Buying a Used Bike? Here’s How to Know If It Will Fit You

Before you hand over your cash, check out this guide to make sure that new-to-you bike will fit you properly.


Buying a second-hand bike often means less chance or no chance for a test ride, and unlike buying a new bike, there’s no chance of exchanging it for a larger or smaller size. Once the transaction is made, you’re stuck with it. And unfortunately, that means there’s a heightened risk of buying a bike that just doesn’t fit you.

Does that mean you shouldn’t buy secondhand? Not necessarily! “Buying a second-hand bike comes with many benefits, ranging from not only financial but many environmental advantages,” says Buycycle CEO and co-founder, Theo Golditchuk. “However, it can still happen that someone is not fully satisfied.”

Often, the dissatisfaction stems from fit or—as Golditchuk has seen more often—a misunderstanding about the bike’s capabilities (buying a heavy enduro-style mountain bike when you just want to ride casually on the trails, for example).

So, once you decide on the type of bike you’re looking for, it’s time to figure out fit. And unlike in a bike shop where they can measure you and you can test multiple sizes of a bike, you need to do a bit of homework on the bikes you’re looking at when buying a secondhand bike, especially if you’re buying it sight unseen and won’t have a chance to test ride it.

You can do a fair bit when it comes to bike fit, but there are certain things that you simply cannot change. As  bike shop owner and fitter Stephen LeBoyer puts it: “You can adjust a lot, but you can’t change the frame size.”

A great price for a bike that doesn’t fit you isn’t a good deal. So, here’s how to know if that used bike is the right fit for you.

Compare Bike Geometry

It’s tempting to think that a small frame is a small frame is a small frame, or that a size 48 is the same from bike to bike or brand to brand. But sadly, much like women’s jeans, bike sizing is not uniform across the board.

“Brands don’t measure the same way,” says Jeff Latimer, a bike fitter. “A 51 for one brand isn’t equal to a 51 in another. I have had several fit clients who bought a bike the ‘same size’ as their old one only to find out the hard way that it’s not.”

You can check your used bike size by getting the make, model, and year of the bike you’re considering. Then, do some Googling or check the bike brand’s website for the sizing chart, which will provide different measurements from the bike.

If you already have a similar bike that fits you well, compare that bike’s geometry chart to your current bike’s geometry, focusing on stack, reach, and standover height. “If your inseam is shorter than the standover height, the bike won’t work for you,” says LeBoyer.

This comparison method works if you’re comparing sizes of similar bikes (like a gravel bike and a road bike) but if you’re looking for a mountain bike and you only have a road bike, you’ll be able to get a rough idea of your ideal size, but there will be some differences.

Take a Few Key Measurements

“The most important measurements you should take when looking for a new bike are height and inseam,” says Golditchuk. Measure your inseam in centimetres (because that’s what most companies use for their sizing), and compare that to the standover height from the bike’s geometry as a starting point.

You can also check your height compared to the bike brand’s size chart to find out what size of that particular model you should be looking for. All of the major bike brands offer sizing recommendations for different bike makes and models, so Google the bike brand, along with size guide, to find suggestions based on your height.

If that’s not available—which may be the case on older models or cheaper non-name brand bikes—ask your seller to measure from the top tube (just past the nose of the saddle) to the ground to make sure that you’ll be able to stand over the bike. If that measurement is longer than your inseam, the bike is almost certainly going to be too big.

bicycle fit measurements

Photo: Molly Hurford

The other measurement you can ask for is saddle height. If you’re concerned the bike will be too big, ask for the measurement from the saddle at its lowest position down to the pedal at its lowest position. If you’re worried the bike is too small, ask the seller to measure from the saddle at its highest position down to the pedal at its lowest position.

A very rough estimate of your optimal seat height is from your hip bone down to your heel, so if that measurement is too short/long compared to the saddle height measurement, the bike is unlikely to fit.

Really concerned or confused? If you have a local bike shop and a good relationship with the staff there, you can go in and ask for their opinion. LeBoyer actually prefers this: He’d rather see someone buy a good second-hand bike in the right size and then come in to purchase additional accessories or to get the fit tweaked, versus having someone come in with a bike that’s the wrong size that they’re hoping to alter.

Test Your the Bike Before You Buy

Meeting the seller IRL to test ride? First of all, be safe: Meet in a public place, bring a friend if you’re nervous, and don’t be afraid to leave without testing/buying if something feels off. (LeBoyer recommends checking if your local police station has a parking lot that’s surveilled and well-lit, or even asking your local bike shop if you can meet outside.)

He also recommends bringing a friend for a safety and quick bike adjustment standpoint. “You should also bring a multitool so you can make adjustments to the seat height,” he adds. “Don’t assume it will have a quick release.”

“If you plan to ride with cycling shoes, bring them with you, as well as the right pedals,“ says Golditchuk. If it’s a high-end bike and a major purchase, do yourself a favour and show up in your full kit, because that will make testing the bike feel more like a regular ride.

A test ride starts with setting the right saddle height, he adds. You likely will need to adjust the saddle height before you test the bike: Do this quickly by standing next to the bike and setting the saddle at the same height as your hip bone.

If you have a friend who can help, Leboyer suggests that you stand over the bike, then put one foot on the pedal at the lowest position and slightly bend your knee, then have your friend help you adjust the saddle so you’re sitting on it while that knee is still slightly bent.

You may need to make some adjustments from there, but that should allow you to get on and start pedalling.

“After a decent test ride, you should have a first impression of the bike’s characteristics and general fit,” says Golditchuk. This may mean stopping and adjusting the seat height up or down slightly—the goal of your test ride is to feel as though you’re “close enough” to a decent fit. Nothing should feel awkward or difficult.

If you’re stretched so far forward that your balance is thrown off, the bike is too big, even if you can pedal it. If you feel like a circus bear on a tiny bike, it’s too small. Yes, you can make some adjustments to improve fit, but you can’t change the frame size once you buy the bike.

Figure Out If It’s ”Close Enough”

Even with new bikes, you may find that you’re between sizes: One is a little too big, the other feels a little too small. Assuming you can stand over the bike and the seat can be adjusted low or high enough for you to pedal comfortably with a full range of motion, you can make changes to make a bike fit better… especially if you’re getting a great deal on it and have extra room in your budget!

There is some adjustability when it comes to fit: You can adjust the saddle height as well as how close it is to the handlebars. You can raise or lower handlebars, add a shorter or longer stem, and even swap out shorter or longer cranks.

“Close enough means that we, as humans, are incredibly diverse and therefore may not always find the 100 percent perfect fit on a second-hand bike,” adds Golditchuk. “Making a final decision on whether to go for a slightly bigger or smaller one depends on various factors and personal rider characteristics. Generally, a slightly smaller frame is more race-oriented, while a slightly larger one can be more comfortable. However, if you find yourself in between two sizes, you can typically adjust both options to fit by changing key components like stem length or bar width.”

All that said—don’t be afraid to walk away from a great deal if the bike simply doesn’t feel like the right fit. “It’s a buyers market out there right now,” says LeBoyer. “It’s not worth buying a bike that’s not the right size, even if it is awkward to test ride and say, ‘No, this isn’t for me.’” Don’t get bullied into making the purchase if the fit is wrong.

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