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Schmeg

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Discussion starter · #1 · (Edited)
Just finished watching a video on HT Party that highlighted crank length and the effects felt on the rider. Steve did a great job directly comparing 155-170 crank lengths. The longer length (170) he mentioned some knee pain.
My Fatbike (Growler) came from the factory with 175’s On a size small frame. Being new to the game I’m not sure why this size frame was spec’d with such large cranks which begs the question. Are most if not all fatbikes equipped with longer crank lengths than dirt bound mountain bikes? And if so why? And if longer cranks are a mainstream situation in the fat community, can crank length perhaps be equally the culprit for knee pain as well as wide Q factor?
Personally, now that I have a full 6 months on my bike with 175’s, at 5’3” with a 28” inseam, I’m moving to 165’s. I feel my hips are flexing way too much and if I’m in a lower gear climbing, it seems way too easy to blow the rear tire riight off the trail even on hardpack. Almost too much torque when I’m out of the seat. I’m just asking these open ended questions to perhaps bring some things to,light. I personally;y don’t have a lot of knee pain, but occasionally;y I’ll get a little if I’m seated and cranking uphill too hard.

Again, are fatbikes equipped with longer cranks (170-175) rather than shorter on a universal basis, or is my Growler an isolated case?. If it is universal, what purpose does it serve? Seems like longer cranks are too much of a good thing sometimes. And it may explain knee pain as much as Q factor.
 
Shorter cranks are still more the oddballs. Most every complete bike I've seen has run 170 or 175s.
 
175s on a small bike is silly, indeed. I feel that most people would benefit from cranks that are proportional to leg length, and 170 is about where "medium" is for the average person. 175 is pretty long. Of course, personal preference comes onto play and I'm not going to tell anyone they should not ride 300mm cranks if that makes them happy. But for average proportion humans who fit a small frame, 175 is most likely too long for efficient pedaling over the miles.
 
They probably just spec'd that bike based on parts availability from the groupset source (maybe they wanted 165s for the Small frames, but all that was available was 175s?). It seems that in general, crank length should be relative to leg length. I just had a conversation about this with a guy I race with who is at the smaller end of the height range, and he has happier knees with the shorter cranks, he makes PLENTY of power with them too, and prefers to spin at a higher rpm. My actual inseam is 36", and 175s seem to be a pretty good length for me, - but when I've ridden my kids road bike on fast group rides with 170s, I keep up just the same as with my 175s.
 
After hanging on MTBR's forums for over 20 years, I've come to the conclusion that crank length is like many other dimensions on bikes -- individual preference.
Handlebar width. Chainstay length. Dropper travel. Etc.
Twenty years ago on the Singlespeed forum, everyone was racing toward long cranks -- 180 - 185mm was common.

Now the opposite is happening. Everyone seems to be racing toward shorter cranks.

Personally I've gone from 202mm (Bullseyes) > 195 (Carumba) > 185 (Surly) > 175 (anything and everything.)
I'm 6'1" with a 36" inseam.

Why have I moved toward shorter cranks?
In no small measure because I ride my bikes completely differently than I did 20 years ago.
I used to do epic rides. My riding buds & I would get on our bikes and head into the hills for epic journeys.
That's it. Just ride.
Now I'm enjoying what we might call 'trail entertainment.'
I'm talking about trails that include options for getting my wheels off the ground.

I don't want my feet so far apart (one in front of the other), a stance that long cranks force.
Setting up for hitting lips is much easier when I'm not turning such big circles.

As for power, I'm still a long crank believer.
Speaking for myself (with long legs.)

In the end, it all comes down to personal preference.
=sParty
 
I also went shorter over the years (currently running 170s on my hardtail and 165 on my FS). Leaving 175s only on my road bike (I'm another 6'+ and 36" inseam guy). I went to shorter cranks as BBs dropped, and found no downsides ;)

Knee pain, for me, is typically an issue at full extension. But I could totally see shorter cranks helping with both knee and hip pain. Sorry for my kurt initial response.
 
Yep, I'm 5'9" with a 31" inseam. Run 170s on my to SS MTBs and 165s on my SSCX, body definitely prefers these shorter options.

With 175s and adjusting the saddle for full extension my knee comes up way too high and it aggravates my hips.
 
I swapped both my Ripmo AF and my 951 XC both large frames to 165 mm cranks from, 175's. Feels better to me and way less pedal strikes. I have notice my hips are less sore with shorter cranks guessing at top of pedal stroke there is less force on them due to shorter cranks and opens up my hip angle more.
 
They probably put 175s on your bike because thats all they could get with all the crappy supply chain issues. I bet you would like shorter cranks considering your height and leg length. I just switched to 165's and really like them. It makes for a much smoother pedal stroke, kind of like an oval chain ring.

A size small bike should probably not have longer than 170mm cranks in my opinion.
 
I'm close to 5'9" and my inseam, in socks is 30.25". My wife had some knee pain and went down to 170 on crank length and I am about to try 165 just to see how it works out. I don't have knee pain, I was just bored and wanted to try it after watching some YT videos. I'll probably head down to Moab on Sunday. If it's noticeably different, I'll report back.

I'm on a 29er with a 30t oval up front and I just put on a 10-51 Shmeagle (Shimano front and back & HG+ chain with AXS Eagle shifting). Should be interesting!
 
are you guys measuring your actual inseams?, - which is often different from what people state based on pant size.
Yes.
Barefoot, book in the crotch, against a wall.
=sParty
 
I went down to 152 and found it took about 2 weeks to adapt, but then I found that it was hard to go back to 170s. The "circles" I had to pedal felt extremely exaggerated, and the cornering stance felt less natural.

On the shorter cranks, it felt more like stair climbing than pedaling circles. I felt that riding the bike like this would result in more "fitness transfer" between bicycle fitness and my fitness on foot. I feel this wasn't the case with longer cranks, in which bicycling didn't help much with my endurance nor pace/efficiency when walking/running.

The increased ground clearance was welcome. The cornering stance was a bit awkward at first, but I realized that it was a welcome change, too.

Regarding knee pain, I generally don't get that with how I use my dropper post (not riding with seat too low), and after my switch to flat pedals (not having feet locked too straight, as my feet like to naturally splay out). My seat height was taller with shorter cranks, but I felt like I could get away with lower without feeling strain on my knee when pushing down at the top of the stroke. The pedal strokes seemed like they were akin to "cheater squats", not bending the knees as much.
 
I went from 175 to 170, on the same rocky trails, the clearance is awesome, I do however seem to be using my lowest gear more as I feel there is a bit less "cranking" power.
Exactly. Because there is less cranking power.
Cranks are levers. The shorter the lever, the more force required to operate it.
There may be other benefits (like ground clearance) but the fact remains: less cranking power.
=sParty
 
I have two rides in on 165's after riding 175's up until now. Bike is a medium (I'm 5'7 with 29.5" inseam) and experienced knee pain for the first time last year. Being 57 has some disadvantages I guess. So far, so good with the 165's. Also, I did drop down from a 34 to a 32 chain ring with the smaller cranks.
 
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