Clipless pedals and sprinting

Over the last few days two of my riding buddies come out of their clipless pedals during a sprint.

I was under the impression that as long as you are pulling straight up and not twisting your foot that you should stay clipped in. I am wrong!

One guy has plastic cleats and it was fairly easy to bend the sole enough for the front of the cleat to come out. I guess the rest of the shoe could follow.

What are the common reasons for coming out during a sprint, when you have the pedals adjusted for normal retention, ie the amount of force required to unclip yourself?

Thank you.

 

Worn cleats, flexi shoes, lousy pedalling technique...?

 

Could also be that their backing plate tension is not high enough therefore making it easier to pull out.

 

In my limited, non-racing experience, the type of pedal you're using can make a big difference. I switched to Crank Bros. Candy pedals on my commuter (a light touring/cyclocross bike), and no matter how much I've yanked up on my shoes, I've never had the cleat pop out. The "eggbeater" retention system and the cleat shape seem designed to make it quite difficult to disengage the cleat without a twist. (I sometimes wonder whether this is a bad thing, in the event of an accident, but that's another issue altogether.)

 

I think that the possibility of a pure upwards release is very design or brand/dependent. With my Shimano SPD-SL pedals, you can in theory pull out of them vertically, although the design is such that the force to release sideways is designed to be very much lower than what it would take to release straight up. In principle, the "clamping" part that holds the cleat in place has a sloped top surface, so that you get some leverage against the spring force when you step down to click in. When releasing sideways (intentionally), the angled shape of the back corners of the cleat gives you a sort of ramp effect, providing leverage to overcome the spring tension of the pedal. The underside of the clamping part has a square cut, however, so that in principle an upwards movement of the cleat is held solidly. But if the cleat flexes a bit, or if the back edge of it is worn a bit, you will get a slight slope of the cleat surface which could result in release, given a sufficiently-high upward force (and perhaps an upwards force that is beyond any normal pedaling motion). The wear-level of the cleat is the biggest variable, as is the spring tension setting of the pedal itself. My belief is that any Look-style pedal, as well as SPD's and SPD-R's, will also have some possibility of upwards release, at a force level that is designed to be well above the normal sideways release force, but can degrade somewhat due to cleat wear, etc.Other pedal types will vary, due to the geometry and design of the "clamping" mechanism, as well as the cleat shape and material. It's a lot like ski bindings. Some designs are such that they respond to forces in all directions and axes, whereas some designs release more easily in some directions than in others. There are also differences in the "elasticity" of the release - basically, how far out can you partially release, and still come back to the retained position, if there is a transient force that goes away? Some bindings do a good job of absorbing short-term transient forces by partially releasing and then coming back, whereas with other designs a sharp jolt will just pop you out of the binding. Bike pedals are more or less overly-simple versions of partial ski binding. (Sorry about going on about this - I just am interested in mechanical designs!)

 

Thanks everyone for the replies.

I will look more carefully in this area of the pedal/cleat system, excellent point!

 

keep your pedals and cleats clean, replace worn cleats, keep the whole lot with a slight bit of lube. Or switch to Speedplay, you're in or you're out - sorry to sound so Draconian.

or as the one poster mentioned - got to work on that technique!

HR

 

I understand that some trackies use clipless and then put an extra strap on top. Unclipping your clipless during a out of seat sprint is a potentially life terminating event.

 

I remember seeing lance armstrong slip out of his cleats several times during one climb. The guy almost lost his other... ball .. anybody remember?

Definitely manufacturing fault.. i doubt its lance armstrongs pedalling technique.. or slip shod equipment preparation.