Rolling Rollers in a Bigger Gear: Momentum Gains vs Torque Cost Question
So, the other day I was riding the course up in Lake Placid for the umpteenth time...when my front derailleur started having shifting issues. I thought maybe I was losing power in my DI2, but it turned out the crank arm was coming loose (!) but regardless, I decided at about mile 40 to ride the big ring. I rode it back to the house at 56, fixed my stuff, and then continued in the big ring.
Note: I ride a 54/40 front, 11/28 rear on 170mm cranks.
Now there are a few sections of the course with sustained climbs or short/steep enough climbs that I did use the Small Ring for about 2 miles of the 56 mile loop. When I got back, I was stunned. I put up a 5:32 on day one -- my best training loop by 13 minutes. The next day I went out -- 18 hours after the previous day -- after another 2.4 mile swim and did it again...only this time I rode a 5:27. Which got me thinking about using the bigger gear for the smaller hills.
When I hit a hill, I would shift to the 28 in the rear, sit up tall, on the nose of the saddle, and use smooth pedal strokes. I was able to keep my watts low enough (I ride 250 and on the hills was pegging it at 275) that my HR never really climbed. I find that my watts spike when I shift to the small ring, so I avoided that as well.
Granted I am race fit and race weight right now, but I am curious to know if there's a "place" for this type of riding on race day? I literally flew over the LP course both days...and I know the Mont Tremblant course has a few climbs where this won't work...but I want to know what you are thinking.
As reference, my average cadence is about 80rpms on race day, and on both LP days it was about 78 for both rides.
I appreciate any input you have...thanks TEAM!!!
Comments
The gearing choice in itself would cause you to shave some time. Dropping 15minutes on a course is pretty cool. Tells alot about your potential, even as you get closer to old fart status.
Conversely, there are days when I just 'need' the small ring. Whether training or a race, if my legs feel tired after the first hour, I spin up the hills more than the rides I referred to previously. Again, it looks like it comes down to 'how do I feel?', 'am I primed enough to big ring it up and over?'.
The more I hang around, the more I appreciate how much tri riding is all about keeping momentum. When we're in touch with that momentum, hills are almost fun!
BTW, my 50/34 quarq is a few years old. This compact setup was recommended by these very smart coaches. But, I'm thinking about getting a new quarq...prob a 54 or 55 for the big ring.....let me know if you know anyone that is interested in buying a compact crank....
What you didn't mention was what the typical previous gear ratios were. 54/28 is just short of 2.0. If you were previously riding something like 40/21, you weren't doing anything different (except straining your chain) and you're just in good shape. :-)
There are lots of people out there who will tell you that most people's highest "efficiency" in an absolute sense is with a relatively low cadence (say, 70ish). If you were over-gearing, it's possible you discovered that spot for yourself...and of course you didn't run afterwards to find out if there was a penalty.
Cheers,
Wm
The hardest part for me to reconcile is the fitness level changes + weight loss...throws everything off...but your stuff here is helping me a lot. Please keep it coming!
I'm assuming your rear cassette is setup as.. The 11-28 includes: 11,12,13,14,15,17,19,21,24,28
You could get the same gearing if you used 40/21 rear. On a side note of course using the 54/28 is hard on the equipment (aka cross chaining)
http://www.bikecalc.com/gear_ratios
As a skinny guy with a tiny FTP, hence low W/Kg, there must be a W/Kg threshold that a rider needs to be above to even consider this type of riding. I am far below that point.
From a strictly mathematical point of view (help William!) there is a point where weight/slope/power (xx% of FTP) where moving forward becomes impossible. You pointed out yourself that several sections required the little ring. For me with a W/Kg < 2.5 (bike + rider), I need the little ring for most of the hills in LP.
If you ride at 250 I assume your FTP is ~350 and your W/Kg (bike and rider) is around ~3.85 or so. Big difference. Consider this, we both ride at a perfectly constant IF = 0.70, no spikes, and with the identical gearing. My effective W/Kg (@ 70%) is 1.7 while yours is 2.7. Because of your power you could ride much steeper grades than I. Simple physics.
I guess my point is this: Power Weenies like myself need to be very cautious of techniques available to the stronger cyclists.
Riding 54/28 will kill your chain superfast especially when you are putting some big wattz on it and I'm totally confident having such a "terrible" cross chaining will even eat up a few of your hard-earned watts.
I just recently have noticed a quite big difference in resistance on turning my crank by hand (during bike cleaning) between 53/28 and 53/21 ... I've not measured it but just give it a try by yourself - you will FEEL (and hear) it
Since I have upgraded to Di2 with bullhorn shifters I'm now shifting a lot more than before and I feel "better" at the end of the hill.
Notes:
I am more worried about getting carried away with the big gear and nuking myself than anything else
I appreciate the input...more time for thinking / plotting / scheming!
I think the reason there is differing opinions is 'size' of rider. No offense to Tim, Jenks, Rich, et. al. But you guys are all "little guys". This is all about gravity and momentum. Two things that don't effect you little guys as much as the big hoss's of the team (as much as you may claim it does, it does not). We are all facing rolling resistance and wind resistance and gravity. So the first 2 stay roughly the same for all of us. The gravity has a multiplier effect with weight, so big guys just have a bigger force pulling us "down" the hills and a bigger force to overcome as we go "up" the hills. I've ridden a bunch of rides with a couple of really strong little guys who just kill me on sustained climbs. It's not just W/Kg, but just lack of Kg's that make a big difference here (but high W/Kg certainly helps). But on rollers where us big guys can get some forward momentum and allow us to carry that most of the way up the hill, now we're talking... The one guy I was riding with (CAT2 racer who is all of 138lbs with the same FTP as me) said he couldn't wait for the couple of bigger up hills so he could get a rest because he was pedaling all out just to stay on my wheel through 1.5 hours of rollers. He was literally resting on the uphills as he gapped me because he was exhausted from trying to stay in my draft going down them. And if he would get ahead of me I would always pass him on the bottom 1/3 to 1/2 of the hill as my momentum just carried me up the bottom part of all hills faster.
Okay, that's a big lead in to my actual point. Because carrying this momentum is so important for big guys on rollers, the 2-3 seconds off the gas to lift, shift to the small ring, then get your cadence properly matched again, causes just enough of a break to make us start fighting gravity again as opposed to carrying momentum and letting the gravity try to come to us. If this constant momentum is enough to get us 2/3 of the way up the hill, it's almost easier to just stay in the big gear, drop the cadence a bit and punch over the hill to lather, rinse, repeat for the next one. Coach P, you have Di2 now, use it and trust it. When I shift to the small ring (especially on rollers, but pretty much anytime) I do a simultaneous upshift of the RD. So you downshift the front at the same exact time you upshift the rear. You cannot really do this with mechanical deraileurs, but with Di2 it makes an almost perfectly cadence matched downshift that allows you to keep pedaling the whole time without lifting off the power at all during the shift. This method gives you almost no momentum loss but will allow you to be in the small ring if the hill happens to be longer or steeper. Might be something worth trying on your recon ride this week and employ at IMMT. If you try this one or two times you will realize how intuitive and simple it is.
Now if the question was about just mashing a bigger gear at a lower cadence for a long time up a sustained hill, I think a lot of that is personal preference. I like to ride at 85-95 cadence, but I know from looking at some of your old race files that you have run quite well off of an 80 cadence for 5 hrs. Not everyone is a spinner...
See Galileo and the Leaning Tower. The bowling ball and the feather fall at the same rate, have the same velocity, etc, once we get rid of the atmosphere. Neglecting losses like rolling and wind resistance (which are obviously not negligible here), gravity is a wash, Bigger force, more to accelerate...it all balances out. This is why the period of an (ideal) pendulum is independent of the mass of the pendulum.
I swear to you, that with no wind resistance and no rolling resistance, there is no difference between riders of the same W/kg, regardless of the absolute values. You have more momentum, yes...but you also have more opposing force (gravity), and it all cancels out.
Where you may have a point, and it needs to be thought through again, is how a big guy vs a small guy has to deal with the "not in a vacuum" part, i.e., how rollers, etc., are different for guys facing different wind resistance, rolling resistance, etc.
I think Galileo was a pretty smart dude(so was that Newton guy) and he was definitely onto something with his bowling balls and feathers in a vacuum thing. However, we don't live in a vacuum. But if we did I could ride my bike hundreds of miles per hour (provided my lungs didn't explode from the whole lack of air thing). But in the real world, things like drive train drag (small) rolling resistance (medium) and wind resistance (large) are VERY real forces. I am simply stating that as these forces increase as a percentage of the total force acting on a body the more important they become.
Let me give you a couple of thought experiments to think about...
First imagine 2 skydivers (Tim Cronk can chime in to tell you that this is in fact what happens)... Let's call the first one Tim and he's 5'-5", 130lbs. The 2nd one is a fat guy called JW Circa 2008 (aka "Fat JW") and he's 6'-1", 230lbs. Both of them are skydivers but Tim actually has a much lower coefficient of drag (wind resistance) because of his much smaller profile. If they both jump put of a plane from 14,000' and hold "roughly" the same falling position, Tim will fall at say 95mph but Fat JW will fall at around 110mph. This happens because the "A" in F=MA for both of them is the same (9.8m/s^2). However the "M" for Fat JW is 1.77x more than Tim's "M". So the "F" that Fat JW has pushing down finds an equilibrium with the force of the air or wind resistance pushing up at a higher speed even though he actually has a slightly higher coefficient of drag. To say this a different way, Fat JW has a higher terminal velocity than Tim and will fall faster. So what does that have to do with momentum and rolling up hills?
My second thought experiment (since you mentioned pendulums) will use a couple of similar pendulums... The period of a pendulum is only independent of the mass of the pendulum if it is an ideal pendulum. BUT... Riding rollers is more like a "Physical Pendulum". Google showed me the equations here: http://hyperphysics.phy-astr.gsu.edu/hbase/pendp.html#c1 So with that nerdy background, let's get to the thought experiment: We have two identical 200 ft long thick ropes hanging from the top of a two cranes side by side... At the end of one rope we have an 18lb bowling ball. On the end of the other rope we have a baseball. We can agree that the baseball and the bowling ball represent roughly the same physical shape, but the baseball is smaller, so theoretically will create less drag (if we pretend our 18lb bowling ball is wrapped in a large leather baseball cover). Now let's pretend we took the bowling ball and the baseball up to a 90 degree angle (200ft out) and let them both go at the same time... Which would fall faster and which would go higher on the other side of our "pendulum" before it slows to a stop? Because our rope is big and heavy it has drag of its own that the weight of the ball will also have to overcome (ball will create force down as it falls creating and using angular momentum on the way up) . If it was a ping pong ball for instance, it might not even make it back up more than a couple of feet on the other side and this will be mostly from the momentum that the weight of the rope itself creates. Spoiler alert, the bowling ball will go much higher up the other side when compared to the baseball. Even higher yet would be if we tied a 230lb Fat JW to the end of our rope. Now imagine the path of our ball being a person on a bike going down a hill, then up the next one... And the drag of the heavy rope going through the air slowing down our balls being the combination of the "Wind resistance" and the "rolling resistance" and our "drive train drag" that our bike riders are up against. The extra angular momentum our bigger rider creates will overwhelm those drag forces allowing our heavier rider to coast up the other side farther. Now add to that that our bigger rider is also likely pushing a higher absolute amount of power to the pedals this whole time and the effect gets magnified even more. Until of course the point at which this angular momentum goes to roughly zero and at that point, it's simply W/Kg that determine speed (assuming little winds on the hill).
I was simply saying that "lifting" to downshift the FD would make this point of 0 angular momentum come quicker. Which is bad if we want the fastest bike split given a similar effort level. Unless of course we could shift without it effecting our momentum. And as a corollary, this is probably a well used spot on the course to use a few extra watts to "carry" this momentum.
We are going a bit off topic here, but....
JW-
In short, you make my point...the difference between TC and JW isn't gravity...it's all the "non-ideal" stuff relating to the other forces. (rolling and wind resistance) The feather and the bowling ball have different terminal velocities in the real world because wind resistance doesn't scale with mass like gravity does. As I think you agree, if we pull a vacuum on the town of Pisa, the feather and the bowling ball hit the ground with the same terminal velocity and take the same amount of time to fall from the top of the tower.
So now, in your second graf, you start addressing the other forces. All I meant in my note is that the difference between JW and TC isn't gravity. It's the other stuff. In your example, your rope makes the assumption of an "ideal pendulum" no longer valid. Forgetting the atmosphere and flexibility of the rope for a moment, the center of mass is different. Lots of things going on, and yes, they have different velocities, etc...
In the case of the cyclist acting as a quasi-pendulum going back up a symmetric U-shaped hill:
If the latter is true, then the bigger rider will get farther up the hill. You really don't need to invoke angular momentum (a property of the wheels, which is perpendicular to the path of the rider), per se.
Your sense of physical reality is probably right...all I was saying is that you were (originally) attributing it to the wrong thing. Gravity works proportionally to mass. :-)
^^ What he said!