Studs vs. bolts

[BDA]

Those would work. Nylon lock nuts can also be found in half height. I thought I had seen them at Lowes but I can't find them online. You can get them at Aircraft Spruce (https://www.aircraftspruce.com/), probably ebay, or some racing supply stores. Another trick half height nut is a "jet nut" which is an all metal lock nut. You can get them on ebay.

[Grumblebuns]

The nut in pic also appears to be a flanged nut. Wouldn’t be surprised if that explains some of the extra thickness.

Perhaps consider an “all metal” lock nut which is shorter than a standard Nylock?
Like this:

I thought I read somewhere that the all metal style locknuts were one time use only due to the damage to the threads when used. I'll measure the thickness of my current nut versus a regular nylon locknut.

[4129R]

Unfortunately you cannot thin down a normal Nylock on a grinder, as the heat melts the plastic. 

[BDA]

You're SUPPOSED to replace all lock nuts every time. I think you can be perfectly safe replacing them every third time or so as long as I need a wrench to turn it in the lock zone. I use the same rule for metal lock nuts except in high heat applications were I'll replace them every time or two.

Edit:
I forgot to say that using nylon lock nuts on threads created by a die means it almost has to be changed every time because those threads cut the nylon whereas the rolled threads of a bolt push the nylon aside.

[GavinT]

I thought I read somewhere that the all metal style locknuts were one time use only due to the damage to the threads when used. I'll measure the thickness of my current nut versus a regular nylon locknut.

Yes, and that's the recommendation for most lock nuts as far as I can tell.
But as BDA says, you can get away with stuff  . . just have to ensure there's "sufficient" drag caused by whatever locking mechanism is employed.

The 'all metal' lock nuts have a triangular deformed area on the exit side but don't seem to be detrimental to the threads from my experience. They are commonly used in high heat applications where a Nyloc would melt.

Anyway, if you like, measure your lower pin length.
I can measure my Type 54 (in bits) which I assume is the same, and compare.

[GavinT]

OK, I've measured the lower pin length - the available length.

51 mm (2.0”)

Does that help?

[Grumblebuns]

OK, I've measured the lower pin length - the available length.

51 mm (2.0”)

Does that help?

Gavin, my overall lower pin extension from the end of the nut to the beginning of the pivot pin tube on the chassis is 2". My nut is not flush with the end of the pin by about 1/8".

I've attached a picture of a locknut similar to what is now on my S2, a used locknut from my TCS and a half height locknut. What would be optimal is to locate a locknut similar in height to the TCS nut. All of the 1/2"-20 nylon insert locknuts that I've checked out have the same approx. height as the tall locknut shown. I haven't checked out the all metal locknut yet. IF I can't find a shorter full height locknut, there may be room to use two of the half height locknuts back to back.       

[jbcollier]

If room is tight, how about a regular nut and split lock washer?  Myself, I would not use half height nylocks as suspension fasteners.  I used to do OPI (out-of-province) inspections and I would fail any car so equipped.

[BDA]

I use jet nuts on some of my A-arm pivots (I might use them on all. I don't remember). They are about the same height as the half height nyloc nut but I think they are stronger.

Half height nuts are designed and intended for bolts that are stressed in double shear (i.e. there is essentially no load on the nut other than what is imparted by tightening and the torque specified is on the order of 1/2 that specified for a full height nut) which makes them appropriate for most of the suspension. However, I would not use them for the radius arm pivot, for example, because it is only in single shear and if the bolt bends, that could put a tensile load on the nut.

Having said all that, JB got me thinking. The front A-arms are in double shear except possibly in an accident. Because the A-arms are not held captive by anything other than a big washer and a nut, an A-arm that is being bent could impart a tensile load on the nut. If the A-arm halves were inside the frame rather than outside, this would not be an issue but they're not so it is. During an accident, it is much better to have even a bent suspension piece remain attached to the car rather than come off the car because of a failure of the nut. I did a bit of digging and found that jet nuts (MS21042) are rated at 160kpsi and the full height aircraft nylon lock nut (AN 365) is rated at 125kpsi. So I feel comfortable using jet nuts on the A-arm pivots. I would note that AN and MS standards are much more rigorous than SAE standards which govern nuts and bolts we normally put cars together with (for example, grade 5 and grade 8 are SAE designations).

Auto safety regulations are another matter and should be followed regardless.

[GavinT]

G’day Grumbles,

I’ve attached a pic of my pin with an A-arm installed. The bush in the A-arm is a stock OEM item.
I’ve measured all four of the lower pin lengths and they’re all the same - 51 mm (2.0”).

The nut in my pic is a thick one and pretty much the same as the left hand one in your pic.
As you can see, it’ll fit OK.

Nut height: 15.02 mm (± 0.05)
A-arm bush inner steel sleeve: 35.05 mm (± 0.02)

So, the math seems to add up.
By process of elimination, I wonder if your inner bush sleeve is a bit too long?

[jbcollier]

I'd be ok with jet nuts as there is a lot more thread length than with the nylock half nuts.

[GavinT]

The front A-arms are in double shear except possibly in an accident.

Nah, the A-arms are in single shear.
The lower damper mounting and the trunnion are in double shear, however.

[EuropaTC]

Myself, I would not use half height nylocks as suspension fasteners.  I used to do OPI (out-of-province) inspections and I would fail any car so equipped.

I've got to agree with John here, looking at those half height nuts they don't inspire me for this application.  I'd want a bit more thread and the ability to get the full torque setting to clamp the inner sleeve securely because if it starts rotating then I've no idea what would happen. Probably nothing, but I wouldn't want to find out the hard way.

While the conversation is about nut height, I did start to wonder about the overall pin length and whether it's been set centrally in the past.  It would be very handy if there were 1/4" of thread sticking out on the rear nut....  

[BDA]

Let me first say that while I do have a degree in mechanical engineering, I only worked as one for a few years and it was a LONG time ago so I don't really consider myself an engineer anymore. I have to make some modifications to what I've posted here.

Gavin:
I was going to disagree with you but the more I thought about it. I have to agree - BUT I think for our purposes we can consider the A-arms to be in double shear and here's why: If the A-arm halfs were welded together at the outboard end and the 'T' section of the frame was solid - no place for the shock - that would look like the double shear picture you posted. Now, that's not exactly the situation we have so in analyzing the stresses, it probably makes sense to consider the pivot to be in single shear for safety but I think for the purposes of what nuts we might use on the pivot, double shear rules work here.

JB & Brian:
In my previous post I didn't consider the number of threads engaged in a half height nyloc nut. I was taught that if you had four threads engaged, you had essentially full strength of the nut. A half height nyloc nut only has 2-3 so I think they should be used only in unambiguous double shear applications so I think JB and Brian are correct about using either a full height nut or a jet nut on the front suspension. A half height nyloc nut is not appropriate there.

While I was researching this I found a couple of interesting points. Jet nuts are infinitely reusable (says Carroll Smith, author of Prepare to Win, Tune to Win, and Nuts, Bolts, Fasteners and Plumbing Handbook
). Also that even though I believe the manual says not to reuse nyloc nuts (and I've heard others say they only use them once), it is perfectly acceptable to reuse them if they can't be turned by hand. This is a practice I've used but at least partially to save money. It was nice to see that stated authoritatively!

[EuropaTC]

Also that even though I believe the manual says not to reuse nyloc nuts (and I've heard others say they only use them once), it is perfectly acceptable to reuse them if they can't be turned by hand. This is a practice I've used but at least partially to save money. It was nice to see that stated authoritatively!

   me too ! 

If a nut stops when the nylon meets thread and I need a spanner to get it to turn, then I also re-use it although I do tend to chuck any nut away that looks a bit on the rusty or "used" side with marks on the flats.    I'm in two minds about nylocs if I'm honest, I feel that the biggest thing stopping a nut coming loose is getting the correct loading and not the bit of nylon in the end. Having said that, I'm not about to experiment with replacing all nylocs with plain nuts !

BUT.....    I'm definitely not a mech. eng. guy so it was interesting to hear the "4 threads" theory.  My dad used to be a fitter and I remember him saying something about having the same depth of thread engaged as the bolt diameter which I've generally followed when doing stuff.  Logically though the number of threads engaged probably makes more sense and is easier to apply. 

Yet again a topic on here has been another school day !