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From https://www.velogear.com.au/media/wysiwyg/spd_cleats.jpg

With SH-56, you can remove your shoes easier.

I wonder if there's a benefit of using SH-51 over SH-56? Does 51 help produce more power (less loss)?

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  • What's your primary need from cleats? For me its more about keeping the foot on the pedal, and not at all about pulling back/up. IE, preventing the foot slipping off. ALSO how often might you fall off your MTB ?
    – Criggie
    Nov 7, 2020 at 11:28

2 Answers 2

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SH56 releases when you pull up on the cleats, ironically defeating the largest benefit you’re trying to achieve by using a clipless pedal system. Using SH51 allows you to benefit from that upstroke.

Before anyone tells me that “you can’t pull up!”, try pulling up more than you push down while sprinting out of the saddle, clipped in. You can actually pick the entire rear end of the bike up off the ground with each leg by pulling up hard enough. Try doing that with flats!

As you said, using SH56 will make it easier to remove the shoe from the pedal, defeating another purpose of clipless systems: better foot retention. Racking up the pedal tension while using SH56 in an effort to make release more difficult defeats the purpose of SH56.

SH56 is a crutch for inexperienced clipless users who haven’t mastered the clip-out movement yet. That’s it. Arguably, it is best to never use it so you completely remove the pull-up-to-release instinct from your body. Simply turn the tension down as a beginner. You’ll pop out in a crash, don’t you worry.

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  • Otherwise good answer, but lifting the rear wheel by pulling on pedals is roughy as possible as lifting yourself by pulling your own hair
    – ojs
    Nov 6, 2020 at 6:40
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    @ojs It is perfectly possible to make a fake bunny hop by pulling your rear wheel up by your legs instead of jumping correctly with your body. You just lift your body and your front whell first and when you are high enough you pull up the right wheel with your cleats. It is a fake bunny hop. Nov 6, 2020 at 8:00
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    @mattnz Fair point, although being clipped in certainly makes it easier to stay attached to the bike. “Work smarter, not harder.” And you shouldn’t really need to have the ability to release upwards; your body should have the reflex to always twist the foot outwards when wanting to unclip. In uncontrolled situations, I’ve never seen a clipped in rider with reasonable pedal tension fail to release. The ones that I have seen always either are inexperienced, or have the tension cranked up so high that it takes a massive, dedicated effort to clip out.
    – MaplePanda
    Nov 6, 2020 at 16:16
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    I've never used SH56s but have pulled worn SH51s out when the tension is low. It's not pleasant if it happens unexpectedly. The advice given to me was good - get SH51s, lean on something and practice lots, both feet. Then ride somewhere quiet and practice, quite a lot. I'd add: don't use them in busy city traffic until you're very familiar., and keep the tension as light as you can. I've had a few unclipping fails over the years, but normally with an additional factor (e.g. blown over twice in one day with only the upwind foot unclipped) and never severe
    – Chris H
    Nov 6, 2020 at 16:16
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    @MaplePanda one of my other failures was with low tension, going very slowly up a >25% incline, very narrow road. A van came the other way and I stopped pedalling and stopped dead on a rough patch of road, couldn't unclip in time and fell over. The mechanism was stiff - it just needed a drop of oil. I can unclip and get a foot down if the back wheel locks up (stick in the rear derailleur, broken spoke snagging chain)
    – Chris H
    Nov 6, 2020 at 16:20
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With sh-56, you can remove your shoes easier.

Let us consider a lock.

If you can open the lock with any key, not just the specific key you have in your pocket, is it a good thing?

I would consider the number one feature of locks that it is opened by only the key intended for it.

A similar consideration applies to clipless systems.

If you can release the cleat with any motion, not just the specific motion intended for releasing it, is it a good thing? No. You may accidentally release the cleat when pedaling hard. The sudden unintended release of the cleat can be very dangerous. If you are pedaling hard and suddenly the cleat releases, it could cause you to fall.

Does 51 help produce more power (less loss)?

Yes, but not via less loss.

With SH-56, you cannot pedal hard or else you risk accidental cleat release and thus falling.

With SH-51, you can confidently pedal with as much force as you can produce.

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