Newish crank arms down to 145mm

[witcombusa]

So lots (finally) being talked about regarding crank arm length.

https://www.youtube.com/watch?v=2GLZnLbFgcw

I think way more has been said about big guys and 177.5 and 180mm arms than has ever been talked about smaller riders. Now arms available down to 145mm.

Now @AngryScientist rides about the smallest frame that I know of so I'm curious if anyone has done any experimenting? I've only used cranks from 165 (road fixie) to 175mm but @ 6' I'm well in the bell curve.

This has to be the least spoken about aspect of bike fit/efficiency.

Thoughts

[Upcountry]

Originally Posted by witcombusa

This has to be the least spoken about aspect of bike fit/efficiency.

You haven't peeked into a Triathlon/Timetrial forum or thread in the last few years... Cranklength is to TTs what Tire Pressure is to Gravel.

[Flinch]

I've got a long standing right side pelvic 'drop' that's plagued me for years - saddle sores and right foot that floats at the bottom of the peddle stroke. I went from 175mm cranks to 165mm, and wowza, magic happened. No more right side evil, and the only effect on my riding was a 4 rpm faster cadence - NO power loss!

Best bike move I've ever made. OK, besides maybe Brooks saddles...no, wait - short cranks, or could be maybe saddle, or...oh foo.

[Nomadmax]

If you really want to get into a rabid, short crank arm discussion, just go to any recumbent forum.

[witcombusa]

I'm not saying in any way that everyone should go shorter. Just that these new arms open up options to the shorter of leg cyclists. (finally) There are real choices now.

[Alistair]

Are the big brands making sub-160 cranks?

Are any big brands spec’ing sub-160 cranks on their bikes?

I mostly ride 170, sometimes 165 or 167.5, because that’s what’s available (stock builds or easily found at reasonable price aftermarket). I’d love to try 150s but spending $300+ just to see if I line them is a bit steep.

[EB]

I’m tall (6’2”) and ignored traditional fit advice to dive into short(er) cranks, mainly because most of my riding is on dirt and rocks now. Shorter cranks means fewer crank strikes. Currently on 170 for my hardtail and gravel bike and 165 for a full squish with a relatively low dynamic BB height. Traditional fit would put me on 175 to 180 cranks.

No downsides in terms of efficiency or pedaling noticed. I’m very curious what going even shorter (eg 160 or 155) would be like. If you are concerned about very short term leverage reduction, like with ratcheting in technical sections, you can drop your chainring size to compensate. This is a non-issue for road-ish riding though.

Everything is a tradeoff though - if you shorten your cranks, you have to raise your saddle (and move it forward, if you’re concerned with maintaining setback). Assuming that’s within range of easy adjustment for your seatpost and saddle, then you have to deal with your cockpit, unless you can manage the increase in drop.

[Jere]

Originally Posted by Alistair

Are the big brands making sub-160 cranks?

Are any big brands spec’ing sub-160 cranks on their bikes?

I mostly ride 170, sometimes 165 or 167.5, because that’s what’s available (stock builds or easily found at reasonable price aftermarket). I’d love to try 150s but spending $300+ just to see if I line them is a bit steep.

https://www.bikesmithdesign.com/Short_Cranks/

https://www.bigandtallbike.com/custo...ing-cranksets/

If you’re using 12 speed you are SOL

[Upcountry]

Originally Posted by Jere

If you’re using 12 speed you are SOL

Sram offers 12 speed Rival AXS crank arms all the way down to 160mm, as does Shimano with their 9200 Dura Ace and 8100 Ultegra lines... So they are moving in the right direction. Sram Red update is due any day now, and I wouldn't be surprised if they followed suit.

[verbs4us]

For decades ran a 170 crank until my 60s, when the effect of various surgeries resulted in a habit of a hip rotation, quad overuse and hip flexor pain. Fitter and PT collaborated to recommend a 150. Could not find a crank I liked at the length but went with TA Carmina (much love for square taper and silver) at 155 from Peter White Cycles. For a few months, the shorter stroke length felt like I was crammed into a kid's tricycle but now it feels natural and flexor pain is gone. Can't give all credit to the crank length, since I did undergo a massive PT program, but I give the crank some credit!

[sparky33]

After a recent experiment with 165s, from my usual 170s, I was pleasantly surprised that a mere 5mm improved comfort for my not-so-great left hip&knee. Turning the gears did feel different at first, but now it feels like a natural spin.
All my bikes are now 165s.
Probably that is the end of my crank shortening phase.

[tommyrod74]

Originally Posted by EB

I’m tall (6’2”) and ignored traditional fit advice to dive into short(er) cranks, mainly because most of my riding is on dirt and rocks now. Shorter cranks means fewer crank strikes. Currently on 170 for my hardtail and gravel bike and 165 for a full squish with a relatively low dynamic BB height. Traditional fit would put me on 175 to 180 cranks.

No downsides in terms of efficiency or pedaling noticed. I’m very curious what going even shorter (eg 160 or 155) would be like. If you are concerned about very short term leverage reduction, like with ratcheting in technical sections, you can drop your chainring size to compensate. This is a non-issue for road-ish riding though.

Everything is a tradeoff though - if you shorten your cranks, you have to raise your saddle (and move it forward, if you’re concerned with maintaining setback). Assuming that’s within range of easy adjustment for your seatpost and saddle, then you have to deal with your cockpit, unless you can manage the increase in drop.

Not to nitpick, but maintaining the same saddle setback (relative to forward pedal - you wouldn't do it relative to BB if crankarm length changed) would necessitate sliding the saddle further back, not forward. This is one reason 165mm cranks didn't work for me, I couldn't get enough setback.

[EB]

Originally Posted by tommyrod74

Not to nitpick, but maintaining the same saddle setback (relative to forward pedal - you wouldn't do it relative to BB if crankarm length changed) would necessitate sliding the saddle further back, not forward. This is one reason 165mm cranks didn't work for me, I couldn't get enough setback.

You're right, forward or backward is dependent on the crank in this case, I misspoke.

The other thing I could add is that maintaining setback may or may not matter depending on your goals and how attached you are to a given pedaling structure. For me, the tradeoff of shorter cranks was worth it for mountain biking, where I'm not as worried about maintaining a certain setback, and everything is really different than road anyway (different Q factor, huge variations in body position throughout ride, etc.). This might or might be important for you - I get why people are attached to a particular leg movement for road riding.

Although some of it is just what you're used to... supposedly early safety bicycles had super slack seat angles so that they'd be familiar to riders of penny farthings.

[mjf]

Originally Posted by Jere

https://www.bikesmithdesign.com/Short_Cranks/

https://www.bigandtallbike.com/custo...ing-cranksets/

If you’re using 12 speed you are SOL

If you only look at Shimano/SRAM in a vacuum, sure?

Rotor's probably the closest in availability to the broader bike brand community

Rotor Aldhu - 150-175mm. Spiders/spindle options, 110x4, 110x5, 110/80 (grx), track, etc.
https://rotoramerica.com/products/aldhu-crank-arms

Several of the many options from smaller makers that

Ignite components road/gravel set - 155-180 stock, custom lengths available. 8 bolt spider/chainrings, nearly any combo of spider/chainrings will work.
https://www.ignitecomponents.com/pro...inferno-cranks

Raketa road crankset - 145-175mm stock options. 8 bolt spider, again nearly any combo spider/chainrings.
https://raketacomponents.com/shop/pr...road-crankset/

Sturdy Cycles- 150-175mm(2.5mm increments) stock options, custom available. 8 bolt spider, again nearly any combo spider/chainrings.
https://www.sturdycycles.co.uk/produ...anium-crankset

Appleman 2xr crankset - 100mm, 130-175mm as stock options, custom available. Proprietary spider, but 110x5, 110x4, 144bcd among others as stock options.
https://www.applemanbicycles.com/shop/2xr-crankset/

WATTshop for SRM power meter based cranks track/road - 145-172.5mm, pedal thread insert to modify length. SRM spider/spindle, so whatever speed or chainring combo you can put together from SRM, track or road.
https://www.shopforwatts.co.uk/colle...igin-crankarms

[Mark McM]

Originally Posted by tommyrod74

Not to nitpick, but maintaining the same saddle setback (relative to forward pedal - you wouldn't do it relative to BB if crankarm length changed) would necessitate sliding the saddle further back, not forward. This is one reason 165mm cranks didn't work for me, I couldn't get enough setback.

But should you adjust setback the same amount as the crank length change? Force is applied through the entire downstroke, not just when the crank is horizontal. So wouldn't you want to adjust the setback just a portion of the crank length change?

For most seatpost/seat tube angles, adjusting the seatpost height will move the saddle backwards about 1/3 as much as much as it is moved upward. So simply adjusting the saddle height for a change in crank length will take care of most of the setback change anyway.