Wheels and Tyres - Nut/Bolt Torques
Recommended/Correct wheel nut torques
Grun: Incidentally why (Haynes again) should my Bay window have a recommended 94 ft/lbs torque when the steel wheels,
hubs, studs and nuts are the same as the T25/T3?
And do I torque my alloys up to the same figure as steels...
Simon Baxter: Customers wince when I rattle their wheel nuts up with the air gun, they've been reading too many forums!
What makes them think twice is when I get the torque wrench out and torque their wheels to 180nm as per book and I have to swing on the torque wrench, making tighter what they believed to be undo-able from the gun! Maybe the higher torque as opposed to the bay is the weight carrying capacity and the weight of the van itself. The track and wheel base are all different too.
Stuckin88: I think it is a case of common sense--I keep a 2 foot breaker bar & 19mm impact socket in me van--do ya wheel nuts up fairly firmly with one of these & yool be ok--
HarryMann: Simon's right, this is because the weight of the van is greater. This may sound either silly to some or obvious to others, but in reality, nuts and bolts are done up to clamp two or more parts together - the nut not coming off is taken for granted when torqued up to the correct figure, and is only much of a design a consideration in some cases, usually lightly clamped parts. Wheel nuts and recesses are tapered, so at anywhere near the correct torque figure, they're highly unlikely to loosen.
But the aim is firstly to provide a clamping force calculated as appropriate, and in cases of fluctuating and even reversing loads, such as a wheel, the clamping force may also be calculated to reduce the chance of fatigue by creating a high static-stress level (e.g. pre-loading). This is probably the case with wheel bolts and studs.
Between 1/2 and 2/3 of the torque figure frequently goes into friction in the threads and the bolt or nut bearing face, so as little as 1/3 produces the clamping force.
I too usually carry a powerbar and 19mm impact socket on board. Knowing that the threads and nuts are cleaned and lightly lubed whenever they come off, to keep corrosion in check, and that the hub face and back of wheel is also checked and cleaned, I usually torque just over 100 ft-lbs* on 15" steels on a Syncro, that can have at least a ton in the back from time to time. 133 is what Bentley says, so knowing that they're clean and the wheel's nicely flat against the hub, I expect I'm easily getting the minimum clamping force that VW hopes for under worst case conditions.
Alloy wheels often have a larger and different tapered contact area to reduce local bearing stresses. You might follow the same thinking, that if the threads are well brushed clean, the tapers aren't knarled and corroded and the nuts run up nicely, you needn't go berserk with the powerbar or torque wrench. But done up to not come off, isn't the only criterion! The clamping force should be much the same as with steels, so also make sure the backs of the wheels and hub faces are clean, flat and not corroded badly, do them up to at least 100 lb-ft and worry not. But be sure to tighten them in a star pattern in 2 or 3 stages, unequal torques are definitely a bad thing on fronts, due to the potential for disc warping.
It is recommended good practice to check them between 35 and 70 miles later, with a torque wrench if possible, but a visual inspection is better than none.
Advice: Always carry a Powerbar/flex head bar and 19mm flank-drive socket
Lubricating wheel stud/lug threads
** If you insist on lubricating lug threads, please be sparing and make sure to compensate for the increased torque likely to result. For example, one lubricant manufacturer recommends torquing nuts to only 85 percent of the factory specification when using their nickel-based anti-seize compound on threads.' '
Keeping the studs and nuts in good condition is a good idea; light wire brushing to remove rust, or muck in the threads and a quick spray with WD40 or similar thereafter helps prevent corrosion and helps nut running up and down the studs...
For more, see the link at the bottom of Wiki on Torques
NB. Recently, a member has had a wheel come off while underway, fortunately slowly. It was a steel wheel and had recently been powder coated It had been put on at a garage by a junior using a pneumatic nut winder. These devices rarely have a properly calibrated torque limiter/clutch. Even if they do, would it be set to suit your vehicle's wheels?
It is really your responsibility to check the wheel nuts yourself, whenever they've been off, as its fundamenetal to vehicle safety, a bit like checking your lights are working proeprly before setting off (as we all are required to and do with our lights and indicators of course)..
Minimum Thread required to attach alternative wheels
A good rule of thumb for all bolts and nuts is to have 1 1/2 times the length of thread, of the diameter of the thread.
So if you have an M14 bolt or stud, then you would ideally want 21mm worth of threads.
If you look at the pitch of the bolt/stud, (I think they're M14X1.5) then divide 21mm by 1.5 and you would have 14 threads.
If you go and grab a stock wheel nut and measure the depth of it, hey presto you'll find it's fairly close to 21mm Smile
Hope this helps.
Andy Syncro-Nutz: You really need about 12mm minimum of thread to put the nuts on to. Which is required by BMSA @ 1.50 Thread pitch.
Warning: Rear brake drum locating/retaining set screws
NB. When fitting alternative wheels at the rear, please note that unless they are recessed for the two small drum locating set screws, then they will need to be removed so the wheel can be pulled up flush and flat to the drum surface.
The clue is that the nuts don't all go on the same amount, and when you tighten them up they don't feel right at all, the torque doesn't come up quickly enough, or at all.
Further Links/See Alsos
Additional relevant information might be found here: Alternative wheels