VendettaRich
New Member
Has anyone switched to the 145 cranks? How do you like them?
145 mm cranks
- Thread starter VendettaRich
- Start date
VendettaRich
New Member
What do you like about them?
Boreen bimbler
Member
I swapped my GRX 170mm for some 150mm a while ago. I find 150mm a lot better. They just felt right straight away to me.
You can ride at a higher cadence easier which I find helps on the long hills as I can ride smoother in a lower gear. I also dropped 2 teeth on the front ring (it was just what I already had) but I can still pedal comfortably at around 5km/h faster with the shorter cranks.
You will have to change your position slightly but that suited me as I could move the bars forward a bit.
Hope that helps.
You can ride at a higher cadence easier which I find helps on the long hills as I can ride smoother in a lower gear. I also dropped 2 teeth on the front ring (it was just what I already had) but I can still pedal comfortably at around 5km/h faster with the shorter cranks.
You will have to change your position slightly but that suited me as I could move the bars forward a bit.
Hope that helps.
ak-tux
Zen MBB Master
How well does it climb steep hills compared to your 170mm? Did you need an adaption period. If you had comparative power numbers, that would also be very informative.
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Boreen bimbler
Member
Steep hills (assuming 15-20% type of thing?) dont seem much different, just easier to use a higher cadence and possibly a little more steering control. I needed no adaption period myself. They just felt a lot better straight off for me.
As I can't train any more I don't use a power meter sorry.
As I can't train any more I don't use a power meter sorry.
There are 2 more topics about short crankarms, so look them up for more information.
As I answered on one of them, i used a 172.2 shimano for about a year, then ordered some cheap 145mm crankarms from Aliexpress for experiment purposes..
The bike is uncomperable more stable then before.. i can keep pedaling hard yet calm even on very high speed (without rocking side to side) and especially when pressing hard on the pedals when getting out of a corner. Also small stuff gets easier, like reach for your water bottle while riding..
(I replaced my normal rims with some deep sections rims,it did made the bike more stable (maby even faster..) but the short arms hands down made more impact!
You do have to remember the short crankarm changes whatever gearing you have (to lower harder gear) for me it was great to reach faster speeds on decents, but I had to change my cassette once again for climbing...
On flats (and decents) the bike finely behave so friendly while pedaling, so i didn't need any adapting time for that..
But on climbs It does kinda feel like im not pushing enough on the pedals,(going from 172.2 to 145 is a lot!!) So maybe thats something you need to get used to..
(I believe it's easier climbing with longer crankarms as you can rock hard on the handlebars from side to side,)
all included.. I'll take the benefits of stable, controllable, and safe behavior of the bike over everything (especially once I'll dial the gearing issue)
hope that helps..
JerseyJim
Guru
I find the anecdotal reports about shorter crank lengths interesting. For those who are running short cranks, what was the process you used to help you decide?
As I look at the studies regarding the crank length and physiology, there are several formulas. 2 of the most well known are 41% of tibia length and 20% of inseam.
I'm not tall (5'-7"), and when I apply these formulas to my physiology 165 mm cranks come out. I've been running 170 mm my whole cycling life without issues. Statistically, more people are taller than me, so I wonder if that's the case for those running 145 mm or 150 mm cranks, how did you come about settling on that size?
As I look at the studies regarding the crank length and physiology, there are several formulas. 2 of the most well known are 41% of tibia length and 20% of inseam.
I'm not tall (5'-7"), and when I apply these formulas to my physiology 165 mm cranks come out. I've been running 170 mm my whole cycling life without issues. Statistically, more people are taller than me, so I wonder if that's the case for those running 145 mm or 150 mm cranks, how did you come about settling on that size?
chicorider
Zen MBB Master
I got my first Cruzbike, a V20, nine years ago. Back then there was not much here on the forum about crank arm length, other than you want to set your bike up so that your knees don't go past 90 degrees as each leg heads into the power stroke, and that shorter cranks can help make that happen. I started with 165mm cranks because they were the shortest readily available cranks on the market. Anything shorter required hunting. I made my way through the learning curve and started putting in some miles, but I did notice some knee strain. I had my son film me while pedaling on stationary trainer, and I noticed that my knees were indeed a little bit past 90 degrees at their sharpest bend. I fiddled with the boom adjustment and also swapped out the 165mm cranks with 160mm. That made the difference. My knee pain was gone, so I rode those 160's for the next several years.
Then, as more people found their way onto the forum, discussions of crank arm lengths became more common, and I started to wonder, "If 160mm was better than 165, would 155mm be better than 160?" There was only one way to find out. I got lucky and found a pair of SRAM Apex cranks that had been shortened to 155 on eBay. It would cost me $100 to answer my question. The shorter cranks excelled on descents, as if I suddenly had an added smaller cog on my cassette. I racked up a bunch of new downhill PR's and a few KOM's. The 155's performed similarly to the 160's on the flats, though I had to mash a little less and spin a little more to avoid knee strain. But when it came to climbing, the 160's were better. I noticed a slight decrease in leverage with the 155's, felt like I didn't quite have the same power for climbing that I had before, and often compensated for this by pushing harder, leading to knee strain and faster fatigue. If I didn't climb all that often, this would not have been a big deal, but climbing is my jam and I do a lot of it, even on the V20. So I went back to the 160's, answered my question, and sold the 155's for $90 on eBay (so answering my question only ended up costing me $10).
I reason I've said all of this is that I believe that crank arm length on these bikes is highly personal, and if one wants to find the ideal length, one will probably need to experiment a bit. Here are some considerations:
* How picky are you about bike fit? I am really picky. I can't help it. I noticed a difference with just a 5mm change in crank arm length. On a different topic, but similar pickiness, I also will not give up my front derailleur and double chainrings because large jumps between cogs that make it harder to find the ideal cadence bug me. Others might need a full centimeter, or more, difference in crank length before they notice a change, just as others prefer the simplicity of a 1x drivetrain and will accept the larger gaps that come with it. There is no right or wrong here--just personal preference and different levels of pickiness.
* What kind of riding do you tend to do? If I didn't like to climb, or rode mostly flat rides, I would probably use 155, or even 150mm cranks. But since I do climb a lot, I want a crank arm length that will maximize that kind of terrain for me. Fortunately, I don't find the 160's to be a detriment on flats or descents, and my knees are happy on all of it. Incidentally, I am 5'4". Prevailing wisdom says I should be riding shorter cranks, based on height alone, but that's not where my experience has taken me.
* My preferred length is not a recommendation; it's just what I've found works best for me after a little bit of experimenting, which I'm glad I did because I don't have to wonder anymore. 145mm might be the best length for you and the kind of riding you do. But what if 150 or 155 is just that little bit better? Would it be worth finding out? Cruzbike will sell you 145mm cranks made by Croder (they look nice), but Croder makes a full size range, starting at 140mm up to 172.5mm, in 5mm jumps. Aerozine also makes short cranks, and they have an interesting added feature with some of their models: a flip-chip where the pedals thread in that gives you a 5mm shift, depending on how you set the chip. You can order a crank that will do both 150 and 155mm, for example. Pretty slick.
SPIRIT Crank Arm
You can choose the crank length that best suits your needs. SPIRIT has 9 sizes, 140/145/155/160/165/167.5/170/172.5 mm to meet cyclists' different demands for shorter crank arms.
www.crodercycling.com
Road Bike - AEROZINE
www.aerozinebike.com
JerseyJim
Guru
Thank you @chicorider for the detailed response. I think this shows that crank length selection at the moment is less of a science and more of an art. When I look at plugging in my measurements into crank length calculators, I'm right on the cusp of 170 mm and 165 mm. For example, I measured my tibia length to be 16 inches, which would give me a crank length closest to 165 mm. However if my tibia measurement was 16.1 inches, the crank length moves to 170 mm. For measurement at home with crude instruments, I'd say 0.1 inch is within the margin of error.
So one could say I'm fine on 170 mm cranks from a biomechanical point of view unless there is a condition affecting my pedaling for which moving to a smaller crank is a good solution. At the moment I'm just curious.
I checked out those Aerozine cranks with the flip chip. While I'm not willing to spend that amount to satisfy my curiosity, I'm willing to spend $40-$50 on an AliExpress crankset to find out if there is some benefit. I know one benefit will be more clearance between my thigh and the handlebars, which could be worth the change.
What I would find way more useful at the moment are custom recumbent handlebars with a longer reach than road bars. That's a big compromise for me as would like to rest my arms further forward without reducing the space for my legs.
So one could say I'm fine on 170 mm cranks from a biomechanical point of view unless there is a condition affecting my pedaling for which moving to a smaller crank is a good solution. At the moment I'm just curious.
I checked out those Aerozine cranks with the flip chip. While I'm not willing to spend that amount to satisfy my curiosity, I'm willing to spend $40-$50 on an AliExpress crankset to find out if there is some benefit. I know one benefit will be more clearance between my thigh and the handlebars, which could be worth the change.
What I would find way more useful at the moment are custom recumbent handlebars with a longer reach than road bars. That's a big compromise for me as would like to rest my arms further forward without reducing the space for my legs.
I went from 165s to 155s on my V20. First ride out I went and got a lot of PRs for power and strava segments. No adaption time required. I plan to try 145s at some point. It is like adding another gear to the top end of the cassette and taking one away from the bottom. Short cranks is about trading some force on the pedals for cadence to make the same or better power. If you do a lot of climbing near the shortest gear on your bike (big cassette and small front ring), when changing to shorter cranks you may want to adjust the gearing to suit. I live in a hilly area. This means I go slow up hills and fast down them, so I find my gearing range challenging to get right. I want more top end so I can pedal to 70+kph, but I need to maintain cadence when climbing 15% hills so find my 36/30 difficult for that. 12 speed with a 10t would be great!
Damien
Member
Could you tell us what your current setup looks like? I live in a hilly area too, so any tips would be helpful.
ak-tux
Zen MBB Master
Interesting discussion. I have also been curious and have done some bit of reasearch.
One thing is clear though, most formulas on crank length are intended for upright bicycles. They tend to yield slightly longer cranks than recumbent specific cranklength calculators. Here is one specifically intended for recumbents:
The Recumbent Bicycle and Human Powered Vehicle Information Center
Recumbent and Human Powered Vehicle Information Center
www.recumbents.com
In summary, after much research , I concluded the following(My personal opinion):
1. Shorter cranks reduce the mechanical advantage(leverage) compared to the longer cranks . Hence, there must be a corresponding reduction in gear ratios to maintain the correct leverage. Shorter crank + smaller chainring. (To eliminate the guess work, I use Sheldon brown's Gain ratios calculator). So, for example, all other factors constant, a 170mm crank with a 44T chainring is equivalent to a 145mm crank with a 38T chainring.
https://www.sheldonbrown.com/gear-calc.html
2. For recumbents, the height of the bottom bracket relative to the pelvis affects the minimum knee angle at the top of the pedal cycle. Hence a probably shorter crank length for say a V20 may be better than for say an S40.
3. Besides mere curiosity, the change in crank should be considered if the current ones are presenting a problem.
Which could be any of the following:
a) Pedal strike clearance (in MTB sitiuation)
b) Front wheel toe strike (in upright road bike )
c) Handlebar knee/thigh strike (on cruzbike/FWD MBB ) or chest strike for upright TT positions
d) knee strain at the top of the pedal stroke
e) A desire to increase the cadence (for stability and handling)
f) You have limited hip or knee mobility (due to past injury or genetics)
4. It does require some experimenation in order to find the most suitable length. Cost can be an issue and I think the best way to experiment is to try low-cost models from AliExpress . (They cost about $50). I intend to pick one someday soon to try. https://www.aliexpress.com/item/1005007240676319.html or https://www.aliexpress.com/item/1005005804968565.html
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Karl42
Well-Known Member
Welcome to the deep rabbit hole of crank length and gearing. If you want a setup with short cranks that is suitable for steep climbing, you might want a lowest gear ratio of 0.8 or even 0.7. That could be a front chainring of 26t and a large cassette sprocket of 32t (26/32=0.81), or 24/32=0.75.
If your crank doesn't allow front chainrings this small, you'll need a much larger cassette. For example, with a 34t small chainring at the crank you'll need a 42t cassette (34/42=0.81). A 1x setup with decent range on both ends might need a cassette as extreme as 11t-50t or even 10t-52t.
This kind of stuff is very easy to explore and compare with this (or some other) online gear calculator tool: http://ritzelrechner.de
There is also a long thread about gearing setups here: https://forum.cruzbike.com/threads/wondering-about-the-fastest-while-wide-range-drivetrain.13367/
You'll find that road components don't easily offer these gearing ranges, so it becomes necessary to either use a crank that allows very small front chainrings, or use an MTB derailleur that allows huge cassettes.
If your crank doesn't allow front chainrings this small, you'll need a much larger cassette. For example, with a 34t small chainring at the crank you'll need a 42t cassette (34/42=0.81). A 1x setup with decent range on both ends might need a cassette as extreme as 11t-50t or even 10t-52t.
This kind of stuff is very easy to explore and compare with this (or some other) online gear calculator tool: http://ritzelrechner.de
There is also a long thread about gearing setups here: https://forum.cruzbike.com/threads/wondering-about-the-fastest-while-wide-range-drivetrain.13367/
You'll find that road components don't easily offer these gearing ranges, so it becomes necessary to either use a crank that allows very small front chainrings, or use an MTB derailleur that allows huge cassettes.
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JerseyJim
Guru
A rabbit hole is a good description of this topic. @ak-tux makes a good point about the difference in body position and how studies are almost exclusively about conventional bicycles. The thing that doesn't change is the physics. While a shorter crank does result in less torque, the lower torque is compensated for by a higher cadence. As a result, the power output is the same. If you're the type of rider with efficient pedaling mechanics, then power can be greater since you can probably spin at a higher cadence.
Gearing is another complex subject, especially when it comes to low gearing. I've settled on a lowest ratio of 0.86 -0.89. That lets me use a 11-46 cassette with a 40T or 42T chainring. This is covered by MTB or gravel bike components as the 46t cog in the cassette is right on the edge of gravel bike and some road bike rear mechs. I'm using SRAM XLPR now which says it has a 44T max, but it handles 46T without a problem.
Gearing is another complex subject, especially when it comes to low gearing. I've settled on a lowest ratio of 0.86 -0.89. That lets me use a 11-46 cassette with a 40T or 42T chainring. This is covered by MTB or gravel bike components as the 46t cog in the cassette is right on the edge of gravel bike and some road bike rear mechs. I'm using SRAM XLPR now which says it has a 44T max, but it handles 46T without a problem.
Karl42
Well-Known Member
On my V20 I have 152mm cranks that have 74mm and 110mm BCD (Bolt Circle Diameter). This allows me to run very small front chainrings with 26 or even 24 teeth. With those cranks, the fit on the bike is already quite precise: if I move the bottom bracket further out as little as 3mm, I get pain in my achilles tendons. If I move it further in, my legs touch the handlebar. And the handlebar is already so close to the body that sitting up is difficult.
For the fit, 150mm cranks would probably be better, as there would be more space to reposition the bottom bracket and handlebar. However, they would require a lower gear, and that means changing a lot of other stuff on the bike. So with respect to the gearing, 155mm cranks (which I also have) would be easier to setup as they don't require such a low gear, but with those the fit on the bike would be even more difficult, and I'm just happy that I found a fit that doesn't give me tendon pain.
My 152mm cranks are some old Sugino XD2 triples, and they are quite hard to find these days. Modern cranksets that are readily available come mostly in 150 or 155mm length, and don't offer the front chainring options I want. That's what I mean with rabbit hole. Changing one part of the drivetrain might lead to follow-up effects that require changing almost everything else (chainring, cassette, derailleurs, shifters, brakes, ...).
For the fit, 150mm cranks would probably be better, as there would be more space to reposition the bottom bracket and handlebar. However, they would require a lower gear, and that means changing a lot of other stuff on the bike. So with respect to the gearing, 155mm cranks (which I also have) would be easier to setup as they don't require such a low gear, but with those the fit on the bike would be even more difficult, and I'm just happy that I found a fit that doesn't give me tendon pain.
My 152mm cranks are some old Sugino XD2 triples, and they are quite hard to find these days. Modern cranksets that are readily available come mostly in 150 or 155mm length, and don't offer the front chainring options I want. That's what I mean with rabbit hole. Changing one part of the drivetrain might lead to follow-up effects that require changing almost everything else (chainring, cassette, derailleurs, shifters, brakes, ...).
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JerseyJim
Guru
@Karl42 I hear you. Once again I see how personal the change in crank length is regardless of what the calculators say about "ideal" crank length. While I am fortunate that I don't have any pain issues, I have compromised my riding position from what is ideal, but it's livable. A shorter crank could bring it closer to ideal.
I've given in to my curiosity and ordered "Cruz Bike" branded cranks from AliExpress. today. I ordered a 165 mm set and a 160 mm set for about $35 each and a 42T GXP chainring for $18. So I'm under $100 total for this experiment. When I'm done with them, I'll be happy to offer them here to any forum members that want to do their own tests.
I've given in to my curiosity and ordered "Cruz Bike" branded cranks from AliExpress. today. I ordered a 165 mm set and a 160 mm set for about $35 each and a 42T GXP chainring for $18. So I'm under $100 total for this experiment. When I'm done with them, I'll be happy to offer them here to any forum members that want to do their own tests.
Karl42
Well-Known Member
Achilles tendon pain has not been an issue for me until two years ago. I guess part of it is due to age. Another reason is that I've started to do much longer rides than before. I used to think that 150km is a lot, but now 200km is the entry-level distance for Brevets, and considered "short". And these ultra-long rides amplify every little problem with fit and discomfort into a big problem.
JerseyJim
Guru
@Karl42 I can relate. It took a few brevet seasons for me to dial everything in for long events. Now I have to do it again for the new bike. Hopefully experience will make the process shorter this time. Ageing is definitely a factor with aches and pains. That's a whole new adventure. I just take some comfort in that I'm healthier because of cycling than I would be otherwise.
