FRONT Magazine UK - Issue 175, 2 ^HOT^
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OPM Issue 1Editor in ChiefMark DonaldEditorTim ClarkPublisherFuture PublishingPages132Cover DateWinter 2006Release Date15 November 2006Previous issueNext issue=Issue 2This magazine is cover dated Winter 2006 and priced at £4.99.
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OPM Issue 84EditorBen WilsonPublisherFuture PublishingPages132Cover DateJune 2013Release Date10th May 2013Previous issueNext issueIssue 83Issue 85This magazine is cover dated June 2013 and priced at £5.99. A free blu-ray disc was attached which included several playable demos.
Playstation: TOM Issue 51Editor in ChiefTim ClarkEditorBen WilsonDeputy EditorLeon HurleyPublisherFuture PublishingPages132Previous issueNext issueIssue 50Issue 52This magazine is dated December 2010 and priced at £5.99
Cranks are one of the most important parts of your bike, allowing you to convert the power produced by your legs into rotational motion that drives the bicycle forward.\nCranks come in a range of lengths, like handlebars and saddles, so knowing what crank length is right for you can be a bit of a minefield.\nGiven that cranks are levers, and we know that longer levers amplify the effect of a given input force, it\u2019s tempting to conclude that longer cranks might increase your power output, but is that really the case?\nOr could using cranks that are too long actually make it harder to pedal because your joints are forced through a greater range of motion?\nIs there an optimum crank length for every cyclist?\nTo solve these and other crank length questions we spoke to Phil Burt, a leading physiotherapist and bike fitter, and Shimano, the world\u2019s largest manufacturer of bicycle components.\nWhy are standard cranks the length they are?\nThe three most common crank lengths for bicycles are 170mm, 172.5mm and 175mm. What size your bike has will likely depend on what size the frame is. Small bikes tend to come with 170mm cranks, medium with 172.5mm and large with 175mm.\nShimano and other major component manufacturers, such as SRAM and Campagnolo, do offer cranks as short as 165mm at most groupset levels, and up to 180mm in some cases. Additionally, specialist manufacturers like Rotor\u00a0make cranks as short as 150mm.\nExtra small frames (typically those with a top tube of 50cm or shorter) are increasingly coming fitted with 165mm cranks, but it\u2019s rare to see 167.5mm cranks, or anything longer than 175mm, specced as stock on frames of any size.\nHowever, given people can vary in height and leg length quite significantly, why is the typical variation in cranks across the size range for most bicycles limited to just 5 to 10mm and at those precise lengths? Is there actually any evidence that suggests this is the optimum range or is it just tradition?\nWhen we put this question to Shimano, it told us: \u201c170-175mm cranks provide an optimal balance between rotational inertia [the torque required to turn the crank], rotational speed [i.e. cadence \u2013 shorter cranks have to be spun faster to achieve the same power output and vice versa], frame design [longer cranks require a higher bottom bracket to achieve the same pedalling clearance] and biometric issues [longer cranks place greater demands on joints and muscles as the turning circle is larger]\u201d.\nBasically, Shimano thinks 170 to 175mm is the Goldilocks zone of crank length for most people and most bikes.\n\n Crank length is measured from the centre of the bottom bracket to the centre of the pedal spindle. Simon Bromley \/ Immediate Media\n\n \nHow to measure crank length?\nCrank length is measured from the centre of the bottom bracket axle to the centre of the pedal axle.\nIf you\u2019re not sure what length the cranks on your bike are, the quickest way of finding out is typically to just look at the backside of your cranks, just below the pedal axle. The length of the crank is usually engraved or printed there.\nIn the event that your cranks don\u2019t have this, you\u2019ll simply need to pull out a tape measure.\n\n\n \n Is there an optimum crank length?\nMaybe, but probably not.\nOne notable study, by J C Martin and W W Spirduso, suggests the optimum crank length for maximal cycling power production (sprinting) is \u201c20 per cent of leg length or 41 per cent of tibia length\u201d.\nHaving tested crank lengths of 120mm, 145mm, 170mm, 195mm and 220m, it also noted the highest sprint power numbers recorded in the study were with 145mm cranks, and that \u201cpower produced with the 145- and 170-mm cranks was significantly (P < 0.05) greater than that produced with the 120- and 220-mm cranks.\u201d\n\n According to one study conducted in a lab, peak power was \u201csignificantly greater\u201d when using 145mm or 170mm cranks, compared to shorter or longer ones. Simon Bromley \/ Immediate Media\nMeasuring leg or tibia length can be tricky for amateurs, and what if your precise optimum crank length isn\u2019t available to purchase? Good luck trying to get hold of 145mm cranks.\nOn top of that, maximal cycling power production isn\u2019t the main concern for every cyclist. Other considerations such as bike fit and cycling discipline can also influence choice.\nShimano believes \u201cthere is no right or wrong and no holy grail in the discussion about crank lengths. The choice for the specific length changes by application, riding discipline and the physiological background and attributes of the athlete.\u201d\nIf you\u2019re thinking about a change, then Shimano says the best method of determining what\u2019s best for you is to \u201cdefine your riding style and preferences, then use bike fitting and pedalling analysis, such as that provided by Shimano\u2019s bikefitting.com network, to study your power output at different crank lengths.\u201d\n\n Shimano believes that having a professional bike fit is the best way to determine your optimum crank length. Immediate Media\n6 simple tweaks to get the best bike fit\nGiven all of this, Phil Burt says the short answer to the question \u2018is there an optimum crank length?\u2019 is \u201cNo.\u201d\nThe longer answer is, naturally, more interesting, though. According to Burt: \u201cThere are likely wrong crank lengths for you, but not necessarily a right one\u201d.\nHe continues: \u201cBikes are designed on the normal distribution curve on height, but it makes a big assumption on the proportions of people\u2019s limbs relative to their height, and that\u2019s where issues can arise.\u201d\nFor Burt, crank length issues \u2013 such as an inability to spin high cadences, difficulty breathing, joint or muscular pain, or the rider\u2019s knees hitting the chest or handlebars when riding in an aerodynamic position \u2013 almost always stem from riders using cranks that are \u201ctoo long\u201d for their bike position or physiology.\nIn contrast, he doesn\u2019t see many problems arising from riders using cranks that are shorter than typical.\nAs you might have worked out, the likelihood that your cranks are too long for you largely depends on your leg length. This is because standard cranks make up a larger percentage of a shorter rider\u2019s leg length.\nA 175mm crank is likely to be a much smaller percentage of a very tall person\u2019s leg length than a 170mm crank is for a comparatively shorter person. Again, though, each person\u2019s individual limb proportions will be different, so it\u2019s hard to make generalisations.\n\n Crank length should be proportional to leg length, but that can sometimes be difficult to achieve if you fall at either end of the sizing spectrum. Simon Bromley\n\u201cThe question should be, \u2018are you using the wrong crank length?\u2019\u201d Burt says, following up with a neat analogy: \u201cIf I have a big box and a small box, and I ask you to jump on one of them 100 times, which one would be easier? The small box. That\u2019s crank length.\u201d\nHow does crank length affect power output?\nBut wait, surely it can\u2019t be that simple \u2013 won\u2019t a longer crank help a rider produce more power\u00a0because it\u2019s a longer lever?\nActually, no. Archimedes was correct that levers amplify an input force, and that longer levers increase that effect, but the world is not a bicycle.\n\u201cThe science is clear,\u201d says Burt, \u201ccrank length is not important in sub-maximal power production, within a range of 80mm to 300mm.\u201d\n\n According to the current scientific consensus, crank length doesn\u2019t affect sub-maximal power output. Simon Bromley \/ Immediate Media\nThe key detail is that the power you can produce on a bicycle isn\u2019t solely dependent on torque (the amount of force you can apply to the crank lever in isolation). Your power output is determined by torque multiplied by cadence.\nWhile longer cranks do produce more torque, they also decrease cadence for a given effort because the turning circle is larger.\nLikewise shorter cranks produce less torque, but cadence increases for the same effort because the turning circle is shorter. The net effect on power output of crank length (within the 80mm to 300mm range) should be negligible.\nThe only real exception to this rule is \u201csprinting from a standing start on a fixed gear bicycle\u201d, Burt says, because the increased leverage of a longer crank can make it easier to get a massive gear off the line.\n\n Due to the specific nature of the events and the kind of bikes used, track sprinting and BMX racing are disciplines where the increased leverage of longer cranks can help produce more power. Joby Sessions \/ BikeRadar.com\nEverywhere else, though, it doesn\u2019t really matter. \u201cWhen you change your crank length, you\u2019re effectively just changing your gearing. A longer crank essentially just gives you a slightly easier gear, and vice versa\u201d, says Burt.\n\u201cIf your bike has multiple gears, though, you can just change gear to compensate for that change and pick the crank length you want for other reasons.\u201d\nAre there any benefits to using longer cranks?\nWhat we define as a \u2018long\u2019 crank will depend on how tall you are and how long your legs are, but the benefits of using longer cranks appear hard to pin down.\nShimano suggests that \u201cmountain bike riders may choose a longer crank to help them generate more torque at lower cadences on steep or technical terrain\u201d.\n\n Some mountain bike riders favour longer cranks to help on steep climbs. Steve Behr \/ Immediate Media\nIt\u2019s worth noting that another solution to riding on steep or technical terrain would be to simply use an easier gear, especially now that wide range cassettes are readily available on both mountain bike groupsets and road bike groupsets.\nIt\u2019s also clear that using cranks that are too long for you or your riding position can potentially introduce other issues surrounding high cadences, breathing, joint or muscular pain, knees hitting the chest or handlebars, as already discussed above.\nSo, unless you\u2019re a track sprinter or BMX racer, there\u2019s very little reason to move to a longer crank, it would seem.\nAre there any benefits to using shorter cranks?\nConversely, switching to shorter cranks could potentially have some benefits.\n\u201cIf you struggle with knee or back problems on the bike, shorter cranks might help\u201d, says Burt. \u201cNot because they directly fix the problem, but because shorter cranks put less load on your joints and hip flexors.\u201d\nFrom a mountain biking perspective, shorter cranks also increase ground clearance, meaning \u201cfewer worries about clipping pedals constantly\u201d, according to Rob Weaver, technical-editor-in-chief of BikeRadar and Mountain Biking UK magazine.\n\n Shorter cranks mean improved pedalling clearance, both on and off-road. Andy Lloyd \/ Immediate Media\nA study on the influence of crank length on performance of cross-country mountain bikers also suggested there may be performance advantages to shorter cranks (170mm) because they improved the time taken to reach peak power with \u201cno impediment to either power output produced at low cadences or indices of endurance performance using the shorter crank length\u201d.\nAlternatively, if you race road or time trial events in an aggressive aero position, short cranks might also be a marginal gain.\nBest aero road bikes\n\u201cFor aero or time trial positions, short cranks are 100 per cent the way to go\u201d, Burt says. \u201cIf you\u2019re riding in an aggressive position using long cranks, you\u2019re going to be closing up your hip angle. This can constrict your breathing and negatively affect your power output.\u201d\nBurt also suggests there could be a small aerodynamic gain to using smaller cranks because \u201cthe smaller turning circle is punching a slightly smaller hole in the air\u201d.\nIndeed, for the Rio Olympics in 2016 the Team GB track team switched to 165mm cranks for the men and 160mm cranks for the women, in order to improve their efficiency in the highly aggressive aero positions that wind tunnel testing suggested they adopt.\nSimilarly, in the build-up to Bradley Wiggins\u2019 hour record attempt, he switched from using 177.5mm to 170mm cranks. Burt says Wiggins (who is 190cm tall) was able to improve his aero position by around \u201c3.5 per cent\u201d as a result of the increased saddle to bar drop and reduced hip closure angle.\n\n Bradley Wiggins switched from 177.5mm to 170mm cranks for his successful attempt at the UCI Hour Record in June 2015. Bryn Lennon\/Getty Images for Jaguar Land Rover Academy of Sport\nAnother noteworthy example is Canyon\u2018s most recent update to its Speedmax triathlon bike, where stock crank lengths have been reduced across the sizing range by 2.5mm, on average.\nThis follows a growing trend on dedicated triathlon bikes (which are designed purely around riding in the aero position) where seat tube angles and crank lengths have got progressively steeper and shorter respectively, compared to road bikes or UCI legal time trial bikes.\nSeat tube angles over 78 degrees are common, for example, with Canyon\u2019s latest Speedmax range offering a seat tube angle of over 80 degrees across all sizes. Contrast this to road bike geometry, where the typical range for seat tube angles is in the low to mid 70s.\n\n The seat tube angles on time trial and triathlon bikes have been getting steadily steeper in recent years. Simon Bromley \/ Immediate Media\nAs with the other examples cited, the idea is to move the rider forward and up over the bottom bracket. This helps reduce hip closure and improve the recruitment of the gluteal muscles, and there are even studies that show it might help improve pedalling efficiency, rider aerodynamics and the transition between running and cycling (if you\u2019re into that sort of thing).\nBurt has another helpful analogy: \u201cIf you\u2019re trying to stamp on something, would you generate more power if you were standing directly above the object, or if you were behind it and trying to reach it at a distance? It\u2019s the former, and that\u2019s why we see track sprinters and the like trying to get their saddles as high and as far forward as possible, within UCI rules.\u201d\n\n I\u2019ve switched to 165mm cranks on my time trial bike to help reduce hip closure and, hopefully, claw back some lost power. Simon von Bromley \/ Immediate Media\n\n \nMy experience with crank length\nAnecdotally, in the past I noticed a 10- to 15-watt difference in my Functional Threshold Power when switching between my road and time trial bike, both of which had 172.5mm cranks.\nAs a result of research for this article, and wondering if it was due to the increased closure of my hip angle when riding my time trial bike, I\u2019ve switched to 165mm cranks on my time trial bike (I\u2019m 183cm tall).\nI can\u2019t say for certain if it will enable me to claw back all of that missing horsepower, but my hip angle has opened up significantly in the aero position and it\u2019s definitely more comfortable.\nI\u2019ve decided to stick with 172.5mm cranks on my road bike because I have to review bikes as stock as part of my job, and size large bikes almost always come with 172.5mm cranks.\nPersonally, I haven\u2019t experienced any issues switching back and forth between 165mm cranks on the time trial bike and 172.5mm cranks on road bikes.\nI\u2019m perhaps not the best example though, given I once accidentally rode for a few months in blissful ignorance with mis-matched cranks on my road bike.\nWhatever route you take, Burt\u2019s advice for avoiding issues is to \u201cuse the same length cranks for all of your bikes, but go 5mm shorter on a time trial bike\u201d.\nThe latter specifically is to reduce the increased hip closure that often occurs in an aggressive aero position.\n\n\n \n What crank length should you be using on your bike?\nTo summarise, there\u2019s no \u2018right\u2019 crank length for every cyclist and or cycling application, but cyclists of all types and disciplines should be wary of picking cranks that are too long.\n\u201cFrom my point of view,\u201d Burt says, \u201cthe only downsides to switching to shorter cranks are the potential cost [if you\u2019ve invested in a crank-based power meter then replacing it may not be cheap] and the small knock on effect it has on your bike fit, but the latter isn\u2019t difficult to remedy \u2013 you just need to adapt your saddle height and fore\/aft setting up and forward a bit.\u201d\nBurt\u2019s ultimate view on the subject is: \u201cIf you haven\u2019t got a problem, you don\u2019t need to change your crank length. If you do, try something 5mm shorter.\u201d\nPhil Burt is a consultant bike fitter and physiotherapist. Having spent 12 years as the Head of Physiotherapy at British Cycling, as well as five years as Consultant Physiotherapist at Team Sky (now Team INEOS Grenadiers), he now offers his services to cyclists of all levels. For more information, head to philburtinnovation.co.uk","image":{"@type":"ImageObject","url":"https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2021\/02\/20210211_SB_5DSR_MG_3728-34b522a.jpg?quality=45&resize=768,574","width":768,"height":574},"headline":"What is the best crank length for cycling?","author":[{"@type":"Person","name":"Simon von Bromley"}],"publisher":{"@type":"Organization","name":"BikeRadar","url":"https:\/\/www.bikeradar.com","logo":{"@type":"ImageObject","url":"https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/03\/cropped-White-Orange-da60b0b-04d8ff9.png?quality=90&resize=265,53","width":182,"height":60}},"speakable":{"@type":"SpeakableSpecification","xpath":["\/html\/head\/title","\/html\/head\/meta[@name='description']\/@content"],"url":"https:\/\/www.bikeradar.com\/advice\/sizing-and-fit\/what-is-the-best-crank-length-for-cycling\/"},"datePublished":"2021-02-26T17:00:21+00:00","dateModified":"2022-01-24T14:52:52+00:00"}] What is the best crank length for cycling? How crank length affects power output and bike fit 1e1e36bf2d
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