x 2.54 to get CM.)
Now subtract 2.54 to 5 CM (1 to 2 inches) to get your stand over height. This extra space is added to give the rider important clearance, as illustrated above. Write this number down.
Visit the Cannondale website, find a bike that interests you. Look at the Specs and Sizing section. Look at the geometry chart. See for example the geometry of Cannondale Quick bikes. Note that the stand over height is listed as dimension F.
A few examples:
Let’s say your stand over height from Step 1 is 71 cm. You would fit a size SM, a frame with a stand over height of 69.9 cm. Pretty easy call.
Let’s say your stand over height from Step 1 is 76 cm. You will see that this number falls right between the size MD and size LG frames. How do you decide? Here are several factors to help you:
- If you are a taller build with longer arms and legs, size up to the LG. Larger frames also have longer top tubes that are likely to fit you better.
- If you are more compact build, with shorter arms and legs, size down to the MD. Smaller frames also have shorter top tubes.
- If you are more fit and athletic, like to ride faster, you will likely benefit from the lower, more aggressive riding position of the larger frame, go with the LG.
- If you are more casual, ride more slowly and like to look around, the MD will give you a more upright riding position.
- If your back and neck are less flexible, thanks to a shorter top tube, the MD will give you a more upright riding position.
Bikes with step through frames accommodate a much wider range of rider heights. Simply because there is no top tube in the way. If you are not flexible, you may like the ease of stepping though rather than having to swing your leg over the top tube.
More clearance is helpful for a serious mountain biker who rides difficult trails. In this environment you will often need to put a foot down, often on rough terrain.
More clearance is better, particularly for a casual rider.
Never ride a bike that is so big that when you straddle the top tube your body hits the top tube. For safety you must be able to comfortably straddle the top tube with your feet flat on the ground.
Road bikes/Metric sizes:
Many of our bikes are made in S, MD, LG, XL sizes, and fit is less critical. For road bikes/racing bikes/endurance bikes fit is more critical than on other types of bikes. We offer up to eight metric sizes, from 48 cm to 63 cm. The reason is that on road racing bikes the rider is often locked in to a fixed position for many hours of riding. So small differences in fit can make a big difference. Experienced riders often know their preferred frame size, saddle height, reach dimension, etc. Really the best way to be fitted to a road bike is in person at an Authorized Cannondale Dealer.