Lock Washers: Split vs. Flat "warped" styles

[Eric P]

What is the difference in function? Why does the factory use one type in one place, and another type in another. I'm replacing a number of fasteners and would like to be consistent...

[Wil Ferch]

In general , a "split" lock washer doesn't do a very effective job of locking altogether ( single point contact)......a serrated Bellevile ( cupped) washer or the Schnorr-brand variant is much better...

Wil

[randywebb]

then there are the wavy ones...

[Jim Sims]

Having reassembled two 911's following the factory parts diagrams I have concluded there was no "rhyme or reason" to what the factory used. Helical split, wave and Schnoor serrated lock washers were used along with plastic insert lock nuts, metal insert lock-nuts and deformed thread lock nuts and then there is the "Duralok" bolt head style used on some of the crank pulleys.

As already mentioned, the helical and wave style lock washers are not very effective in severe vibration or periodic loading cases.

[Grady Clay]

I tend to agree with Jim and use the absolutely original hardware unless there is some compelling reason to change.

The most common problems are someone leaves off important hardware or doesn’t replace “use-once” components.

The locking techniques have evolved from the earliest VWs to the latest Porsches as the technology changed. It would be instructive and fun to document all the different techniques. Porsche followed the DIN Standards (now ISO) for almost all hardware applications. I think the reason we see such a wide variety of methods is both the differing requirements of various parts of the 911 and the favor of the various department engineering staff. I have had good results using OE or OEM hardware with very few exceptions.

It is probably worth noting the exceptions. I’m sure I won’t note all.

I think the most significant in terms of safety is the ’69-’71 ball joint to strut pinch-bolt hardware. My opinion is every one of those should be upgraded to the wedge pin and proper associated hardware.

Of course there is the cylinder head stud issue. This is two-fold. First was the pulling of the studs out of the magnesium crankcase. Then there was the breakage of the studs in SCs and Carreras.

The magnesium case transmissions have a stud pulling issue with high power.

There was a resonance issue with ’73 RSR flywheel bolts (6-bolt crankshafts).

Note that none of these issues have to do with loosening of the fasteners. If the proper hardware is in place, in good condition and is properly torqued there is seldom an issue. Porsches just don’t fall apart.

The big exception is constant velocity (CV) joint fasteners. This is a major issue and has been well covered in Pelican rcecale, Randy’s classic thread.
”Reconstructing Constant Velocity (CV) Joints” and other.

Best,
Grady

[dean]

I think it might be the wavy ones go with Alu parts and the splits go on steel parts.

[Eric P]

Interesting...

I'd like to use wavy ones in places where I disassemble frequently (for example, unbolting the rear swaybar to drop the engine...done frequently on a racecar. The bolts currently have split washers and it just seems damaging. Then again, maybe I should replace them frequently...dunno...)

[billyboy]

I know that the split lock washers do tend to dig in and scar aluminum pieces.

The bolts currently have split washers and it just seems damaging.