Shimano Crank Arm Safety Plate

[Wannabe]

Where will I be able to find this item in Cape Town? Busy with a hybrid Gravel Bike build, and want to use an old set of Shimano cranks, but this plate got donated to a friend when he was looking for one.

 

 

[David Marshall]

There are a few versions so you need to know your crank model when you order.  Chances are that yours is too old and inconvenient for the agent to stock.

That said many people are riding around without one or one with the pin missing and are none the wiser.  I haven't heard of one saving the day 'so I wouldn't worry about getting one.

[DieselnDust]

What David said 

[Wannabe]

@David Marshall. I was led to believe that piece of plastic is quite crucial, in that it helps space the gap between the two sides of the crank arms, preventing over torquing and help with retention of the two crank arm bolts.

The friend I gave my one to chucked his away, thinking it was superflous. He then started having problems with the bolts working loose, one incident the whole crank arm worked loose. After inserting the lock plate, he never had that issue again.

Edit: After a bit of googling, it seems David and Diesel are more or less correct in that it's main purpose seems to ensure the crankarm is located properly on the crank (if not, the tab will stand proud and not sit flush)

Thanks Gents.

 

Edited August 12, 2025 by Wannabe
Added content

[cadenceblur]

and always install with "open" part facing OUT as I understand it.

[DieselnDust]

2 hours ago, Wannabe said:

@David Marshall. I was led to believe that piece of plastic is quite crucial, in that it helps space the gap between the two sides of the crank arms, preventing over torquing and help with retention of the two crank arm bolts.

The friend I gave my one to chucked his away, thinking it was superflous. He then started having problems with the bolts working loose, one incident the whole crank arm worked loose. After inserting the lock plate, he never had that issue again.

Edit: After a bit of googling, it seems David and Diesel are more or less correct in that it's main purpose seems to ensure the crankarm is located properly on the crank (if not, the tab will stand proud and not sit flush)

Thanks Gents.

 

The tab is there to act as a last resort safety to prevent the crank arm coming off of the bolts come undone and the end cap tension adjuster has also fallen out. It has no influence on spacing anything 

[droo]

19 hours ago, DieselnDust said:

The tab is there to act as a last resort safety to prevent the crank arm coming off of the bolts come undone and the end cap tension adjuster has also fallen out. It has no influence on spacing anything 

It does confirm that your BB spacing is correct. If the pin doesn't slot in, the left crank is in the wrong place on the axle. 

The same can be achieved with a manual and a vernier though.

[tubed]

Theoretically you can ignore the plastic bit and just line up the crank arm and torque the bolts to the correct setting and be good to go. Sometimes you need a 'boer maak n plan' a long bolt or threaded rod, big washers and locknuts to get you 'home'.