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I'm 174 cm (5 feet 8½ inches). Major bicycle manufacturers recommend a medium or medium to large frame size MTB's with an effective top tube length of 59-62 cm for my height. However my bike (a 26" MTB) has only 54.5 cm effective top tube length. However, my bike has a 120mm stem which makes the reach longer but still I am not feeling comfortable on the bike during long rides. I am also lifting the saddle close to the maximum limit seatpost allows as per the calculation method of saddle height to inseam ratio.

In theory, with a longer stem, I supposed to have the same length from the saddle to the handlebar as bigger sized frames but I think it doesn't work in practice. Because when I wanted to fully lean on the bike I can't keep my back straight. I also have a major pain on the left side of my sit bone and discomfort between my shoulder blades during long rides.

I also have too much muscle tension and fatigue after the rides. Especially on my calves and iliotibial band area. Stretching those muscles gives a big relief but I can't recover before 3 days at least. I usually ride only 40 kms without even reaching to my zone 2 once or twice a week.

Below is a short video of me on the bike. It's not ideal but it might give you an idea.

https://youtube.com/shorts/bB01nmw4EU4?feature=share

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    For bike fitting questions we can always give better advice if you can post some side on pictures of you sitting on the bike
    – Andy P
    Jun 12, 2023 at 15:30
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    Using a formula based on leg length measurements fails to determine a correct saddle height in 2 out of 3 people. youtu.be/D57cjn9XElc There are too many variables that the formula doesn't take into consideration (foot length, ankle flexibility, hamstring flexibility, calf muscle strength, injury history, cleat position, pedalling style (heel drop, or toe pointing), type of shoes and pedals. The video also concludes that it is worse to have the saddle a little bit too high than too low.
    – Robert
    Jun 12, 2023 at 19:46
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    @Ender 52kg 174cm are very good body proportions for a cyclist. Thin and fit. From the picture the saddle seems a little big. But from this angle it's hard to tell its width. Could it be too wide for you? Have you measured your pelvis / seatbones width? Online tutorials can be found. Only judging by the fact that you are male, 52kg, 174cm, it would be rare for you to have a wide pelvis, and a saddle with its maximum width of more than 140mm might be too wide for you, forcing you to sit more forward, on its narrower part. Do you know how wide your saddle is?
    – Robert
    Jun 12, 2023 at 19:56
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    @Ender If you don't have a trainer, maybe you can go on an empty road and ask a friend to ride alongside you and take a short video of you from the side when you are on the bike spinning 80-90rpm at moderate effort. But please be careful to road traffic.
    – Robert
    Jun 12, 2023 at 20:05
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    @Ender The video is very informative. I have updated my answer. You can edit the question to include the video as well. It is helpful, and you will get better answers.
    – Robert
    Jun 16, 2023 at 13:16

1 Answer 1

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Some general points about frame size

It really depends on your body proportions (for example long arms and torso, but short legs, or long legs and short torso, etc.), and your flexibility, how easily you can extend your legs and bend your back. Your height alone is not enough to decide ideal frame size.

I'm 1,87 and ride a 54.5 with 120mm stem road bike. And Chris Froome for example is 1.86 and rides 55mm effective top tube. But these are road bikes, and by design the handlebars of road bikes have longer reach. My MTB, on the other hand, has 58.5cm effective top tube and 90mm stem. So, if I add the two together it equals 67.5cm, only 1cm longer than what you have, even though I'm 13cm taller. So my frame might be even more strongly regarded as "too small" for me by various online charts, yet I'm perfectly comfortable.

For some people it works to have a smaller frame. If it works for you individually, a good bike fitter can decide. Or you can study your position in more detail, film yourself from the side on a trainer, and try various adjustments to see how it feels. You could also rent another bike and see how it feels. If you want to do a bike fit for yourself, there's a book written by Phil Burt that you may find helpful.

For road bikes, another measurement that affects the overall reach is the handlebars' reach, and the brake levers position on the bars. If you move the brake hoods forward on the bars, lower, and then rotate the handlebars back at the stem, you can effectively increase the reach by around 1 to 3 cm. Or you can find handlebars with longer reach.

Usually it's when the reach is too long that people feel discomfort.

I can think of some bike adjustments that can make the bike feel like the reach is too short when in fact it isn't:

  • Is the saddle tilted down too much, causing your pelvis to slide forward?
  • Is the saddle fore/aft set all the way, or too much forward?
  • Is your handlebars width correct? I.e as wide as your shoulders, on a road bike;
  • Is the saddle too wide, forcing you to sit more forward on it?
  • Are your handlebars too low, with no spacers under the stem, and/or the stem flipped down? This could also cause hip impingement and pain;
  • Is the crank arm too long, and you feel the need to move forward to be on top of the pedal at 3o'clock, the power phase? This can also cause hip pain.
  • If you are using clip-in pedals, are the cleats set too far forward on the shoe? When we push on the pedals, there is some reaction force that pushes our bodies back towards the rear of the saddle. If we move the cleats further back, and push on the pedals using more of the middle part of the foot rather than the toes, then this effect is increased. A rear cleat position is always considered safer and more ergonomic. But this will also affect seat height, because it changes the effective leg length. So if you move the cleat back by let's say 5mm, then you should lower the seat height a little bit, let's say 10mm.

In response to the video of you on the bike

I don't see anything extremely wrong with your position, I think you can make that frame size fit. There are, however, some observations and tweaks I can suggest, based on what I've studied online about bike fitting.

  • Indeed, the reach of the bike seems a little bit short. But nothing crazy. I don't think a longer reach will necessarily help. In general, increasing the reach has these effects: a) it puts more weight on your hands and shoulders; b) it closes down the hip angle, because you lean your torso forward more, the knees will have to come closer to your chest at the top of the pedal stroke, and people with not very good hip mobility find this uncomfortable;

  • Your torso is fairly upright, and the hip angle open, you seem to have no trouble raising the knees and getting through the top of the pedal stroke. I think you can tolerate a longer reach, but it doesn't necessarily mean it will solve your issues. It may make them worse;

  • The saddle height seems a little bit high. Doing a rough measurement of the knee angle on the video shows about 150 degrees knee extension, or 30 degrees flexion (away from full extension). knee angle

  • This dynamic knee angle is recommended to be in the range of 35 - 40 degrees from full extension in Phil Burt's book (or 145 to 140 measured from these body markers: 1. great trochanter at the hip, on the femur; 2. lateral epicondyle at the knee, still on the femur; 3. lateral malleolus at the ankle, on the fibula). Other bike fitters recommend an even wider range of 33 to 48 measured dynamically (while you pedal). People with poor hamstring flexibility usually need a lower saddle. You can do this test, or other similar flexibility tests for the hamstrings and see how you compare. knee angle recommendation

  • With an optimum saddle height the pedaling motion should feel smooth and fluent all the way around, without excessive tension behind the knees, and without the need to rock the pelvis from side to side on hard efforts.

  • The ankle also plays a role in saddle height. Several studies showed that changes in saddle height are mostly absorbed by the ankle (people compensate for a high saddle by pointing their toes down, and for a low saddle by dorsiflexing the ankle back). So, in theory, people with a high range of ankle mobility tolerate a larger range for saddle height, while people with stiff ankles have a narrower range in which they feel comfortable. An ankle flexibility test is presented in this video. In your video, your ankles look nice and stable, in a neutral position. But this is on a flat road at easy pace. When going uphill at a harder pace for example, people tend to dorsiflex the ankles, and saddle height should be set to allow for this, i.e not excessively high.

  • I see you are wearing a backpack. On long rides it may put too much tension on your body, and may make small issues worse, especially if the straps keep sliding off your shoulders (when you reach for the water bottle for example, or when standing on the pedals and rocking your body left and right) and you feel the need to shrug, and keep constant shoulder tension, to prevent it from falling. I, personally, cannot tolerate a backpack at all on the bike. On long rides I carry all I need inside a frame bag between my legs + a saddle bag (under the saddle). If water sources are scarce along your route, you can get a bigger bottle, or try to fit a 2nd one under the down tube, even if the bike comes without dedicated mounts, there are strap-on adapters.

What changes I suggest for you to try

  1. Try a lower saddle height, it is generally safer. I estimate a 3cm drop from what you have now will bring you more into that recommended range. You should be able to place your heels on the pedals and spin at an easy pace without losing contact with the pedals at the bottom, and without the need to shift left and right on the saddle. This bike fitter recommends starting low and working from there.
  2. Move the saddle all the way back. This will: a) reduce the weight your hands and shoulders need to support, and make your upper body feel more relaxed; there's this test you can do; b) take some tension off your legs as well, and make the pedaling motion easier, as more of your weight will be shifted back and be supported by the saddle.

On the bike your body weight is distributed among the 3 contact points: saddle, pedals, hands. I believe you are putting too much weight on your hands and legs and not enough on the saddle because it is too high and forward.

Note: You may be used to riding in your current position, and any changes that you make might feel wrong at first. You should give your body some time to adapt to the new changes, a few easy rides on the course of a week or two. Don't do very long or hard rides immediately.


About Knee Over Pedal Spindle (KOPS) method

The KOPS method doesn't seem to have good biomechanical reasoning behind it, and it is popular mostly by repetition, and many bike fitters criticize or disregard it completely, like this one, or this one.

There's nothing wrong with having your knee behind the pedal spindle. And given your chondromalacia, I would set it as far back as it goes, to reduce the load on the knees. This effect can be seen off the bike as well, for example with the lunge exercice. Try and do a lunge with the knee more in front of the toes, and then move the knee further back. You will notice the tension on the knee goes down as you move it further back. This video demonstrates.

Midfoot on the pedal

Another thing that many bike fitters consider to reduce the load on the knees while pedaling is to use the middle of the foot (or as far back from the toes as possible) to push on the pedal. This reduces the tension of the calf muscles and the forces that go through the knee. But to be able to do this, a low enough saddle height is required. You can do a little experiment off the bike, climbing some stairs using only the front part of the foot, and then again but with the entire foot down, and see which feels more comfortable to you. This video demonstrates something similar.

Low gear high cadence

What is also recommended to reduce the load on the knees is to use lower gears but higher cadence. If you find difficult to spin at 90rpm for more than a few minutes, it might be an indicator that the saddle is too high. When the saddle is too high, the tendency is to apply the power in impulses at a lower cadence, rather than smoothly and fluently across a larger portion of the pedal stroke using a higher cadence.

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  • Actually I'm setting the saddle all the way forward as my knees getting further back from the pedal spindle at 3 o'clock position if I set it any more backwards. Crank arm length is 170mm.
    – Ender
    Jun 12, 2023 at 16:55
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    @Ender Phil Burt in his book says that a saddle too far forward can cause more trouble than if it is too far back. It also puts more weight and tension on your arms and shoulders. You can try to move it to the middle of the range. But note that moving it back will also change the seat height because of the angle of the seat tube, by a ratio of 1 to 3. So if you move it back 1.5cm, you should lower the height by 5mm, to keep the effective seat height the same.
    – Robert
    Jun 12, 2023 at 17:43
  • Sounds good. I'll give it a try.
    – Ender
    Jun 12, 2023 at 17:45
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    @Ender About crank length Phil says that it is more ergonomic to spin the legs in smaller circles by using a shorter crank. 170 is not too long. I also run 170, being 1.87m tall. You could safely try 160. My wife uses 155, she's 1.67m tall.
    – Robert
    Jun 12, 2023 at 17:50
  • Wow, I didn't know they can be that short but I think it does not cause a major issue.
    – Ender
    Jun 12, 2023 at 18:09

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