worf928

Ja. No worries. Sometimes when you really think about these 'best practices' you just end up with more questions.

I don't know. For the modern Porsches that use the heavy steel lug bolts, I think the better question is: is the wheel hub steel or aluminum. If the latter then it's the hub that we need to worry about.

For the old Porsches that used the black anodized Aluminum lug nuts I can say that I've never found one 'just' worn out. I've found them partially stripped from over-torquing. I've found the threaded wheel hub studs damaged from cross-threading. I've twice had to 'creatively' remove the collet portion of the nut when the hex part was snapped-off when someone (not me!) used an air wrench, in one case to tighten and in the other case to attempt to loosen with a deep 12-point socket with a crack the whole length off it.

But, never seen one just wear out. I've had the wheels on and off my '91 that I've owned for 20 years probably.... 50 times. Same lug nuts.

worf928

I propose an experiment: next time you change your wheels, do your process on one side and on the other do it too, except rather than do the final torque 'on the ground' chock wheel so it doesn't spin, torque the bolts, then put it on the ground.

Then see if both sides need the 1/4 turn after 100 miles.

Next time I R&R wheels on one of mine, I'll do the same (minus the air wrench) and see if one side of mine has lugs turning or not.

worf928

Hmmm.... well, if you decide that you need to re-torque your wheel lug bolts (as you can see from the above my jury is still out on that one) then loosening the bolt before torquing seems to be a 'best practice.'

Note that you just need to every-so-slightly loosen the bolt. 90 degrees, in my experience on the heavy steel lug bolts on the modern Porsches, makes them really loose, and that ~20-30 degrees is sufficient to break the bolt loose. Those bolts go from <100 Nm (sorry, I only do metric) to the spec 160 Nm with less than a quarter turn.

I would suggest further, that if you do decide to re-torque your bolts in the above fashion that you unload the wheel (off the ground), chock it (a real wheel chalk or just a 4x4 block of wood) and then torque.

At the risk of being boring...

The whole concept of torquing bolts to a spec is sorta like aiming a gun and then closing your eye before you pull the trigger. The actual physics involved is to produce a clamping force within a specific range where that range is tight enough so that the fastener doesn't loosen due to vibration, heat expansion/contraction, etc. and not so tight that the fastener and the thing it's clamping get damaged. Turning a nut or bolt and measuring the force required to turn it is simply the easiest way we have to get a 'good guess' at the clamping force. The actual way to reach a specific clamping force is to measure elongation of the fastener (if a bolt) or stud (if the the fastener is a nut.) It is the elongation that determines the actual clamping force. The problem with measuring rotation force is friction. Friction gets in the way. A rusty galled bolt at the spec will have less clamping force than designed-for at the torque spec. A new 'greased-up' bolt will have, unless grease is part of the spec, too much clamping force at the spec torque.

This is why when you build engines, heads and other super-critical components are first torqued to a relatively low spec and then turned a specific number of degrees. For some of the more exotic components the 'spec' is not torque at all, but a minimum and maximum bolt elongation specification which has to be measured after the fastener is tightened.

The whole notion of periodically 'checking' torque comes - AFAIK - from industries where dynamic forces are extreme and fasteners from time-to-time come loose. The best practice of loosening before 'checking torque' was a result of institutional learning. After X to Y number of 'checks' fasteners would break. If I recall correctly - which I may not - the breakage was due to two things: humans not paying attention when using the torque wrench and fatigue of the fastener due to impulse loading even with humans paying attention.

mgordon18

Challenge accepted! I will do this, but front/back rather than side/side. All you need to do to be able to torque the rears off the ground is set the parking brake. Do you think it would make a difference to do it this way? If so, then you'll have to explain to me how to chock a wheel that's in the air.

I'm swapping wheels tomorrow anyway, so we can get our results quickly.

worf928

Side-to-side would factor out wheel size/weight/width and powered or steering difference. But, I would hope that any effect is independent of those.


I use a stub of 4x4 wedged between the ground and the tire at the 5-o-clock(-ish) position. The extact dimensions of this “Porsche Special Tool; locally acquired” depend on how high you get the car. I have a variety of them. But assuming you get the wheel 1 - 1.5“ off the ground a 4x4 will work fine. So might a brick The main thing is to cover the width of the tread.

I also use these “special tools” to loosen lugs when I forget to do it before it’s on stands...

Alas, had we decided to perform this experiment last weekend, I’d be with you: I swapped Summers onto CarChick’s 911 MT and flushed the brakes on her 981.

worf928

Ah! But, I can 'check the torque' and see if a week of driving requires that 1/4-turn. So, I'll do that.

mgordon18

We're still talkin' about cars, right?

I put the whole car in the air on jack stands, so it's pretty far up there (safety first!). I'll do front/rear experiment and see what happens. If I can get my son out to the garage to sit in the driver's seat and press the brake pedal, I'll do side/side.

991carreradriver

My comment was specific to Center Locks. For lugs, I always loosen prior to setting the final torque. That fastener will tighten further than the original setting and will be representative of the proper torque setting. Practically, none of this fine adjustment makes a difference for street driving.

HenryPcar

This is what I use :

mgordon18

OK. The experiment has begun. I torqued the driver's side wheels in the air and the passenger side wheels on the ground.

More info in the next few days...

worf928

Only if you consider the Porsche Cayman to be a car.

I just checked the bolts on the wife's 991. Two of them gave me about 5-ish degrees of rotation. The rest, not a bit. It's her DD. So it got used every day last week and traveled at least 100 miles.

The 981 hasn't moved enough for a valid test.

Very interested in your findings.

mkpierro

Use a breaker bar before you raise the car to loosen the lug nuts a little.

Got_Corners?

this is so funny to me. I do the exact. Same. Thing. With my 13yr old.....and my brother has a '18 GTR that I have to hear about. The cost of 'free labor' these days....🙄

LargePuppy

Wow this has gotta be one of the longest posts in how to change a wheel I’ve come across in a looooong time

TheFatArmadillo

I wanted to thank you for this tip. I had to do my wife’s Q7 winter tire swap today and had ordered these based on your recommendation, had never heard of these little items before. This made one of the easiest changes I’ve ever done. Thanks again!