Unable to remove wheel

So what the f*ck is brake hole size?

It's a Mack Truck. The Yanks talk different.

Nope.

Basically correct. Provided the friction force between the components is greater than the torque forces applied to the wheel then the bolts themselves do not see any additional shear loading on top of the tensile load that has already been applied to them by tightening them up.

The studs themselves are not strong enough to cope with

Bollocks. Take an average car and assume 50/50 weight distribution, total weight 3000 lbs, weight per corner 750 lbs. On a dry road with an optimum tyre coefficient of friction of about 1.0 then the maximum contact patch load is about the same as the corner weight i.e. 750 lbs before the tyre slips. Of course the wheel studs are inboard of the contact patch so assuming a 4 inch PCD stud pattern and a 24 inch diameter tyre we need to multiply the contact patch force by 6 (24/4) for a final value of 4500 lbs twisting force at the studs during an emergency stop. You could increase that on the front wheels for weight transfer effects but it makes no difference to what follows.

A 12mm x 1.75mm grade 10.9 150,000 psi steel wheel stud has an Ultimate Tensile Stress of about 20,000 lbs. Maximum shear stress is about 60% of UTS i.e. 12,000 lbs. Multiply by 4 or 5 wheel studs and clearly the total shear strength of the studs is massively higher, by a factor of 10 or so, than the maximum possible shear force that the brakes could apply to the studs via the tyre grip.

Simple common sense or in many people's cases direct experience will tell you that if the wheel nuts are not tightened the studs don't just snap - the nuts eventually fall off and then so does the wheel. No matter what the vehicle the studs or bolts are sized, and placed at such a diameter, that the shear load on the studs can never come close to their maximum possible shear stress. To do otherwise would be lunacy and cause potential breakages and accidents every time the nuts weren't tightened properly.

As to the effects of lubricant between wheel and hub, clearly this reduces the coefficient of friction somewhat but even if that drops as low as 0.15 the clamping force times the cF will still exceed the shear force if the nuts are done up properly. In practice, for lubricant to reduce the cF substantially there needs to be a lubricant layer of a certain thickness and with only a thin smear of grease plus the clamping force of the studs that layer squeezes away to practically zero so the effects are actually very small. That's why a crankshaft bearing seizes when the oil pressure fails because even though the surfaces are still oiled there is no longer a boundary layer of oil for the crank journal to float on.

Even with the best moly lubes it's not possible to drop the static cF between highly loaded components such as bolt threads by more than about 40% because the lube just squeezes out and the components still make metal to metal contact. Contrast to lightly loaded components under floating friction lubrication where the cF can drop to close to zero such as when a vehicle is aquaplaning or a crank journal is operating properly in its bearing.

So a smear of Coppaslip or similar between wheel and hub is good n'kay. It prevents corrosion, doesn't actually reduce friction by that much and makes no difference to whether the nuts will come loose.

What about lubricant on the wheel studs? The torque loadings are specced so that even though they are generally done up dry you will not exceed the yield point if normal lubes are used. They are actually specced very much overkill so that even when rusty and knackered they still keep the wheels on and you can overtorque them to a significant degree without breaking them. In fact with old and rusty fittings the dry friction is so high that the clamping load can actually be very small. Some lube positively helps to correct this. In no case does lube make a bolt prone to coming undone. If that were the case engine big end bolts would be in dire trouble as they are always assembled with lubricant which actually helps to achieve a given clamping load with less torque and shear stress. In fact the perfect bolt would have zero friction and be done up with very low torque settings.

With brand new wheel bolts and nuts I might go so far as to say it wouldn't be the best idea to use the slipperiest possible modern thread lubes like ARP lube and still stick to the stock 65 ft lbs or whatever but I can't imagine many people doing this. Ordinary grease or Coppaslip will be just fine however. You might use the lower limit of the torque spec spread if you were fussy.

So a smear of Coppaslip or similar on the wheel studs is good n'kay. It prevents corrosion, doesn't actually reduce friction by that much and makes no difference to whether the nuts will come loose.

Perhaps the problems that have been encountered on old lorries are more to do with painting over rusty surfaces on drum and wheel, several coats probably, which could then crush and fall off over time which might lead to wheels becoming loose, as the vehicles are not used professionally it might be years before tightness is rechecked, the possibility for a falling off wheel in between checks is there. And the shear forces of a thick paint surface on rust are probably not too good either.

I think it's more your 1st point, a coat of enamel paint's thicker than the elongation of a wheel stud, as the paint deforms the tension in the stud drops to zero & the nut comes undone.

:-) I've seen that happen on an old coach and the driver had to jump on the scaffold pole to shift it. I can still undo my wheel nuts with a wrench which extends to about 15", but I tighten them with the standard length, and I've never had a loose wheel.

ALDI have a very basic torque wrench (and a very basic battery charger) on Thursday 6th October, but I rarely have to remove a wheel these days.

Krak? More like Krap.