If you started riding as a kid, sizing a bike was probably as simple as measuring your height. But as an adult cyclist, a lot more factors come into play to make sure you have a solid bike fit that allows you to ride with efficiency and without aches or pains.
To help you nail down the right bike fit for you, we asked experts for advice on what mistakes to avoid when sizing a bike and others key factors to keep in mind when you’re getting a professional fit.
Avoid These Mistakes When Sizing a Bike
If you’re heading to a bike shop soon for a pro fitting, here’s what you need to keep in mind so you ride out of the store comfortably.
1. Mistake: You rely on certification to determine ability
The fit system itself—be it Retül, SICI, Guru, or any other methodology out there—is just a tool. You can get a good fit using just about any fit system, but you might like one approach better than another, given that they are based on different philosophies.
How to fix it: What matters most is the experience of the person doing the fit. “I frequently see people search out the fit equipment before the fitter, and that’s not a good approach,” says Ian Buchanan, cofounder of Fit Werx.
If you walk into a shop with four certified fitters, one may be a master fitter with 10 years of experience and another may be a freshly minted graduate of the first-level certification course. Both may do great fits, but the reality is that fitters only gain experience by doing fits. You should know what you’re getting.
“Interview your potential fitter,” says Buchanan. “Ask, how long have they been doing bike fits? Do they have particular specialties, like triathlon fits or working with riders with anatomic issues such as leg-length discrepancies? What is their philosophy? How do they use the tools for which they are certified to properly fit you? These are all fair questions for which an experienced fitter will have ready answers.”
If you have a bad fit experience, it doesn’t necessarily mean that the methodology was wrong. The same system in the hands of a different fitter might yield different results.
2. Mistake: Your fitter is old school—too old school
Bikes have changed dramatically since the 1980s, and so has bike fit. Equipment has driven some of that change, including clipless pedals, but frame geometry is another factor.
In the 1950s, for example, a racing bike had a far lower bottom bracket than one made today. So when you see an old picture of a racer on a bike showing just a fistful or so of seatpost, consider that more seatpost would be showing on today’s bikes with more contemporary geometry.
Or, take knee-over-pedal-spindle (KOPS) methodology. “Originally, it was a gauge for setting weight distribution,” says Cascade Bicycle Studio founder, Zac Daab, referencing a 1972 training manual from Italy. KOPS was an easy way to get the rider in the ballpark for proper front-rear weight distribution, which is important for handling, but today’s fitters don’t need a plumb bob anymore as a guide for weight distribution, freeing them up to consider power production and injury prevention when determining proper knee placement relative to the pedal.
How to fix it: Have a conversation with your bike fitter, getting a sense of whether they are not only up to date with technology, but also understand the history of why fittings are done the way they are and how they have changed over the years.
3. Mistake: Assuming a fit comfortable inside will be comfortable outdoors
Fits take place in a relatively static setting. The bike sits on a trainer, which doesn’t allow dynamic movement underneath the rider and tends to encourage pedaling at a single intensity in a single position (hands on the hoods and butt fixed in place on the saddle). Some of us make it worse by trying to look good during a fit.
“All of that adds up to a fit that may not fully translate outdoors,” says Daab. “You can adjust the pieces of the bike only so far in the lab. Optimizing position in that static environment, in a sitting position, can be a little misguided.”
How to fix it: First, to give yourself the best shot at a successful fit, try to forget that you’re being watched. Just ride.
Second, put a little effort into it because your position changes when you’re going hard because you stop thinking about it and focus only on what you need to do to sustain the harder effort. Putting more effort into the pedals may, in fact, reveal to the fitter any technique issues that could use addressing.
4. Mistake: You don’t try to understand the technology and fit
It’s easy to be wowed by technology during a bike fit. A fitter may use multiple video cameras, infrared tracking, pressure monitors, and other fancy equipment. The fit process itself may seem quasi-magical, but it’s important to take the time to understand it.
How to fix it: Bike fitting is an art and a science, but it is explainable.
If you have questions, ask. If something doesn’t feel right, speak up. If you wonder why a fitter is making a particular change, inquire. You may not love the answer if, for example, the reason you have back pain has more to do with posture and inadequate core strength than anything fit-related. But you should still ask. “There should always be a ‘why’ for any given fit change,” says Buchanan, “and it shouldn’t sound like malarkey that someone just made up; it should make sense.”
5. Mistake: You don’t start with the right frame size
Bike fit isn’t just about getting the right saddle height and the perfect-length stem to hit your reach number. It’s about putting the rider on the bike in a way that’s good for comfort, power transfer, and handling. With the wrong size bike, one (or more) of those has to give way because the physical geometry of the frame won’t allow optimal fit. Know what you will need bike size-wise before you pull the trigger on that bike you found online.
How to fix it: You might want to pay a visit to your fitter before you start shopping. Whenever Greg Combs, a master fitter with Velo Smart in Southern Pines, North Carolina, gets a fit request that starts with, “I got this bike on Craigslist...,” his warning radar goes off. “There’s a misconception that people can buy something that’s close to the correct size, and the fitter can fix it,” he says.
6. Mistake: You change equipment without changing fit
Sometimes a bike fit includes changing parts like a handlebar, stem, or saddle, but each swap affects your fit. For example, the pressure-mapping system that some fitters use can show hot spots and broadly indicate the best saddle shape for your anatomy and pedaling style.
“People often think that changing pedals and shoes dramatically alters seat height, but more often than not, it’s pretty similar,” says Daab. “Saddles are another matter. We’ve found up to 1.5-centimeters difference in saddle heights between some models, measured from the rails to the top of the padding.”
How to fix it: Pay close attention to part swaps. If you’re moving from one brand to another because, say, you got a new bike, take hood length into account when setting reach to the bar, because that’s the most common hand position.
7. Mistake: You get fitted on one bike, not all your bikes
It might seem obvious, but fit for road bikes is different than mountain bikes. That’s partly a matter of geometry and equipment differences, like flat bars versus drop bars. But it’s also a reflection of how we ride each kind of bike.
How to fix it: Get a pro fit for every bike you ride.
Mountain bike fit is important, for example, because the position is more dynamic. Road and cyclocross bike fits are broadly comparable, with perhaps small changes. “Often, I find that when people say their ’cross bike position is different, it’s because their road position is all jacked up,” says Daab. “In an ideal world, your hood position on both bikes is optimized pretty similarly.”
8. Mistake: You think a bike fit will fix all aches and pains
Chronic issues often have complex causes. Daab relates the story of a woman who suffered lower back pain. A previous fitter had made her position more upright, with a shorter reach to the handlebar, but the pain didn’t go away.
Daab suspects that the issue wasn’t purely bike fit, but also insufficient core strength. Fitters will often address chronic issues by offering advice on exercises or stretches that might help. “Be open to that advice,” said Daab. “Sometimes it’s hard for people to have their perceptions challenged.”
How to fix it: Give yourself time to adjust to a new fit. You’re challenging your body to move in ways that are subtly but powerfully different. Changing years of ingrained movement patterns does not happen overnight.
9. Mistake: Assuming one bike fit sets you up for life
If you started riding in the 1970s or 80s, you probably had a bike with 170mm crankarms and 39 to 52 or even 42 to 52 chainrings. Today, crank lengths vary, and those are almost unheard of gear combinations. Chances are that, 40 years later, you probably can’t muscle that kind of gear anyway.
“A lot of riders who started riding back then rode powerful, low-cadence pedaling styles, but it’s too demanding on their joints over time,” says Buchanan. And as your gearing changes, so too do your pedaling style and your fit. That’s to say nothing of other age-related issues like chronic overuse injuries, and general wear and tear that can necessitate fit changes.
How to fix it: A fit should last for awhile, but if it’s been, say, a decade since your last one, or you’re having chronic pain issues, it might be time for a refresh.
10. Mistake: Not factoring technique into your riding issues
“A fit can’t change 15 years of ingrained habits that contributed to whatever issues you’re having,” says Buchanan. “No matter what I do with seat placement, if someone is over-rotating his pelvis, its effects aren’t going to go away.”
Buchanan ends up talking about riding technique in more than half the fits he does to encourage people to change their riding style in a positive way.
How to fix it: When you change your position, you may also have to change pedaling style or cadence, or another crucial technique. Give it the necessary time for muscle recruitment patterns to re-shape—the process can take months.
The notion of a bike fit as a quick fix is seductive, but people have to be willing to put in the time during and afterward to get the most out of a fit.
