Front Stub Axles

[guy mayers]

Just a little query for you all, albeit a significant safety one.... The stub axles are handed, one has a normal thread and the other has to be "tightened" to remove the nut. Which one belongs on which side of the car?
I ask because my Stratos has the normal one on the right side but my Fiat Spider is the other way around. Now one of them must be assembled wrong and I'm praying it's the Spider as the hubs were both slightly loose and this may be the cause of the brake problems I've been experiencing! BUT I dont want to dismantle the front of the car needlessly!
When I rebuilt the Spider everything was replaced and I'm sure it's been reassembled as labelled on disassembly plus my Fiat 124 Haynes manual states that the RH stub axle has a LH thread. Is a LH thread a normal thread, one that you rotate clockwise to tighten?
Guy

[roger001]

As far as I understand it, the nuts should be handed so that normal (forwards) hub rotation tightens the nut i.e. the RH side of the car has the normal direction of the thread.

This is the same as with knock off hubs on wire wheels.

[rutthenut]

I'd agree with Roger on that.

The theory (and practice) is that normal forward rotation of the wheel would aim to 'tighten' the lock nut - certainly not to undo it.

So, right hand wheels would have nuts that tighten in a clockwise direction. Left-hand fitment would have the 'odd' thread.

[chris.richard]

Just discovered that my car had been assembled the wrong way round, like Guy's Spyder. Glad I changed to 5-stud hubs, it wouldn't do to have a wheel come off, would it? :p

[John]

Light commercials, such as the Transit and Bedford CF, have hubs which tighten right hand thread on the off-side and left hand thread on the near-side as Roger and John have described. Wheel nuts were stamped LH on my old CF. Guy, do the hub nuts have locking pins?

[chris.richard]

My Fiat 131 & 132 Haynes manuals say the same as Guy's 124 manual. I've 'googled' this and turned up references for Minis and MGs, both left hand thread, left side.

Is the Haynes text a typo that's been 'copy & pasted' without being spotted by proof readers?

[chris.richard]

Still thinking about this one. The washer between the bearing and the nut cannot rotate because it has a tongue to fit in the groove on the stub. The nut therefore is not subject to any rotational forces from the wheel/bearing, so it shouldn't matter what thread the nut has. So why have handed threads? Hmmm. :confused:

[guy mayers]

Just in case some idiot mechanic loses said washer, doesn't realise it's significance and replaces it with a normal one perhaps? :eek:
Guy

[chris.richard]

I'm told that handed stubs were a 70s/80s thing and now they're all RH threads. Probably in case the split pin came out.

[Arthur]

As with many things, there is a theory, and there is culpability.

If you were a designer, and it was that easy to appear to be "on the ball" and "safety conscious", and heaven forfend any suggestion that economics of spares supply means more different parts equals more income, you'd do it.

So taking the left front, is the stub axle carrying the nut realistically going to turn within the hub under heavy braking? (or any other circumstance?)
Come on Guys, you've tried to remove these, and probably bent a variety of huge bars and cheap sockets in the process. No way are they going to come off if correctly tensioned.
If they are NOT correctly tensioned, I doubt very much whether any amount of handedness will help.

Mind you, and here's the cruncher, if you have a look at left-hand threads across loads of machines, they are usually introduced as a design change to a prototype AFTER a disaster, and the disaster is usually vibration-based. In this instance, it's of no significance which way the theory goes, its a change to cure an observed problem. Now THAT solution will be carried forward through every subsequent similar design...........so what you find is odd fasteners in odd places. Do you replace or modify them? Your call!

[Andrew Way]

Am I correct in thinking these nuts are not tightened much more than finger tight?

[chris.richard]

Andrew - 0.2 KgM I think. My torque wrench doesn't go that low!

Arthur - Still doesn't answer why 3 Haynes manuals for Fiat have them one way round, while MG, minis, and everybody I've asked has said the other way round!

[Arthur]

Chris,

As the man says, it all depends.

If Fiat have decided that vibration loosening is the problem, and that orientation works, then that's how you fit Fiat hubs.

If BL (or whoever the hell they are these days) have decided that torque loosening is the problem to solve, then theirs go in the other way round.

That's it, at the end of the day.
The only people I trust are those who build big Diesel engines, and Tractor builders, who go into this kind of thing to some depth, and have to indemnify every solution they provide.
So It may sound odd, but have a look which way round Ford fit them them to 7-litre tractors, and go with that - you won't go far wrong!

Other option is decent fasteners - in this case, the method of locking the nut. Don't go for Nylock; use either the manufacturer's part, which is normally "beam locked" - that is, the top couple of threads are slotted to root depth, and the "beam" formed is deformed prior to you fitting them.
Better type is the "K-Nut" which has a 3-lobe deformation crimped into the finished nut. Cheap ones either won't come off, or strip the threads off on removal. Good ones (and you will know by the price, which is eye-watering) are infinitely re-usable, and will not come off of their own accord, ever.

What was that torque figure for - not for stub shaft retaining nuts, I hope, which amongst other things pre-tension the bearings, and need to be whatever the manufacturer specified. Last I remember doing were on a Nova, I think, and came in at about 150 lb.ft - about double the head bolts, as I recall. What the hell that is in NM, or KGM, I know not. Consult tables once again.
200 NM = 150 Lb.ft
My table says the tightening torque for 7/8 UNC (common stub shaft size) is 287 NM (212 LbFt). 3/4 UNC is 179 NM (132 LbFt). 5/8 UNC is 100 NM (132 LbFt).

Problem with silly numbers is usually a cocked-up conversion factor. Don't believe anything that looks wrong. Big Nuts = TIGHT.

[chris.richard]

Chris,
Don't believe anything that looks wrong. Big Nuts = TIGHT.
But as you say, these nuts pre-tension the wheel bearings. If you torque up to "T", or "FT", the bearings will seize once they warm up & expand.

[chris.richard]

There must be some structural difference here Arthur.
The Fiat figures are:- Torque to 14.5 lbft to bed in bearing, back right off, then re-tighten to 5 lbft, then back off 30 degrees.

[Andrew Way]

My 131 manual agrees with these figures. I questioned them when I built my hubs up as it seemed so low but a friend with lots of experience with Fiats confirmed this as he's known these bearings to be knackered after a few thousand miles if over tightened.

[chris.richard]

My torque wrench wont go this low, so i think it'll have to be a ruler and a bottle of water until I get the feel for it.

[guy mayers]

Fiat front bearings are the tapered variety and very sensitive to the correct tightening procedure. Not only can overtightening lead to premature failure due to overheating and seizure (which can also ruin the stub axle) but if they are too loose then this allows play in the disc which can have the effect of knocking the pistons back into the callipers leading to a spongy brake pedal feel, endless bleeding and constant frustration. Beleive me, this is the problem I had with the Fiat Spider brakes. The procedure detailed by Chris matches my manuals for the Fiat but he has omitted to say that the hub should be rotated several revolutions in both directions to ensure that the bearings are fully seated before the nut is slackened off. If you get it wrong don't be tempted to reuse the staked nut. One day you will regret it!
The rear bearings (Lancia Beta) are of the normal variety and, having a big nut, need to be torqued FT.
Guy

[colin artus]

Front wheel bearing endfloat is given as .025 to.100 mm.

Colin

[chris.richard]

If you get it wrong don't be tempted to reuse the staked nut. One day you will regret it!

The stub axle has two grooves, so you can always restake in the other groove......
This website and this author take no responsibility......

[Arthur]

Fair enough, It's while since I did back-to-back Taper Rollers. Or indeed hybrids, with one taper, and a self-aligner. Usual now (for front drive) is a pair of directional axial load sphericals, or a pair of split inner race uni-directional thrust bearings.

I suppose all you can say is follow the manufacturer's advice. All I was trying to do was poit out one reason why the same apparent problem may have two diametrically opposite solutions......

I believe the professional mod is to calculate the pull-up for pre-load, machine (grind) a hard steel tube to space the inner races, then bang up the nut. Course, you need a ground spacer for every damn pair of bearings........
I remember talking to Peter Hignett, who used to run John Bintcliffe in his Fiesta days - he reckoned he was running 5 to 7 degrees negative at the front, and the wheel bearings lasted 20 minutes. (you get a lot of precession.........)

Whoopee.

[Andrew Way]

My torque wrench wont go this low, so i think it'll have to be a ruler and a bottle of water until I get the feel for it.

And if the Queen is buy try using a rule :D

[chris.richard]

And if the Queen is buy try using a rule :D
So, it's one rule for you, and another for the rest of us? :D

[Andrew Way]

That joke would have made more sense if I hadn't mistyped "busy" as "buy" - doh!

[mogul_x]

My torque wrench wont go this low, so i think it'll have to be a ruler and a bottle of water until I get the feel for it.

Chris,

Don't they have small torque wrenches over there? I have one that goes from 25 to 250 INCH pounds. That's a minimum of just over 2 ft-lb. I've gotten a lot more use out of it than I originally thought I would when I bought it.

It's a Sears Craftsman item - not sure you have Sears stores over there, but I know you can shop online. Otherwise, there must be a similar product available elsewhere.

Taking a quick look at Sears' website, I saw a torque screwdriver that is adjustable from 2 to 36 inch-pounds. Can't think of anything outside of scientific equipment that needs such precise adjustment...

[Andrew Way]

Oooh thats a big one! I've a Norbar that goes down to 10 inch pounds.

[mogul_x]

Oooh thats a big one!

I get that a lot... ;)

Sorry, I couldn't pass up a line like that!