Hope Say Their Super Short 155 mm Cranks Are 'The Sweet Spot'
Last year we covered the surprisingly strong scientific evidence that, despite popular opinion, shorter crank arms don't compromise a rider's power output or pedalling efficiency, and in fact, may offer certain biomechanical advantages when compared to typical 170 or 175 mm cranks.
After making shorter cranks for e-bikes, Hope Technology have been experimenting with crank lengths over the last year with staff and athletes, going as short as 140 mm. They say that 155 mm is "the sweet spot" for mountain biking. As a result, a 155 mm version of their Evo crank is now available to buy.
You know it's science when there's a diagram.
 | "The main benefit for gravity orientated riding is it allows you to get a more neutral body position on the bike allowing your hips to rotate to be more forward facing, increasing stability and having greater control of the bike." |
Hope Say the shorter cranks offer the following advantages:
• "Body weight remains more centred on the bike increasing stability and making it easier to shift your body weight around."
• "Quicker to 'spin up' which can help when transitioning from descending to sudden steep uphill features." (This claim is supported by this study).
• "More ground clearance for reduced pedal strikes."
• "Lighter and stiffer due to shorter length."
Other than the length, the specs remain the same as Hope's other Evo cranks. They use 30 mm diameter axles with axle lengths to suit most bikes from XC, DH, SuperBoost and Fat bikes.
Because shorter cranks reduce the overall leverage between the pedal and the tyre, requiring a faster cadence, Hope recommend dropping your chainring size by 2 teeth for every 10mm reduction in crank length. So, if you'd normally run a 34-tooth chainring with a 175 mm crank, you'd want a 30 -tooth ring with a 155 mm crank. Hope make chainrings as small as 28-tooth. Note this will also increase ground clearance when the cranks are level.
The Evo 155 is in stock at dealers now.
Pricing (RRP)
Inc. Axle and Spider: RRP £290 / €360 / $365 (ex tax)
No Spider: RRP £255 / €320 / $320 (ex tax)
For more information, go to hopetech.com.
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This has been my advertising shtick for years!
basically, it should be height dependent, like wheel size should.
Kinda like the more reps at lighter weight vs fewer reps at heavier weight debate
Not necessarily better or worse, but definitely different.
disclaimer: i just smoked a bowl.
What shortening cranks does is different. It's like going from 10 full reps with 10 pounds, to doing 20 half reps with 10 pounds.
Per the article linked from this one: "In other words, riding with shorter cranks requires a faster cadence (and longer cranks a slower cadence); but with the right cadence, the crank length doesn't significantly affect the metabolic cost of pedalling at a given power output."
Spinning is winning.
The benefits are numerous, IMHO, from the fewer pedal strikes, the having your feet closer (I would think anyone with a moto background would appreciate, less knee bend angle, etc.
Doesn't take long to adapt.
My 165 XTs are still fairly new - and weren't easy to find - so I will hold off on going shorter, but I sure as hell won't be going longer ever again.
But people who move slower, but can generate more power in that timeframe, how does this help them?
I'll use track sprinters. All studies show that everyone has the exact same leg speed when running. But...the difference between you and Usain Bolt is how much force he is generating at push off of each stride that propels him forward.
Knowing that, how does it apply to guy with a bum knee riding 175mm cranks and a 30 tooth ring ?
Making him switch to 155mm cranks and a 28 tooth ring...I just don't see it being of any benefit. You're pulling 20mm of leverage off a guy who can't generate much force to begin with and removing the leverage he depends on to get that 30 tooth up a grade.
Drop him to a 28 tooth ring with that bum knee, you've taken away a relatively large 20mm mechanical advantage and given him an only slightly smaller chainring to turn...but he has to turn it faster and at more repetitions to do the same amount of work.
That sounds like agony to my bad knee.
So when you say "he has to turn it faster and at more repetitions", you're right, but you're forgetting (or glossing over) that now instead of moving your knee through a certain range of motion, you're moving it through a smaller range of motion. And according to the science, the human body is similarly efficient in both scenarios.
So the question is would you rather do 10 full squats on your bad knee, or 20 half squats? It probably depends on the person, and what's going on with the knee.
For me, I'll take the clear advantages of my 145mm cranks (way way way fewer pedal strikes), knowing that the science indicates that I'm not losing any significant power.
*** not a medical professional and may be talking completely out of my ass.
Comparing the same power output and pedaling force, you're spinning a longer crank slower and bending your knees more than with a shorter crank.
To make an educated guess as to why crank lengths have been consistent over time, take the related example of wheel size: 26 was the standard for mountain bikes for a long time before people started experimenting with bigger sizes. What I would call 'market inertia' - the tooling already exists, everyone is making money and not looking at a high-cost way to differentiate their product - made it easy for companies to keep the same wheel sizes. In other words, no one had to think about it, so they didn't. Once somebody starts looking into it and advocating for different options (Canfield in the case of short cranks), then others start following.
Not arguing against the quasi-science, just applying it to my bones.
I'm not short, I'm 5'9", but the first time I hopped on a bike with 175mm crank arms I felt like something was off. I didn't like it at all. I kept them because I was poor at the time and everyone said you pedaled more efficiently with them, but that most likely isn't true.
Anyway, I really can’t tell any difference between 170 and 175 in terms of just pedaling the cranks. I rode 170s on my trainer and had to check what size they were. Definitely no loss of power.
I’m not opposed to giving shorter cranks a try, and I’m kind of curious. But I think they would have to be at least 160-165 before I could register any difference. Other than fewer rock strikes, what do you feel the advantages are?
Glaring typo - should be "DON'T compromise." Also, pedal (one L) ing.
Not to nit-pick, but the entire point is negated without NOT in there. Is anyone reading articles before they're published?
You could have them all quick/master links if you wanted. Berm Peak did it, worked great, but $$$.
But you also have to use lower gears, & spin gears faster to gain same power output!
take 2 6ft tall sticks and make them touch at the top and put their bottoms on a flat surface and seperate their base by 350mm(175mm x 2). now measure the height. the answer is that it is only 1/3rd of an inch shorter than 6'. now do the same for 165 cranks and you get a delta between the two of .76mm.
so it does change the CoM, but only be the length of your penis.
(sorry, that joke was the entire reason I did the math. don't @ me. LMAO)
Idk I built a track bike with 165s, I'm low posting af on that thing, and 50+ miles on that thing is less painful on my knees than my road bike where I can coast. All confusing, but my road bike has 175s - not saying short cranks are better for your knees, but I think the whole leg extension thing has more to it than ppl think.
MTB community: BLAH
HOPE 10 years later: short cranks sweet spot with colorful chart
MTB Community: Innovation
That and more bikes have been coming with shorter cranks than in years past. People are more accepting now, because they’ve been on shorter cranks.
I can feel my way climbing up a rock garden better with this combo.
Maybe it doesn't match what the adverts, but its my experience.
www.youtube.com/watch?v=WPOZbG7ibEE
Unlike with road biking where I'm in the same position for hours, on the mountain bike I'm all over the place anyway. Difference cadence, different body position. Shorter cranks seem like the least of the changes going on.
Maybe my pedal strikes were due to bad form. I'm willing to accept that. Regardless, problem solved. 155 seems a cm too far for me, just because it's no longer necessary. Then again, a crankarm weighs about 200g, so shaving 1/16 off two of those is a solid 25g savings!
I think part of this is profit driven...hey we can make the cranks use less material, ship more in the container and charge the same price. Now how can we convince them this is a good idea? Get on it VP marketting.
Yes - short cranks spin up faster, makes sense. No way to the claim that short cranks have same power, the longer lever has more power. This is why they suggest smaller chainrings- you can’t push the same gear up a hill with 155mm cranks thst you can with 175mm.
Also running 165mm on the regular bike, looks like those are obsolete now?
Also, the stance isn’t exactly wider with longer cranks. It’s purely more hip and knee flexion. To be wider, your pedals would have to wider. Hope that makes sense.
See also their claims about the Pro 4 flanges being fractions of a mm wider and how that would be a huge improvement on wheel stiffness (despite then changes only affecting spoke length requirements by about 0.2mm for most), then making their own narrow hub standard for their first complete bikes.
I just find it hard to believe anything they say, no matter how many colourful charts and infographics they make. See also: Magura.
The thing with the length vs. stability for me is that if you have someone stand in front of you try to push you over, your feet being spaced further apart fore-aft will make it easier to resist than having your feet closer together. I know that's not a parallel for riding, but in almost all instances extra width improves stability (to an extent obviously, we don't all need 820mm bars).
Even 34T /52 is almost unridable, tough to balance if the cadence is low.
26T /52 doesn't have to be slow, if the cadence is fast enough.
26T/50T is so low a gear that you’re spinning like crazy, but going so slow that you’re wobbling around. 26T/52T needed for 155 cranks would be unrideable.
I have 2 quick links in my chain because I tried a smaller (oval, too) chainring and shortened the chain for it but didn't like it, and a second quick link is the easiest way to put the missing one back.
In the era of dropper posts, shorter cranks make a ton of sense. Prior to droppers/2010 or so, the reduced saddle to crotch clearance descending was just too much to deal with.
I actually built some bikes for super short cranks for tests (published in Mountain Flyer about 6-7 years ago. They were pretty great and there wasn't a power output disadvantage, but it was too hard of a sell for most people.
How are frames designed around cranks? Beyond having a reasonable minimum for BB height?
"but it was too hard of a sell for most people"
Ok, but why? What did they not like?
Your stance does get narrower, which does mean you get a little higher. But not much. Going from 175 mm down to 145 mm cranks, you would raise the saddle 30mm, but only end up 10mm higher up when standing (based on a 30 inch leg length). Meaning you've lost 20mm of clearance.
Did you go for +20mm on a 27.5 fork, or did you stick to the 29er fork? Or something in between?
And did you go to a super small chainring? I'm considering a 28 tooth combined with an e13 9-45 tooth cassette to get some ground clearance back.
Sorry about all the questions, just excited to hear from someone who tried something similar. Hopefully your username isn't referring to this particular setup
...unless you really need the slightly lower stand-over, or lower stack...
So 180/165 full 27.5 it is.
This is for my park/shuttle/winch and plummet bike. I am planning on getting a lightweight trail bike with 29er tires to cover the rest. Crank length on that bike is TBD - probably in the 155-165 range, depending on the BB height of the bike. All of this depends on how the full 27.5 conversion goes. If it's more versatile than I'm daring to hope, it could end up being my only bike.
The stance being shorter makes a tiny difference but it's not enough to worry about.
If you want to test what it feels like on a rigid post bike, you can just wait until the top of a downhill that doesn't require any pedaling and raise your saddle 20mm and see how it feels. You probably won't like it much, and that's why nobody really tried to use shorter cranks on mountain bikes in the 80s or 90s or 2000s.
With a dropper, of course, it's no problem. But those weren't common prior to 2010 or so, which is why we're all still on the same 175mm cranks still - the bike industry moves slow.
-W
Considering how many times I've heard bike fitters mention how common it is to see too high of a saddle and the associated hip rocking, robbing people of power, and potentially causing joint damage... well, perhaps not needing to send the saddle sky-high to make it feel good at max flex is a good thing overall.
"If you want to test what it feels like on a rigid post bike"
I don't want to. I have droppers, I will always have droppers, and shorter cranks often allow the use of a longer dropper: since the top saddle height is higher you're that much further away from having to fully slam the post.
"wait until the top of a downhill that doesn't require any pedaling and raise your saddle 20mm and see how it feels."
I have. Yes it's weird, but less weird with 180+mm of drop, even it's kinda like 160-170mm since that bottom height gets raised. But it's not world ending, can be gotten used to, and again, matching the saddle raise to the crank shortening numbers exactly is not always necessary.
I know I mentioned droppers a lot, but that's because if you're high-medium-posting with a rigid post, maybe short cranks just aren't the right fit for that ride style any way. Many of the benefits of super short cranks, like better/easier bike-body separation, easier to get real low without burning up your rear-ward calf and glutes, etc, just don't matter as much if there is a tall saddle in the way.
I ended up getting a new patrol, because that’s basically what I wanted from my sentinel, and the 29er up front is great for taking the harshness out of brake bumps.
But if you love a full 27.5 setup I think Frankensteining a 29er is a really viable option. Enjoy!
I built up the rear wheel yesterday. I will see how I like the mullet and then maybe make the move to full 27.5
As for the small chainring, I may end up running an e13 helix gravel cassette with a 9-45t range to help. Something to consider.
You really need to try doing a sustained ride with with short cranks with your normal (for 170/175 cranks) saddle height, then try the same ride with the saddle raised to get full extension. I think you'll find out quickly which you prefer.
-W
What did you find to be a good bottom bracket height with shorter cranks? Did you find yourself able to lower the BB as much as you shortened the cranks? Or did you find that if cranks get 20mm shorter you can only go, say, 10mm lower? Pedal strikes don't always occur at the very bottom of the pedal stroke, so I'm wondering what you found to be a good compromise
In theory, you could put 110mm unicycle cranks or something on a mountain bike and run a super low BB, and while your pedal strikes wouldn't be a big problem, you'd wreck your chainring/chain unless you ride really smooth trails.
Overall, though, you can basically drop the BB about the same amount as you shorten the cranks.
edited to add: unfortunately in this article, it does not state if this applies to every inseam and leg length or just the average. Hard to say that everyone should ride one crank length. Kinda how we don't recommend everyone ride the same width handlebars.
Think of shorter cranks like you might think of a shorter whitewater paddle: back in the day, whitewater boaters used really long paddles, > 195cm, but over time the paddlers found that using a shorter length improved efficiency and increased cadence.
Too ess as ch their own, but I learned about short cranks years ago while riding muni, found 150mm cranks to be the sweet spot, so no surprise that prefer the same on a bike.
For perspective, I’m 6’ tall, riding 150-160mm cranks on all my bikes.
However, I bought their GXP BB to go with it. Just like your experience - HOT GARBAGE. That BB was trashed in 3 months. Cleaned it and repacked perfect and the cranks still had play (torqued perfect) and sounded like gravel. Disappointing. Never reached out to see if they could help me, but maybe I should have.
I just bit the bullet and found a decent deal on a Chris King GXP BB and have been happy days ever since. Noticeable reduction in drag.
Having such a small range of crank lengths available is more convenient for bike companies but worse for riders.
I am now trying to find 165mm cranks for my road bike. The 172.5s feel absurdly long.
And being more forward does make sense in terms of balance with how much longer frame reach is.
And shorter makes sense with lower bottom brackets.
So if all other things are equal (and I'm not arguing they are or aren't), this otherwise makes good sense in keeping up with frame design.
Now... on an eBike it makes sense. And with the direction eBikes are going with the likes of that TQ motor... I may actually own an eBike in the next 5 years.
Reality: Our marketing team
The fact, is that everybody has different length legs, different amounts of flexibility and different sized feet, and therefore require wildly different crank lengths. Shimano produce cranks for their world tour teams in almost limitless incremenets for this exact reason.
If you turn an ignorant blind eye to all the well documented facts about bike fitting, sure, everybody needs 155, but otherwise it's just absolute nonsense.
At my local gymnasium, I am regularly engaged in activities like heavy, weighted lunges, where my feet are nearly 3' apart, combined with 170 lbs of added resistance and knees/legs articulating asymmetrically. Low an behold, my hips are scarcely rotated, even in this extreme condition.
Now, what I would buy is that shorter cranks would allow frame designers to lower the BB by 10-15mm, which would absolutely have an impact on trail performance.
Obviously, my legs at 6'4" do different things to someone whos 5'nuthin. We ride different frame sizes, so why not anything else?
annoys me that a taller rider just gets their seatpost extended (basically), so where a shorter rider is balanced centrally on a bike, a taller rider is sat on top of it, weight pushed forward over the bars more. This was massively mitigated with the advent of longer travel 29ers. A few companies have dabbled in connecting wheel size to frame size, but i think it should be the norm', along with bar width and crank length.
I switched from 175 to 170mm cranks and will never go back, but I tried once 165mm and everything was just too twitchy.
Are short cranks trending in XC???
Another study quoted in the link above for "female XC riders. Macdermid found that riders reached their peak power nearly 1 second quicker on 170mm cranks than they did on 175mm cranks." This was also done in a fitness lab on a stationary bike. iAlso female XC riders have shorter legs on average than your average male. So this could easily be a confounding variable that was not take into account.
I will grant that shorter riders may benefit from shorter cranks. I'm 6' tall with a 36" inseam so for me I don't get knee or hip pain from spinning 175s but I see how some people could. Less pedal strikes would be nice. shorter cranks hit rocks less. If you like shorter cranks I'm happy for you. I am interested in sharing peoples experiences with different crank lengths on pinkbike. I think the current science does not represent real time riding conditions and thus it's conclusions are incomplete at best. I think people should have a wide variety of crank lengths to choose from. It's just not as simple as 175,165 or 155 are best.
The article you posted a link to concludes with "Don’t let others decide what size cranks you should use." I agree.
Lets get Levy back on the impossible climb on the same bike with different crank lengths for some real pseudoscience.
Hear Hear!!!
Yea, I basically agree with you, and ultimately choice is good. I only shortened mine on one bike that was really bad with the strikes, not for any knee or efficiency issues. With todays low BB and big BB drops, designing around shorter cranks with the knowledge that they likely won't actually cause issues, could be a great thing.
2 your 12 speed cassette will become redundant because in the easiest gear you’ll be spinning like a cat on acid
3 smaller derailleur cages could make a comeback - a positive
4 - 10 speed even 9 speed cassettes could make a comeback - positive
Personally I’ll sticking to 165mm & 34 tooth chainring
Not convinced
www.pinkbike.com/news/bike-check-remy-mortons-chainless-mini-mullet-park-bike.html