Thigh Length and Seat Angles

I am often asked if a rider with a long thigh measurement needs a shallower seat angle. The above line drawing represents two riders with the same inside leg measurement. As a result, they have their saddle set at the same height, and they are using the same size frame.

If the inside leg measurement is the same and one has a longer thigh measurement from his hip to his knee, it follows his lower leg from his knee to his heel is shorter. Conversely, short thigh, longer lower leg. As you can see from the sketch the position of the knee varies only slightly.

The exact knee over pedal (KOP) is not a precise measurement anyway as one is pedaling in circles, and it makes little difference if the rider sits back and pushes forward or is more over the pedals pushing straight down.

For the purpose of this drawing, I made the thigh length of the blue leg the same as the lower leg of the one represented by the red line, and vise-versa. The above line drawing could represent an unlimited number of riders with the same inside leg, with the red and blue lines being the extremes. If the inside leg measurement is a constant, it follows that as the one measurement increases the other decreases.

This simple drawing does not consider the length of foot. {Shoe size.) As the toe points down at the bottom of the pedal stroke, the foot becomes an extension of the leg. This of course affects saddle height and frame size but does not change the position of the knee by any large amount.

So, the answer is no. Once you have the correct size frame the seat angle should be right for that size frame. Then if your saddle is positioned at the correct height, the length of your thigh has little bearing on anything.

Also, as a footnote, some people agonize over the fore and aft position of their saddle. If you view that too considering what I have said here, it is less important. More important is the position of the handlebars in relation to the saddle. See the links below for more info on that.

You can read more about my frame design philosophy here:

And another article on Riding Position Simplified:

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Saddle too low?

If I see someone riding with their knees splayed outward it is often a good indication that their saddle is too low.

It may also be the rider is overweight and has a large belly to contend with, but not always.

Stand with your back to the wall and raise one knee forward and upwards towards your chest.

There is a limit to how high your thigh can go. Once that point is reached, the only way you can make your knee go higher is to move your knee outward and then it can travel an inch or two higher.

Squat with your knees together and you can’t go as low as you can with your knees spread apart. In non-medical terms, it is the limit of travel of the ball at the end of your thigh bone in its socket in the pelvis that restricts your movement beyond a certain point.

It amuses me to see riders with aero bars in a low horizontal tuck position, riding with knees splayed outwards. Any aerodynamic advantage they gain by the low tuck position is lost because the outward knees has increased their frontal area by 20% or more. Not only that, but the outward spread thighs is like an open ended “V” catching air as they travel forward.

In order to achieve a low horizontal position, one must be flexible enough that the pelvis remains near vertical and the back bone or spine bends forward. Three things affect the angle of the thigh bone in relation to the pelvis. The saddle too low, the saddle too far back, and the back too low, but only if it causes the pelvis to rotate forward.

It is rarely I see someone with their saddle too high. One can feel that they are stretching at the bottom of the pedal stroke, or they are rocking side to side on the saddle as they pedal. But a saddle too low may feel fine, but it is not necessarily the most efficient riding position.

If your knees are splaying outwards it should be easy to spot, just look down. Knees should pump straight up and down like two pistons, and should pass an inch or so either side of the top tube. If you suspect your saddle is too low, it rarely does any harm to raise it. Put a piece of masking tape around the seat post to mark the original position. Raise it by a small amount 1/8 in, or 1/4 in. Maximum. (3 mm. to 6mm.)

Ride for a week or so, then possibly you can go up a little more until you find the sweet spot. Saddle height is not a fixed thing. As you lose weight and muscles stretch a saddle needs to be raised. The questions you need to ask yourself after raising the saddle is, does it feel better, do I feel stronger, and am I going faster.

To reiterate, few ride with a saddle to high, but many ride with their saddle too low, because it feels fine. Unless you try raising it a little you will never find out. I feel any person’s ideal saddle height is the point where the saddle is almost too high, then down a tad from there.

The leg needs to reach its full extension at the bottom of the pedal stroke, without stretching to reach that point, in other words the power is on right to the end of the pedal stroke, and definitely not reach its upper limit at the top of the stroke.

Footnote: I couldn’t find a better picture to illustrate this piece, except the exaggerated one at the top. But it did lead me to realize how BMX riders manage to pedal straight with their saddle so low. The saddle nose is positioned up which causes the pelvis to lean back thus increasing the angle in relation to the thigh. I'm not suggesting you try this on your road bike.

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What does the length of your forearm and the price of fish have to do with stem length?

This method of determining handlebar stem length has been around forever. My cycling experience dates back over 67 years and it was practiced then, and many years prior. Actually it is not a bad guide and works for most people.

Of course in an age of computerized bike fitting, this may seem to be bordering on an old wife’s tale, but believe it or not, back in the day before computers people figured shit out using only the power of their mind, and the wisdom of old wives.

Place your elbow against the nose of your saddle and if your fingertips do not fit behind the handle bars as shown above, then your stem is probably too short. If the bars are more than 2cm. away from the finger tips your stem maybe too long.

When I was racing I used a stem that placed my fingertips one centimeter from the bars. Now as a mild concession to my aging body I’m using a stem a centimeter shorter. If you are wondering as I did for many years what the length of a person’s forearm has to do with stem length? I will explain.

When I am determining frame size I take into account three body measurements.
1. Inside leg length (Often referred to as inseam.) measured crotch to floor without shoes.
2. Overall height.
3. Shoe size. (Length of foot.)
I do not require body length because I have overall height minus inseam. I do not require arm length because this is relevant to leg length and foot length combined.

Human bodies although all different do generally follow certain rules of nature. We have the same basic design and structure as most other animals on this planet except we walk on our hind legs while most others walk on all four. So it follows a person with long legs will also have long arms; short legs, short arms.

Four legged animals generally walk on their toes (and finger tips) whereas we stand and walk on our heels. So some people have a long body, but short legs and it is not unusual for a person with this build to have longer feet, and also longer arms. The long arms are not out of proportion if you consider the leg length is a combination of inseam plus the length of foot.

When pedaling a bicycle the toe is pointing downward at the bottom of the pedal stroke so the foot becomes an extension of the leg, which is why it has to be taken into consideration when determining frame size. The person with short legs, long feet needs a larger frame than their inseam alone would suggest. The larger frame with its proportionally longer top tube will also accommodate this rider’s longer body and arms

The length of the forearm is proportionate in length to the length of the foot. Take one of your shoes and hold it against your forearm and you will see it is the same length as the distance from your elbow to your wrist. In other words the big bones in your forearm are the same length as your foot.

So assuming you are on the right size frame and your seat is set at the correct height, then chances are if you have very long feet then you will have a short inseam and a long body.

Because you have long feet you also have a long forearm and if you do this little elbow against the saddle trick it will show you need a long handlebar stem which will be right for your long body and arms.

A person with very long legs for their height will also have long arms but will have a short body and small feet relative to their height. Small feet mean short forearm and a shorter stem which will be right for their short body. Because this rider has long legs his saddle will be set high making a greater distance from the seat to the bars. This will accommodate his long arms.

There is another method for determining stem length which states: “A rider seated with their hands on the drops of the bars, will have the front hub obscured from view by the handlebars.” This works in the same way, longer body calls for a longer stem and vice-versa.

The only thing is that this method could be affected by the head angle of the frame and the length of fork rake. I prefer the length of forearm method because it is simpler. It works for most people but there is a small percentage that it will not. I always say if you are comfortable and happy with your current position, don’t change it. Go by the old “If it ain’t broke, don’t fix it” adage.

And what does all this have to do with the price of fish? Nothing at all, but it got your attention.

This is a rewrite of a post from the very early days of the Bike Blog. At the time it was shot down by a reader as “Utter Rubbish.” I repost it today for the reasons I did the first time. Not to get people to rush out and buy new handlebar stems, but rather to explain that before the days of high tech bike fitting, people managed to get by. I hope also I have explained why this method did have some merit, and the reasons why.

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Riding Position Simplified

There is so much information available on bike riding position, it can be confusing to both beginners and experienced riders alike. A whole cottage industry has sprung up dealing with bike fit, and one can spend a great deal of money, and often be no better off.

So let’s forget about computer programs and magic formulas, and look at the basic issues we are dealing with. Assuming our bike is the right size, and not too big or small by extremes, how can we find a good place to start? Find a position that is both efficient and comfortable.

There are really only two main issues we need to concern ourselves with. That is saddle height, and position of your arms in relation to your legs. Whether you are looking for an extreme aero racing position, or a more upright leisure riding position, the same principle applies. You need an efficient position, whether your goal is to go fast, or ride in comfort.

1.)    Saddle height. Imagine you are doing squats with a weight as shown in the picture above. Note that when in the lowest possible squat, the knees are spread apart. That is because the hip joint in the pelvis has a limit to how far it can travel. When you reach that limit the only way to squat any lower is to spread the knees apart.

When you see someone on a bike riding with their knees spread, it is often an indication that their saddle is too low and the hip joint has reached its limit of rotation. An extremely low back position, or the saddle positioned far back will exacerbate the problem because you are rotating the pelvis forward. However in most cases if the saddle is high enough, no matter how low your back, at the top of the pedal stroke, the hip joint will not be at or near its limit.

When doing squats with a weight it is hard to lift from the lowest position. It would be much easier if you started from the half way position. In other words, leg muscles work more efficiently near the top end of the lift. So if you can ride a bike with the saddle as high as it can be, you are pedaling with more efficiency that with the saddle set low.

How high would be too high? Well, if you are stretching for the pedal at the bottom of the stroke, and your pelvis is rocking side to side, it would indicate your saddle is too high. With one crank at its lowest point, your toe should be pointing down, but not stretched. You should be then able to lift your butt 1/4 inch (6mm) above the saddle. If you can lift yourself more than that, your saddle needs to go higher. When riding, it is easier to tell by feel if a saddle is too high, but not so easy to tell if it is slightly too low.

2.)     Position of arms in relation to the legs. When pedaling at maximum effort we are pushing down with more than our body weight. The only thing holding us down is our hands grasping the handlebars. Power is transmitted through the arms, shoulders, and back muscles to the legs.

Look at the top picture of Peter Sagan. With the crank arms horizontal and the pedal on its downward stroke, the red line line drawn from the hip joint to the pedal, is approximately parallel to a line drawn from the shoulder to the hands on the drops. In other words arms are in exact opposition to the legs.

Notice I said approximately. The lines do not have to be exactly parallel, but if there is a wide difference this is not a good position. It doesn’t matter what your back angle is, horizontal or a leisurely 45 degree angle. Arms opposing legs still apply.

Many recreational riders make the mistake of raising their handlebars higher and higher to achieve a more upright back angle, when a better approach might be to fit a shorter stem and raise it less. (The resulting back angle is the same.) If the arms are not opposing the legs, backache can result, or you find yourself constantly sliding forward on the saddle.

Weight distribution too comes into account. Weight should be distributed between the pedals, saddle and handlebars. If the bars are above the saddle then all the weight is on the saddle.

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Crank Length

A reader recently asked me a question about crank length and suggested I might write an article on the subject. 

There is a reason I haven’t touched on this subject before in over eleven years writing here. It is one of those subjects like "Knee over Pedal." I feel it is unimportant and irrelevant.

However, when I started to think about it, I realized I could maybe throw some logic on the fire, rather than adding to the huge pile of horse shit that is already out there. The whole reason to mess with anything like crank length is to improve performance. Go faster for the same amount of effort.

Were it that simple someone would have figured it out long before now and we would all be using something different than we have been using for the last 100 years. And if ever there was a case for the old adage, “If it ain’t broke, don’t fix it,” this is it.

The part that most fail to grasp is that increasing crank length increases leverage, meaning (In theory.) you can push a bigger gear, but unless you can pedal this higher gear at the same RPM for the same amount of effort, you are not going any faster.

Because you have increased crank length you have also increased the diameter of the pedaling circle. Any advantage in leverage is canceled out by the disadvantage of the greater turning circle.

Your feet, and the leg muscles that drive the feet, are having to move a greater distance (Therefore greater speed.) per revolution of the crank. You may as well stick with the standard length crank and pedal the lower gear. You are traveling at the same road speed, relative to the speed your feet and legs are moving.

Also if you are switching from a 170 to a 175mm. crank, that is one centimeter greater pedaling circle. Your saddle needs to stay in the same place. (Let’s assume for this argument that your saddle height was right to start with.) If you lower the saddle by 5mm. your knees will be coming up a full centimeter higher at the top of the stroke.

Better to leave the saddle where it is. Your crank and pedals will still be at the center of the turning circle you are used to. The extra length of the crank will be equally spread 5mm. extra reach at the bottom of the stroke, and 5mm. higher at the top of the stroke.

I notice longer cranks are being touted as a cure for various leg pains. Often leg and other pains are because the rider is not in the peak of physical condition. Start any exercise regimen, not just cycling, and the participant will often feel discomfort. All one can do is slowly and carefully work through it, until the body becomes accustomed to the extra stress being placed on it.

I fail to see where pedaling in a larger circle can help. It is placing more stress on the body, not less. It is akin to telling your doctor that walking is painful, and he suggests you walk faster and take longer strides. Just because long legs can accommodate longer cranks, doesn’t mean they should, or that there is necessarily an advantage in doing so. Try adjusting your saddle height first. It costs nothing and it is less of a shock on your system.

Here is another analogy. A person with long legs could climb stairs two steps at a time. He may get to the top of the building quicker, but one thing for sure, he has expended a lot more energy in doing so. Just because he can climb stairs two at a time, doesn’t mean he should.

Of course there is nothing stopping him climbing stairs two at a time, and there is nothing stopping him from fitting different length cranks, I am just pointing out that anyone saying there is some big advantage in doing so, is simply blowing smoke.

So how did we arrive at the crank lengths we use today? Let’s first look back in history to the forerunner of the chain driven bike, the high wheeler.

The big wheel was around 60 inches or five feet diameter, cranks had to be short in order to keep the wheel diameter as large as possible.

When the chain driven bike came on the scene in 1885, there were no restrictions on crank length. However, its invention was soon followed by mass production of bicycles and standards had to be set. It was England that started the bike industry and so set the early standards. Even today the world uses half inch pitch bicycle chain as standard when the most of the world uses metric measure for almost everything else.

The standard crank length was soon established at 6 1/2 inches for most bicycles. Because twice 6 1/2 is 13 inches, which is an average stride length for a leisurely walk. However, later it was found for racing bikes 6 3/4 worked better. 7 inches was too long for all but the tallest riders. That 1/4 inch either way made a big difference.

Do you ever wonder why Campagnolo offer a 172.5 mm. crank? Up until WWII Britain led the world in bicycles and components, including the high end racing equipment.  6 3/4 inch cranks were the standard for racing worldwide.

After WWII, Italy really moved into the component market. 172.5 mm. is pretty close to 6 3/4 inches. So this became the new standard. It did in the UK anyway. Everyone I knew, myself included, used 172.5, a few taller guys used 175. It is interesting that Campagnolo is the oldest established out of the big three companies. Campagnolo, Shimano, and Scram, and they still only offer 170. 172.5, and 175mm. crank lengths. Maybe it is all we need.

There may be a case for 180 cranks for someone with exceptionally long legs, say 36 inch or longer. Conversely, 165 cranks for a person with 29 or less inseam. But this whole range of crank lengths throughout the complete range of body sizes I feel is just hype put out there by the bike fitting industry.

Many of the best bike riders in the world range in height roughly between 5’ 7” and 5’ 11.” They ride small to mid-size bikes, and use standard length cranks. It has always been that way for years. Of course there are exceptions, but he day tall, long legged guys using long cranks, start dominating professional racing, is the day I will change my views on crank length.

Certain things in bicycle design were established many years ago, and remain the same because it happens to be right. Half inch pitch chain, already mentioned. 27 in. wheel diameter. (Measure your 700c tire.) 73 degrees is the best head angle for a road bike. The same with crank lengths.

The original crank lengths set over 100 years ago were: 6 1/2 inches (Almost exactly 165mm.) 6 3/4 inches, which is right in between 170 and 175mm. And 7 inches (Slightly less than 180mm.) That is all the range you need. It works, why fuck with it?

To sum up, yes there is a case for different crank lengths, but only over the relatively small range of a centimeter and a half. 165mm. to 180mm. This should accommodate the extreme range of leg lengths well beyond normal averages. Campagnolo's range, 170, 172.5, and 175 is fine for most of us.

Remember too, I don't have a pig in this market, I’m not trying to sell you anything. My final advice, just enjoy the bike, and stop trying to over-think it.

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