Shorter Cranks for Climbing
 

I am 5'11 and a 185 lbs and am typically more comfortable on a 53.5-54cm (within certain geometries). I currently own a Ridley Helium in a medium which is like a 56.

I have the bike setup to fit me and it's not uncomfortable on long rides. My question is...

I have a long ride tomorrow that is mostly climbing (15 miles up 4000' and another 7 up 2000'). Would it benefit to slide the seat up a half cm and throw a 172.5 crank on there? (I typically ride with a 175)

I've got the crankset here in the garage and it would take me all of maybe 30 min to set it up. Just not sure how much the shorter crankset would help, if at all.

Thanks!

-Sean

While I am a proponent of shorter cranks for short people (I'm 5' 1") and I do find that short cranks work well for me when climbing as much as anything, at your height I doubt that it will make a difference. You could experiment with it sometime but at your height it could go either way.

I'm your height and prefer 170 cranks. I swapped the 175s on my Long Haul Trucker for the 170s and much prefer them. Despite how close they are, they definitely made a difference.

Ive got a Gravel / Endurance bike that's 53.5cm. Short wheelbase with a little toe overlap and I have 172.5's on that one. It weighs in right at 9kg and is a solid fit. And while I can spin on that bike I dont get the power out of it like I do on the Ridley. The Ridley is built for climbing and that it does. I also can accelerate and put the power down with the longer cranks and of course it helps that it weighs in at 7.4kg.

I'll have to try the 172.5s on the Ridley later this summer and see if I can spin a little more with the shorter cranks on the climbs (too late to swap them for tomorrows ride). My thinking is that with the shorter cranks I might get a slight increase in cadence and save my legs for the longer climbs vs putting out slightly more power at a lower cadence with the longer cranks.

My endurance bike came with 170's and that felt weird. Like riding a walmart or a kids bike. It's crazy how much difference 2.5mm makes.

-Sean

I will say that the shorter cranks worked out very well for me. My knees thanked me. When I installed them, I was commuting in the Ozarks, with plenty of big hills. I preferred the shorter cranks, and still do now that I am back in Western, PA.

I'm 5' 11" with 34.5" legs. I have pretty much always ridden short cranks, usually 165 mm. The few times I tried longer cranks, even when for hundreds of miles, I disliked them. On the two bikes I recently test rode, one with 172.5 and the other 175, the 175 simply wore me out faster. So when my new bike came in, I immediately had them change it to a 165 mm crank.

For me, I feel it allows me to maintain a higher cadence and also stay in the drops more without my thighs hitting my gut so hard. What little I might loose in torque can be made up by shifting to a lower gear.

Glad I stumbled across this thread. I'm 5' 11" and am rebuilding the drivetrain on my Litespeed with 172.5 9 speed cranks, can not get 172.5s anymore. Was about to order 175s until I saw your replies. Going to go with 170s, hope it works out OK.

UPDATE: I've been riding my Litespeed all summer and totally forgot about the shorter cranks. Honestly, I can not tell any difference.

So you use shorter cranks - then you have to spin faster to get the same power, right? The power to rpm curve is different for different folks. For some people, continuous power decreases at high rpm because of the oxygen costs of spinning fast. Get on your trainer and spin at 120 for 30'. See what your average power or speed was. When one runs out of gears on steep climbs and rpm drops, then leg force has to increase with shorter cranks to get the same power. That sucks. Thus it depends on the rider, their training and physiology, and on the course. I'm 5'6", short legs, ride 170 and 175 cranks. I wouldn't go shorter. It's like, "why would I do that?"

I have no opinion on the best crank for you. We are all very different, both on our body's dimensions and what works best for our musculature. But I see two red flags in your posts. Raise the seat 1/2 a cm? That 's huge! Have you been riding a too low seat this whole time? For me, 2mm is noticeable, 3mm (1/8") is real. Different people advocate different levels of seat height change for differing crank lengths, from non to 1/2 the crank length difference and a few, the whole crank length difference. I've never seen twice the difference.

Also, you seem to be OK on 175s. 170s feel really bad. So half way between OK and really bad is going to be better? Now I am like you are currently. I rode 170s never thinking about it until my first true race bike came with 175s. For me that was huge! Now I hate 170s and 172.5s feel short. But I am longer limbed than you. Was 6'1/2" until I started shrinking with long limbs. I ride a 59. It may be that you have "trained" yourself to be comfortable on a longer than optimum cranks and now find, because of that training, that shorter cranks feel "wrong".

Ben

Physiologically it may be more comfortable, but you aren't changing your gearing range, so shorter cranks alone aren't going to make it easier to spin. You need the same cadence to go the same speed regardless of crank length.

So how did the ride go and did you even change anything for it. I'd be leery of crank changes or something I can't change back easily during the big event.

Ben -

Thanks for the feedback. In the original post you quoted, I meant sliding the seat forward (up towards the bars not up in the air). Reading back I can certainly see how that can be misinterpreted.

The ride I went on was a 6500' climb up to Mt. Saint Helen's. In this climb there is a 15 mile pull that is no less than 6%? Often I saw 8%. While I live in a hilly area I dont have any long climbs like that to train on unless I get on the turbo with Rouvy or something like that.

So my thinking was to close the distance from the seat to the bottom bracket thus getting more of my weight over the pedals for the long slog. Then by dropping to 172 5s on the cranks it would be easier to spin and keep my cadence up while doing that climb and at the same time slightly decreasing the pedal stroke to make up for some of the slide forward over the bottom bracket.

I did slide my seat forward the 1/2 cm. It did help with pushing down on the pedals and I felt that it did take away a bit from the pull at the bottom of my pedal stroke. It also made good use of my satorius muscles and they were pretty mad at me by the end of the day.

I did not get a chance to swap out the cranks for this ride although in hindsight I wish I had because I struggled to keep a cadence above 65 rpm on some of the hardest parts of the climb and I feel that would have helped.

The thing that would have helped most overall would have been properly training for the ride. Because of my work schedule leading up to it I wasnt able to ride for almost 10 days in a row and when I finally did get back on the bike, it was crammed into a short amount of time and not enough of it pulling 220 watts for 15 miles.

-Sean

Sorry, Double Post.

Changing the cranks to a smaller size decreases the range of the pedal spin (a smaller circle). It will make a difference in mashing vs spinning. The power output is the same but the muscle group in extreme cases would be different.

The ride was brutal. It was the hardest ride I ever did. I was the slowest of the 8 of us. It was mostly from not properly training leading up to it. I strongly feel that the slightly smaller cranks would have helped "slightly" but overall I think properly training for it would have helped most.

Alot of the guys that had not done this ride before said it was the hardest they had rode as well.

2 hours at your FTP hurts.

-Sean

Small crank length differences don't change power output, only preferred cadence. And small differences to crank length only change that preferred cadence a small amount. If you were in your smallest gear, you wouldn't have magically found more power with a 2.5mm shorter crank to go from mashing to spinning. If you weren't in your lowest gear, then you really can't complain that you wanted a higher cadence.

Absolutely agree. The difference would have been marginal. Although, you can put out more consistent power for a longer time at a higher cadence.

Wrong. It would have been worse. Longer cranks would have helped. If you want to use shorter cranks to spin faster, you have to gear a lot lower, low enough that spinning the longer cranks at that rpm would feel like you were thrashing your legs, say 90+ cadence. Dropping crank length 5mm won't even be noticeable at that cadence except that you'd be even slower and cadence would drop because you wouldn't have the muscle power to move the cranks any faster. Except really, you probably wouldn't notice particularly except that you legs would be even more tired.

Moving your saddle forward and thus limiting your ham and glute use is really counterproductive. The longer the climb, the more you want to spread the muscular effort around.

Regear your bike so that climbing that grade, you're spinning ~80 in your second lowest gear. A bailout gear would have been nice, huh? You can use an online gear and cadence calculator to see what that gearing would be.

Odd that your sartorius muscle would become sore. Do your knees stay right over your pedals when you push down and not wobble? Never had that happen - usually my whole quads are quite evenly sore, even to the touch sometimes.

High tempo , spinner, might favor shorter cranks, slow tempo, often standing, may advantage leverage of longer ones,..

Maybe, but I found that riding my old MTB that came with 175mm cranks to be harder on my knees when climbing out of the saddle and have less of an issue with 170mm cranks. A key biomechanical factor is the angle of the knee bend when you start the power stroke and less is more. Though it may be that this factor was actually playing out a lot while I was in the saddle and just noticed it more out of the saddle.

Otto

Longer cranks do give you more leverage. However, I'll always go for shorter cranks just because I can maintain a high cadence more comfortably. I have a fairly low and aero position even when on the hoods. So longer cranks are going to be uncomfortable for me just in the extra little bit of shove they give my thighs as they push into my gut. Perhaps if set my bars a little higher, it would be different, but then I'd be wasting watts on long rides.

At the times you struggled to stay at 65 rpm:

1. Was this for a significant amount of time?
2. Did you have a lower gear you could have shifted to? If so, why didn't you?
3. Do you struggle on your normal rides to keep a decent cadence on the hills you ride?

If you only had to struggle briefly when a grade suddenly got steep, then not a big deal. But if you don't have the gearing to let you maintain a decent cadence for the hills you regularly do, then you might want to change the front crankset, rear cassette or both.

Just remember when changing crank lengths, if you do go shorter, and you didn't have a low enough gear with the longer cranks, then you'll definitely be in trouble with shorter cranks.

Great that you did the ride and finished. Don't wait too long before doing another.

All else, I go to my 2 foot gear..

This is not true. In the same gear the pedal speed (Not Cadence) must be faster with the longer cranks to keep the same cadence. By reducing the length of the cranks it does a few things, slows the pedal speed and opens the hip angle and reduces the knee flex over the pedal stroke. It's not going to give anyone more power or make them go faster but at the same pedal speed as the larger cranks the cadence would be higher thus increasing endurance over the 15 miles of climbing. Granted this is very marginal as we are talking about a 2.5mm difference in crank length which amounts to a 5mm overall circumference when looking at pedal speed.

The reasoning for the saddle forward was two fold. To make up the slight difference in saddle height with the shorter cranks and to open the hip angle for the longer climbs. It was 1/2cm of difference and was actually pretty comfortable for climbing.

Typically I try to spin at 75-80 rpm when I have steep climbs (+6%). In anything less than a 6% grade, I can typically sit at 85-90 without issue. My bike is typically setup 50/34 x 11/28 when I am in the hills which is most of the time. The struggle I had on this ride specifically is that it was 15 miles at 6-8% grade. I just don't have a regular ride that has a 2 hour climb at +6%. So my cadence slowly dropped over the length of the climb. .

Knees don't wobble. Just had a bike fit a month ago and the fitter started with KOPS (he was more of a "classic" fitter). He had me slide the seat forward during the fitting as this frame (As mentioned in the OP) is at the large ends of frame sizes for me. Sliding forward shortened my reach and opened up my hip angle a little bit and gave me a little more power comparative to where the seat was previously. I thought it interesting as well that I didn't get cramping in any other muscle groups besides the satorius. Toward the end of the final climb I had to massage them a little bit while riding to keep them from cramping up.

This was my thinking initially for switching to shorter cranks.


1. Yes - It was a 15 mile climb over 5% and most of it was 6-8%. So 2 hours of climbing. I started out around 75 -80 RPM but couldn't maintain for the 2 hours.

2. No. I ended up in 34x28 by the end of the first 30 minutes of climbing

3. No. But my normal rides dont have 15 miles of climbing. Some of the climbs i normally do have in upwards of 12-14% grade but thats only for a short distance and I think the longest climbs i have on my regular routes are 4-5 miles at 4% - 5%.


My initial thought was shorter cranks would be more comfortable at a higher cadence for the long climb. I notice on my regular climbs of 2-3 miles that on my road bile with 175mm cranks its a bit of work on the climbs but there seems to be more acceleration as I stand up and sprint to get over the tops. On my gravel bike with 172.5mm cranks (Its also 4 pounds heavier but is a better fit for me) It feels like I spin more over the top and its not the quick acceleration that I get with the longer cranks. I notice it on group rides as well. The shorter cranks feel more "Spinny"


Anyway - Thanks all for the feedback. Its great to learn from your experiences. I may try to do this ride again later in the season and I will swap out the cranks if I do just to see if it feels different. I'll probably be in much better shape later in the season as well so it won't really be a good comparison.

Wilmingtech. While I am a HUGE proponent of short cranks, there are limits. While I ride with 140mm and shorter cranks(125mm at the moment) , there is no way that I would recommend that you ride 140mm cranks at your height.
You could experiment with 172.5mm cranks by all means but the results really could go either way.
The limiting factor with short cranks often ends up being the feeling that you can't really stretch your legs out far enough. This is the opposite of course from cranks that are too long which forces people to stretch their legs too far and introduces dead spots in the cycle at top dead centre.

No one is stopping you from trying the 172.5mm cranks, so at this point I think you should try them before further hypothesising about them. It really could go ether way.