When I bought my 52cm Trek Domane in 2022 it came with the stock 170mm crank arms (AL2 Claris 8-spd) which now mostly lives on the Saris trainer with TR. I got the complimentary store bike fit and then later upgraded seats and a longer stem to “roll my hips forward” which has been fine with no real pains to speak of while riding.
Last year I bought my 52cm Emonda SLR frameset to build up and essentially copied the fit with the same saddle, which also is fine (running Force D2 setup).
Where my question comes now is reducing the crank arms on both to either 160 to match the online calculator or 165 to make a smaller adjustment first. I guess I’m concerned about wearing out my knees as a few days after riding they seem to hurt a little more than they used to.
I made a list of the replacement parts and costs for doing this and know I’ll need to raise and move the seat backwards the same amount. Never cut the steerer tube on the Emonda so have 60mm of spacers (+ the cable cap) below and 10mm above to work with. Domane has 20mm (+ FSA cap) spacer below and 10mm above.
I’m fine with changing them myself and also considering another bike fit since it’s been a few years and almost 2,600 miles (mostly indoors on the Domane). I have a 450 mile, 7 day event next July (RAGBRAI) on the Emonda that I’d love to have dialed in and be more efficient if this change will help.
I’m about 10cm taller and about a 7cm taller inseam. I love my switch to 165’s and have even considered going to 160’s. At your height and inseam, I would personally give the 160’s a go. Worse case scenario they aren’t the right choice, and then you at least know.
I am the same height and changed from 170 to 165 to 160 over the last 8 years. I have found no negative differences in any change and will go down to 155.
FWIW - I recall Neill Stanbury mentioning in one of his videos that you need to change the crank arm length by at least 7mm to really even notice it. Meaning, that changing from 172.5mm to 170mm is almost imperceptible, but going from 172.5mm to 165mm is very noticable.
I think the general point was, don’t make bigger jumps than you should without evaluating along the way.
I focused on comfort, and I really noticed no issues from the start of those switches. I felt smaller cranks would be better for knees and aero position over the long term and have not seen anything that would go against that.
I use 165mm on indoor trainer and 170 on gravel bike and I don’t really notice issues with I switch.
This is good to know too as the Emonda is an easy arm-only swap where the Domane being 8-spd would require a full groupset upgrade to get to 160mm (R7000 minimum level) unless I just get a RS-200 165mm crankset. I’d prefer to match the trainer with what I’ll be riding outside though.
I know there are other brands too. I could also just upgrade the crankset/BB/cassette to 105 and use single gear ERG mode on the Saris.
I have a Stages SB20, so 165mm was as low as I could go, but agree with you otherwise. I also had to go to 105 (was on 11 speed when I went down from 165 to 160mm - that was the only Shimano option then). I have Ekar on the other bike, and it’s been hard for me to get a 165mm crank for it cheaply.
Recently took the leap to switching to 165mm from 175mm. Firstly I am about 8cm taller but I don’t think height is too relevant as I have a friend who loves 165’s and he is at about 182cm in height. Once accustomed to the reduced leverage I am getting along with the shorter arms very well. Enough so that I will stay with them and have also made the change to my gravel bike. One of the big drivers for me is the reduced peak load on the knees at the top of the pedal stroke. All this being said if you do not have any knee issues or problems getting low enough then shorter cranks are not an absolute need. Some riders, myself included ride long cranks for many years without issue but many more can and do benefit from going shorter.
I went from 172.5 mm to 165 mm and love the improvement that I have seen. I have had issues with hip impingement where in a reasonably aero position my knees would “massage” my stomach. I adjusted the gearing slightly to accommodate for the slightly smaller lever arm, but that was really easy. Overall, if you are worried, @Topcat5, don’t be.
In case you want quality cranks in smaller sizes, have a look at Rotor’s offerings, you can order their Aldhu cranks in sizes from 150 mm to 175 mm.
When are we going to see manufacturers start to support this movement/trend towards shorter cranks. It would be great to have more optionality when making a purchase (I realize this introduces supply chain headaches).
Just bought a GRX 610 2x crankset to replace my GRX 810 crankset because Shimano doesn’t make the 810 in 165mm.
I’m 170cm tall and the switch to 160 cranks (starting at 172.5, then 165, then 160) has been great. Especially on the flats, I can spin in a much more unrestricted way. Even subjectively, it just feels nice.
Most people around me tell me they don’t like short cranks because then they’d have to spin faster and it’ll take more effort - but that’s untrue. Your rpm goes up, but you’re spinning smaller circles. Effective cadence is about the same.
Second Rotor cranks. Not only do they have a broad range of available lengths but very stiff and light. Only real downside is they are pricey. I have only found it tougher on sustained climbs.
This! WTH is with 172.5?! Find me one person riding 172.5 who has a measurable benefit over both 170 & 175.
I have a set of square taper 145mm cranks from Bikesmith Design sitting in a box, waiting for me to take up crit racing on circuits where pedal strike is a concern. I find that they do naturally call for a higher cadence (the bro-science maths say to target 115rpm compared to 100rpm on 165s). I had them on my bike for a month or two after damaging a pair of 170mm 105 Octalinks & whilst sourcing the 165s I have on there now. The 145s came to feel natural, to the point that the replacement 165s felt weirdly long.
If you really want to mess with your own legs (& bike fit!) & your riding mates’ heads, put something absurdly short on like 115mm & pedal around 140rpm.
This! WTH is with 172.5?! Find me one person riding 172.5 who has a measurable benefit over both 170 & 175.
I find that they do naturally call for a higher cadence (the bro-science maths say to target 115rpm compared to 100rpm on 165s). I had them on my bike for a month or two after damaging a pair of 170mm 105 Octalinks & whilst sourcing the 165s I have on there now. The 145s came to feel natural, to the point that the replacement 165s felt weirdly long.