Decisions, decisions!

[les]

I have clean dry components for the front suspension, and I'm mating the splined torsion bar ends to the front and rear arms. As these are not moving parts,(as far as splines can be) I thought grease might encourage movement, but then again no lubrication might encourage wear.
So I've decided on using wd40, but I would like opinions in case I have overlooked something.

[JimK]

Leaving off any lubrication will encourage the suspension arm to bind itself to the torsion bar splines for ever

For any metal-to-metal joints, whatever they are, I put some sort of protection on them. I have a little grease between front and rear arms and copperease on the torsion bar splines. All nuts are assembled with a little copper grease.

I use copper grease as I reckon the copper is less likely to wash out over time.

[rayofleamington]

I use grease as the splines need to be able to move in order to get all the parts aligned , and also to aid dissassembly.
Without any protection the arm will rust to the bar, making it more difficult to work with in 15 years time.

[les]

Mmm, How about thick wd40! Looks like a rethink may be on the cards. Thanx for replies.

[Willie]

See your point Les, you wouldn't want to encourage interspline movement
But you could also say that if there is some sort of friction reducer on the
splines then it will help to prevent metal to metal wear if some play develops.
Then again the grease could have set hard after a few years but is still
likely to prevent the ingress of water. The half shaft splines run in oil all
the time but still wear over time. I hate to think how much more quickly they
would wear if they were unlubricated.

[bmcecosse]

WD 40 = Water Dispersal fluid # 40. It is NOT a lubricant, nor is it a penetrating oil - it's for Water Dispersal. The splines should be liberally greased - moly grease is good. And leave the exposed splines covered in a dollop of it too.

[les]

Thanks for your considered opinion Willie, seems you know what I'm trying to put across.

[JimK]

Thanks for your considered opinion Willie, seems you know what I'm trying to put across.

I understood that you didn't want to encourage movement, but the nuts and bolts should do all the discouraging that's needed. I'd say that if you bolts the two halves of the suspension arm together OK and similarly attach the end nuts to the torsion bar then there is no possibility of the arm coming off the greased splines.

If it's allowed to move then the forces involved mean it's going to move whether or not you put any grease on it, and as Ray says it will massively help come the time you need to dismantle it. Metal-to-metal contact is almost always bad - moving parts will wear and static parts will rust together.

If you don't grease those splines you'll regret it. Maybe not today, or next week, but one day.*

*With apologies to Humphrey Bogart

[Willie]

JIMK Les was pondering if greasing the splines would encourage wear BETWEEN THEM, not that it might enable the splines to slide off.

[JimK]

JIMK Les was pondering if greasing the splines would encourage wear BETWEEN THEM, not that it might enable the splines to slide off.

Really? Maybe I didn't spot what he meant...

How could grease possibly allow wear? I don't get it. You'd get a very thin film of grease filling any space between metal surfaces but it wouldn't make space where there wouldn't have been any, and it will keep water out.

If there is a mechanism I'd like to hear, just because I'm an engineer and therefore curious

[Kevin]

How could grease possibly allow wear? I don't get it.

I think that the question posed by Les is interesting as I hadnt though of that point of view before. I am sure that correct type of lubrication is required between all metal parts to reduce long term wear as it reduces the forces of friction which cause the wear rather than put extra pressure on the parts that can move setting up a form of hydraulic pressure, and although I believe there are some plated surfaces and materials that dont require lubrication but that is not relevant to this application.

[chickenjohn]

I would agree with whoever said use copper grease, its good stuff!!!

[Kevin]

I would agree with whoever said use copper grease, its good stuff!!!

Agreed John and the best way to buy it is in a can similar to the type that ordinary grease comes in as its expensive if you buy it in the small tubes.

[Willie]

Well it seems a sensible question to me. When the splined surfaces are new
it should take some pressure to join the sections together if the splines have
been made to the correct tolerances. If they have been exposed to stress
over many years as is the case with the Minors then, inevitably, there will be
some play developed. All the Minors I have played with have had slightly
sloppy fits on these splines and certainly were not difficult to reassemble. All
Les was wondering was if greasing these well used splines would encourage
accelerated wear.

[bmcecosse]

Why is 'copper' grease thought to be good ? Molybdenum has excellent lubricant properties - copper very little.

[JimK]

Why is 'copper' grease thought to be good ? Molybdenum has excellent lubricant properties - copper very little.

For the torsion bar splines it's not really lubrication we're after, it's longevity of corrosion protection and ease of dismantling in umpteen years' time.

When machined, hard metals have quite a rough surface at the microscopic level. If you assemble a titanium bolt in a component of the same metal then that bolt is probably never going to move again because the surfaces have bound themselves together.

Copper has the benefit that it fills the surface roughness, thus allowing the surfaces to slide past eachother. It's for assemblies rather than sliding joints - so torsion bar splines but not suspension pivots.

I guessed that the torsion bar would be spring steel and thus quite a hard surface, so I made the decision to use copper grease.

I use Castrol LM for sliding joints (as specified in the workshop manual) and general nut-and-boltage, and Copperease for high-torque and stressed assemblies.

[bmcecosse]

Moly grease for me !!