Crank Length: The Long And The Short Of It.

Crank length is a heavily debated subject in bike fitting as there hasn't been any definitive studies showing that either longer or shorter is better. In fact, a number of studies have shown that there isn't much difference in maximum power output between a big range of crank lengths:

Martin and Spirduso (2001) tested cranks from 120mm to 220mm and didn’t see a significant difference in maximum power between 145mm and 170mm.

Barratt, Korff, Elmer and Martin (2011) also tested cranks ranging from 150mm to 190mm and didn’t find a significant difference in maximum power output.

I think that this can be explained by the fact that both studies found that the length of the crank affected the cadence that the riders used. The shorter the crank, the faster the cadence. So why is this?

Muscles fibres have a speed that they are most efficient to contract at. This leads to the joints (and therefore the pedal) to move at a certain speed. As the picture above shows, when using the same cadence, a pedal on a longer crank has to travel further than a short crank in the same time and therefore moves faster (requiring a faster muscle contraction). Therefore, as we lengthen the crank, the cadence slows so that the muscle fibres contract at their most efficient rate. So why isn't power significantly affected?

Power is a result of torque (the twisting force on the crank) times speed (the cadence of the pedals). A longer crank can produce more torque (due to the longer lever) but uses a lower cadence. The short cranks make up for the lower torque by using a higher cadence to get near enough the same power output.

So should you be worrying about your crank length?

On the face of it, if there aren't any power gains to be had then the short answer should be no. But I believe that if there isn't much to be lost power wise when dropping a crank length then why shouldn't we consider it for certain situations. I believe there are 3 exceptions to consider:
1) Riders that have severe restrictions in their hips,
2) Shorter riders,
3) Time trial and triathlon

Hip Restrictions

If a rider is very tight around their hips (tight rotator muscles, hamstring, hip flexors, joint capsule etc) then the higher the knee needs to travel up to get over the top of the pedal stroke, the less efficient they will be. This often causes the knee to move away from a straight up and down as the body finds a way around the restriction (either around the outside or rocking the hips to the side). This causes knee traces like the circular pattern above. A shorter crank means that the knee doesn’t have to travel as high to get over the top of the stroke and therefore the rider can get on the power quick.

Shorter Riders

Shorter riders have proportionally shorter legs and therefore will have to further into hip flexion to get over the top of the pedal stroke compared to taller riders on the same length crank. Again, a short crank may be more efficient for a shorter rider and put less strain on the knees as they won’t have to bend them as much. I have had great success putting riders that have saddle heights of 71cm and less on 165mm cranks. Here are a couple of testimonials:

Peter 

“Up until June 2012 I had previously been riding between 8 and 12 hours a week on 170mm cranks. During this time I had problems with my back and knees and spent painstaking time and money at sports doctors and changing different equipment on the bike to try and rectify the problems. I changed  shoes and had custom footbeds and numerous seats! At the end of 2011 I entered the Haute route Alps Geneva to Nice 780 k and 21,000 metres of climbing 7 timed stages. There would be no hiding from injury and bad fit during this event! I went to see Ben Hallam at Bespoke cycling who used the Retül system and adjusted my cleats and the recommendation of going to 165 mm cranks. I am not the tallest of men and was a little sceptical about a mere 5mm difference in crank length. Well size does matter after fitting 165mm Rotor cranks with standard round rings, the difference was remarkable my average cadence on my usual loops round Kent were up between 7 and 10 rpm and my pedal stroke was noticeably smoother and my knee problems eradicated. It is so noticeable how much easier it is to spin the pedals and push earlier in the stroke.”

Rachel

“I just wanted to let you know that your advice to change from the 170mm down to the 165mm cranks has really worked for me. I made the change in August and have noticed how I pedal much quicker and more efficiently now. I used to like pushing a harder gear, but have since realised that just focusing on keeping my legs spinning fast to maintain speed saves my legs getting tired.

Last year I did my first 25 mile Cycletta event in 1 hour 53 mins and I did two 25 mile Cyclettas, one in September and the other in October, both in just over 1hr30 mins. I attribute those faster times to being able to maintain my speed easier and climb easier with the 165cranks.”

Time Trial and Triathlon

During my career, I time trialled on everything from 175mm to 180mm cranks but last year started experimenting with shorter cranks. I'm currently using 170mm (I’m 6 feet 1) and I’m considering trying going shorter than that. The theory behind using shorter cranks is as follows: Using a shorter crank means that you don’t have to come as high with your knees (into hip flexion) to get over the top of the pedal stroke. If you hip flexion angle isn't as acute, you can more comfortably lower the front end of the bike and keep the same hip angle over the top of the stroke. A lower front end and resultant flatter back should reduce your drag coefficient and if your power doesn’t significantly drop with the shorter cranks, the end result is that you go faster. The picture above is of Courtney Ogden. While this is taking things to the extreme (115mm cranks) is a good example of how the reduced crank length allows a more aerodynamic position. The time that short cranks may be a disadvantage is accelerating out of corners due to the reduced torque. Therefore may not work as well for short distance, tight and technical sprints or prologues.

Are shorter cranks for you? 

The cheapest way to find out is to book a follow up fit at Bespoke. We will recreate your set up on our Retül Müve jig and we can then experiment with everything from 155mm to 185mm. Give us a call to book a session in.

Germain Burton at Bespoke Cycling

A  few weeks ago, Bespoke had a visit from Junior Olympic Development Squad rider Germain Burton. Germain is the son of former international 6 day rider Maurice Burton who raced alongside Ian Hallam, the uncle of our lead fitter Ben Hallam. Germain famously won the 2010 BEC CC Hill Climb at the age of 15; beating riders like former national road champion Kristian House, multiple national champion Dean Downing and two time national hill climb champion Dan Fleeman. He has continued to progress and last year won multiple junior races on the continent.

Germain Burton's Initial Knee Trace

Germain came to see Ben due to a recurring pain on the outside of his knee that had been nagging on for a month. From the initial Retül scan, Ben could see that there was a rotational movement happening during the pedal stroke with the knee coming closer to the top tube on the down stroke.

Germain Burton's Final Knee Trace

On closer examination of Germain’s set up, it was noted that both cleats were set very heel in and the Sidi shoes had very little support. Germain has excellent flexibly and an incredible amount of control (when asked, he single leg squatted straight to the floor and back up). Therefore, there was no apparent need to have that amount of rotation at the foot. The cleats were straightened up and a set of Sidas custom footbeds inserted to help control the mechanics of the foot. As you can see above, this helped the knee to track in a straighter line with fewer loads on the outside of the knee.

3 weeks on and we’re happy to report that Germain is not feeling the pain on outside of his knee and was able to recover enough to attend the 6 day GB training camp last week. Germain has already been back to talk through refining his core stability training and Bespoke is looking forward to helping him towards his target at the Junior World Road Championships in Florence this September. 

The Fabulous Baking Bonts

Heat-mouldable shoes have been around for a long time, but they've really taken off in the last couple of years. Bont are at the forefront of the technology, and they've been joined by Shimano and others taking it into the mainstream.

Heat moulding essentially means baking the shoes to soften the carbon fibre sole unit, then moulding it to precisely the shape of your feet - this helps attain a perfect fit and superb support all round.

Many people are put off by the thought of doing this themselves, so we're pleased to offer a shoe moulding service in the shop. Our shiny new oven is ready and waiting - the whole process takes around 20-30 minutes, so give us a call on 020 7837 0647 to book an appointment. Just £20 per pair.

Helena's Big Adventure. Chapter 1 - Introduction

Joining the Bespoke team has been great! I have only been here a short while but have learned a lot. I see a lot of cyclists and triathletes of all levels every day. Ben Hallam suggested trying to do a triathlon myself and the more I speak with people coming in the shop, the more I want to do it. I'd like to do it for research reasons and I like a challenge too!

Being new to this triathlon "thing", I came across few things. One is that there really are no full triathlon calendars available, unless you are a member of a club. The other is that I do not know much about it. I have known few people competing in Ironman competitions and triathlons, but all I ever heard about is clocking miles and struggling to fit training in their daily routines. So I have had to read and research a bit about the sport.

After looking around I really wanted to do The Blenheim Triathlon, because I was told it's a very popular one. This, however, will have to wait till next year maybe because there are no spaces left. So I have settled for Henley-on-Thames super sprint on 23rd of June. And who knows, maybe I could do a half Iron (wo)man next year?! ;)

I have to mention that I have been ill for a while now and have been taking medication since November last year. My diet is very restricted and I had stopped doing sports for a while so I expect this will be a challenge.

I can cycle and run a bit, I can float in water too, but how to do it all together is a big mystery! My friend talked me into signing up for a 5km run on 1st of June, so I have been running a bit, however weather and health have not allowed me to train as hard as I want to. I am very grateful to my friend however, because she got me out of bed and moving. I found a swimming pool near me and have done a 200m swim now. I wanted to do more, but stopped myself, and good I did. I can really feel it in my upper back and arms, and have discovered I need to build up slowly.

I started doing yoga this year and have found it harder that I thought it would be. I used to do Olympic weightlifting, so I always thought that yoga is for people who don't want to do real exercise. I was wrong! I

admit it!

Things to do now. Keep running. Learn to swim properly. Get back on bike. And how to put it all together?

A warm welcome to LOOK

We're pleased to announce that we now offer frames and complete bikes from legendary French innovators LOOK.

We have a 566 and a 675 already in-store, with the range-topping 695 on the way to us shortly.

For more information see http://www.bespokecycling.com/brands/look, pop into the shop, or give us a call on 020 7837 0647.

Look what just arrived...

The eagerly awaited Garmin Edge 810 GPS. Just arrived today, the first stock in the UK - exclusively to us Garmin premier dealers.

We love Garmin units for their unparalleled clarity, reliability and ease of use. The new 810 takes this to a whole new level, with an improved user interface that's snappier than ever. It can even pair with your smartphone via bluetooth so that friends or relations can track you online!

We're stocking the Navigator bundle, which comes complete with mapping for the whole of Europe. £479.99 - first few in stock now, pop into the shop or call us on 020 7837 0647 to order.

Shimano Cleat Covers

We've had people asking for these for ages - well, I'm glad to say they're finally here! Shimano cleat covers - handy rubber covers which clip over your SPD-SL shoe cleats... make walking easier, reduce cleat wear, make a heck of a lot less noise when walking about... In stock now, only £15 a pair.