Compendium of Internet Fit Advice


#861

[quote=Guy]Internet Fit Advice ShartQ: I’ve been having a recurring problem in one of my knees. On occasion, I get a sharp pain in my left knee under load (behind the lower part of the kneecap, specifically) in the first 15-20 minutes of a ride. The pain mostly dissipates quickly and doesn’t recur strongly as long as I don’t mash carelessly. Overwhelmingly, it occurs on a bike with 175mm cranks. The others in the fleet are 170/172.5.

The SQ: has anyone else experienced knee problems or other noticeable issues due to a minor difference (175 vs. 172.5) in crank length? I’m 5’11" but with stubby 30"-inseam legs. Do I replace the crankset with a shorter one or is it more likely that this is being caused by another fit-related variable?[/quote]

5’7" 69cm saddle height short legged cru.

175 - GTFO, I like my knees. Yes it’s a sharp pain.
172.5 - had some problem on a long ride, usually not too bad
170 - no problem
165 - teh best. Just as easy to mash, easier to spin.

I have some leg length discrepancy. I think shorter cranks allow larger margin of error.


#862

[quote=tamaso]
That being said, I have a really hard time believing crank length alone is responsible for the presence of sharp pain. Wiser men than me have said that knee issues rarely have to do with the knee, but moreso with mobility/flexibility (muscle, ligament, joint) issues ‘upstream’ (quads, IT, hips) or ‘downstream’ (lower leg muscles, ankle, achilles). If you’re not already doing some self-work with foam roller/balls/stretching on the whole system, I would suggest that.[/quote]
i agree 100% and I think that’s why I have zero pain with the shorter cranks. Your joints don’t have to bend as much. The fit can be sloppier before issues come up and that’s a great thing.


#863

Thanks folks. Time to troll eBay for 170mm, but the point regarding flexibility makes a lot of sense too. I had a relatively sedentary winter and this issue started occurring with frequency a couple of months back when I increased my weekly mileage into the 125-150 range (usually spread over 2-3 rides).


#864

I have also fucked around with >170 cranks in the past but couldn’t get my knees not to hurt with them. Shortcranks58cmcru


#865

what kinda cranks you looking for?
i have an extra set of campy record 10 speed in 170mm, these are silver aluminium cranks…
i went to 175mm…


#866

Replacing a 4500 triple. I’m considering just going full MTB gearing on it and getting a 40/28, but the triple isn’t too annoying with barends and the big ring is nice to have. However, I’d be down to swap if for some reason you need a 4500 triple…


#867

i typed a long post earlier and deleted it cos way TMI.

cliffs: We think about crank length mainly at the 12 and 6 oclock positions: more open hip angle at top, and less distance traveled vertically by the femur.

this isn’t really a big deal though, the longer your femurs are, but this is part of the reason they say shorter people benefit more from shorter cranks: a singificant (allegedly) different in hip flexion/extension.

my crackpot theory: think more about the positions of the crank at the 3 and 9 oclock positions. I suspect the knee issues are more about the force being exerted at different angles of knee flexion mid stroke downwards (3) and the effort, more importantly, pulling the cranks over the “dead spot” for the other leg around 9.

this diagram is interesting


but it fails to take into account the forces generated by the contralateral leg into the joints when the ipselateral leg is in the recovery phase.

also: your nerves are programmed to have each leg doing opposite motions. Sitting in your chair lift your left leg swiftly. Did you notice that your right leg pushed down into the floor? I’d wager that you almost can’t NOT do that.
I think this may have something to do with knee pain: a combination of forces by the pedal at 9 from the other leg at 3. Also, the flexor/extensor reflex in both legs additionally generates another force/muscle inhibition that may result in less stability at the knee joint when the knee is in different degrees of flexion in the Anterior posterior plane.

okay. That was literally as short as I can write that…
It was just a thought. I started to have knee pain last summer. medial Bursitis. 175mm cranks, 79-80 cm saddle height 5’9-5’10 depending on how slouchy/in pain lower back I am. Started in one knee, migrated to the other. Also was related to autoimmune shit, though, which precipitated it faster.


#868

what kinda cranks you looking for?
i have an extra set of campy record 10 speed in 170mm, these are silver aluminium cranks…
i went to 175mm…[/quote]

Also pretty sure I still have a set of 10sp SRAM Force GXP 130bcd cranks…


#869

3 o’clock, 9 o’clock theory is legit. I mean KOPS is kinda bullshit as a reference point but the angle of your knee when you’re pushing down at 3 o’clock matters IME. I had 177.5mm cranks for a while, and they just didn’t work for me. 175mm sounds so close but I don’t have the same issues anymore. I’m tallish and have an 81-82cm saddle height but for whatever reason I cannot handle tarck approved levels of setback and long cranks just make you have to sit further forward. I suspect it has something to do with femur length and my preferred cleat position (slammed back).


#870

Who here has dealt with a leg length difference? I went to a clinic for my back problems this morning, and the doc ask if I thought one leg was longer. I’ve suspected that’s the case since it feels that way on a bike. Up to now whatever’s going on has not been an issue riding, but now that I’m dealing with issues off the bike I’m wondering about it.


#871

I have a leg length difference. Chiro always asks if I have problems. I say no because I htfu. Really, one leg wants the saddle at a different place than the other. I guess there are shims and other things but it’s minor so I don’t really worry about it. I think most people DO have different length legs.


#872

I have a 1 1/2 size difference in my feet, and clipless was just not doable for me, even after messing with many different cleat positions. Now I just run bmx platforms and feetbelts and my feet find the spot they want to be in.


#873

I think most people are asymmetrical to one degree or another. If this is causing you issues, it might be worth considering trying to sort out whether the imbalance/difference is ‘functional’ (meaning a result of short/stiff/low-mobility joints, muscles, ligaments) or whether it is somewhat more ‘physical’/permanent (e.g. difference in bone, result of injury etc.). This could be assessed by a skilled physio, or maybe through some kind of imaging.

Shimming, etc. might just be kind of kicking the ball down the road unless you can isolate what is really going on, since you might be better suited addressing a functional length imbalance through mobility or strength work.


#874

Most (all?) people have at least a small leg length discrepancy which can be a result of many different factors. Injuries, scoliosis, difference in growth, muscle tension, etc.

It’s pretty easy to see if/how it’s affecting you on the bike. Set up on a trainer, wearing bib/shorts, with a friend or a video camera and check two things:

  1. Have the friend/vid focus on your hips, from behind. When pedaling your hips should remain “flat” i.e., neither hip should drop when you are at the bottom of your pedal stroke. If both hips drop its an indication that your saddle height is too high. If ONE side drops it is an indication that that leg is shorter than the other. Your hip will dip as you are trying to reach down to the pedal to make up for the discrepancy.
  2. Have the friend/vid focus on your pedal path, so the entire pedaling stroke is in frame (this is best done with a camera rather than eyeballing it). Focus on the bottom of the pedal stroke on both sides. If you are pointing your toe more on one side vs the other it is a good indication that that leg is shorter than the other.

Cleat shims really are the best method to compensate for discrepancies, on the bike. If you add any, be sure to do so incrementally. You don’t want to shock your body with a drastic change, as that would have the opposite effect.


#875

we are squishy sacks of meat that change size every day.
thank you for playing


#876

Welcome to tarck wilhelm. As a matter of procedure we ask that you please switch your avatar pic to this

Edit: :smiley:


#877

excellent mansplaining new guy


#878

Thanks. I’ve done a fit or two in my day.

I love all the new fangled computational fitting devices, but sometimes all you really need is a good eye and to ask a few questions. Using a computer to put a rider in a “good” or “aero” position is the easy part. Making sure said rider is comfortable for more than a ride around the block is another story.

/oldtimerfitsemirant

Also, TC, I love the newguy avi


#879

I don’t typically have pain issues associated with cycling but the Rando 400K (24 hours) from last weekend really fucked my hands.
The outside heel of my hand swelled up to an enormous red bubble which i’ve never previously experienced. It took 3 days before the swelling went down.
My pinky and ring finger would occasionally feel like they had fallen asleep and would tingle or feel numb.
I also had the skin at the heel of the hand start peeling from what I’m assuming was a light blister but didn’t have puss or anything to indicate it was a real blister.
I noticed that the hand with the worst swelling was my left hand which is also on the same side of my body as my titanium collarbone. Not sure if that is related. I’m also right handed if that matters.

I also had some pain on the top/front of my knees and had to pop a few advil to dull the pain. No sign of pain after the ride though, on and off the bike.

This is my current setup. Any advice? Should I finally get a professional fitting now that i’m doing longer rides?
I don’t do any exercising to strengthen my core, only cycling daily. I’ve been stretching & using roller way more this year than any year previously.


Rawland Stag shred portal by Andrew Squirrel, on Flickr


#880

welcome! i have the same hand issues.

it is not uncommon for long distance and endurance cyclists.

your ulnar nerve is the one that is getting pinched and causing the problems in your pinky/ring fingers. it doesnt look like you have a whole lot of drop and i would make the assumption that you are probably fit well enough for your bicycle but little details like handlebars and hoods might be the thing. for me, i get tired and when i get out of the saddle i lean on my palms on the shoulders of the bars - this is a bad habit and i am trying to break it but at 250+km my dgaf level is high.

things you can do: different bars, padded gloves, padded tape, habit breaking.

edit: core exercises. do not lean on hands, rely on core strength. and your midsection will look good.