The Cadence Conversations

[ratz]

I’m sure I’ll improve I don’t see any way I’ll match my typical DF cadence. Mostly an issue of stability at high cadence

You will and you'll likely exceed it if you focus on it; as you adapte you'll slide forward on the bike; after that happens just work on your boom length to avoid "hop throw" fowards and backwards. that plush an ever improving spin will clean up you cadence. It just takes time.

 

[Balor]

You will and you'll likely exceed it if you focus on it; as you adapte you'll slide forward on the bike; after that happens just work on your boom length to avoid "hop throw" fowards and backwards. that plush an ever improving spin will clean up you cadence. It just takes time.

Yea, my average cadence seems about match my DF cadence now (given shorter cranks), after a few years on MBB bents. Max cadence is about 150 vs 160 on trainer though, but that is of limited use to me - I can still his very respectable speeds while pedalling this way (only downhill of course).

You body does adapt - but finding out what EXACTLY adapts, limits of this adaptability and how the process can be sped up or helped along is very interesting!

 

[ed72]

Anybody who has ridden 200 mm or 145 mm cranks knows that optimum cadence varies. Anyone who has ridden fast criteriums or at the other extreme, say a long tour, knows that optimum cadence varies. Although we can't peer into our muscles, the fiber type also affects optimum cadence. Our muscles tend to seek a specific torque. Spinning at 120 rpm at 50 watts is extremely inefficient at that output whereas trying to output 250 watts at 50 rpm cadence puts much strain. All else being equal, cadence should increase as power output increases or said another way, lower power and lower cadence go together. When noodling along at 20-22 mph, my cadence is 72 rpm but it increases to 90-92 when at higher speeds. I use 172.5 mm cranks.

At a low exercise intensity of 50W, they found that pedalling in a small gear at 110 rpm put more than 60 per cent of their power into moving parts of their own body, including thighs, knees and feet while only 40 per cent of it actually went into spinning the cranks. It was a massively inefficient way to ride.

https://www.cyclingweekly.com/fitness/why-amateurs-shouldnt-try-to-pedal-like-chris-froome-191779

http://members.home.nl/vd.kraats/recumbent/pedal.html#Cadence and efficiency

 

[Balor]

That's not about movement per se, cranks are going in circles and should be perfectly balanced.
It is about internal friction that I've described above - and joint friction is only a small component.

I'm reasonably sure that when you do cadence drills, your autonomic processes home in on most effective patterns of firing your muscle fiber bundles - hence it should be possible to get your internal friction down to reasonable levels at high cadence, but not after a lot of training. That's what track cyclists do.
Plus, like Osiris noted, when you spin very fast AND output very high wattages, your muscles fire much more fibers in sync - hence likely much less internal friction losses.

 

[ed72]

Which of the following is more efficient using an 11 speed 11-32 cassette?

1. 53x25 at 50 watts and 60 rpm?

2. 36x28 at 50 watts and 100 rpm?

3. 24x19 at 50 watts and 100 rpm?

 

[Balor]

Descending efficiency I presume
Larger chainrings result in higher efficiency because chain does not 'bend' as much (larger diameter) and less chain tension - less frame stress.
Plus crosschaining.

 

[ed72]

Descending efficiency I presume
Larger chainrings result in higher efficiency because chain does not 'bend' as much (larger diameter) and less chain tension - less frame stress.
Plus crosschaining.

The first option has both higher mechanical efficiency (as you mentioned) but it also is more efficient metabolically. Option 3 is a mini-nightmare and probably a recipe for knee pain.

 

[Balor]

Option 3 is a nightmare and probably a recipe for knee pain.

Yup, spinning *too* fast is also not very good for knees, mine do hurt after 'cadence drills'.
They did come in handy for 'hill surfing' like I said, sprinting up steep 'horseshoes' is extremely effective average speed wise.

 

[ed72]

I'd have to dig up the study but it showed (if my memory is correct) that low chain tension AND small ring/cog combinations can be as low as 80% efficient compared to big/big combination at high tension being 95-98% efficient.

Who wants to toss 20% down the drain?

 

[Balor]

Yea, counterintuitively more chain tension leads to higher efficiency, but than chain tension can case the frame to bend and that can lead to rolling resistance losses from driving wheel misalignment (most notable on RWD bents, because they are 'one large chainstay').

 

[ed72]

Yea, counterintuitively more chain tension leads to higher efficiency, but than chain tension can case the frame to bend and that can lead to rolling resistance losses from driving wheel misalignment (most notable on RWD bents, because they are 'one large chainstay').

Paging Mr. Planing.....

 

[ed72]

What can be seen in the first link to a 2014 TdF power file is the relationship between power and cadence. When the heat is on and more power is needed, cadence is increased. When going along more modestly, cadence is in the 60-70 rpm range but ramps to 90-100 when going hard.

The second file shows an "average" cadence of 82 rpm on a hard TdF stage. Average doesn't really show the same effect as the first file; namely, appropriate cadence varies.

https://www.trainingpeaks.com/blog/2014-tour-de-france-power-analysis-week-1/

http://home.trainingpeaks.com/public/workout/MIM3PEJE55W3J6PJ26DBD35XXQ

 

[Balor]

Paging Mr. Planing.....

He actually knows that, and this is rather well-known fact in framebuilder circles (just esoteric enough not to be widely known outside).
His 'planing' applies to frame tubes (and upper chainstays), NOT lower chainstays that should be made as beefy as physically possible (and I think he expressly mentioned that somewhere).
Steel actually has advantage over other frame materials here, because there is little room for truly oversized chainstays between the tire and the crank/chainring.

I'm following a blog of an aluminium welder and more than 90% of broken chainstays are right lower ones. Very common.

 

[Balor]

I think the best bike from comfort/power delivery/aerodynamics standpoint is beam bike with VERY fat lower chainstays (and no upper chainstays), designed around large Q-factor cranks and 'boost' rear hub.

It would also help to have an I-beam (running horizontally) inside the chainstays.

 

[ed72]

It was too esoteric to mention earlier but indeed, frames, rims and tires do flex especially under higher loads, which is a good reason to up the cadence at high power. I tend to like my brake pads not too close to the rim on all my bikes. Wheel and frame movement are about equal on many bikes although I suspect one can forget about frame flex on a Cruz.

https://www.bikeradar.com/us/road/gear/article/bicycle-brake-rub-wheels-vs-frame-49344/

 

[ed72]

I think the best bike from comfort/power delivery/aerodynamics standpoint is beam bike with VERY fat lower chainstays (and no upper chainstays), designed around large Q-factor cranks and 'boost' rear hub.

It would also help to have an I-beam (running horizontally) inside the chainstays.

Like the "Black Hole"

https://bicycledesign.net/2010/03/a-hubless-wheel-from-the-past-the-black-hole/

 

[ed72]

I can feel the chain's inertia during the dead spots when accelerating down gentle slopes, so, the planing hypothesis sounds good. However, the fastest climber review was a Specialized Diverge in carbon but that was not explained within the planing context. It is possible that chains store inertia and help get the pedal stroke over the top. Maybe. This would argue for higher cadence.

The short chain and ultrastiff front on a Cruz must be more efficient than a LWB bent but I have never seen data proving it (just need two calibrated power meters, one on the crank and other at the wheel). Flex in the drivetrain can be a consideration WRT cadence but doubtful an issue on a Cruz.

I have only broken one frame. It was steel. Touring bike loaded to 100+ lbs total. I was sprinting a hill. Snapped the downtube at the shell but it was a little rusted. I did break a dropout in the 70's, a Miyata. It was covered by warranty. My carbon seatstay was cracked/smashed by the airlines on the way over to PBP in 2015 and I kept stopping to figure out why the brakes were rubbing on climbs. So, bikes with all sorts of material do break. Oh, I forgot.....I have a cracked magnesium frame. My Aluminum Klein circa 1983 never broke anything other than my butt.

 

[Balor]

The short chain and ultrastiff front on a Cruz must be more efficient than a LWB bent but I have never seen data proving it (just need two calibrated power meters, one on the crank and other at the wheel).

You will not get frame losses this way, they happen at the tire contact patch on one end and in your own legs in the other end.
Only chain losses, and those are on the order of a 3-4 watts max. Maybe if you use chain wax with lots of beeswax like I do they are greater (it is tackier), but likely not by much and offset by absolutely incredible longevity.

 

[ed72]

You will not get frame losses this way, they happen at the tire contact patch on one end and in your own legs in the other end.
Only chain losses, and those are on the order of a 3-4 watts max. Maybe if you use chain wax with lots of beeswax like I do they are greater (it is tackier), but likely not by much and offset by absolutely incredible longevity.

I don't believe there are any frame losses....frames don't heat up. Frame flex can cause rims to hit the brake pads and frame flex will distort the tire contact patch. Neither would get measured.

I don't know about chain loss differential between LWB and MBB bent. Older chains did not have much flex, which would favor the better chainlines on a LWB. The 11 speed chains are so efficient and have better flex that I am not sure whether additional losses are incurred. If a newbie rider has chain tubes and a second idler (like on an M5), they are losing 10 watts per well placed sources. Chain losses are proportional to cadence in this instance (dragging across idlers and thru tubes); however, this isn't as much of a consideration on a Cruz.

I am always amazed by some riders who claim to be pedaling at 100 rpm but when riding behind on a club ride and as I match their stroke revolution by revolution my meter reads 80. I think the bottomline is that experienced riders will eventually self select the right cadence for them.

 

[IndianaDave]

All
Just read this entire thread with my insomnia and want to THANK YOU for all of your wisdom.

I've been a serious cyclist for years, researching and experimenting. This thread is one of the most informative reads EVER. Makes me wish I were 20 instead of 80.

Indiana Dave
2 months in on my first Bent ... V20
Photo is with 305s. Have 406 and 700 wheelsets for both Fun and Fast