I have switched my crank from 170mm to 160mm (based on the internet crank length calculator) for about 1-2 months now. I have been riding about 1000 miles with the new cranks.
About my body composition: height: 167cm, inseam: 75.5cm.
I raised my saddle up about 10mm, and back 5mm. Lowered the stack about 5mm.
Before changing to 160mm
I think my riding style has changed a lot. Before, I barely get out of saddle even in a very pretty steep hill. I could ride a long steady hill well. But in flat, my knees hit my stomach when I am in aero position. I think I am a rider who is stronger in neuromuscular than cardiovascular.
Performance:
After the crank arm length increase and overall fit adjustment based on previous, I found my self standing up a lot more. Even with some moderate hill, I would stand up. It became hard for me to seat down and power through the climb. This is ok for a short climb, but I am worry that it is affecting my performance in long climb. I felt so much better in flat tho, high cadence and more aero position.
Lastly, I felt like I canāt perfectly output a burst power like before.
Comfort:
I do notice some discomfort with the new crank arm and fit. Lots of pressure build up on my right palm, I have to let go of my hand from time to time; my right tricep sores every time after a long ride, which I topically donāt experiencing. And my lower back sores more often than before, I need to get up and stretch more often.
I am thinking of going back to 170mm or try 165mm as I think that 160mm maybe affecting my performance. Anybody has similar experience? I would to hear from all of you.
Iāve found that it has taken me a little time to adjust to shorter cranks. It felt weird at first even just going from 172.5 to 170mm, but I wouldnāt change anything now.
For reference, Iām ~179-180cm with a ~86cm inseam.
Did you actually remove a 5mm spacer from under the stem?
If so, why?
Raising the saddle to account for the short crank already has the impact of āloweringā the handlebars by about 10mm (prior to any change since the bars remain at the same height).
Dropping the bars 5mm will make the bars about 15mm lower than your saddle compared to the bike before any changes. Perhaps that was a goal with this overall?
Add in the 5mm of additional setback and you also opened the reach to the bars above and beyond the height change (which does that via the angles involved).
If my summary of the above tracks with your changes, the complaints you mention all jive with having a a saddle to handle bar reach & drop that is more than you need.
Raising the bars 5-15mm would seem an easy start in addressing the issues and see how that works.
Yes, I have removed a 5 mm spacer under the stem, because I want to see how low I can be and I assume this makes my position more aerodynamic ?
Dropping the bars 5mm will make the bars about 15mm lower than your saddle compared to the bike before any changes. Perhaps that was a goal with this overall?
I think it is part of the goal, as my knees were hitting my torso when I ride in aero position and the issue has been resolved.
Raising the bars 5-15mm would seem an easy start in addressing the issues and see how that works.
Thats a good point. I will add the spacer back to see if I can ride like before.
So, do you think that the riding style change is caused by the stack and reach change?
Low can be more aero, but not always. Itās far more complicated than that, especially when comfort is sacrificed.
Well, shorter cranks lead to a smaller circle and more open hip angle to a degree. But the final result also matters with respect to bar height.
When short cranks lead to taller saddle, that ādropsā the bar and lowers our upper body. Result? That open hip angle from shorter cranks decreases from the drop.
It may not be enough delta to nuke the crank change, but it is not a guarantee to be as open as if you also RAISED the bars the same amount as the saddle height. Doing this maximizes the hip angle opening, but comes at the cost of taller overall height.
If itās not obvious, this is why I bristle at āsimpleā solutions like short cranks to solve problems. They are certainly valid and worth using, but just like every aspect of bike fitting, even a single change can have multiple impacts that should be considered (and sometimes adapted in tandem).
Yes, in conjunction with the obvious delta that the smaller pedal circle also plays.
Your (dis)comfort issues seem a direct result to taking bar drop and reach too far, specifically if they came about after the changes and you had none of that before. Moving (in 5mm steps) up is the easy and obvious next test to try.
Make a change, ride and see how it feels for comfort and any other impact.
As to you overall pedaling and effort observations, those also jive with what is needed when using shorter cranks. If you aim to hold the same power output, you have to push harder or faster on that shorter crank. Results may lead to deltas in feel seated and standing. Not good or bad, but certainly different.
As an aside - a friend recently got Look cranks which come with an insert allowing you to effectively move where the pedals screw in and therefore adjust crank length without swapping the cranks. Several of the indoor smart bikes have similar setups. Any idea why this hasnāt become more widespread? Would seem like a no brainer - fewer SKUs for groupset manufacturers to produce and for retailers to stock, and bikes become more adjustable which should be a selling point for customers. Swapping cranksets is at least pretty mechanically easy compared to swapping integrated bars but gets expensive quickly!
Doesnāt seem like it should be a particularly expensive solution, and even if it was would still expect to see it on more high end groupsets. Maybe increased chances of something going wrong? Or patented by somebody other than Shimano and SRAM and they donāt want to pay up?
mcneese,
Thank you very much for the comprehensive analysis.
I will put the 5mm spacer back next step.
I do not think I have hip impingement issue, and it is not my reason to change my crank, but knees hitting my torso is my major concern with the long crank.
You are right. My original issue was only knees hitting my torso in aero position. Now that I have lower back soreness and discomfort in palm. And felt that hard to output power in climb while seated and not feeling ārightā to perform burst power.
Sure, shorter cranks can help with that knee to chest issue (no hip impingement need or referenced by me).
Right, with the shorter crank, you reduced your leverage because the gearing and tire are the same. If you are down to your lowest gear and feeling too much resistance and/or too slow cadenceā¦ and thatās forcing you to stand, you may want to consider lower gearing.
This is one aspect that also gets overlooked. It may not matter to everyone, but some riders moving to shorter cranks need to get lower gearing (at least on the bottom) to help with climbing. So, depending on what you have for potential options, a cassette (and derailleur) with a lower low gear is worth consideration.
Do small changes, and only one change at a time. This goes for tech support problems too.
If you change too many things at once, you have upended the whole system, and backing off what is causing problems will become far more difficult. Iāve seen people have to reinstall servers because they made too many changes at once, and it got in front of them, they lost controlā¦
My current gearing are front 50-34, rear 28-11.
My bike rear derailleur only supports up to 28t. If I want to increase the teethes, I need to change the derailleur which is quite expansiveā¦
I just miss the feeling that I can power through climbs while seated. Do you think going back to 170mm or 165mm crank make sense more or give a try to raise 5mm in stack first?
The 5mm stack increase is essentially free and takes just minutes to do. Iād suggest that and some rides to see how it feels.
ETA:
The other thing Iād suggest testing is moving the saddle forward 5mm. Fore-aft location is the blackest of black magic in fitting, but I think it is worth checking to see if you prefer a more forward position for bar reach/drop as well as pedaling.
Sometimes, a rearward bias can sort of nuke power and ability to crank it out. This could relate to your seated power climbing issue, so Iād give this a shot too before spending any more money.
Lower can be more aero, but not always. Narrower is almost always faster and you donāt have to be super low to get aero. Slammed stems seems to be one of those old school cycling traditions that wonāt die and is mostly based on people wanting their bikes to look āproā. So many amateurs rolling around with slammed stems with almost straight arms and hands on their hoods. Bike looks pro at the coffee shop, but itās often making people slower and less comfortable/powerful on the bike.
If you care about being faster, test your positions. You donāt need a trip to the wind tunnel, you can get some good data for free by using the chung method or rolldown and the golden cheetah opensource tools.
Subtle changes in riding position can cause huge problems. Itās basically a repetitive motion, and the body gets accustomed to it over time. So throwing in a change will likely upset things while riding. Like something as āsimpleā as new shoes and cleats. If they are off a degree or three, and the position of the pedal axle to the ball of the foot can cause major problems in some people. Give you body enough time to acclimate to the changes and see what happens. Some changes you can undo, and others you canāt (my hip replacement changed the angle of my foot at the end of my leg, and it took me a few months to get over the new usage of all those muscles. I found ones I had no idea I had!).
I bought new shoes, and cleats, and even used a device that is supposed to plot where the cleats are on the bottom of the shoes, and tried to copy that as accurately as I could, and still had an incredible amount of knee pain. I ended up giving up because I lost any idea what I did wrong. They are in the pain cave, and I look at them every time as I put on my old shoes for a ride. And it could be off a couple of fractions of an angle, and I apparently canāt get it right enough. sigh One of these days, Iāll pick them up, and the template and try to get them dialed in.
I made the decision to switch to shorter cranks for some of the same reasons that the OP did. I couldnāt get any lower and spending any length of time in the drops was just too hard because my knees wouldnāt stay out of my chest. When I first made the switch, I got a new set of cranks for my old bike that is dedicated to the trainer. Going from 172.5 to 165, I put the seat up 10mm, and put the seat forward 5mm to maintain reach. I was able to open up my hips enough that I COULD go lower. When I decided to get a new bike, I actually went UP a frame size, and ended up with a reach to the bars a full 15mm longer, and stack to the bars about 5mm higher. However, unlike the OP, I feel like itās easier to put the power down, and Iām definitely more comfortable on the hoods, tops and drops. I can still do long climbs while seated, but the greater distance to the bars makes it easier to stand. I think that the more forward position also made it easier to increase my gearing, going to a 52/36 from the previous 50/34 (no change in the rear). The gearing feels more natural and easier to stay in my natural cadence zone. I think that I can still go lower, but donāt want to try anything until I can get back to my bike fitter.
So, I have added the spacer I removed when changing my crank; it is actually a 10 mm spacer instead of 5mm. I did a z2 in trainer afterwards; I dont felt any more pressure build up on my palm and lower back soreness. Maybe the intensity is not high enough to cause those soreness.
The original motivation of moving my saddle back 5mm was to reduce the palm pressure built up because i thought that there maybe too much weight in front after I increase my saddle height.
I am pretty happy with my current result. Thank you again for pointing it out!
However, I was contemplating if the crank was too short. On the trainer/bike I felt like I cant fully utilize neuromuscular strength of my leg. Particularly, I āfeelā that the crank turned to next position before my muscle (quads and hamstring) can generate maximum contraction/extension
Perhaps I was trained with 170mm crank for a long time? I was doing the top kick, bottom slide, and rear pull up motion in TR session and got used to it.
With 160mm crank, my leg cant felt that anymore, thus I cant perform burst power in steep hill.
I had ride about 1000 miles with the 160mm crank, 2 races. I felt like I cant perform in the climbā¦
Maybe it was just my thought? I just need more time to get use to the shorter crank?
Yeah, I think we have a different fit after changing the crank. I have moved my saddle up 10mm and 5mm backward, and the stack 10mm lower.
With your new bike, you have increased your reach 15mm, but saddle 5mm forward, and stack 5mm higher.
Maybe crank length does not play a major factor in here. It is always good to have a fitter to take a look. I should probably consult a professional fitter for this matter.
So shortening cranks does affect the gearing (technically gain ratio), this may be part of the reason you stand up as you will need to use easier gears than before.
Youāve opened hip angle via shorter cranks but then closed it off by moving saddle further back and bars down. Youāve also altered reach a fair amount.
Most important question, are you faster now with your new position?
Now theyāre are advantages to longer cranks, in that you can have a more forward position with glute engagement.
I still think 160 mm should work for you though and that you can sort out this position by playing around a bit more.
Reading into this - it feels that the saddle and bar position changes have made it hard for you to sit up and push the power on climbs. We often want to really drive through the heel using hamstrings and glutes when climbing but your position changes may have limited that ability. Worth really tuning into the feeling whilst climbing to try and understand where the issue sits.
If I look at the relationship between the saddle and the bars on the new bike, Iām more stretched out and feel more relaxed in an aero position. I think that the big difference between our fits is the saddle position in relation to the bars and how that affects the ability to put power through the pedals.
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