Rotating weight-shoes and pedals

[Dan Le foot]

Most of us know that rotating weight is far more important than non rotating weight on our bikes. Some sources quote 4X as much.
So what about shoes and pedals? Are these considered rotating components like wheels?
I’m considering replacing my road Sidis and Speedplays with MTB Sidis and XTR pedals on my road bike. (Already did it on the cross bike)
But between shoes, pedals and cleats the MTB setup is about 150 grams heavier.
What do you think?
Dan

[cp43]

Go for it, pedals are easy to swap. Ride with the XTRs for a while, I bet you won't notice a difference.

:beer:

Chris

[Ferrous (Fe)]

While you may or may not immediately feel/notice the difference the difference is there just like the extra mass on your wheels.
Think of runners who stress over their shoes they use for competition, the reason they do is because they're having to pick up those extra grams/ounces with each stride multiplied by thousands of strides, the fatigue is real. In cycling you're picking up that same extra weight with each pedal revolution (again multiplied by thousands of pedal revolutions).
I say every little bit helps, I certainly need every advantage I can get in my favor ;)

[gdw]

Go for it. I switched from Sidi Dominators to Lake MX220's, much heavier shoes with vibram soles, several years ago and knocked 40 minutes off my previous best time at the Leadville 100.

[mflaherty37]

At one time I crunched those numbers. That one is much harder to determine than the wheel weight. The pedal speed isn't very high, but because the pedals and shoes are offset the imbalance creates an inefficiency. And because the pedal and shoe speed isn't very constant like a wheel, it is always accelerating or decelerating. Not a lot, but I think it might be worth more than carbon tubulars.

[David Kirk]

I know running and cycling aren't perfect analogies but..........put on some work boots and try to run. Or put on ankle weights and walk. Cycling feels similar to me.

I used to ride in carnacs (very heavy for some odd reason) and switched to D2's (pretty darn light) and the difference was profound.

I haven't experimented with pedal weights but i'll bet the feel would be similar if you had a large weight disparity.

dave

[FlashUNC]

For most of us mortals, the difference isn't that stark.

I'd use mountain shoes on my road rides, if I didn't get hot spots using smaller cleat patterns.

[Mark McM]

Most of us know that rotating weight is far more important than non rotating weight on our bikes. Some sources quote 4X as much.
So what about shoes and pedals? Are these considered rotating components like wheels?

The shoess and pedals have a little bit more effective inertia due to their rotation, but not a lot more. The extra inertia of rotating mass is proportional to the angular velocity times the square of its radius. In the case of mass at the periphery of the wheel, this works out to be an affective inertia of twice its mass (not 4X, as stated above).

The shoes and pedals have a much lower angular velocity than the wheels, and only about half the radius of the wheels. When riding in 3:1 ratio (just a little bit smaller than a 53/17), the effective inertia with 175mm cranks is only 1.09:1, or less than 10% more.

Think of runners who stress over their shoes they use for competition, the reason they do is because they're having to pick up those extra grams/ounces with each stride multiplied by thousands of strides, the fatigue is real. In cycling you're picking up that same extra weight with each pedal revolution (again multiplied by thousands of pedal revolutions).

No, a cyclist is not "picking up that same extra weight with each pedal revolution" like in running. The weight of the shoe/pedal on one crank is exactly balance out by the weight of the shoe/pedal on the other cranks, so no extra force/energy is required to lift the shoes/pedals against gravity.

[zap]

snip

No, a cyclist is not "picking up that same extra weight with each pedal revolution" like in running. The weight of the shoe/pedal on one crank is exactly balance out by the weight of the shoe/pedal on the other cranks, so no extra force/energy is required to lift the shoes/pedals against gravity.

If one pedals circles and utilizies all related muscles, you are lifting up.

[93legendti]

I'd think it would be something you'd notice.

[Mark McM]

If one pedals circles and utilizies all related muscles, you are lifting up.

You are lifting your foot and leg. You are not lifting the shoe and pedal. The gravitional forces on each shoe/pedal on opposite cranks cancel out, resulting in zero net force to raise or lower a crank.

[zap]

You are lifting your foot and leg. You are not lifting the shoe and pedal. The gravitional forces on each shoe/pedal on opposite cranks cancel out, resulting in zero net force to raise or lower a crank.

Man, your going to have to explain that one to me in more detail.

[weiwentg]

I'd think it would be something you'd notice.

I think you'd notice the extra weight as well, but it would slow you down less than you think. it's a third of a pound, not a whole pound.

[Louis]

You are lifting your foot and leg. You are not lifting the shoe and pedal.


What's the difference between the shoe and the foot that's in the shoe? The molecules are doing essentially the same thing.

[benb]

Man, your going to have to explain that one to me in more detail.

It's like a balance scale with equal weight on each side.. to move one side up or down you are just overcoming the friction of the pivot since the weights are always in balance.

Another example is a see-saw.. if the two kids are the same weight it doesn't matter how much they weigh when it comes to moving the see-saw back and forth.. they only have to overcome the friction of the pivot, not each others weight.. i.e. it is no harder for two 200lb people to use the see-saw then it is for two 100lb people to use the seesaw.

Or two weights suspending from a simple pulley.. if they are of equal weight even if they weigh 1000lbs each you are going to be able to pull them back and forth without a huge amount of effort.

[Louis]

But why the distinction between the shoe and the foot?

It's like a balance scale with equal weight on each side.. to move one side up or down you are just overcoming the friction of the pivot since the weights are always in balance.

[93legendti]

I think you'd notice the extra weight as well, but it would slow you down less than you think. it's a third of a pound, not a whole pound.
Yes.

[d_man16]

I'm guessing that it's more comfortable? Then the decision is made for you my friend.

150 grams is the mass of a Royal with cheese, since we're using the metric system :rolleyes:

you'll notice that your more comfortable on the ride before you'll ever notice the mass.

~D

[zap]

But why the distinction between the shoe and the foot?

There is none.

We're talking about forces greater than gravity.

The iliopsoas muscle lifts the leg, foot, shoe, pedal and some percentage of the crank arm all in concert with the other leg that is trying to rip the other side of the bb apart.

[Mark McM]

What's the difference between the shoe and the foot that's in the shoe? The molecules are doing essentially the same thing.

Yes, you're right, the shoe and the foot might as well be as one in this instance. And while we're at it, we don't even do a lot of work in lifting the leg either, since the weight of the legs are largely balanced out as well. If you've ever ridden with just one leg, you'll know that you have to do a lot more work lifting the leg at the back of the stroke than you do when you are pedaling with both legs - the descending leg (assisted by gravity) is doing much of the work of lifting the rising leg. And this is another of the reasons that the bicycle is such an amazingly efficient machine.

[Louis]

Yes, you're right, the shoe and the foot might as well be as one in this instance. And while we're at it, we don't even do a lot of work in lifting the leg either, since the weight of the legs are largely balanced out as well.

I agree. :)

[Dan Le foot]

Thanks everyone.
I didn’t think it was that complicated. :confused:
We spend a lot of $ shaving 150 grams off our wheels. (I think I can tell the difference especially on climbs). I didn’t want to negate the weight savings on the wheels with heavier shoes and pedals if they were considered rotating weight like wheels.
Both the Sidi Genius (Road) and Dominator (MTB) are equally comfortable riding But it is more comfortable walking around with the MTB shoe. No coffee covers needed. And if I forget the coffee covers and need to take a comfort break on the side of the road, I run the risk of getting dirt in the road cleats that keep me from clicking in. I also wear out the Speedplay road cleats in one season and cost $40 to replace them. (I don’t think I ever replaced a SPD cleat)
I found an etailer that is selling new 2011 XTRs for $140. I think I’ll give them a try. If I’m slower on the climbs I can blame it on old age or the fact that the new Seven Ti frameset (in production) is a pound heavier than my current primary ride (Time VXR)
Dan

BTW. The discusion got me thinking. The VA made me a light weight cycling prosthetic leg years ago that is about 2 lbs lighter than my current leg. As a walking leg the light weight version (all ti and cf) sucks and it reallt isn't very comfortable riding either. But a 2 lb weight savings at no cost.....hmmm. I just may dust it off and give it another try. ;)

[oldpotatoe]

Thanks everyone.
I didn’t think it was that complicated. :confused:
We spend a lot of $ shaving 150 grams off our wheels. (I think I can tell the difference especially on climbs). I didn’t want to negate the weight savings on the wheels with heavier shoes and pedals if they were considered rotating weight like wheels.
Both the Sidi Genius (Road) and Dominator (MTB) are equally comfortable riding But it is more comfortable walking around with the MTB shoe. No coffee covers needed. And if I forget the coffee covers and need to take a comfort break on the side of the road, I run the risk of getting dirt in the road cleats that keep me from clicking in. I also wear out the Speedplay road cleats in one season and cost $40 to replace them. (I don’t think I ever replaced a SPD cleat)
I found an etailer that is selling new 2011 XTRs for $140. I think I’ll give them a try. If I’m slower on the climbs I can blame it on old age or the fact that the new Seven Ti frameset (in production) is a pound heavier than my current primary ride (Time VXR)
Dan

BTW. The discusion got me thinking. The VA made me a light weight cycling prosthetic leg years ago that is about 2 lbs lighter than my current leg. As a walking leg the light weight version (all ti and cf) sucks and it reallt isn't very comfortable riding either. But a 2 lb weight savings at no cost.....hmmm. I just may dust it off and give it another try. ;)

Really don't want to belabor this or get into a weight saving does this or that argument but on a 85,000 gram rider and bike package, I don't think you are 'feeling' that 150 gram wheel weight savings. What I think you are 'feeling' is improved stiffness of the rim/wheel package.

[toaster]

Taken to an extreme, 20 lb shoes on both sides obviously would add to rider fatigue.

So, any weight savings would make pedaling more efficient.

I didn't get the see-saw analogy at all!

[Kontact]

Much is made of the rotating weight theory, but the actual energy it takes to accel/decel a 500 gram rim over a 400 gram rim is so negligible that it isn't worth worrying about.

Mass is mass, though, and there's no reason to ride a 15 pound bike with Frankenstein shoes. Light shoes are good for the same reason light stems are good - less to haul up hills.

I'm considering the moldable Bonts. Light and made for my feet.

[John H.]

XTR pedals are super sweet- you will like them. Don't worry about the weight.
You could go with a lighter SPD shoe like the Specialized S-works MTB. It is basically their road shoe with SPD drilling and some tread- very light and comfortable.