SPD's power advantage....Myth?

cee

from the climbing technique article on the front page......

according to cycling coach Dr Auriel Forrester of Scientific Coaching: “Pulling up on the pedals decreases power output as it interferes with the all-important downstroke on the other side – specifically, you can’t pull up against gravity at the same rate or same force as you can push down with gravity!”

why do commuters go to the bother of wearing spd shoes? Surely knowing that there is no power advantage (in fact a disadvantage is suggested...) why not wear shoes that are easier to walk in....

mountain bikers often quote a 'feeling of connectedness to the bike'...and I can understand that...particularly if it helps to lift the back wheel over roacks and roots etc...

I guess I have often thought that spds could help promote a good pedalling technique...but of course this is possible on flats too.

what are your reasons?

amnezia

there is a power advantage - the power transfered to the pedals is greater than flats because the connection to the pedals is better.

alfablue

Maybe a myth, however on switching to spd's my g/f could suddenly conquer hills that had previously defeated her. Could be the pedals enforced better technique, who knows, but for whatever reason they are better.

I hate my feet skidding off the pedals, and I hate toe straps, so spd's are a no brainer.

tgotb

Even when you're pushing down, power transfer is better because your feet can't slip off the pedals. And even if you're not pulling up on the pedals (which I'm not sure many people really do anyway), a positive connection can allow you to push the pedal forward at the top of the stroke and back at the bottom, which are recognised components of a good pedalling style.

Personally, whenever I ride without SPDs I get fed up with my feet slipping off the pedals. Especially painful if the metal part of the pedal then imbeds itself in your leg...

iPete

I've been riding single speed this week (broken shifter cable or something yada yada) and being able to lift away from the lights is awesome. 0-20 in 5 pedal strokes, I couldn't do that with flats!

That aside, I'm not sure I could live without anymore, I find it much easier to think about pedaling in circles when clipped in.

rjsterry

I've lost the ability to use flats without sliding all over the place - I'm so used to pulling up, that i can't stop when I'm on flats and keep lifting my feet off.

Most cycling shoes are designed to use cleats, and wouldn't work on flats. trainers are just rubbish for cycling in - they're designed for running. Also, I'm sure Dr. Forrester knows his stuff, but I'm pretty sure I pull away from the lights a darn sight quicker when I'm pulling up as well as pushing down. Lastly, I'm not sure gravity has much to do with it unless you are out of the saddle - when you pull up, you are pulling against your saddle, but when you push down, you are just pushing against your weight.

cee

I should add...

I have never ridden in SPD's....so i couldn't honestly say that a is better than b....No agenda here...

i have been thinking about trying them recently but that line in that article caught my eye as one of the reasons a lot of people quote as why spds are better...

Oddjob62

I would NEVER go back to flats.

I don't know what the good Doc is talking about. I can't say that my power output is better, but i know when i'm really pushing hard and out of the saddle, if i don't have my feet attached my back foot moves from the "ideal" position. This obviously can never happen with clipless.

Also I ride fixed.... and trying to leg brake with no attachment is rather tricky.

pastryboy

When the pedals are at 6 o clock you can push forward/pull backwards at the same time to start the next stroke - can't do that with flats.

I know for a fact when I'm on SPDs going uphill is easier and I do pull upwards.

tjwood

I've never used SPDs, but with decent (grippy) flat pedals and appropriate shoes, once you've placed your foot on the pedal it stays there until you deliberately remove it. No slippage. You can certainly pull in either direction at 6/12 o'clock.

Given that, I can't see how there is any mechanical advantage to having your foot physically connected to the pedal. How is the physics any different in either case?

snailracer

My usual post when this topic comes up:
http://www.bikeradar.com/gear/category/ ... s-10-35398

Stops your feet sliding around, no straps= foolproof release.

I never see any bikes with them because nobody knows they exist. Probably because they are cheap and don't make much money for the bikeshops.

They are also ugly, which is either good or bad, depending on your priorities.

meanredspider

A few points that struck me as I was reading this:

- I sure I can spin my feet faster attached than unattached. That's only really useful at terminal speed down hill but it IS useful
- Standing and leaning over the handlebars up steep inclines I certainly pull a lot
- I do for sure pull when I'm accelerating. I'm less conscious of doing it when cruising but I do do it.
- He's right that you can't pull up with the same power as you push down but it isn't a one-or-the-other choice: you can do both - with your butt and arms taking the load.

Aguila

amnezia wrote:

there is a power advantage - the power transfered to the pedals is greater than flats because the connection to the pedals is better.

+1.

The pulling up thing is irrelevant. People actually very rarely do this. The power advantage is because you have a stiff cycling shoe sole directly connected to a pedal via the clipless system. You are not wasting energy bouncing a squashy sole up and down on a pedal that you are not very firmly attatched too (so also losing energy via small lateral movements vs pedal too).

EKE_38BPM

@tjwood - How can you not see the advantage of having your feet "physically connected to the pedals" in the perfect position for efficiency, technique and power.
As has been said earlier, cycling shoes are designed for cycling whereas "appropriate shoes" (by this I guess you mean trainers) have been designed for something else (running, basketball, tennis etc) and have soft, deformable soles that sap power when cycling as they compress.
No matter how grippy flat pedals are, you will never be able to pull up to get that little bit more. I don't often pull up, but I do on occassion and I get that little bit more. Pulling away from the lights or climbing a steep hill, that little bit more can help.

You ask how the physics is any different. My answer would be:
Better power transfer due to a non-compressible sole
Better technique due to foot always in the best position
Improved efficiency due to less wasted energy (adjusting foot position, compressing the sole)

I think that about covers it.

EKE_38BPM

Now that we've covered SPDs, should we move onto:
Should helmets be compulsory?
Is it OK to ride with headphones?
What FG ratio?
Should I get a hybrid or a road bike for my 2 mile commute?

nich

I go up hills quicker on spds than I do on flats, nuff said 8)

snailracer

Aguila wrote:

amnezia wrote:

there is a power advantage - the power transfered to the pedals is greater than flats because the connection to the pedals is better.

+1.

The pulling up thing is irrelevant. People actually very rarely do this. The power advantage is because you have a stiff cycling shoe sole directly connected to a pedal via the clipless system. You are not wasting energy bouncing a squashy sole up and down on a pedal that you are not very firmly attatched too (so also losing energy via small lateral movements vs pedal too).

The stiffness of the shoe only makes a tiny difference - most of the squashiness is down to the foot itself, and there's nothing you can do about that (unless you swap your feet for hooves ).

So, then, the main difference is that you're not sliding about, and even that can be minimized with grippy pedals.

In fact the difference between clipless and well-chosen flats/shoes is so small that it's difficult to measure with any repeatability, which is probably why I've never come across any published efficiency gains.

Aguila

snailracer wrote:

Aguila wrote:

amnezia wrote:

there is a power advantage - the power transfered to the pedals is greater than flats because the connection to the pedals is better.

+1.

The pulling up thing is irrelevant. People actually very rarely do this. The power advantage is because you have a stiff cycling shoe sole directly connected to a pedal via the clipless system. You are not wasting energy bouncing a squashy sole up and down on a pedal that you are not very firmly attatched too (so also losing energy via small lateral movements vs pedal too).

The stiffness of the shoe only makes a tiny difference - most of the squashiness is down to the foot itself, and there's nothing you can do about that (unless you swap your feet for hooves ).

So, then, the main difference is that you're not sliding about, and even that can be minimized with grippy pedals.

In fact the difference between clipless and well-chosen flats/shoes is so small that it's difficult to measure with any repeatability, which is probably why I've never come across any published efficiency gains.

Sorry don't buy that at all.

Compare my nike air whatevers with my carbon soled cycle shoes and tell me the squashiness is in my foot, no.

Actually there is very little soft tissue between tarsal/metatarsals and the skin of your feet (unless you have very fat feet ) so the difference is clearly in your shoe.

As for published efficiency gains: don't confuse lack of evidence with evidence of lack.

eg strictly speaking there is no evidence that parachutes work, but not many people will jump out of a plane without one.

http://www.bmj.com/cgi/content/abstract/327/7429/1459

meanredspider

snailracer wrote:

The stiffness of the shoe only makes a tiny difference - most of the squashiness is down to the foot itself, and there's nothing you can do about that (unless you swap your feet for hooves ).

So, then, the main difference is that you're not sliding about, and even that can be minimized with grippy pedals.

In fact the difference between clipless and well-chosen flats/shoes is so small that it's difficult to measure with any repeatability, which is probably why I've never come across any published efficiency gains.

I can't agree with almost any of this.

The reason why good running shoes are good is due to their energy-absorbing characteristics. If your feet were THAT squishy, you could run on concrete in bare feet.

And I was able to measure the difference between cycling in clips and clipless (0.5-1.0mph difference in average speed for my commute)

I honestly don't care what other people use but I know what I'm going to stick with....!

jamesco

pastryboy wrote:

When the pedals are at 6 o clock you can push forward/pull backwards at the same time to start the next stroke - can't do that with flats.

It's pretty easy to rotate the leading foot a few degrees so that the crank will turn, though admittedly not as easy as at, say, 10 o'clock.

I think the main reason SPDs lead to faster riding is that the riders who choose to use them for commuting are such hard-arses that they'd clear off on a penny-farthing

rolf_f

EKE_38BPM wrote:

@tjwood - How can you not see the advantage of having your feet "physically connected to the pedals" in the perfect position for efficiency, technique and power.

This pre-supposes you have gone to the trouble of a cleat fitting. This is the point though - if cleat fittings are worth doing (if!) then clearly the benefit is only achieved by wearing cleats. Having had such a fitting, I'm not totally convinced but at least I know if it does work, I'm getting the benefit!

Ultimately, the feet are surely the most critical contact point so not having that contact point the most wooly of the lot (ie flats, straps etc) is a good thing.

Flat pedals with pins do locate your foot quite well - no excuse for feet to slip around on them especially if your soles have tread that the pins can sit in. Unfortunately, the problem is if you don't get your foot in exactly the right spot first time, you have to take your foot entirely off the pedal to try again - no chance of sliding your foot into the correct position. So you might as well use clipless

EKE_38BPM

Penny-farthings, the original fixies, and we all know how fast they can be.

jimmypippa

meanredspider wrote:

snailracer wrote:

The stiffness of the shoe only makes a tiny difference - most of the squashiness is down to the foot itself, and there's nothing you can do about that (unless you swap your feet for hooves ).

So, then, the main difference is that you're not sliding about, and even that can be minimized with grippy pedals.

In fact the difference between clipless and well-chosen flats/shoes is so small that it's difficult to measure with any repeatability, which is probably why I've never come across any published efficiency gains.

I can't agree with almost any of this.

The reason why good running shoes are good is due to their energy-absorbing characteristics. If your feet were THAT squishy, you could run on concrete in bare feet.

And I was able to measure the difference between cycling in clips and clipless (0.5-1.0mph difference in average speed for my commute)

I honestly don't care what other people use but I know what I'm going to stick with....!

You can run on concrete in bare feet. I used to like plimsoles for running because they lacked all the crud in expensive trainers. If you land toe first, your calf muscles absorb the shock and return it.

Landing heel first is just wrong.

meanredspider

jimmypippa wrote:

You can run on concrete in bare feet.

For how long and how often? I suggest at my age and size I'd soon suffer from plantar fasciitis if I tried this.

It's slightly off the point, however. Trainer soles are typically designed to absorb impacts. They do so by absorbing energy which is released as heat. Hi-end cycling shoes are the exact opposite. They are as stiff and hard as possible.

It's a principle that is applied in motor racing transmissions - ultra-stiff engine mounts, unsprung clutch plates, aluminium (rather than rubber) transmission donuts. All of these reduce parasitic losses.

snailracer

meanredspider wrote:

snailracer wrote:

The stiffness of the shoe only makes a tiny difference - most of the squashiness is down to the foot itself, and there's nothing you can do about that (unless you swap your feet for hooves ).

So, then, the main difference is that you're not sliding about, and even that can be minimized with grippy pedals.

In fact the difference between clipless and well-chosen flats/shoes is so small that it's difficult to measure with any repeatability, which is probably why I've never come across any published efficiency gains.

I can't agree with almost any of this.

The reason why good running shoes are good is due to their energy-absorbing characteristics. If your feet were THAT squishy, you could run on concrete in bare feet.

And I was able to measure the difference between cycling in clips and clipless (0.5-1.0mph difference in average speed for my commute)

I honestly don't care what other people use but I know what I'm going to stick with....!

Good running shoes do not absorb energy - they are like springs and return energy.

I am also faster with toe cups - but using the same fairly squishy shoes. With harder-soled shoes, I am not measurably faster (over a 9 mile commute). For me, it's the lack of sliding around on the pedal that seems to make the biggest difference.

tjwood

All you've done is argue about shoes. This is nothing to do with pedals... ;-)

supersonic

There are many types of trainer soles though, from the deeply cushioned, to the very thin. Look at track running shoes and spikes - minimalist.

At very low cadence, you can increase power output with SPDs by pulling as you are working against the high tension of the chain, which will be high as you drive that gear. The effect is much less at higher cadences. While power maybe increased at some revs, efficiency may be less when actively pulling up, as the extensor muscles are usually much better developed than the flexor muscles.

As usually it depends on the cyclist - some find gains ,others don't, and for the off road cyclist are other things to consider.

snailracer

Aguila wrote:

snailracer wrote:

Aguila wrote:

amnezia wrote:

there is a power advantage - the power transfered to the pedals is greater than flats because the connection to the pedals is better.

+1.

The pulling up thing is irrelevant. People actually very rarely do this. The power advantage is because you have a stiff cycling shoe sole directly connected to a pedal via the clipless system. You are not wasting energy bouncing a squashy sole up and down on a pedal that you are not very firmly attatched too (so also losing energy via small lateral movements vs pedal too).

The stiffness of the shoe only makes a tiny difference - most of the squashiness is down to the foot itself, and there's nothing you can do about that (unless you swap your feet for hooves ).

So, then, the main difference is that you're not sliding about, and even that can be minimized with grippy pedals.

In fact the difference between clipless and well-chosen flats/shoes is so small that it's difficult to measure with any repeatability, which is probably why I've never come across any published efficiency gains.

Sorry don't buy that at all.

Compare my nike air whatevers with my carbon soled cycle shoes and tell me the squashiness is in my foot, no.

Actually there is very little soft tissue between tarsal/metatarsals and the skin of your feet (unless you have very fat feet ) so the difference is clearly in your shoe.

As for published efficiency gains: don't confuse lack of evidence with evidence of lack.

eg strictly speaking there is no evidence that parachutes work, but not many people will jump out of a plane without one.

http://www.bmj.com/cgi/content/abstract/327/7429/1459

Leg muscles generate power. This power is "wasted" in every non-rigid link between muscles and pedal. This includes skin tension, "opposing" muscles, tendons, joint cartileges, ankle and metatarsal ligaments, tendons, etc. of which the sole of the shoe is just one link. Obviously some shoes have harder, less "lossy" soles than others, and should be able to demonstrate higher efficiency if the instrumentation was sensitive enough, but hard-soled shoes aren't necessarily clipless. And soft-soled shoes aren't necessarily lossy.

Love your link, btw

jamesco

Aguila wrote:

As for published efficiency gains: don't confuse lack of evidence with evidence of lack.

eg strictly speaking there is no evidence that parachutes work, but not many people will jump out of a plane without one.

http://www.bmj.com/cgi/content/abstract/327/7429/1459

As a skydiver, I can assure you that the empirical evidence for the efficacy of parachutes is convincing, although I can't imagine you'll get many people to sign up for a double-blind test

snailracer

Power and efficiency are different things.

Minimizing losses is maximizing efficiency. Clipless helps, as do grippy pedals and efficient shoes.

Maximizing power is not about maximizing efficiency. That would be like saying a car engine gets the most mpg when you are flooring the accelerator at maximum revs. On a bike, maximizing power is sprinting. In this case, no-one cares about efficiency, it's about how furiously you can crank without your feet flying off the pedals. In this case, the winner is clips with straps because there is no way your feet will slip off the pedal. Ask any track sprinter why they don't use clipless.

The Rookie

Even standing up the most force you can apply to the pedals is your body weight, push/pull and for every kg you pull up, your also pushing an extra kg down, so that's 2Kg gained of force.

I can't 'pull' all my ride, but even sitting I can on my steeper bits and gain power, AND by using different muscles to when not pulling, so not tiring my normal peddling muscles, I get a power and an 'efficiency' (on the basis my normal pedaling muscles stay fresher) gain.

Makes me puff and pant like someone on a 20/day habit as well, so 'push/pulling' is increasing my Oxygen consumption!

Simon