Originally Posted by Slakker

Will do. Car control Sat and Autocross Sunday but not sure if that will get them hot enough to find out. Next track days are 5/20 at Hallet and 5/22 at MotorSport Ranch in Cresson, TX.

Originally Posted by mglobe

So Mark, tell us how you calibrated yourself as a human torque wrench? Exactly what procedure did you use. I'm assuming that you tighten the lug nuts with a wrench, and then come back afterwards with a torque wrench set to te proper torque?

Originally Posted by Coochas

My old Boxster had a pad deposition problem the first time I used PFC. It had wicked vibration. I cured it by simply doing repetitive hard stops. I never had the problem again and continued to use the same pads for years.

Originally Posted by mglobe

So Mark, tell us how you calibrated yourself as a human torque wrench? Exactly what procedure did you use. I'm assuming that you tighten the lug nuts with a wrench, and then come back afterwards with a torque wrench set to te proper torque?

Originally Posted by Ray S

This thread...........zero to "kiborted" in 3 pages.

Congrats.....

Back on topic, it sounds like pad deposits on the rotors to me. I've experienced the same problem on my 986 with pagid pads. I think Coochas gives good advice below. However if the deposits are bad this may not solve the problem. In that case new rotors may be your best solution.

Originally Posted by mark kibort

brother! another "Value Contributor".

Originally Posted by mark kibort

the uses of steel lug nuts probably gives a higher stud stretch than use of aluminum...

Originally Posted by mark kibort

...so my torquing at 90 might be equivalent to actually higher than 96 ft-lbs using stock aluminum lugs. I think mike brought that up

Originally Posted by winders

At the same torque they do not.



It isn't.

T = (K D P)/12

Where:

T = Torque (ft-lbs)
D = Nominal Diameter (inches)
P = Desired Clamp Load Tension (lbs)
K = Torque Coefficient (dimensionless)

Originally Posted by TXE36

How do you know this? If people were reliable "human torque wrenches", then torque wrenches wouldn't exist or be nearly as common.



The most obvious answer is they were under torqued before.

There is actual science to bolt torques but one of the problems with the measurement is that it is indirect. What you are trying to set is the tension on the fastener, since there is no easy way to measure that, the "stand in" is measuring the friction required to turn the threads. In cases where you can measure bolt stretch, connecting rods for example, sometime the tension spec is the actual measured bolt stretch and not torque.

And therein lies the rub - bolt torques are usually specified for new fasteners. Grease or anti-seize on the threads can cause a bolt to be over tight even if torqued to spec (if the spec doesn't call for the lubrication - some do). Thus, when working with used fasteners, I usually under torque a bit by either using the low end of the spec or judgement based on experience.

Case in point, the torque spec for BMW E36 wheel bolts is something like 85-90 ft-lbs. I don't use wheel bolts, I use studs and lug nuts. The spec for the studs is 75 ft-lbs dry. That is the spec I use and have been using since I got the car in 2009. Freshly mounted tires need one re-torque after their first hot session and then they stay at 75 ft-lbs until I take them off. I've observed this behavior for years and I do check them, but after that first re-torque I've never found a loose one.

Over torquing is bad because it can damage the fastener even if it doesn't snap it off. I hate working on vehicles that the previous mechanic monkey torqued everything.

TL;DR Torque the lugs to spec using an actual torque wrench.

-Mike

Originally Posted by mark kibort

you might be right.. i was just referring to what Mike had said. sounded logical at first.
However, if the Aluminum deforms, woudnt that skew the stud stretch for the same nut torque?

Originally Posted by winders

Might be? That's a industry standard formula. Notice that there is no material type information in the formula. That means the materials used does not matter as long as they do not exceed their elastic limit.

As long as the aluminum lug nuts are not torqued past their elastic limit, and they are not at 96 ft-lbs, there is no deformation and no failure.

The 10.9 stud stretches the same when an aluminum or steel nut is tightened to 96 ft-lbs.

Originally Posted by mark kibort

thanks.. that makes sense also. But, as a note, i think I also got the scenarios mixed up... Mike was referring to "used" lugs vs new ones. that's where the same torque values give even more stretch and he backs off the value due to this... interesting theory. but along the lines of your response, that shouldn't matter either, no?

Originally Posted by winders

As long as the elastic limit of a stud is not exceeded, the stud does not permanently stretch regardless of how many times the lug nuts are tightened and loosened. It goes back to its original dimensions when the lug nut is loosened.

The same is true for lug bolts.

Originally Posted by mark kibort

thats reassuring and makes sense too. i was going a little on the light side thinking that it was a wear element. so, i then go back to one of my primary concerns .. just wear on the wheel centers. probably more psychological there too, as the good rims can handle all the torque we can toss at them.

Originally Posted by winders

Going on the "light side" means you don't get the clamping pressure the specified torque provides. That can be bad for the integrity of the joint and allow the fasteners to loosen. Neither is good so you should always use at least the specified torque.