Struggling to find the right size bike for you? Well, you’re not alone. Judging by the number of times we get asked for sizing advice you’re in good company. It’s a question that can be hard to answer, however. Bikes, like humans, aren’t one-size-fits-all. There are so many factors to consider, not limited to your size as a human being, your riding style, the trails you ride, and any fit or body limitations you may have. So, here’s my answer to the what size mtb should you buy question — it depends. Great show — see you next week.

Instead, what I’m going to try to do, is lay out the pros and cons of a bigger frame vs a smaller frame. What benefits do you get from going bigger? Are there any drawbacks? Is smaller better? I personally fall between a large and an extra-large on most frames. I’ve been in your shoes many times. I’m going to walk you through my thought process when it comes time for me to buy the right size bike. 

For this test, we were lucky enough to have two Ibis Exies — one extra-large and one large. Zach joined me for the test so we could each do a lap on each size then gather our thoughts and compare the differences. So what did we find? Stick around.

What type of MTB rider are you?

Before we talk about ride quality, let’s talk about possibly the most important factor when choosing a size — your riding style. I’m assuming you fall between manufacturer-recommended sizes and don’t have a clear-cut answer on which one you should buy. Otherwise, you would have already bought the size you clearly need. With this assumption, you should technically fit on both sizes. Most manufacturers build some overlap into their size charts. For example on the Ibis Exie, there’s an inch of overlap between each size. So instead of fretting so much about if you’ll fit on the bike (you most likely will), try to think more about how and where you like to ride. Those two sizes are going to ride very differently out on the trail. The bigger size is going to be more stable, forgiving, and confident. The smaller one will be zipper, quicker, and more agile. Now ask yourself, how do you ride a bike. Are you actually a playful rider? Do you put your heels down and plow? Really think about it. 

I’m not trying to bash on “playful” riders here, but I think most folks who consider themselves playful, aren’t really that playful. Sure you might jump all the side hits, enjoy slapping berms and picking tight and twisty lines, but I don’t think that’s “playful.” Or maybe I should say, that style of riding doesn’t require a smaller frame. Now, a playful rider to me is Josh Brycland, Danny McAskill, the 50to01 crew, Kade Edwards… you get the idea — folks who can 540 a downhill bike and land backward. They’re constantly found tricks, jumping and spinning. Most of those guys aren’t out doing basic trail rides at their local network. You don’t have to be that extreme to be playful, but I would argue that most folks tend to ride with a pretty average style — myself included.

Size MTB Ride Quality

We found a few obvious differences as well as some that were less expected. Let’s start off with the basics. One of the bikes is bigger than the other — that’s just how that works. With the bigger frame, comes a bigger sweet spot. What I mean by “sweet spot” is where your weight is balanced and centered between the wheels. Get outside this sweet spot and bad things start to happen. The bigger frame gave me more room to move around on the bike before I started falling off it. It gives you more stability and more confidence on the bike. Switching to the smaller frame, I felt an immediate shrinkage of the sweet spot. It was easier to get my weight outside of the bike and into the danger zone. It required me to always bring my A-game and be laser-focused to stay centered on the bike. The second you start to lose your focus, the bike reminds you by doing something squirrely and weird — hopefully, it’s not a painful lesson. A smaller sweet spot isn’t all bad, though. The advantage is that you’re able to affect the bike more with your rider input. That makes the bike more maneuverable, more lively, and quite a bit easier to get off the ground. I think it takes a higher level of skill and bike handling to ride a smaller frame. If you’ve got the skills to make it happen, it’s not a bad way to go. Unfortunately for me, I don’t.

One of the most surprising differences between the two sizes was overall speed. The bigger frame was faster — just about everywhere. When Zach was on the extra-large and I was on the large, I couldn’t keep up. I can’t usually keep up with him anyway, but it was even more apparent when I was on the smaller frame. Once we switched and I was on the extra-large, I did a much better job of holding his wheel. On straight sections, winding bits and through the rough parts, the extra-large was simply faster. It rode smoother, held a line better, and kept its momentum. The large, however, had an advantage in tighter corners, especially back-to-back corners. It was able to get around the corner faster and back up to speed easier. Maybe the best way to describe it is the extra-large is faster and the large is quicker. Overall, the large was only faster for <10% of the entire trail.

Another less obvious observation we made was the bigger frame cornered much better than you’d expect. My daily driver has a very long and stable wheelbase, yet it is one of the best cornering bikes I’ve ever ridden. It sounds so counterintuitive, and I can’t quite put my finger on exactly why. My best guess is the bike feels more stable in the corners allowing you to ride it more confidently. Going back to the “sweet spot” topic, the bigger sweet spot allows you to more easily find the center on the bike so you can keep both wheels weighted evenly. Your weight isn’t too far forward or rearward. I have a theory that chainstays have been getting slightly longer these days for this reason. It helps keep that front wheel weighted a bit better. Just a thought.

Speaking of corners, at the shop it seems a lot of people are scared that they won’t be able to get a bigger bike around a switchback or tight corner. I personally think that most folks worry too much about it. I’ve yet to find a rideable switchback that I couldn’t get around on my extra-large frame. While a longer bike will always be a bit tougher in tight switchbacks, modern geometry has made it a bit easier than in days of old. Steep seat tubes that keep your weight more forward help a ton in this department. Shorter fork offsets help a bit here too. What’s going to help the most, however, is proper technique. A little planning goes a long way for getting any bike around a tight switchback. Set up wide, keep your chest low, and point with your belly button. You’ll get around that uphill switchback just fine. When it comes to downhill corners, don’t try to steer the bike — lean it over baby.

MTB Size Fit considerations       

I’m a believer that it’s easier to make a big bike feel smaller than it is to make a small bike feel bigger. Let’s talk about why. When you try to make a smaller bike fit bigger, you have a couple of ways to do it. You can slide the saddle back on the rails which effectively makes your seat tube angle slacker — no one wants that. You can also add a longer stem to the bike, which is going to slow down your handling and bring your weight more over the front of the bike. Again, not ideal. When you try to make a bigger bike fit smaller, you do the opposite of the above. You slide the saddle forward which will give you a steeper seat tube angle. You can also throw on a shorter stem making your handling more responsive. You do need to keep in mind your size and shape as a human, though. Everyone is different and has different fit limitations. If you have a bad back and can’t hunch over to reach the lower handlebars on a smaller frame, maybe go bigger. If you have super short legs, maybe you need the smaller frame simply to reach the pedals. You can only go so far with these adjustments before you’re just downright uncomfortable. Making sure the bike fits before you buy it, is always the best bet.

Final Advice For what size MTB you should buy

I’m going to give you the same answer I’ve given to hundreds of YouTube commenters. I’m not going to tell you which size you should buy without seeing you on the bike. Sizing someone up for a bike over the internet is a recipe for disaster. So, come see us at the shop and sit on each size. Better yet, take one out for a demo if you can.

I understand that getting on the bike before you buy isn’t always an option. In that case, do your best to understand the pros and cons of each size. Really ask yourself what type of rider you are, look at the trails and terrain you ride frequently, figure out if you have any fit limitations, study the bike’s intentions and its size guide. Compare geometry numbers from a bike you know fits. Don’t fall into the trap of only looking at the reach measurement. That’s not always the best indicator of how big a bike will feel. You need to also consider the seat tube angle, head tube angle, stack, wheelbase, chainstay… You can see this gets complicated quickly.

If you’re going to make me give out specific size advice, I’m going to say that the majority of riders will probably benefit more from the stability, forgiveness, and confidence from the larger frame than they will from the increased agility and maneuverability of the smaller frame Take that with a grain of salt and go sit on the bike. 

Thank you for attending my Ted Talk. See you next time.