Crankset stiffness?
 

When people talk about how one crankset is stiffer than another, what are we talking about here? Crankarms? Chainrings? Being a weak and mortal, I surely can't tell the difference between one to the next beside the total weigh so please elucidate me.

I have had quite a few bikes and quite a few cranksets. I have yet to notice a crank flex. I'm a firm believer that the frame / bb is going to flex enough to hide any crank flex I get.

I remember an article in a bicycling magazine a few years back testing cranks. The difference of flex from best to worst was in fractions of a mm. They even stated it wasn't nearly enough for anyone to ever notice.

I haven't noticed any crank flex either. I have ridden bikes with square taper, Mega-EXO, and BB30. The only difference I feel is the flex in the frame, not the crank.

Crank flex is not an absurd thing to occur. On one of my fixed gears, I had 3-4mm of clearance between the end of the crank arm and the drive side chainstay. At some point, I flexed it enough to knock the paint off in that spot. It was a higher-end crankset on a very stiff aluminum frame, but I'm a fairly strong and heavy rider.

Especially when you're considering the vector of the force being applied to the crank, crank plex seems like a pretty minimal thing. If I had to guess, what most people attribute to crank flex is probably BB flex.

****ty cranks and chainrings can flex noticeably but not any decent racing parts I've used.

You can flex them but it takes alot. The BB usually gives up first but either way, it takes a lot. I raced BMX alot and up until my 30s , where you do alot of standing starts and then literally torque the whole bike under you. I've twisted crank arms, BBs , pedal axles , bar stems ... pretty much you name it. But thats the price you pay if you ride the balance between strength and maximum light weight.

I thought I felt the left crank arm (6700) flex once, going up a ~20 % grade, toward the end of a long day when I was tired and just wanted to get to the top. But I've never felt it again, so it was probably in my imagination.

Crankset stiffness?
 

Whether its the bb shell or the crank, there is definitely a difference with 10 speed external bearing cranks and the older internal bearing
Cranks

I can induce chain rub and. Even throw a chain on 9 speed and older cranks
. Never done that with new stuff either shimano or Fsa