Your Ride: Dynamic Bike Fit
The fit of the bike is essential to the performance of the rider. A properly chosen frame and properly fitted bike will allow you to ride the drops for many miles in comfort, corner with confidence and lay down the power when it is needed (if you’ve got it). One rider’s dream machine can be another rider’s torture device however. A bike that looks great on paper and gets a great review can be a disaster for you. The most excellent bike, if it doesn’t fit you well, can make it impossible for you to pedal efficiently, relax or control your cornering effectively. It can increase aerodynamic drag and decrease power. No quality or quantity of training, nutrition, weight loss, tactical brilliance or anything else I might try to impart will let you perform to your potential if your bike is not set up properly for you.
Bike fit has two major aspects: The geometry of the frame and then the way the bars, stem, seat and cleats are adjusted. You probably have a bike already and most frames that are even close to the right size can be made to work okay if you are willing trade out a stem or seat post, so I’ll start with the adjustments and then give you some tips on how to know if your current frame is not right for you and the whole thing should be traded out.
There are many ways to do a bike fitting. They can be divided into two major categories that might be called static and dynamic fitting. In a static fitting, various formulae are applied to anatomical measurements and the results are then used to adjust the bike. In a dynamic fitting, the adjustments are made after examining the rider actually pedaling the bike. Dynamic fitting methods are more likely to arrive at optimal riding positions since they actually take into account many factors related to effective riding rather than only bone lengths. Dynamic fittings can arrive at different fits for rides who have different body weight distributions on similar skeletons, or who have different levels of flexibility, while static fittings would not.
There are many traditional rules of thumb with regard to bike fitting that can help you get close to an acceptable fit but if one simply follows the rules of thumb without taking the end goals of comfort, aerodynamics and power into account, the fit will be less than optimal. For instance, one such rule says that the drops of the handlebar should be horizontal. This is a fine starting place but most modern handlebars have an ergonomic-bend that is designed to fit in the palm of the hand. Tipping the bars a few degrees one way or the other from horizontal can greatly increase the comfort and feeling of control when you grip the ergo-portion of the bar.
Let’s go through the elements of bike fit on an existing bike. They are: cleat position and angle, leg extension, seat set back, seat tilt, stem length, stem height, bar width, bar angle and brake-lever height. Each of them affects power, control, aerodynamics or comfort, if not several of these, so each is important to rider performance. For many of these adjustments there are traditional rules. Where they differ from my suggestions, I’ll do my best to explain.
Positioning Cleats: Fore-aft position
Find the first metatarsal head (the boney lump at the base of your big toe). Tradition says that the “ball of the foot” should be directly over the pedal spindle. Most riders will pedal more smoothly with the pedal spindle a bit behind the first metatarsal head, perhaps under the middle of the ball of the foot. Many riders who have been instructed to ankle but never achieved that mysterious magical movement find that it suddenly becomes easy or even unavoidable when the cleat is moved back a little from the directly under first metatarsal head position. Be willing to vary the cleat position a little and see what it feels like, but as a starting point try 6-11 mm behind the first metatarsal head, with riders whose feet are around size 39 needing the smaller set-back and riders whose feet are up near size 48 needing the larger set-back.
Positioning Cleats: Angle
If you ride Speedplay or other free-floating pedals you don’t need to worry about this one. If you ride any of the common limited float pedals, cleat angle can make the difference between a lifetime of miserable knee problems and a lifetime of happy pedaling. Sit on your bike and pedal naturally. Stop pedaling with one foot forward. Try turning the heel to the outside. If there is a bit of movement before you feel the resistance of the retention mechanism, you’re good. If your natural foot position when pedaling is pressing against the retention mechanism, loosen and rotate the cleat until there is a little free float there. Once you have some float for outward rotation of the heel, try swinging the heel inward. Again, if there is some free float, you’re good, but if you are contacting the end of the float immediately, you need to rotate the cleat. Repeat this on the other foot. When you are done you should be able to rotate both heels a little in or out without resistance. On a no-float pedal your natural foot position should align with the cleat position so that the cleat is not forcing your foot to turn in or out.
(Note: If you have flat feet and knee pain despite properly adjusted cleats and bike, there is a good chance that you will be helped by a firm arch support inserted in you shoe.)
Positioning Cleats: Side-to-Side
For most riders this adjustment will have no effect at all. For a few it matters. Most for whom it matters will do best to have the cleats mounted as far out as possible, and thus the feet as far in as possible, without having the ankles hit the cranks.
You may have noticed that I didn’t mention seat height as a separate variable even though it is obviously important. This is because moving the seat up or back will increase leg extension, and moving it down and forward will decrease extension. The symptoms of too low a saddle (knee pain, loss of power and overworked quadriceps muscles) are also caused by a saddle too far forward. The symptoms of too high a saddle (sore overworked hamstrings, sore butt from rocking, loss of power) are also caused by a saddle too far back. Because saddle height and saddle fore-aft adjustment interact to determine knee extension, you may need the to make adjustments to one and then the other several times. Let’s start with saddle height. Traditional methods of setting the saddle height often involve taking a percentage of the inseam length. These methods ignore the length of the foot and the angle of the ankle. Some riders pedal more effectively with their toes more “down” than other riders with the same inseam, and need their pedal-to-saddle distance set correspondingly higher. Those who are stronger with a lower heel need their saddles set lower. It would probably be possible to measure inseams and feet and typical ankle angles and then to derive a formula for saddle height, but there is a much easier way.
Once you’ve adjusted the cleats, sit on the bike and pedal against mild resistance. Ask yourself if you are able to pedal smoothly and with power through the bottom of the stroke, or if you are reaching (stretching, rocking or nearly locking the knee) to get through the bottom of the stroke. If you are reaching, lower the saddle in 1 cm increments as much as necessary to achieve smooth flow through the bottom of the stroke. Now, whether or not you just lowered the saddle, start raising the saddle in 3 mm increments until you loose smoothness or begin to stretch uncomfortably. As soon as you reach this too high position, reduce saddle height by 5 mm. That’s it. Correct saddle height is just a few mm lower than the point at which you lose smoothness. If you find that when the saddle height is set in this way you still feel crowded over the top of the stroke, consider raising the handlebars or getting shorter cranks.
Saddle fore-aft adjustment
The traditional way of setting saddle fore-aft involves dropping a plumb bob from the front of the knee (or just under the knee depending on whom you ask) and looking to see if it bisects the pedal spindle (or falls behind it by one, two or some other number of centimeters depending on who you ask) while the foot and crank are held horizontal. This method is often referred to as KOPS (Knee Over Pedal Spindle), and I wonder if it is merely coincidence that the acronym is the same as the name of the famous Keystone slapstick comedians. Why is KOPS so silly? Consider two riders identical in every dimension except that one has huge feet and the other has tiny feet. To achieve KOPS, the big-footed rider will have much greater knee bend at most or all points in the pedal stroke than the small-footed rider. There is general agreement in the cycling biomechanics community that knee angle is an important variable. Adjusting knee angle by arbitrarily setting knee over pedal spindle is unlikely to be the best solution.
Saddle-fore-aft adjustment affects another important bike comfort and control variable: weight on arms and hands. Too much weight on the hands means that you have to keep your arms and shoulders tense to support that weight. It makes your hands tired and keeps you from breathing deeply and freely. It increases the tendency to lock the elbows rather than support the weight with muscle tension. The weight on the bars decreases as the saddle moves back, even if the stem is shortened at the same time, so saddle fore-aft adjustment can allow upper body relaxation, easy breathing and good bike control. Bent elbows, which are easier to achieve if the hands are weighted only lightly, decrease numbness of the hands and soreness of the elbows.
Set your bike on a trainer or go for a ride on the road. The harder you pedal the more weight is lifted off your hands, so pedal against a decent resistance at a realistic cadence. Now, try to switch your hands, both hands at the same time, from the drops to the hoods and back. If you need to push off, move your saddle back 5 mm and repeat the test. Keep going until you can actually remove your hands from the drops and hover with your hands just next to the drops with only a little extra tension in your low back and belly, and not feeling like you’re going to slide off the front of the saddle. If the saddle fore-aft is set correctly then when you stand to sprint you will push straight up rather than pushing back and having to use your hands to pull you forward. If you have to pull yourself forward when you stand, you’ve got the saddle too far back. Note that many riders will not be able to get far enough back on the style of seat-post that has the clamp centered on top of the post but will need the style with the clamp a bit behind the center. Some will need more set-back and a few will need the centered clamp. Riders with heavier arms and chests will need saddles farther back than riders with the same skeleton and less upper-body mass.
The traditional rule was that saddles should be level. Modern saddles have so many lumps, bump and curves on them that it’s hard to know exactly what it means to set the saddle level. Besides, many riders will be more comfortable with the saddle tilted a degree or two one way or the other. If you feel pressure from the nose of your saddle when you ride the drops or you feel the saddle pitching you forward onto the bars, you need to adjust the saddle tilt, and you may need a different saddle. If you feel pitched forward, try raising the nose of the saddle a degree or two at a time until you no longer feel pitched forward. If you feel pressure on the nose of the saddle, first try tilting it up a degree or two more. This may seem counterintuitive, since raising the nose might be expected to increase pressure. For many riders, raising the nose of the saddle will cause the pelvis to roll back enough to relieve the pressure. If this doesn’t work for you, try tilting the nose down. If you can’t find a tilt that eliminates the pressure without pitching you forward, try a different saddle.
Stem Length and height
The old traditional way to determine stem length was to place the elbow against the nose of the saddle and extend the fingers toward the handle bar. If the fingers just reached the bar, you had a touring fit. If there was a 1-2 cm gap between fingers and bar, that was a racer fit. The newer traditional way is to sit on the bike with your hands on the drops and look down toward the front hub. If the bar obscures the hub, your stem length is about right. Why stem length should be different depending on neck length or fork rake is hard to fathom.
My preferred way to determine stem length is to set up your bike with your bars and an adjustable stem. Set the stem short and then gradually lengthen it until you just begin to feel overstretched. Go back 5 mm. That’s your stem length. Now look down the road as if you are riding normally and then try looking up. If your head rises barely or not at all and you have to roll your eyes up to look up, your bars are too low. In this condition the muscles in your shoulders, your upper back and the back of your neck are pulling the neck as far up as it will go at all times and they will become tired and sore. You will ride the tops to relieve the pressure even though this makes you aerodynamically inefficient. Set the bars as low as possible to still allow some upward movement of the head with hands on the drops.
If you don’t own or have access to an adjustable stem. It is possible to do a pretty good stem fit by addressing length and height in the opposite order. If your thighs hit your chest or you have to rock to let your thighs come over the top of the pedal stroke, the bars are too low and should be raised by adding spacers, flipping the stem or getting an up angled stem. When the stem is as low as it can be while still allowing you to pedal smoothly, if the back of your neck and tops of your shoulders get sore on longer rides, get a longer stem. When you are set up with the correct stem length the angle between your upper arm and torso while riding the drops will be 90-degrees or a bit more. Ideally you would borrow longer stems or buy them from a shop that will allow you to return them until you find the ideal length and angle.
Bar width is the only bike fit variable in which the traditional measurement method still applies. The correct width of the bars is equal to the distance between the outside top edges of your shoulder blades, called your acromion processes, when you are standing up straight with your shoulders comfortably back. To find your acromion processes slide your fingers along the tops of your shoulders out towards your arms. The outside edge of the bony lump on top of the outside of each shoulder is an acromion process. Have an assistant measure the distance between the acromion processes across the back. That’s your center-to-center bar width.
As mentioned earlier, the traditional way of setting bar angle does not always achieve the optimum level of comfort. Sit on your bike and move your hand into the drop, leaving your wrist neutral (not cocked up or down). Notice if you need to cock your wrist at the last moment to grip the bars. If you do, tilt the bar up or down until your wrist can remain neutral as you grip the drop. If the rearward extensions of the drops are now far from horizontal, consider getting a bar with a different bend or even getting an old-fashioned round-bend bar and building it up with padding under the tape to achieve an ergo bulge in the correct spot.
Brake hood position
Brake handles can be twisted in or out for optimum comfort when riding the hoods and can also be moved up and down on the bar. The traditional way to set brake hoods was to have the tips of the brake handles horizontal with bottoms of the drops. Why riders who choose a brand of components with longer brake levers should all want their hoods higher on the bars is beyond my comprehension.
Set your brake hoods high enough that you can comfortably ride with the web between your thumb and forefinger pressed against the hood and your hand fully gripping the hood, not pushed back onto the bar. Set your brake hoods low enough that you can reach the brakes and shifters comfortably. If you can’t achieve these two conditions simultaneously (typically because you have small hands) consider a special bar for smaller handed people or a shim that causes the brake handles to sit closer to the bar.
Do you have the right frame? Do you need a custom frame?
If you managed to make all of the above adjustments successfully, you should now have a bike on which you can comfortably pedal in a straight line or on a trainer, and this is a good start. Since there is a great deal of potential adjustment in seat post height, saddle setback and stem length and height, it’s possible to achieve a decent aerodynamic pedaling position on a variety of frames. How do you know if you’ve got the best frame geometry for you?
Now that you’ve made the adjustments, how does your bike handle. If you had to use an extremely long or short stem or an extremely set-back seat post to achieve your position, you may have changed the weighting over the wheels so much that the bike no longer handles well, if it ever did. For most riders, the bike will handle well if about 45% of the total weight is on the front wheel, though some longer torsoed riders prefer closer to 40% on the front wheel. It’s very rare to have good bike handling with less than 35% or more than 54% of the weight on the front wheel. If you like how your bike corners and descends and the front end seems stable but nimble whether you are seated or standing, you’ve got a good match. If the front end seems skittish or sluggish, you’ve got a problem match.
If you’ve got a problem match that doesn’t mean that you necessarily need a custom frame, though that is one possible solution. There is quite a range of frame geometries available in different brands of stock bikes. You will need to do some research to find the right frame for you though.
Unfortunately I can’t give you a formula for optimal frame geometry. The bad news is that two riders with very similar heights, inseams, torso lengths and bone lengths may ride best on rather different bikes. Flexibility and weight distribution will dramatically impact ideal fit. The best I can do is suggest that you use the above system for fitting and tell you that if you can achieve the goal elements of a good fit on a given bike and have it handle well, the bike is suited to you. The best way to choose a frame is to set yourself up as well as possible on an existing bike and then search out a frame that allows you to get that position without making any extreme adjustments. If the front end is too light, you’ll need a shorter top-tube and longer stem. If the front end is too heavy, just the opposite, though frame angles and fork rake also affect handling so the only real way to know if a frame will be right for you is to ride the bike, or another bike with the same geometry.
(I’d like to thank Steve Hogg of www.cyclefitcentre.com for several of the ideas in this article. He has the most complete and intuitive knowledge of bike fitting of anyone I’ve met or worked with. I’d suggest contacting him via his website if you have a particularly difficult fitting situation.)
Scott Saifer, M.S. has been coaching professionally with Wenzel Coaching since 1993. His clients have won numerous District, National and World Championship medals in part perhaps because of the fit of their bikes. For more information about Scott and the services of Wenzel Coaching, check out www. WenzelCoaching.com
(This article first appeared in ROAD Magazine)