I’m building up an Aethos II frame with the SRAM Force AXS group set. I’m going back and forth on crank length. Based on what I’m hearing and reading, here and other sources, I’m considering shorter crank lengths than I’m used to. I’ve just used stock 172.5 on my last two bikes, but I’m leaning toward 165 mm cranks for greater comfort. I’m 58 and 5’10.” My concern here is that the cranks would be too much of a change for me after decades on the stock cranks.
If the 165s are recommended, then my other conundrum is gear ratios. I’m looking at the 48/33 chain rings to pair with the 10/33 cassette based on the X-Range Gearing chart provided by SRAM. My head scratcher here is whether the chain rings would be too small based on the shorter cranks.
I realize maybe the shortest, best answer is to get a bike fit. I have one scheduled, but I’ll have to do it on my 2020 Roubaix, which obviously has a different geometry. Even with the increased stack on the new Aethos, it’s still 25 mm less than the Roubaix, for example, so I’m not sure how effective a fit would be in resolving my concerns. First world problems, right? Any advice is appreciated.
I’m 5’6” and had been riding 170 cranks for many many years. When I tried 165’s they felt pretty short at first but eventually they felt OK. But I wasn’t about to get 30 new cranksets for all my bikes…so I still ride mostly with 170’s. Some cranks, Like Cybrei are available in middling sizes, like 167.5. So I do have a couple of cranks that are 167.5, and those don’t feel drastically different when pedaling but they do give me a little more room without my knees hitting my chest. So…why not try 170s or 167.5? 172.5 all the way to 165 seems like a big jump.
There’s no necessity to change your gearing when you go to shorter cranks. 165mm with the combo you’ve suggested sounds great (and is something I’ve run before also). I’ve put 165mm cranks on 6 bikes over a few years now and never changed the gear ratios.
Changing to a 3rd-party crank can really extend your options of crank length and gear ratios. Out of roughly 30 bikes, about half of mine have 3rd party cranks - Easton, Race Face, Rotor, Garbaruk, Cybrei, SRM, THM, Praxis, Appleman, Cane Creek (eeWings), Extralite….
The down side is cost (in some cases the 3rd-crank are really at a premium price) and complexity, meaning that you know your SRAM crank will working perfectly with your SRAM drivetrain and SRAM Dub bottom bracket….but what about that SRM crankset with a 30mm spindle?? And which chainrings will work? Does that Praxis crankset work with a direct mount chainring? Can I get Praxis chainrings for my Rotor Crankset? Which BB do I need? Etc….
I have pretty much always gotten the various cranksets to work great on various Shimano and SRAM drivetrains….you just have have to plan ahead a little.