PeteHski

One experienced fitter I know suggests not compensating (at least initially) for saddle height. So you get an equal reduction in both leg extension and hip compression. From there you can decide for yourself how to split the reduced motion.

There are also less downsides from running your saddle too low vs too high. I have experimented with that myself and was surprised how low I could drop my saddle without causing any issues. Raising it on the other hand even slightly above a certain point causes problems with saddle comfort and the back of my knees. So I settled on a saddle height a good 5-10 mm below what I could still comfortably pedal. Power was totally unaffected by running that much lower, even on long seated climbs.

terrymorse 

I don't accept that range of motion loss is inevitable, because for the majority of people it is not inevitable.

The most significant age-related cause of range of motion (ROM) loss is inactivity, and ROM is improved through training -- even in the elderly. Keep exercising, maintain flexibility. Pretty simple.

It can be concluded that age-related decay of mobility in the joints herein studied can be efficiently contrasted with an active style of life and that a training period can further improve the mobility of the lower limb. -- Morini et al 2004

Carbonfiberboy 

That's right and is a big reason that I do all my strength work at the gym through the full range of motion of the joints involved. My squats are ass to grass, etc. I spend a good bit of time stretching every morning, too. Just going to the gym was enough stretching until it wasn't.

PeteHski

I never said it was inevitable. But for anyone who does happen to get stiffer joints or knee pain through age or injury then shorter cranks are a good option with no real downside beyond personal preference. This is a good summary of the implications of changing crank length:-

https://www.applemanbicycles.com/res...-crank-length/

Mtracer

Thanks for this link, it was very informative. And within that article, there was a link here that I'm showing just so no one misses this. It's really good:

Shultz's Article

I've just installed my shorter crankset today and will be giving it a go tomorrow.

easyupbug 

Well said Peter and my exact experience. I have seen photos of getting my first two wheel bike (w/ training wheels) at 3 and that was 70 years ago. I have always been and remain active but now Cortisone shots for osteoarthritis are keeping me on two wheels with 165mm from 175 and 172.5 and raised bars. Except of course for my lovely Italians which are not getting the miles.

datlas 

Interesting. Assuming saddle height is based on full leg extension, one should adjust this for cranks. Ditto saddle fore/aft, and hence stem length, if you want to keep the same “fit” with shorter cranks.

I realize this is not a rigid geometry issue, but hypothetically if you want same positions you would need to adjust all three of these.

PeteHski

This is the very assumption that this fitter was questioning. Some riders are limited more by their knee/hip angle at the top of the stroke, so they may be compensating for this by raising their saddle above their optimum for leg extension. Another prominent UK fitter said that most riders who came to him had their saddle set far too high (typically 10-20mm too high!).

So shorter cranks give you a wider fitting window for both leg extension and compression.

Deontologist

I went from 172.5 to 165 to 141 to 124mm cranks and my favorite length is probably 124mm but 145mm is very, very similar. 6' tall

I used to get really bad back pain and spasms even with 165mm, although it was an improvement over 172.5. I have 0 back pain after cycling now with 141 or 124mm.

I tried a 89mm crank length once and had difficulty balancing on the bike.

noglider 

Wow, @Deontologist, those are really short! 155 mm are noticeably short for me, though I don't mind them.

canklecat

I noticed a little more difference in crank length when I was "younger" (late 50s-early 60s) and only cycled for exercise. My various bikes have cranks from 170 and 172.5 through 175. For awhile I preferred 170 when my cadence was around 90 rpm. I found it more difficult to find a sweet spot with 175 cranks, and constantly fiddled with seat height and other adjustments to minimize knee twinges. (FWIW I'm 5'11" with 33" inseam, average leg length, longer torso.)

But by late 2020 my neck pain (old injuries and arthritis) had worsened to the point that I cut back on riding from around 6,000 miles a year to 500 miles a year. I started jogging and walking instead and doing more full body calisthenics including squats without weight or minimal weight (20 lb water jugs at home).

After awhile I noticed my knees, legs and lower back were no longer picky about crank length. Outdoors I usually ride a Diamondback Podium (2012 or so manufacture) that the previous owner had fitted with 175 Ultegra crankset to replace the FSA original. At first I thought I'd replace it, despite liking the older solid cranks like that year's Ultegra. But after awhile I adapted to the 175 cranks.

My 1989 Centurion Ironman still has the original 172.5 cranks, and I've tried it with 170 cranks (that 170 Dura Ace crankset is now intended for my early 1990s Trek 5900 OCLV). For the past couple of years the Ironman is mostly fulltime on my indoor trainer with the 172.5 cranks. I don't notice any difference between it and the Diamondback with 175 cranks.

The one time I did find myself getting picky about crank length was the year I tried Shimano Biopace ovoid chainrings on two different bikes, the Trek 5900 with 170 cranks, and Ironman with 172.5 cranks. The oddball Biopace rings felt better to me at a slower cadence, around 70 rpm, and with shorter cranks. For whatever reason those Biopace rings felt weird with longer cranks and at a faster cadence. But they felt good grinding up climbs at slower cadence.

I've added more weight workouts in the gym and that seems to reduce my sensitivity to crank length, saddle adjustments, etc. And my aerobic capacity has gone to hell after a bout with COVID in late 2021, so I quit trying to spin at 90 rpm and mostly grind along at 60-70 rpm now. My legs are pretty strong compared with my lungs, so the slower cadence suits me better now.

Same with the Matrix spin bikes in the gym. No idea what the crank lengths are. I haven't even bothered clipping in since my shoes are all fitted with SPD-SL or old school Look Delta, while the gym bike pedals have SPD on one side, flat on the other. I just wear Adidas Daily 2.0 sneakers (comparable to Five Tens) with relatively stiff-ish soles suitable for weight training, rather than my cushy running shoes. Takes a minute to dial in the saddle height and position -- and the saddle height post has fairly coarse adjustments in full centimeters, rather than the infinitely adjustable seatposts on "real" bikes. After that it doesn't feel much different from my own bikes, although the pedaling sensation on the spin bikes is uncommonly smooth compared with "real" bikes outdoors or on the trainer. But my output, heart rate, etc., are the same. No knee or hip problems.

Based on a sample group of ... me ... my conclusion is that reasonable full body strength training may reduce sensitivity to crank length and even saddle position.

BlazingPedals

I am thinking of going shorter on my avatar bike. Not because of flexibility issues, but because it's always been a bit too much of a stretch from seat to pedals for me, and it doesn't adjust except by varying the crank length. At my age, I think I should stop waiting to grow into it.

PeteHski

Does it really have a fixed saddle height with no adjustable seatpost?

BlazingPedals

As you can see in my avatar, it has NO saddle. The seat is built into the frame. The original way to adjust for leg length was an extendible boom in front; but I was too short even for that (at 5'11".) I ended up having to cut the frame and bond it in place as short as I could make it - which is still about a half-inch too long. It was never a problem when I was younger and my body was more adaptable, but now my body is getting less tolerant of the stretching.

PeteHski

Ah, that makes sense now thanks.

Trakhak

I imagine there's a reason that sticking a cushion behind your back won't improve the fit.

noglider 

@canklecat, my understanding is that Biopace was intended for slower cadences, so your finding makes sense.

BlazingPedals

The limiting factor is the part of the frame that's in my crotch. That represents a hard limit to how far forward I can slouch. Adding some padding starting 6-8 inches behind the front of the seat might alter the curve in the lumbar area, and help push me forward a bit, although it'd be into the frame.