After you have picked what type of bike you want to get, you need to make sure you get it in the right size. Fitting will be very important if you want to put in a lot of miles, and it’s really hard to fit the wrong size bike. If you are buying used, read this full post. If you are buying new, the great people at the bike shop will help you find the right size. You don’t want to look silly on the wrong size bike.
The size of the bike is almost always listed on the seat tube of the frame.
All the different bike brands will have a guide for sizing. For instance, if you were going to buy a Trek Marlin 5 the recommended size for 5’,3.4” – 5’, 7.7” tall is the Medium. They have a nice chart listed on the site with all the recommendations:
Now the size will often change based on brand and model. If you are a medium with the Trek Marlin 5, you might still be a small for a similar Specialized mountain bike. So, you really want to find the brand recommendation for that same year and model. I’ve been able to search this info on the internet for older bikes that I have been interested in. If you can’t find it, you can use a similar newer bike for your starting point from the same brand. Ultimately you always need to test ride the bike and see if it seems like a good fit.
To complicate things, different bikes will use a different method for sizing. For instance, my Felt road bike is a size 54cm, and my mountain bike is size 16.5”.
The standover height is one of the main measurements I use for sizing a bike. This is the distance from the ground to the top of the top tube of the frame. If you can’t stand over the top tube comfortably, the bike is too big. Last thing you want is to be uncomfortable every time you have to stop at a traffic light. And you might want a bit of extra room if you are buying something for off road in case you slip off the pedals, your privates will appreciate it. You can use your inseam to help estimate your bike size. If you have a 32” inseam you aren’t going to be comfortable on a bike with a 33” standover height. Top tube height isn’t much help for many woman’s models, however.
A bike that is too small will generally be harder to determine than one that is too big. Beside the top tube, if you have the seat down all the way and still have trouble reaching the pedals, it is way too big. If you need to raise the seat all the way up for comfortable pedal reach, it is probably too small.
Bringing a friend with when you test ride the bike is a good idea. Somebody watching you ride it will often see if it seems too big or small. They can also make a video and play it back so you can watch how you look on the bike.
Hope these tips help you get the right size bike. Good luck shopping!