Due to the success of my previous blog about crank length ‘Crankset length, what’s that really about?’, another blog on this subject: Good Crank Length. Enjoy reading!
Why is crank length so little talked about when selling bicycles? Let’s start with some background on this part.
No part of the bike is as underrated as the cranks.
I sometimes jokingly say: ‘The length of the crankset is more important than the size of the frame’. To make it clear what an impact this part has on the entire cycling movement. After all, it is typically a part that receives minimal attention when buying and selling bicycles. As a result, I see many cyclists at our bike fits with the wrong size crankset, with all the consequences for their cycling pleasure, comfort and performance on the bike.
The cycling movement is actually completely related to the rotation of the crankset.
It serves as a lever to transfer force to the chain, which in its case sets the cassette and thus the rear wheel in motion. Why is there so little attention for this essential component? I want to bring about a change in cycling in the Netherlands regarding crank length and positioning on the bicycle. It is time that attention was paid to this when purchasing the bicycle.
Are you unsure about the crank length on a bicycle yet to be purchased? Then come by for purchase advice before purchasing the bicycle.
Common crank length sizes
In the Netherlands, the most common sizes are 170mm, 172.5mm and 175mm. There is a good chance that your bicycle is fitted with one of these crank lengths. A difference between the smallest (170mm) and largest size (175mm) of 5mm. In the revolution 1 cm. Very little if you think about it…. Short cyclists of, for example, 155 cm, want to enjoy cycling with this, but also taller cyclists, for example, 197 cm. A difference of 43 cm in length, and probably also more than 20 cm in inside leg length. The first person will probably be fitted with an XS bicycle frame and the second person with an XL bicycle frame. Which means many centimeters difference on all sizes of the frame. While in most cases there is at most 5 mm difference in the crank length, pretty crazy right?
Problems due to incorrect crank length
For taller cyclists of 180 cm +, the problems are often not too bad *, there is often one of these three sizes suitable because they have enough inseam to turn these sizes of crankset without overloading their joints or back. The latter is more often the case with people under 180 cm.
*without including other physical characteristics or details
Physical or biomechanical
Traditionally in cycling, or the bicycle industry in general, the idea is that we need a fairly long lever (crankset) to generate a lot of power. Naturally, this principle is also correct, only biomechanically is different. In fact, when the crankset is too long, a lot of power is lost because power can only be delivered later in the revolution. The ‘dead center’ is much longer than with a correctly sized crank.
Overload injury from the crankset
In addition to the ‘longer’ dead center in the rotation, as just described, injuries due to overload and a movement that is out of proportion are lurking. The most common complaints I see due to cranks that are too long are: knee complaints, ‘wobbly’ legs, lower back complaints, upper back and neck complaints, groin complaints and saddle pain.
Other crank lengths
Fortunately, smaller sizes of cranks are available, albeit a lot more difficult. When we talk about HollowTech cranks (modern cranks), 160 mm and 165 mm cranks from Shimano have become increasingly available for a few years now. Campagnolo has also added 165 mm cranks to their range. At first only if you got them from Germany or England, but now they are also (reasonably) readily available in the Netherlands. Sram has been selling 167.5 mm cranks for years, but you often have to get them from abroad.
For old-fashioned bottom brackets it is a bit easier to get a good crank length
There, for example, Miche sells various sizes under 170 mm. But not many people still cycle around with this technology from the past. In Japan, various brands of Hollowtech cranks are made in all sizes between 120 mm and 170 mm, although you must speak Japanese or have an interpreter to order them. The above indicates that it is not always easy to get shorter crank lengths than 170, 172.5 and 175 mm.
The importance of a good length crankset
Above you have already read a number of reasons why it is important to ride with a good crank length. Even 2.5 mm shorter can sometimes provide a lot of relief in the joints or muscles. A crank cannot be adjusted, so the size must be right. A frame can be ‘adjusted’ by changing the position of the saddle or handlebars, or by making an adjustment in the saddle or stem. Which means that we can sometimes still make frames fit that are a size too large or too small. In addition, the crankset initiates the cycling movement and everything that comes after that in the cycling position is in conjunction with this movement. Very often an adjustment of a crankset to a different (correct) length in combination with a good adjustment can remove your complaints on the bike and thus increase the cycling pleasure!
What does the literature say about crank lengths?
I often get the question whether a shorter crank also means less power/wattage. Fortunately, various studies have been done in the past to provide a clear and substantiated answer to this.
In 2001, James Martin/ University of Utah already concluded that the difference in wattage a cyclist delivers with various crank lengths (120 mm, 145 mm, 170 mm, 195 mm, 220 mm) is small.
He also concluded that the cadence decreased significantly as the crank length increased. Which argues for riding with shorter cranks to be able to maintain a high cadence and therefore speed more easily.
If you find it interesting, the full research is below.
John McDaniel of Kent State University also researched this in 2009.
His conclusions after examining the effect of different crank lengths on the wattage:
- Small effect
- Significant only at extreme lengths
- 170mm cranks compromise power of the tallest and shortest riders by no more 0.5%
- No change in joint power contributions
And the most important sentence from his conclusion:
“Cyclists can ride the crank length they prefer without concern of decreasing maximal power”
This opens the way completely to riding with a shorter crank. Something that gives many ergonomic and aerodynamic benefits without reducing the wattage that is pedaled.
Reaction of cyclists to an adjusted crank length
Peter van Vuuren wrote this in a review about the crank length after his bike fit with me:
(………..) During the bike fit he told me that I was riding with cranks that were way too long. I had 172.5mm, Aron’s advice is 160mm! I thought how is that possible, last year I had a new shift group put on it, there was no mention of shorter cranks because of my height (1.69 mtr). Aron clearly showed me (by means of video recordings) where he can create a better cycling position for me, especially at the knees and buttock-back region (………..) After a few weeks I had gotten hold of the 160 mm cranks . Aron mounted everything professionally and took another measurement (………….) First ride and what a difference, I feel the pressure on my pedals for the first time, it takes less effort, so heart rate remains lower. (………..)
You can find Peter’s full review in the Google profile of De Biomechanieker.
Peter’s story is not an isolated one. Every week I can help people with their complaints by fitting a correct crank length and the associated adjustments to the positioning on the bicycle. In Peter’s case, in addition to an enormous improvement in comfort and therefore increased cycling pleasure, his average speed has also increased enormously and his heart rate has decreased. A win on all levels.
In Jorrit’s case, after adjusting the crank length, his knee complaints were a thing of the past: “After trying everything to get rid of my knee complaints, the Biomechanieker helped me out 🙂💪🤟“
My own experiences with different crank lengths
To interpret my experiences that I describe below, here are some details about me personally:
- length: 1.77 m
- inside leg length: 80 cm
- leg length difference of 2.5 cm
- left leg 2.5 cm longer than right leg
When I started racing in 2007, my bike had a 172.5mm crank. At that time, as a beginner, I didn’t even know that there were different crankset lengths. At that time I regularly experienced lower back and knee complaints. Nothing serious yet, it always went away. Strengthened by the many comments from fellow cyclists: that pain is part of it / you get used to it / it will decrease by itself, I continued to cycle on my bike and equipment without a doubt.
A few cycles further in 2012 I could no longer ignore my complaints. I got blood circulation problems in my legs and serious back and knee problems. The pains during cycling got the upper hand over the cycling pleasure. At this time I was seriously considering ending my cycling career early. (read more about these cycling pains in my blog: Cycling pains, isn’t that normal?!)
Switch to a good length crankset
After switching to 170 mm cranks + a good adjustment of the bike, these complaints were largely a thing of the past. Cycling became enjoyable again and rode 81 races at a semi-professional level in 2013 without developing serious complaints.
The following year, due to my leg length difference (more than 2.5 cm), another adjustment was made.
I started riding with 2 different crank lengths.
Right 165 mm and left 170 mm. An adjustment that is actually rarely if ever done. If you go purely by what is written on the internet about this, you absolutely should not do this…However, the result of this unusual crank combination was that I became even more comfortable on the bike, could deliver more power and even less experienced back pain. In addition, over time I also sat more upright in the saddle. Because of years of riding around with the wrong size crankset, I was sitting crooked in the saddle.
With the 165 mm and 170 mm crank combination I cycled around with great pleasure and comfort from 2014 to early 2022.
Good crank length, even smaller cranks?
Strengthened by my experiences as a bike fitter at De Biomechanieker, my own experiences with shorter cranks and curiosity about what even shorter cranks would bring me, I made the step to a 160 mm / 165 mm crank combination at the beginning of 2022.
What a world of difference. Again. The first ride with these cranks didn’t feel like riding a bike but like flying. It was that easy. For the first time in all my years on the bike, I felt completely free and unfettered in the circular motion of the cranks. The dead center in the revolution seemed to have disappeared. The pressure on the lower back that was still there disappeared like snow in the sun. But the most interesting discovery of this new crank swap was yet to come…
Effect shorter cranks
After the crank change I had to adjust the saddle height and saddle setback. When shorter cranks are mounted of, for example, 5 mm, this generally also results in a higher saddle position of 5 mm. With this we can achieve the same leg extension in the rotation. The shortening of 5 mm in the crank therefore ultimately gives a difference of 1 cm in the complete revolution. Which also gives an inch of reduced movement in, for example, the knee joint. The upper leg will also remain one centimeter lower during the revolution. This in turn has a direct effect on the pressure experienced on the lower back and can even reduce neck complaints.
Yet the critics among us will still say: ‘What difference is that one cm going to make?’
What we must realize is that the average cyclist/cyclist/mountain biker easily pedals at 70 to 90 revolutions per minute. Due to this repetitive movement, the centimeters of reduced movement in the joints / reduced pressure on the lower back quickly add up.
The difference that is made with 5 mm of crank shortening can rightly be called enormous!
More aerodynamic cycling position due to a good crank length
The most interesting discovery has to be the above. After a few rides with the short cranks, I felt that I had room to sit deeper, despite the higher saddle position. After experimenting a number of rides, I ended up with a 2.5 cm lower steering position. The total difference in drop, taking into account the 5 mm higher saddle position, is therefore 3 cm.
Thanks to the shorter crankset, I was also able to adopt a more aerodynamic cycling position. Profit on all levels!
Conclusion ‘A Good Crank Length’
A good crank length is crucial for a cycling position with comfort and optimal wattage. The crankset is the part with the greatest impact on the cycling position. A good, personalized crank length can work wonders for solving overuse injuries, increasing cycling comfort and endurance in longer rides. In addition to all these advantages of a good crank length, even shorter cranks can always be considered. Both theory and practice show that this has ergonomic advantages and that this is not at the expense of the delivered wattage.
Guidelines from De Biomechanieker for a good crank length
Below you will find 2 tables with guidelines for the length of the crankset per centimeter inseam. The 1st table shows my guidelines for adult cyclists, the 2nd table shows my guidelines for youth riders up to and including 16 years old. Please note: In various cases I deviate from these guidelines with my advice. For example, due to limited flexibility, old or current injuries, age, abdominal fat, size of the upper legs, operation of the knee joint, leg length difference, etc. I also use adjusted guidelines in the case of a time trial bike or triathlon bike! So use these tables only as a guideline, for 100% conclusive advice come by for a complete bike fit, bike fit advice or purchase advice.
| Table from 17 years old | |
| Inseam in cm | Cranklength in mm |
| 59-60-61-62 | 150 |
| 63-64-65-66-67-68 | 155 |
| 69-70-71-72-73-74 | 160 |
| 75-76-77-78 | 165 |
| 79-80-81 | 167,5 |
| 82-83-84 | 170 |
| 85-86-87-88 | 172,5 |
| 89-90-91- enzovoort | 175 |
| Table up to 16 years old | |
| Inseam in cm | Cranklength in mm |
| 50-51-52 | 120 |
| 53-54-55 | 125 |
| 56-57-58 | 130 |
| 59-60-61 | 135 |
| 62-63-64 | 140 |
| 65-66-67 | 145 |
| 68-69-70 | 150 |
| 71-72-73 | 155 |
| 74-75-76 | 160 |
| 77-78-79 | 165 |
| 80-81-82 | 167,5 |
| 83-84-85 | 170 |
| 86-87-88 | 172,5 |
I’ll be happy to help you. Visit Heenvliet or Rotterdam to find out for sure what the right size is for you!
Sources: https://www.researchgate.net/publication/11923708_Determinants_of_maximal_cycling_power_Crank_length_pedaling_rate_and_pedal_speedhttps://www.researchgate.net/publication/11923708_Determinants_of_maximal_cycling_power_Crank_length_pedaling_rate_and_pedal_speed
Myths and Science in Cycling by John McDaniel