Shimano Cranks Stopper Plate

[love2fly]

Hi there

I noticed a bit of a split in the "stopper plate" on my FC6700 cranks at the pinch bolts.

How essential is this part and can I get a replacement? If so, does anyone have one available?

Cheers

[David Marshall]

They are available and not expensive but be careful as there are different ones for different cranks.

 

As to how necessary they are - I don't think they do too much.  I see a lot of bikes with the pins missing or the whole plate damaged or even gone.

[droo]

As far as I can work out the only reason for that thing's existence is to make sure the crank is properly positioned on the spindle. Once the pinch bolts are tightened it serves no purpose at all - it's definitely not going to stop the crank falling off if the pinch bolts fail.

[DieselnDust]

38 minutes ago, droo said:

As far as I can work out the only reason for that thing's existence is to make sure the crank is properly positioned on the spindle. Once the pinch bolts are tightened it serves no purpose at all - it's definitely not going to stop the crank falling off if the pinch bolts fail.

This is one of those USA market driven parts. Not needed outside of Stupidville

[love2fly]

2 hours ago, droo said:

As far as I can work out the only reason for that thing's existence is to make sure the crank is properly positioned on the spindle. Once the pinch bolts are tightened it serves no purpose at all - it's definitely not going to stop the crank falling off if the pinch bolts fail.

Thanks Droo, much appreciated. Makes perfect sense but you don't know for sure till you know .....

[love2fly]

22 hours ago, David Marshall said:

They are available and not expensive but be careful as there are different ones for different cranks.

 

As to how necessary they are - I don't think they do too much.  I see a lot of bikes with the pins missing or the whole plate damaged or even gone.

If I were to get one, is it LBS and Cool Heat only?

[DieselnDust]

2 hours ago, love2fly said:

If I were to get one, is it LBS and Cool Heat only?

Yes, I have not seen any aftermarket options for that part 

[love2fly]

This is the price for the MTB version....they are beyond insane....

[RobertWhitehead]

I had an M8000 that did not have one of those and the non-drive side crank arm kept falling off. No matter how tight I made the bolts it kept sliding off. 

 

I had the same issue on the trainer and what I found to work was taking a piece of wire around the outer bolt before dropping into the hole. 

 

That little thing really boggles my mind. That little pin breaks off quite easily over time but if there's lots of gunk and crap the arm stays in place but the moment you clean the crank and spindle it continues to come loose. 

[droo]

15 hours ago, love2fly said:

This is the price for the MTB version....they are beyond insane....

Desertcart is an import site. Shop there and you deserve what you get.

Ask your LBS. Sometimes the interwebs are not the answer.

[nick_the_wheelbuilder]

On 11/28/2023 at 7:03 PM, RobertWhitehead said:

I had an M8000 that did not have one of those and the non-drive side crank arm kept falling off. No matter how tight I made the bolts it kept sliding off. 

 

I had the same issue on the trainer and what I found to work was taking a piece of wire around the outer bolt before dropping into the hole. 

 

That little thing really boggles my mind. That little pin breaks off quite easily over time but if there's lots of gunk and crap the arm stays in place but the moment you clean the crank and spindle it continues to come loose. 

The left arm will only fall off if part #5 (look at the diagram above) isn't snug.

Install the crank arm (without stupid stopper plate) in this order:

1. Slide crank arm onto spindle.

2. Snug down part #5 (I forget what it's called - I'll call it the spindle end cap, for lack of the correct name)

3. Tighten pinch bolts.

The pinch bolts squeeze the crank arm onto the spindle, preventing the spindle end cap from unscrewing. If that end cap stays put, so does your crank arm. 

[RobertWhitehead]

10 hours ago, nick_the_wheelbuilder said:

The left arm will only fall off if part #5 (look at the diagram above) isn't snug.

Install the crank arm (without stupid stopper plate) in this order:

1. Slide crank arm onto spindle.

2. Snug down part #5 (I forget what it's called - I'll call it the spindle end cap, for lack of the correct name)

3. Tighten pinch bolts.

The pinch bolts squeeze the crank arm onto the spindle, preventing the spindle end cap from unscrewing. If that end cap stays put, so does your crank arm. 

Agreed, in theory this makes perfect sense, But, in practice this was not the case on multiple cranks. 

[DieselnDust]

19 hours ago, nick_the_wheelbuilder said:

The left arm will only fall off if part #5 (look at the diagram above) isn't snug.

Install the crank arm (without stupid stopper plate) in this order:

1. Slide crank arm onto spindle.

2. Snug down part #5 (I forget what it's called - I'll call it the spindle end cap, for lack of the correct name)

3. Tighten pinch bolts.

The pinch bolts squeeze the crank arm onto the spindle, preventing the spindle end cap from unscrewing. If that end cap stays put, so does your crank arm. 

Spot on and this is the procedure in the Shimano dealers manual. The pin in the safety plate of my old XTR 960 crank fell out many years ago but the drank never comes undone because I followed the fitment procedure. The end cap is a preload tensioner that pushes the crank against the bearing labyrinth seals and the inner race of the bearing, preloading it. If the correct procedure is followed then the crank arm should never come loose and the bearings should last a long time.

Edited December 1, 2023 by DieselnDust

[nick_the_wheelbuilder]

I have see that if there are too many BB spacers installed, the end cap doesn't thread in far enough, and the crank arm falls off within 20km.

Ask my riding partner on my first Sani2C - 15km into stage 1 and we had to go full McGyver-mode when his left crank arm came off and the end cap went missing.

Incidentally, a QR skewer works well holding things together. Better than cable ties.