Clutch Pressure plate

[europa88]

I've searched, but cant find a definitive answer. Do you need locking washers of some description on the bolts holding a pressure plate to the flywheel?

[cwtech]

NEED?  ....Maybe not, but HIGHLY recommended.

Every vehicle that I have experienced had lock washers on the pressure plate bolts.

They are shown in the Lotus Manual, as well.

[jbcollier]

+1

Use lock washers!

[Grumblebuns]

What type of lock washers are we talking about. Do pressure plates use a special lock washer?

 Split type lock washers are suppose to be not very effective in keeping bolts tight.

[europa88]

What type of lock washers are we talking about. Do pressure plates use a special lock washer?

 Split type lock washers are suppose to be not very effective in keeping bolts tight.

This was my point, as although the manual does show a washer, it doesn't specify what type. I have used split washers, but am aware of their limitations.

[jbcollier]

The factory used split lock washers.  I have only used split lock washers on clutch bolts over 35 years of pulling wrenches.  Never had an issue.

[europa88]

https://www.youtube.com/watch?v=PTpN-hkZom4

Link to the reconditioning of my flywheel

[gideon]

A few minutes with Google turns up some good evidence that split lock washers are not effective, e.g. this page

https://www.boltscience.com/pages/helicalspringwashers.htm

[BDA]

I haven’t been a fan of lock washers since I read Carroll Smith’s Prepare to Win in which he’s pretty disparaging of them. I think they can be effective based on the experience of a buddy of mine:

One of his first projects out of engineering school was to find out why a machine was shaking itself literally to pieces. Actually, nothing was working, not split lock washers nor even nylon lock nuts but the “points” on the lock washers actually dug into the nut and the piece before they let go. That tells me that in a less severe environment, they would have done their job.

It doesn’t seem that all split lock washers are designed to dig in like those lock washers and so if I had to choose one, I’d use AN (aircraft) lock washers purely because if it was designed to be used on an airplane, it would be more likely to work. If I was really worried about vibration, I would used safety wire or Loctite - usually safety wire because it is absolutely effective and it is a visual indication later that that bolt was tightened properly. I also think it looks cool!  Admittedly, it is over kill on a road car and is a pain in the ass to do and undo.

Just my thoughts on lock washers…

[cwtech]

A few minutes with Google turns up some good evidence that split lock washers are not effective, e.g. this page

https://www.boltscience.com/pages/helicalspringwashers.htm

Very interesting! - Thanks for posting this.

From the video:  "Complete self-loosening can result from repeated transverse joint movement."
....I'm not sure the pressure plate is subjected to this frequency of movements.
....Also, pressure plates are usually secured with six or more bolts.
....How can a car go 50K-100K miles without pressure plates loosening from using split lock washers?

[TurboFource]

We used these at one place I worked.. https://www.nord-lock.com/nord-lock/products/washers/

[dakazman]

    You can take the easy route and add the lock washer to the bolt, tighten to proper torque using bolts ready for safety wire. The pressure plate uses 6 bolts, in three pairs of two, so safety them together, end of problem. Piece of mind for the price of six bolts.
  Dakazman

[Grumblebuns]

The key is to use high quality lock washers, not your garden variety hardware store stuff and probably should not reuse them.

Although not absolutely not required, safety wire pliers though pretty expensive, make the task so much easier. When I get that point, I'll think about wiring the bolts

My stock flywheel bolts were still tight after 40k miles when I removed them for my engine rebuild so it kind of says something on the effectiveness of the original split lock washers.. On reassembly, I'll use the Belleville conical spring style or the Nord lock style washer and new bolts. I haven't seen testing to see if the alternative lock washers are any more effective in keeping bolts tight then the regular split lock washers.

https://www.mcmaster.com/products/standard-washers/lock-washers-4/belleville-spring-lock-washers/   

[Bryan Boyle]

Of course...it should be said that safety wire should be installed correctly.  It's easy NOT to.  While the implications on the ground are different than in the air...still, doing it right is never wrong.

Youtube has a good video on how to.  And Joji...the right pliers aren't that expensive... 

https://youtu.be/grO_q4sDcjU

[GavinT]

When was the last report of a pressure plate coming loose in service?
Blue Loctite ?