# Thread: single nut locking torque

1. ## single nut locking torque

As of this year we're using 10 inch wheels (Keizer CL10) with single locking nut.
We tried to calculate the needed locking torque that we need. We got approx. 160 Nm in the calculations.
We used 180 Nm for safety factor.
When we drive the car the single nut gets loose after around 20 minutes of driving.
We tried to calculate again and again, still we got the same results.
Is someone familiar with single lock nuts and willing to help us?
If you use single lock nuts what is your locking torque?

Thanks for the help,

Boaz Cohen
BGRacing
Ben Gurion University
Israel

2. ## Nut Case

Maybe its not a nut problem but a hub, stud or bearing problem.

3. You cannot look at the locking torque only. You need to "translate" that in pressure on the rim. What is the resulting axial force coming from the wheel torque To do that you need to take into account the pitch of the thread. A fine thread will have a different effect that a gross thread.

The other issue is that you may need left hand or right hand thread depending the side of the car you are looking at. I let you guess why. You also need to look at the driving or braking torques that are not necessarily the same.

4. Originally Posted by firstboaz
Is someone familiar with single lock nuts and willing to help us?
There is a long thread (sorry for pun) on this topic --
http://www.fsae.com/forums/showthrea...d-wheels/page9
This link is in the middle of the discussion, where I think it gets interesting...but you may want to start at the beginning.

There are probably other threads too, but this is the first good one my searching turned up.

5. We had the same issue until we started using anti-seize on the threads. Use plenty of antiseize on the splines (if applicable), spindle, and the threads of the nut.

6. Originally Posted by maxhouck
We had the same issue until we started using anti-seize on the threads. Use plenty of antiseize on the splines (if applicable), spindle, and the threads of the nut.
Wet Torque and Dry Torque are two different specifications. 180 NM WET will put substantially higher axial load on the threads than 180 DRY. If you aren't knowledgeable on this concept, you might one day wonder "why it broke".

7. Lets start with this: What is the goal of this nut?
Is it to apply a torque? Or to apply a clamp load?
I would argue it is the latter, in which case, installation torque is not actually the most accurate measure. IF you get the nut to fully snugged down (no play in joint) and then turn it a specified angle, using the stiffness of your bolt, wheel and hub as springs in series, you can calculate the clamping force applied by the nut. If you can figure out the underhead friction coefficient as well, then you can use this clamp load to also determine your prevailing torque for locking.
I hope this is helpful. If you have further questions about bolted joint systems, feel free to ask.

8. Aren't center lock wheel nuts required to have a locking feature as well?

^^caantoun is on the right track. There are lookup tables in places like Machinery's Handbook and online that can help you figure out clamping load vs. tightening torque for various thread pitches as well, I wouldn't try to calculate it from first principles.

9. Originally Posted by Drew Price
Aren't center lock wheel nuts required to have a locking feature as well?
T6.3.2 Any wheel mounting system that uses a single retaining nut must incorporate a device to retain the nut
and the wheel in the event that the nut loosens. A second nut (“jam nut”) does not meet these requirements.

10. Drew,
I agree, a lookup table is likely a good place to start, although with the thread pitch and joint stiffness it actually isnt that tough a cookie to crack. For a first hack at it though, tables all the way!
If you really want to knock the judges socks off though, have some test data quantifying the nut factor of the joint and the joint tension vs. joint angle. These are tests OEM's run for every single joint on the car.
This is likely a bit much, but is something worth thinking about. Always good to know how much work you *could* put into something. But its even better to know how much work you *need* to put into it.
If you only need a +/-15% estimation, you'd be right to stop with a table estimation and some simple validation work.