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Experience Weight Changes? Don’t Miss This Critical Bike Adjustment

Nothing feels better than hitting the road in a brand new saddle after a bike fit. Everything is dialed in, and your bike is perfectly aligned with your body for maximum comfort and strength.

But, after a while, things start to feel a little less than perfect. This change might be particularly noticeable following an extended time off the bike. Maybe you’re just getting back into it after the cold season. Or maybe you’re coming off a busy holiday full of rich foods and very little exercise. Either way, you notice that your bike isn’t as comfortable as before, and your pedaling just doesn’t feel as powerful. But why?

This is a common conundrum for cyclists, and few realize the cause. Quite simply, the reason could be your weight. Whether you’ve put on a few pounds or trimmed them off, changes in weight can alter your position on the bike.

Longtime cycling coach and expert bike fitter Darryl MacKenzie has seen it happen many times, so he’s here to help us explain what’s going on. Here’s a closer look at what to adjust on your bike when your weight changes. 

How a Weight Change Affects Your Position on the Bike 

To understand why a cyclist’s weight would affect their positioning on the bike, use your imagination for a moment. Picture two riders. These two men are exactly the same height with precisely the same leg length. The only difference between the two is that one is about 25 pounds heavier than the other.

Due to their identical height and leg length, you might think that these two riders would need the exact same saddle height. But that’s not the case — and it’s all because of the weight difference.

The heavier rider will likely have a little bit more natural padding (body fat) around his butt. This will increase the distance between his sit bone and the saddle. If he doesn’t account for that in adjusting his saddle height, then his body positioning will be different in one critical way: his knee angle — the angle from your ankle to your knee to your hip when your pedal is at its lowest point.

Why does adjusting your bike matter? 

“The most important angle on the bike is your knee angle,” says Coach Darryl. To explain why, let’s look at what happens when that angle changes in either direction. 

When You Gain Weight 

One of Darryl’s clients came to him during a recent winter complaining of pain in the back of her knee. It didn’t take Darryl long to figure out what was going on: She had gained 12 pounds. On top of that, she wore bike shorts with thicker padding for the cold weather.

That combination raised her sit bone a few centimeters off of the saddle. Because of that, her knee angle now extended farther when she reached the bottom of each pedal stroke. Her symptoms of knee soreness were a telltale sign that her seat was too high, so Darryl spotted the need for bike saddle adjustment immediately. 

When the effects of weight changes get bad enough, you can almost hyperextend your knee while you pedal. This can cause serious discomfort that doesn’t go away for days after a ride.

When You Lose Weight

Now, consider another one of Darryl’s clients. Coming in regularly for bike fits, he always dials his knee angle into to precisely the same number: 35 degrees. 

He usually just needs a small adjustment when he visits for a refit. However, he came in complaining on one occasion about his troubles when climbing hills. Lo and behold, his knee angle was at 42 degrees, a major difference from his ideal. 

What happened? He had recently lost a lot of weight, and that meant his sit bone was closer to the saddle. Now his saddle was too low. Here again, the signs were clear to Darryl for a bicycle seat adjustment. 

“The saddle height directly affects the power to the pedals, especially for climbing hills,” says Darryl. “If you find you’re not climbing as fast as you should, one of the first places to look is to confirm that your saddle height is ideal for you.”

Your seat is probably too low if you’re not getting enough power when you pedal. Essentially, you can’t extend your knee enough, so you’re not getting maximum strength out of your legs.”

When Do You Need To Adjust Your Saddle?

If you find yourself in either of the above situations, you need a saddle height adjustment. When you lose or gain enough weight, you will eventually start to feel the effects of the change of your knee angle.

But how much does it take? Is a pound here or there enough? The exact number depends on your size and weight to begin with, but Darryl generally says 8 to 12 pounds is enough to require an adjustment. For many cyclists, fluctuations of that amount are not uncommon, especially during the off-season or the holidays.

So, if your weight does change by that much at any given time, Darryl stresses that you shouldn’t wait to get an adjustment. Maybe you’re trying to lose 25 pounds, and you’ve lost 12. Don’t wait until you get to 25 — you may never get there, or you may be riding for months at the wrong height until you do.

“You don’t need the full three-hour bike fit,” Darryl notes. When your weight changes, a quick adjustment will get you back to the right angle for maximum comfort and power when you ride.

Get Your Saddle Height Right 

Your saddle height is critical for your cycling success. And it all starts with your knee angle. To get your saddle in the right spot, you need to start with a good bike fit. Many mechanics just measure from the bottom bracket, which isn’t where you connect with the bike, so that will make your angle wrong from the start. Instead, work with a coach who knows how to set your height correctly from pedal (not bottom bracket) to saddle.

Once you have this set, make sure you keep that height in the right spot. Those little adjustments when you gain or lose weight will make a big difference in your cycling.


Look for more insights from Coach Darryl over at his website.

Photo by Martin Magnemyr on Unsplash