Crank Length vs. Compact Cranks

[chessclubloser]

Here's a thought. If one was considering buying a new crank for a road bike and was somewhat interested in getting a compact crankset but also had long legs and thought there may be some advantage to getting a 180mm crank, which is the better choice? You see you can't have both as far as any (non-custom) crank options I've seen. The only company to offer the 180mm crank is Shimano and only on their Dura-Ace crank. They also have a compact crank now but it only goes to 175mm. Maybe in time a 180mm crank length will be available in a compact crankset but for now it's an interesting dilemna. Any thoughts?

[Chris Helwig]

A compact crank just doesn't give you enough of a gear for sprinting in road races and crits. 50x11 will leave you at a big disadvantage against riders using regular cranks. Success in road racing often comes down to a sprint of some sort, even if it is a sprint out of a break. A regular crank is the obvious choice, and 180mm for your leg length would be a good choice.

[Graydon]

I concur... no need for compact here in Southern Onterrible. I don't even think you need a 39 (vs. a 42).

As for crank length, with your tree trunks, IMHO you should at least be on 180's.

[SIBO]

I think that depending on your riding style would depict the crank type. If you can spin and that is your riding style then why not go compact. There is no gear overlap like in traditional gear set up. If you are racing Track, Mtn and road wouldnt it be better to race and train the same gearing? Here is an example...53X11 is 130 gear inches 50X12 is 113 gear inches. Basically how far you will go with one turn of the crank. Wow looks huge......27 inches per revolution...... Rider A does a minute sprint at 60 rpm and depletes his glycogen rapidly and reaches 37 kph. Rider B spins up to 90 rpms and reaches 49 kph and gets there faster with less effort and using less muscle glycogen. Can he maintain for a minute , sure he can because that is how he trains... will it work for everyone, maybe not but if you can spin high cadence and that is how you train and race give it a try. If you are a heavy rider and suffer on the climbs, even around here, why not try it. Its only money, Shimano makes an Ultegra verson that is compatible with your front derailleur. Limited length. My thoughts are dont knock it until you try it, I will be a guinea pig and try it this season.......

Sibo.

[Graydon]

That argument assumes A sprinting at 60rpm and B sprinting at 90rpm. What rpm do most people sprint at in reality? If 'A' and 'B' both have a maximal sprint somewhere in the range of 120rpm, then it all comes down to power, and power will dictate which size of gear you can push.

You have a point... if it were all about the biggest gear you can mash, why aren't more people riding 60x11? But on the same note, if we talk about gear-inches, why aren't juniors on restricted gears keeping them when they move up to senior races? Why aren't pros riding compact (ok, except for the really, really steep mountain stages). Locally, Vinnie D is one of the best spinners I know and has a well honed sprint from all that track work, but in the club races come down to the wire, it's bye bye junior gears! Will he be losing the junior gearing this his first debut season in senior?

[SIBO]

Peer Pressure, He will dump the Junior gears like a Celibutt girlfriend... Not sure the spelling on that but it looks good. Again, age,training, adaptation all come into play...Who you are racing, where you are racing. Ben Johnson almost beat the guy on the horse.... Every year in Lisbon there is a race downtown between a guy on a donkey and a Lambroginni..... the guy on the donkey wins most of the time. Conditions , traffic, mindset, when the conditions are perfect and you have a perfect day anything can happen. 200 meters to the finish...... break a chain, miss shift, flat, get bumped and go down, a 100 k race is only 200m long if you think about it. If you arent in the top 10 for that last sprint all the gearing, the 14 lb bikes and podium girls mean nothing.... Enjoy the whole race, the tactics, the snot missles, and feel good to race another day....
Sibo

[Chris Helwig]

I would estimate 90% of Ontario races come down to a sprint, either from a breakaway or from the bunch. Solo wins or wins up climbs are very rare. The Vinnie D example is a good one. He sprints well on the track, can smoke me in a sprint with track gears, but in a club race when he has a 52x14 and I have a 53x11 I can win the sprint pretty much 100% of the time. You must be able to sprint to win, and I gaurentee you you won't win much with a compact crank. Race Liege Bastonne Liege maybe a compact is good or up Caesars Head in SC, but Ontario racing a compact would be a poor choice at best.

[SIBO]

Yes you are correct. A word keeps comming up....WIN. What does that mean? At best most of us might win a club race. Ill never win an ocup road race, unless the pack goes down and I ride through . Vince kicks ass on a level playing field with the gears he has been training on, What ever gear he trains on for this season the harder he trains the faster he will go . You cant sit in on the track and rest the whole race then win. If he keeps up the track and races the road with Big Boy gears he only has one foe... the mental game. The seasoned racers with their games and tactics will wear him down like an old pair of jeans. Elite racers need gearing to match their aponents. Use them wisely you win. Us average guys- Winning? its about feeling good about yourself and the thrill of competition, win or just finish. 10th or 50ith its the same amount of points isnt it? 404's and 20ith place, ksyriums and 25th or alex295 and 40ith place, same points same fun and same payout---a good time. I think the elite guys win or lose through tactics, missed chances and slow reaction and good day-bad day as apposed to equipment. If Graydon is winning most club races if he was to switch to compact cranks I still think he would win most club races because it takes more than just gearing to win, he would adapt his breaks,sprints,climb tactics to do what it takes to win . Floyd use to ride his mtn bike and gord frazer couldnt touch him ... in the early days. Same with Roland Green. What ever you are comfortable with ...

Sibo

[Chris Helwig]

Even if your goal is to have a decent placing and have fun, being able to sprint more effectively at the end will leave you with a higher placing and more enjoyment. If you are sprinting for 30th on compact cranks, using regular cranks you may be able to sprint for 20th, wouldn't that be more enjoyable? No matter who you are you have to sprint in most races to achieve what you relatively think is a good placing. If Graydon raced on compact cranks in club races he would still win some races, but certainly not as many. Even if he was in a break of 4 riders, unless he can solo off the front he needs to outsprint the other 3 at the end. Even Graydon on Compact cranks wouldn't win as many sprints even out of small groups. If you are a newer rider, don't produce much power or a heavy non competitive rider compact cranks make sense. If you are a competitive cyclists racing they don't.

[SIBO]

Yes for sure. Or a Tri or Du dude might get more adv on them....

[Chuck Norris]

Crank arm length and gear ratio are two different discussions.

Arm length is trading off leverage for cornering clearance, acceleration, and saving your knees. If you're looking to churn a low cadence with no regard for acceleration or strain on your knees, longer cranks are where it's at. If you're jumping out of a corner and winding it up fast, shorter arms will be of benfit.

Some would argue that compact gears are a marketing solution to a problem that doesn't exist. At least not to anyone racing in this province it doesn't. If you're competitive, compact gears can be a slight disadvantage. We're only talking about a few teeth (6%) difference. To some, this increase in cadence would be a big deal.

All this 60x11 talk is getting me excited.

[chessclubloser]

Crank arm length and gear ratio are two different discussions.

Arm length is trading off leverage for cornering clearance, acceleration, and saving your knees. If you're looking to churn a low cadence with no regard for acceleration or strain on your knees, longer cranks are where it's at. If you're jumping out of a corner and winding it up fast, shorter arms will be of benfit.



Before I disagree, yes, crank length and gearing are two different discussions, read the first post and you'll see what the argument is. Now, maybe I'm reading the above quote wrong but it sounds like your suggesting that longer cranks are worse for accelerating, when actually it's quite the opposite. They give you a longer lever arm, thus meaning that with the same amount of force on the pedal you can produce more torque which (all else being equal; cadence and gearing) will produce more power. Also, longer crank arms aren't bad for your knees... necessarily. It depends on what length suits your femur/leg length and riding style. I have a 36.5" inseam (rather long) and could most likely benefit from longer cranks. But if you have short legs then having longer cranks could be bad for your knees, just the same as having rather short cranks and long legs could also negatively affect your knees.

The argument suggested in the original post is whether a person with long legs should go for a long (180mm) crank or compact gearing; seeing as you can't have both. There is currently no manufacturer I know of offering 180mm crank arm length with the 110mm bcd needed to run compact gearing.

I think Chris makes a really good point. When racing in Southern Ontario there is minimal, if any, time spent in the 39x25 or 39x23 gear let alone needing anything like a 34x23. But there are advantages to having a 53x11 or 54x11 gear at your disposal, especially if your a more powerful rider who likes to sprint.

[Chuck Norris]

To answer the original post - I'd agree. If you're racing, 180 53x39(or42) would be a better choice than 175 50x34.

Regarding length vs acceleration. A longer arm does equal more torque, but it also equals a larger circumference of travel for your pedals/feet/legs. Plus, you'll be the last guy on the gas out of the turns (Hershey Centre anyone?). A google of "bicycle crank length acceleration" will give you a whole pile results where the conventional wisdom is that shorter cranks = faster acceleration. It's counter-intuative.

I smell a horsepower vs. torque debate coming.

[chessclubloser]

How come the convention among BMX riders is to use longer cranks? On every site I checked that had something on bmx crank length, they suggest that a rider with a 28" inseam (rather short) use a 175mm crank (about the median stat) and it goes up and down by about 10mm from there. In most of the articles I read, they even mentioned that they weren't quite as good as spinning high cadences but since the 'holeshot' is the most important part of a bmx race, acceleration is key.

[Graydon]

We have two separate issues here, pedal acceleration and bike acceleration.

Bike acceleration is solely the product of the Force acting on the mass of you + your bike. More torque applied to the chain = more force, and therefore longer cranks = more force = faster acceleration for unchanging mass no matter how you slice it.

For pedal acceleration, remember we are going in circles here, and it isn't appropriate to speak in linear terms. We must use angular acceleration/velocity, which is degrees/second (per second). Thus, two riders pedalling at 90rpm, regardless of crank length, have exact same angular velocity. Change from 80rpm to 120rpm in 4s, and still, the angular acceleration is the same regardless of crank length.

The question then becomes, does crank length affect the RIDER'S ability to maintain a given angular velocity (i.e. 90rpm) or does it affect their ability to accelerate, say from 80-120rpm for a sprint. The answer, you will find, varies between individuals. It will depend on bone lengths, joint angles, seat height, and muscle fibre. For some, especially larger riders, they will do better on longer, and vice-versa. Purely from a physiological standpoint, if every race was a flat (or constant uphill of light grade), we'd all be on 220mm cranks pedalling 60-70rpm.

As for pedal clearance... if you are worried about 5mm, you'll probably be hitting your pedals just as often on 175's. I doubt the cornering precision for anyone is less than half a cm. "Pedalling faster" coming out of corners with shorter cranks is just not correct either when you do the math on it. Remember, most 170, 172.5, and 175 cranksets all use the same length crank arm just with the hole for the pedal axle punched +/- 2.5mm from the 172.5mm spot.

[Chuck Norris]

This is getting really nerdy! Awesome! Breaking out my slide rule and making a few assumptions:

Q factor of 140mm
BB height 273mm
Pedal axle length 60mm

I get a max lean angle of about 37 degrees on a pair of 175mm cranks and about 35.5 degrees on 180mm cranks - unless I've botched it. Some would argue that this is significant. Others not.

I can't answer to the BMX analogy.

OK. Let's get into horsepower vs torque!

[Graydon]

I think you got the math right based on those numbers. On my specialized with 180mm cranks, the distance from the centre of the bike to the outside edge of the pedal axle (the outermost point that will contact ground first) is ~140mm. The height from the ground to the bottom of the pedal at this point is about 80mm. Thus: cotan(80/140) = 30 degrees. For 175mm cranks: cotan(85/140) = 31 degrees.

So I guess the argument remains, is 5mm, or ~1 degree, meaningful? I won't deny it isn't... maybe it also depends a bit on how you ride. Do you countersteer the corners? Do you lean the bike (motoGP style) or lean the body (motocross style)? I'd argue bike geometry (pedal style/length, BB height, Q-factor, wheel base) will affect your ability to corner a lot more than a 5mm change in crank length.

Anyone have an idea what the typical variation in BB height is among different bike manufacturers? That might be useful info to know for someone who rides crits vs. time trials vs. road races... or anyone wanting to play around with longer cranks!

[Graydon]

...And torque is force applied at some angle and at some distance from a point of rotation (i.e. longer the distance, the greater the torque). Power (prefer watts over horses) is force (resolve the vector components of the torque) x distance (angular displacement) / time.

Refresh my memory, what was the argument here?

[Graydon]

Sica and I were talking about this in more detail... and I must admit I was wrong. After doing the math, I take back what I said about compact being too "small" for around here:

If you calculate the gear inches, a 50x11 is actually a bigger gear than a 53x12. So if you never normally use an 11T with your standard 53-39 setup, you could actually get a bigger range (better low end and a higher top end) from a compact crankset with a 50-34/36 and and 11-23, but ONLY if you changed your cassette to an 11-23. If the biggest you have is a 50-12, that is only marginally bigger than a 53-13.

However, the fact still stands if can push a big gear or if you value being able to wind it up in the final straight, a 53x11 is still bigger than anything you will get in a compact. A 54x11 might not even be too big for a flat finish around there parts.

You can play around with the different combo's here:

http://www.sheldonbrown.com/gears/

[SIBO]

Right on Brother.......

[Ted Velikonja]

A little advice Graydon, even if you are, never say "I'm wrong" and "Sica" in the same day let alone the same sentence.

[SIBO]

Ceramics & aerodynamics: FSA powers into 2006

Ivan Basso (R) visits FSA's new European HQ
Photo ©: FSA

Compact chainsets like the K-Force MegaExo
Photo ©: FSA

The Plasma handlebar and stem
Photo ©: FSA

The Platinum Pro Megaquad bottom bracket
Photo ©: FSA

The RD460 wheelset
Photo ©: FSA

The speedy RD488 wheelet
Photo ©: FSA

Dedication to innovation and quality has seen Full Speed Ahead grow to become a major bicycle component manufacturer. For 2006 the company is focusing on ceramic bearings, improved aerodynamics and its trademark compact cranksets to steam away from the competition.

By Cyclingnews staff

The driving force of bicycle component maker Full Speed Ahead is well captured in their name. FSA stays ahead of the competition through design innovation and manufacturing expertise. FSA's manufacturing base is in Taiwan, but they are truly a global company, with offices in the USA & Italy that collaborate to direct FSA's component development. FSA offers solutions for speed across a broad range of bicycle components; from headsets to wheels; cranksets and bottom brackets, Vision Time Trial & Triathlon bars and handlebars & stems.

A particularly interesting product from FSA to be launched for 2006 is the K-Force MegaExo Compact chainset. CSC's Ivan Basso used an FSA SLK Compact chainset with 50X36 chainring combination in last season's Giro d'Italia and Tour De France, riding to stage wins in the Giro and a superb runner-up spot behind seven time Tour winner Lance Armstrong in France. This marks the first time a rider using a compact chainset equipped bicycle has been on the podium in a Grand Tour.

FSA is a strong believer in the compact crankset, Doug Stuart of Full Speed Ahead told Cyclingnews that "a compact crankset is about 15% lighter than a triple set, and weighs 50 grams less than most non-compact double chainsets. And we find that the smaller, more rigid 110mm bolt circle diameter is simply a more efficient platform for pedaling. The Q-Factor is the same as a standard double, yet another advantage over a triple." FSA's K-Force MegaExo Compact chainset uses outboard bearings and an oversize spindle that is stiffer and lighter than most cranksets, which provides optimal power transfer for the rider. That's why Ivan Basso has already made the switch for 2006 to FSA's K-Force MegaExo Compact. And to make for the smoothest shifts possible, FSA has also developed a front derailleur specifically designed for compact cranksets.

Another key initiative for Full Speed Ahead is the introduction of ceramic bearings.

For the last few years, Full Speed Ahead has been working with their extensive array of sponsored teams to test, improve, and refine an often neglected product that can provide significant performance advantages. FSA's Claudio Marra explained to Cyclingnews that "our testing shows that ceramic ball bearings are 20% more rigid, 10X rounder and 60% lighter than standard steel ball bearings, which reduces friction. We have found that using ceramic ball bearings can provide speed increases of up to 4%, or a forty meters distance gained over every kilometer."

FSA's ceramic bearings are not actually ceramic; they are made from pure, solid silicon nitride balls that are mounted in hi-spec carbon steel bearing raceways. To make them, the manufacturing process is long (70 days), complex and expensive. "First off, the ceramic powder is synthesized and pre-treated. Then the silicon nitride material is stamped into spheres, sintered, then specially ground and worked into a perfectly round shape before final assembly." But the cost is worth is, as Marra points out, the performance advantages and longevity (ceramic bearings outlast steel bearings by 5-20X) are real. Marra then explained that "we combine these ceramic bearings with super low-friction seals and a special lubricant in an optimized system; the advantages are hard to see with the naked eye, but you can tell on the bike."

Ceramic bearing kits are offered for FSA's own products, like the MegaExo crankset and RD-400/488/600/800 wheel series but also for many other brands of bicycle components.

FSA's Doug Stuart told us that "our ceramic bearings are a big breakthrough so we decided to make them for brands like Mavic, Zipp, Spinergy, Campagnolo Shimano and even Lightweight carbon wheels. Plus we offer ceramic bearings for Campagnolo Record and Chorus bottom brackets and even derailleur pulleys."

FSA is also busy creating a focused range of high-performance wheels that are designed and built as an integrated system. Perhaps they haven't received the attention they deserve but, like other top FSA products, they benefit from advanced materials and relentless attention to detail. FSA's top of the range wheelset for 2006 is the RD-488. This wheel is a real racing weapon, with a 50mm carbon fiber tubular rim laced to 20 spokes in front and 24 in back. FSA's RD488 wheels don't have just any old aero spoke, but custom drawn Wheelsmith AE-14 spokes. FSA specially designed these spokes to have not only a fast aero profile, but to also to absorb road vibration.

No wheel system could stand without a hub, and FSA's RD488 wheels have specially selected quadruple ground and polished bearings and special end caps that seal them shut no matter what the weather. FSA attention to detail is evident in features like the radiused flange holes that provide 100% support to front & rear spoke elbows. And all of FSA's 400 series wheels have hubs with a clever mechanism where the entire internals can be removed with two 5mm allen keys. Plus the FSA's RD488 wheelset can be upgraded with a ceramic bearing kit if you need even more speed. Another addition to FSA's 400 wheel range is the RD-460, their first high-performance disc-brake compatible wheel. Suited for cyclocrossers who don't want to mess with tubulars but want the safety and security of disc braking, these new hoops have 24 Wheelsmith 14 gauge butted spokes front and rear.

As seen on the Cannondale six13 of Gilberto Simoni as he battled to second place at this year's Giro d'Italia, FSA's new Plasma carbon fiber integrated bar and stem are now available.

This sleek, swoopy steerer is light and stiff; just the type of upgrade that can make a bike special again. Plasma is available in three widths (40-42-44) and four lengths (100-130) that will fit almost any rider. Another FSA stem that is clearly race proven is FSA's 100% CNC machined 140 gram OS-115 model, used by speedy sprinter Robbie McEwen as he rode his FSA bar & stem equipped Davitamon-Lotto Ridley to two stage wins in the Giro d'Italia and four in the Tour De France. Yet another FSA stem that is clearly a standout is the new for 2006 OS-150, forged and CNC finished for high-strength and light (155 grams) weight.

Throughout the incredibly comprehensive range of Full Speed Ahead bicycle components, the evidence is clear. Where other manufacturers often choose to focus on just one material, FSA looks for the right material application for the right job. They use three grades of carbon fiber, four different grades of aluminum and three diverse types of steel to create Full Speed Ahead bicycle components. Doug Stuart summed up FSA's philosophy up by telling Cyclingnews that "We work with our advanced engineering capabilities and then integrate the key input from all our sponsored riders, from Ivan Basso and Robbie McEwen to mountain bikers like Gunn Rita Dahle, Christof Sauser and our Gravity guys like downnhill rider Sam Hill, just to name a few. FSA then uses our state of the art manufacturing to create great possible components. That way, when consumers choose FSA, they know they are going to win with us."






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