We\u2019re commonly asked, \u201cDoes bike geometry affect power output?\u201d Or more specific questions like, \u201cDoes my saddle position affect my power output?\u201d To get to the truth of the matter, we interviewed an expert.<\/p>\n
Brian Gordon is a kinesiologist, certified Body Geometry Fit Specialist and Mountain Bike Product Developer for Specialized. Over the past few years, he has used scientific methods to fit hundreds of riders for maximal power, endurance and comfort and encountered nearly every bike-fit scenario you could imagine.<\/p>\n
After our conversation, we discovered that the simple answer to the above questions is \u201cno.\u201dBut it\u2019s a little more complicated than that. From Brian we learned a solid principle you can use to make sure your bike\u2019s geometry is not affecting your power output. Here\u2019s that simple principle explained.<\/p>\n
Before tackling the problem of bike geometry affecting your power output, you need to make sure you\u2019ve eliminated the variable of a poor bike fit. There is no set formula that uses torso length, reach and inseam to prescribe a perfect fit. Since the body is in motion, and each person\u2019s body moves uniquely, bike fitting is an art as much as it is a science.<\/p>\n
While cycling is inherently uncomfortable to some degree, especially for new riders, excess or recurring pain while riding is generally an indication of a poor bike fit. It\u2019s best to get the problem resolved as soon as you can.<\/p>\n
When it comes to getting a bike fit, there are plenty of options out there. Select Specialized dealers will have a Body Geometry Fit Specialist like Brian on staff that will take a holistic approach to making sure your position is optimized. If this isn\u2019t an option for you, ask your local shop to see what they provide in terms of bike fitting \u2014 and go having done your homework. Remember that bike fitting is not an exact science, so getting it right may take some trial and error.<\/p>\n
Once you have a proper bike fit, you will have certain measurements t you can use when setting up a new bike. In most cases, these measurements will include the distance between three main contact points: your pedals, saddle and handlebars.<\/p>\n
Let\u2019s assume you were fitted on a road bike, but now you\u2019ve got a new TT bike you need to dial in. The measurements you have can serve as a good starting point, but often riders find that their familiar position is suddenly uncomfortable on their new TT bike. The reason? The geometry of your bike.<\/p>\n
TT bikes have aerodynamic shapes themselves, but they are also meant to make you as aerodynamic as possible on the bike. As a result, they have a very aggressive geometry. This means that the angles of the frame are intended to position your body far forward and low on the bike.<\/p>\n
The appeal of positioning your bars super low in order to get your upper body as low as possible is where most riders step wrong. When your bars are the axis, or governing factor of their bike fit, a cascade of adjustments follow causing problems.<\/p>\n
Because your bars are low, you generally find your hip angle very closed off. A practical explanation of this is that your knees get much closer to your chest than when you are on your road bike. This sharp bend in your hips reduces power output and puts a lot of strain on joints in your body.<\/p>\n
The natural reaction to this is to move your saddle further forward so that your hips don\u2019t have to close so far when pedaling. While you may feel you have resolved the problem, you\u2019ve caused a problem you cannot fix. Your hips are too far in front of your feet, and you can\u2019t move your cranks to compensate for that. Whoops!<\/p>\n
We learned from Brian that the solution to this problem is to establish your crankset, or more specifically the center of your bottom bracket, as the axis of your bike fit. It is a constant you can use as a reference for all other adjustments to your saddle and handlebars.<\/p>\n
Using the same scenario of your new TT bike, the end result would most likely see you with handlebars high enough to allow you an open hip angle when pedaling, and a saddle position that puts your knee over the ball of your foot at the front of the pedal stroke.<\/p>\n
With the center of your bottom bracket as the axis of your bike fit, you\u2019re able to more easily find your ideal position on a variety of bikes with different geometry. Gravel bikes, cyclocross bikes and mountain bikes have \u201cslack\u201d geometry (backward leaning) and move your body in the opposite direction of TT bikes \u2014backward. Be that as it may, the same principle applies. If you rotate your bike fit backward, using the bottom bracket as the axis of your bike fit, you\u2019ll ideally find an equally efficient position.<\/p>\n
While your power output should not be limited by a bike\u2019s geometry, you may notice a difference from bike to bike. There are plenty of reasons for this that, in an ideal situation can be overcome.<\/p>\n
While the approach of using your bottom bracket as the rotational axis of your bike fit will work for most bikes, there are outliers. Certain bikes with extreme enough geometry may make it impossible to position your saddle or handlebars appropriately. The most common scenario for this is a downhill-oriented mountain bike that simply won\u2019t let you get your seat far enough forward. If that\u2019s the case, you hopefully don\u2019t want to do anything but go downhill on that bike anyway!<\/p>\n
While it is rare to see a bike that won\u2019t let you get your saddle far back enough, it is possible and more common when a rider is on a frame that is too big for them.<\/p>\n
Another thing to keep in mind with drastic changes in geometry is the fact that you may have to retrain muscles and muscle groups to engage in different ways while pedaling. A TT bike will put increased strain on your neck and shoulders while an enduro-oriented mountain bike may require greater core engagement to maintain stability when placed far backward on the bike. Give yourself time to get used to your bike fit in every case.<\/p>\n
Having said all of this, there is a psychological component that comes into play for many riders. If you are using the \u201cwrong tool for the job\u201d like a TT bike on a mountain pass, that can put a mental limiter on your performance. Many riders simply struggle to perform equally in all scenarios.<\/p>\n
A big thanks to Brian Gordon from Specialized for providing some great insight on this topic!<\/p>\n
“Does Bike Fit Affect Power Output” is one topic\u00a0we covered\u00a0in last week’s episode of the\u00a0Ask a Cycling Coach podcast<\/a><\/em>. Listen to the episode’s full recording below to hear this and other questions from cyclists get answered by our certified cycling coaches.<\/p>\n