moving to clipless/SPD...

[Greenbank]

I bought a new bike and the SPD springs were done up really tight (there is no advantage to doing this unless you are a competetive MTB rider imo)

Climbing serious hills on fixed. Having an unclip moment when pulling up hard hurts a lot.

I'm fairly sure the spring tension only affects how hard/easy it is to twist out horizontally.  It doesn't affect the force required to pull the cleat, vertically, out of the binding. In theory you should be able to pull the cleat out of the sole of your shoe before the binding lets go.

Look at how the bindings operate, they open outwards to release the cleat. The twisting motion means much less force is required to open up the bindings; the shape of the cleat means that the bindings are pushed open from the inside when the cleat is twisted, but that doesn't mean you can't pull the cleat out with a bunch of vertical force.

Having the spring tension down low makes it easier to pull out with just a vertical force, hence I have them done up tight since I'm often pulling up *hard* on the pedals.

[EDIT] Here's a good image: http://www.drakescycles.co.uk/smsimg/50/1962-7238-full-pdm980-50.jpg

The back of the cleat is held by the rear unmovable binding, the tip of the cleat will lift up. The less tension in the spring the easier and further the swiveling front binding will move out away from the cleat.

[Biggsy]

I'm fairly sure the spring tension only affects how hard/easy it is to twist out horizontally.  It doesn't affect the force required to pull the cleat, vertically, out of the binding. In theory you should be able to pull the cleat out of the sole of your shoe before the binding lets go.

I'm not so sure about that.  The retension system of most clipless pedals isn't that sophisticated, and I would be surprised if racing cyclists use high tension only to deal with accidental rotation.

I haven't put it to the test myself, though.  It would be a bit of an ankle buster.

[LEE]

I bought a new bike and the SPD springs were done up really tight (there is no advantage to doing this unless you are a competetive MTB rider imo)

Climbing serious hills on fixed. Having an unclip moment when pulling up hard hurts a lot.

I'm fairly sure the spring tension only affects how hard/easy it is to twist out horizontally.  It doesn't affect the force required to pull the cleat, vertically, out of the binding. In theory you should be able to pull the cleat out of the sole of your shoe before the binding lets go.

Look at how the bindings operate, they open outwards to release the cleat. The twisting motion means much less force is required to open up the bindings; the shape of the cleat means that the bindings are pushed open from the inside when the cleat is twisted, but that doesn't mean you can't pull the cleat out with a bunch of vertical force.

Having the spring tension down low makes it easier to pull out with just a vertical force, hence I have them done up tight since I'm often pulling up *hard* on the pedals.

I'm not conviced that the springs are big enough to have any effect on pulling vertically out of the pedal.  The tension of mine is so low that my cleats slip into the bindings with hardly any pressure.  

I can still honk until my shoes are nearly coming off without pulling out of the bindings though.  That would be a complete design flaw.  The main requirement of a binding is that it NEVER pulls out vertically, that's it's raison d'etre.  

There's no point in having a variable amount of vertical release pressure (is there?  Why would I want that?)

Pro cyclists couldn't sprint at all if bindings opened like that surely.

Edit.  I can believe that Chris Hoy could pull the cleat out of an SPD binding vertically but that would be due to him bending the metal jaws (accounts for the usual practice of using toe-straps as well)

[Biggsy]

Pro cyclists generally use higher retension force than utility and recreational cyclists, and the springs are strong in the kind of pedals they use.  Why?

[Greenbank]

I'm not conviced that the springs are big enough to have any effect on pulling vertically out of the pedal.  The tension of mine is so low that my cleats slip into the bindings with hardly any pressure.  

That's no surprise, the cleats are shaped so that they clip in much easier by guiding apart the bindings. You'll barely notice any pressure required to clip in.

If the front part of the pedal is hinged (as in the previous image) then at some large amount of force it will pull open the bindings enough for the cleat to pop out. The looser the spring tension the less upward force is required.

I can still honk until my shoes are nearly coming off without pulling out of the bindings though.  That would be a complete design flaw.  The main requirement of a binding is that it NEVER pulls out vertically, that's it's raison d'etre.  There's no point in having a variable amount of vertical release pressure.

Pro cyclists couldn't sprint at all if bindings opened like that surely.

Again, the force required to pull them out vertically is much more than the force required to twist them out. Most of the time you'll never get near the force required to have one pop out vertically.

I've had it happen once, when the spring tension was low and I was really pulling up on the pedal climbing a hill on fixed.

It's not meant to happen, but the design of most SPD pedals means that it can happen. Since tightening the spring tension I've never had another occurrence.

Pro (road) cyclists will be using Look style pedals, or SPD-R, etc which is a quite different design and probably not susceptible to this with the same order of magnitude of forces.

[LEE]

I think that, if you can pull out vertically, on any clipless pedal, then the mechanism failed (possibly due to twisting foot slightly).  I don't think the spring tension has any noticible effect, Pro or not.  The spring tension is there purely for engagement and (twisting) disengagement.

Any design that has a variable release tension, in the vertical plane, is dangerous.

[Greenbank]

I think that, if you can pull out vertically, on any clipless pedal, then the mechanism failed (possibly due to twisting foot slightly).  I don't think the spring tension has any noticible effect, Pro or not.  The spring tension is there purely for engagement and (twisting) disengagement.

Any design that has a variable release tension, in the vertical plane, is dangerous.

The design of SPD pedals makes it a possibility (you only have to look at the image of the pedals I posted).

My point is that if you have the pedal spring tension too loose, then the force required to pop it out vertically is within the realms of the average human pulling up hard on the pedal.

If you set the tension higher then the force required to pop it out vertically isn't within the realms of the average human and so it should never a problem.

The more you twist your foot then the less upward force is required, another reason to have them done up tighter than the loosest setting, especially if your pedaling stroke is far from perfect (and I'm not saying mine is).

I was simply responding to your statement of:

I bought a new bike and the SPD springs were done up really tight (there is no advantage to doing this unless you are a competetive MTB rider imo)

with a reason why I would have the SPD spring tensions done up tight for something other than competitive MTB-ing, namely for taking a fixed into hilly terrain (or even pulling away hard from lights gets me to roughly the same levels of power input and low cadence).

[Zoidburg]

The design of SPD - if you look at the engagement faces on the cleat they will not pop out vertically, it's an arrow head design, once in it does not pull out unless the cleat has worn away to a point where it no longer engages correctly.

New SPD cleats don't pull out, even with less tension.

[LEE]

The design of SPD - if you look at the engagement faces on the cleat they will not pop out vertically, it's an arrow head design, once in it does not pull out unless the cleat has worn away to a point where it no longer engages correctly.

New SPD cleats don't pull out, even with less tension.

That's certainly my understanding.  I can certainly imagine a cleat with worn/rounded edges pulling out of a binding but that would be a mechanical failure.

Having a variable (vertical) release tension would cause no end of injuries.

I just googled Shimano SPD tech spec. "pedal will not release unless foot is twisted outwards"

OK, that answers my question.

[Greenbank]

The design of SPD - if you look at the engagement faces on the cleat they will not pop out vertically, it's an arrow head design, once in it does not pull out unless the cleat has worn away to a point where it no longer engages correctly.

New SPD cleats don't pull out, even with less tension.

That's certainly my understanding.  I can certainly imagine a cleat with worn/rounded edges pulling out of a binding but that would be a mechanical failure.

Having a variable (vertical) release tension would cause no end of injuries.

I just googled Shimano SPD tech spec. "pedal will not release unless foot is twisted outwards"

OK, that answers my question.

Fine. If you want to believe that the small spring will always hold no matter how much upward force is employed then who am I to try and rock your world.

The point is that one end of the cleat is held by the fixed binding which will act as a pivot so the other end will be pulling upwards at an angle to the normal of the plane of the bindings, which means there will be a component of that force pushing the binding open. It then comes down to whether that force is enough to pop open the binding or not.

I will continue to tighten my pedal release springs because I know that on the loosest setting it's within the realms of possibility to pull out of them applying vertical force, even with brand new cleats.

Having a variable (vertical) release tension would cause no end of injuries.

Again, on the loosest setting the force required to pull out vertically are beyond the average rider, so instances of it will be very uncommon.

The vast majority of people who can pull more than 1000W peak will have their pedals done up tighter than the loosest setting, and so instances with strong riders will be uncommon.

[Biggsy]

I think Greenbank is right.

As an experiment, a shoe with an SM-SH51 (the most common) SPD cleat can be pulled out of an M520 pedal vertically, without rotating, if the pedal jaw is partially levered open with a screwdriver.  The rear end of the cleat is held by force from the spring pressing on the rear edge, which is variable, and not very great at the lowest setting.

[Biggsy]

[EDIT] Here's a good image: http://www.drakescycles.co.uk/smsimg/50/1962-7238-full-pdm980-50.jpg

The back of the cleat is held by the rear unmovable binding, the tip of the cleat will lift up. The less tension in the spring the easier and further the swiveling front binding will move out away from the cleat.

Agreed, except you've got the back and front mixed up (if I'm understanding right).  The swivelling binding is at the back.

[Greenbank]

[EDIT] Here's a good image: http://www.drakescycles.co.uk/smsimg/50/1962-7238-full-pdm980-50.jpg

The back of the cleat is held by the rear unmovable binding, the tip of the cleat will lift up. The less tension in the spring the easier and further the swiveling front binding will move out away from the cleat.

Agreed, except you've got the back and front mixed up (if I'm understanding right).  The swivelling binding is at the back.

Yes, I noticed that when I got to my bike to go home and looked at it. Doesn't matter which way round it is for my argument to stand.

As the swivelling binding is pulled up the distance between it and the front (fixed) binding increases. Also, the distance from the cleat to the pedal increases slightly, which means the cleat is angled slightly (pointing down towards the front binding). As this angle increases the contact patch of any ridge on the front of the cleat is reduced up until the point that there's nothing holding it clipped in (the same happens with the contact with the rear/swivelling binding). As more upward force is applied the swivelling binding is pulled further back and at some point the distance between the bindings increases to the point that the cleat and pop out.

The less tension in the spring the easier it moves back and therefore the less upward force is required to pop it out of the binding.

[Zoidburg]

Running it that loose is beyond how it is meant to work.

It should not pull out vertically, it's not designed to.

[Cudzoziemiec]

I've only been using clipless a few weeks. No actual "moments" yet, but a couple of "emergency disengagements" - one when I'd only just fitted them a quarter of an hour before and was riding around trying to get the hang of them. I unclipped, stopped, put my foot down - and found that actually it was still clipped in! I then found that in an emergency, panic push-pull-twisting of the foot releases the clip!

[Steve Kish]

In the 1980s when I was racing, I used to commute across London with standard clips and straps, done up tightly.  I developed a decent technique of staying clipped in and leaning against lamp posts, railings and walls when still strapped in at red lights etc.

Clipless (original white Look pedals) were a Godsend, as I could still grab stuff but could twist my foot out in emergencies.

[nutkin]

I am amazingly clumsy, yet I've had relatively few clipless moments. When I first changed though I had a friend riding with me who kept shouting 'unclip!' every time I came up to a junction. This helped a lot!

Like boab, I've had a clipless moment whilst turning round stationary. I ended up lying in the road unable to stand up as I was still attached by the leg stuck underneath the bike. I had to be helped up by two helpful forummers. Not to be recommended. 

Oh, and remember to check the screws in the soles are in place. It is impossible to unclip when two fall out and very, very difficult to pull your foot out of the shoe when wearing overshoes. Lesson learned. 

Go for it!

[Ham]

The design of SPD - if you look at the engagement faces on the cleat they will not pop out vertically, it's an arrow head design, once in it does not pull out unless the cleat has worn away to a point where it no longer engages correctly.

New SPD cleats don't pull out, even with less tension.

That's certainly my understanding.  I can certainly imagine a cleat with worn/rounded edges pulling out of a binding but that would be a mechanical failure.

Having a variable (vertical) release tension would cause no end of injuries.

I just googled Shimano SPD tech spec. "pedal will not release unless foot is twisted outwards"

OK, that answers my question.

Fine. If you want to believe that the small spring will always hold no matter how much upward force is employed then who am I to try and rock your world.

The point is that one end of the cleat is held by the fixed binding which will act as a pivot so the other end will be pulling upwards at an angle to the normal of the plane of the bindings, which means there will be a component of that force pushing the binding open. It then comes down to whether that force is enough to pop open the binding or not.

I will continue to tighten my pedal release springs because I know that on the loosest setting it's within the realms of possibility to pull out of them applying vertical force, even with brand new cleats.

Having a variable (vertical) release tension would cause no end of injuries.

Again, on the loosest setting the force required to pull out vertically are beyond the average rider, so instances of it will be very uncommon.

The vast majority of people who can pull more than 1000W peak will have their pedals done up tighter than the loosest setting, and so instances with strong riders will be uncommon.

I suspect everyone is right and wrong here ;-)

First, there are Shimano "Multi Release" cleats (ie, cleats which pull out vertically) as in here http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Pedals/PDM505/SI-45C0B_EN_v1_m56577569830617303.pdf

So clearly 1) Cleats can be designed to release upwards in an SPD system and 2) in normal circumstances single release shouldn't. However, the factors in real life mean that the alignment geometry of your foot, cleat and pedal are unlikely to be perfect. Also, wear certainly comes into play with play. The tighter the spring, the less the impact of any misalignement/wear, as you have to have correspondingly more force to clip in and out.

[Feline]

Yeah my understanding is that Shimano's black cleats will ONLY release if you twist, whereas the silver cleats will release in more than one way. Mine are silver (thankfully), but I probably don't have the power to yank them out in a vertical direction while pedalling anyway. I have found that a 'panic movement' does release them even if its more of a sideways movement than a twist, and that is the only reason I havent been lying around on the ground with a bike attached to me more often 

[Cudzoziemiec]

So the difference is in the cleats themselves, the part attached to the sole of your shoe, rather than the "trap/hinge/connector thing" attached to the pedal? I would have assumed the opposite!

[Biggsy]

Yes, the difference is in the cleats.  However, the black cleats will also realease vertically if you are able to overcome the spring.  That's why it's important to have the pedals tensioned enough for your needs and strength.  The lowest, or near-lowest, setting on SPD pedals is OK for most cyclists, but some should increase it more.

[fred the great]

If you fall off the bike, your clipless pedals will normally unclip automatically.

Why? I have no idea but I've tried it when my front wheel slipped into a muddy gutter

[Greenbank]

Yes, the difference is in the cleats.  However, the black cleats will also realease vertically if you are able to overcome the spring.  That's why it's important to have the pedals tensioned enough for your needs and strength.  The lowest, or near-lowest, setting on SPD pedals is OK for most cyclists, but some should increase it more.

This is what i've been trying to say.

I know they're not designed to come out like that, but they can in extreme circumstances.

Some here are saying that it's impossible for them to ever come out vertically.

[Biggsy]

If you fall off the bike, your clipless pedals will normally unclip automatically.

Why?

Because you or the bike will rotate during the fall.  Your feet are extremely unlikely to stay in line with the pedals for the whole incident.  Some cyclists remain clipped in, though, if the pedal tension is set high.

Personally, my only concern is that I might not be released soon enough and so may fall more awkwardly than I would otherwise.  My falls have in fact been more injurious since using clipless pedals - which would put me off if it wasn't for the great comfort, efficiency and security when pedalling.

[Steve Kish]

Some here are saying that it's impossible for them to ever come out vertically

I use black (single only release) cleats and if the pedal spring tension is quite low, I can yank my feet out on a pure vertical stroke, but this is also dependant on how worn the cleats are.

FWIW, on another forum, I'm running a poll about SPDs, as a guideline for anyone who is undecided about using them.  

Of the current 28 answers, 25 say that once they'd tried them, they'd never consider reverting to normal pedals again; of the other 3, one is a downhill MTB rider, where trailing his foot against the floor is part of the accepted technique.