I have some replacement SH51 cleats they only release when you turn your heal away from the bike. Based on this is there a left and right cleat. If so it could explain the arse bruising uncleating fail I have just had, the first in I reckon 5 years.
ND
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Copied from evans
Shimano SH51 SPD Cleats are single direction release cleats.
No, left and right cleats are identical.
The pedals will also release if you twist your heel in towards the bike. I sometimes find this is easier. Though this is not recommended, as your feet might hit the frame/bottle/spokes etc.
they should release when you turn your heal either way. But obviously turning your heal inwards is harder to achieve the angle needed.
The multi-release mean you can pull up out of them too which is why most people don't use those.
Only 2 reasons I can think are:
1. You have not got the new cleats at quite the correct angle on the shoe so you can't get quite enough twist.
2: you have a worn pedal mechanism which when combined with a new cleat means you are having trouble disengaging as they are supposed to. Any problems clipping in and have you backed off the adjusters after fitting the new ones and re-set them up?
My SH51 on M505, M540 and M530 pedals definitely unclip when twisting in either direction.
Ah misread what they meant by single direction
Old pedals could be the answer, I aligned the cleats as best as I could using the old shoes as reference so hopefully not misaligned (I worry about my knees). I shall back the springs off as much as possible to see if that helps
Cheers
Old SH51 cleats will fail to disengage. Been there done that, had the bruises. Change them before you can't get the bolts out 😳 .