1. Who developed the Disc-Lock Safety Wheel Nut?
The Disc-Lock principle was developed by Scotsman, Alistair McKinlay, in response to the growing problem of wheel loss from moving trucks, buses and trailers. Its revolutionary design has resulted in a safer and more reliable wheel nut than ever before and has been heralded as the most innovative development in wheel nut design since the 1930s.
2. Where are Disc-Lock Safety Wheel Nuts manufactured?
Disc-Lock Safety Wheel Nuts are manufactured under license in Taiwan. (M5 to M16 Disc-Lock Locking Nuts are manufactured at the Disc-Lock Plant in Hiroshima, Japan.)
3. How does the Disc-Lock Safety Wheel Nut work?
The Disc-Lock Safety Wheel Nut is split into two sections, both of which have interlocking rising cams, which are joined together to form one assembly. When subject to vibration or road shock the interlocking cams of the wheel nut attempt to rise against each other. As the angle of the cams is greater than the pitch angle of the thread on the stud the Disc-Lock Safety Wheel Nut locks and will not come loose.
4. What are the chances of losing a wheel if Disc-Lock Safety Wheel Nuts are fitted?
The chances of ever losing a wheel from a moving commercial vehicle when fitted with Disc-Lock Safety Wheel Nuts, assuming the nuts have been fitted correctly and are in working order, are significantly reduced.
5. Can we fit half of the studs with Disc-Lock Safety Wheel Nuts and half with conventional wheel nuts?
No, to ensure that the wheel remains secure Disc-Lock Safety Wheel Nuts must be used in full sets.
6. Which systems can be fitted with Disc-Lock Safety Wheel Nuts?
All spigot-mounted systems can be fitted with Disc-Lock Safety Wheel Nuts. In fact the Disc-Lock Safety Wheel Nut fits 90% of all commercial vehicles, trailers and buses, as well as most agricultural vehicles.
7. What about conical wheel systems?
The Disc-Lock Safety Wheel Nut cannot be used on conical wheel systems or the DIN spherical system.
8. Can the Disc-Lock Safety Wheel Nut be re-used
Yes, the Disc-Lock Safety Wheel Nut can be re-used, but before refitting it should be inspected in the same way as one would inspect any wheel nut before reuse.
9. Does the Disc-Lock Safety Wheel Nut require a different torquing to conventional wheel nuts?
The Disc-Lock Safety Wheel Nut should be torqued to axle manufacturer’s instructions for torque settings. However, Disc-Lock recommends its nuts are torqued to 700Nm (515 ft lbs) on M22 and 7/8” nuts in order to achieve optimum clamping force.
10. Does the Disc-Lock Safety Wheel Nut maintain a 'torque tension' relationship?
Yes, because of the special locking feature of the Disc-Lock Safety Wheel Nut it always maintains a 'torque tension' relationship.
11. What sizes of the Disc-Lock Safety Wheel Nut are available in Europe?
Disc-Lock Safety Wheel Nuts are available in the following sizes: M18, M20, M22, M24, 7/8” x 14 UNF and 7/8” x 11 BSF.
12. Does Disc-Lock manufacture left-hand thread wheel nuts?
Yes. Disc-Lock does manufacture left-hand thread Disc-Lock Safety Wheel Nuts. They are available in size M22 only.
13. What material is the Disc-Lock Safety Wheel Nut made from?
The Disc-Lock Safety Wheel Nut is manufactured from 1045 steel, heat treated to Rockwell C 32-36 and coated with Dacromet.
14. Does the Disc-Lock Safety Wheel Nut have a special coating
Yes, the Disc-Lock Safety Wheel Nut is coated with an anti-corrosion coating – Dacromet – which has passed a 500 hours salt spray test.
15. Is the Disc-Lock Safety Wheel Nut corrosion resistant?
Yes, the Disc-Lock Safety Wheel Nut exceeds industry standards for corrosion resistance.
16. Will the Disc-Lock Safety Wheel Nut operate effectively if painted in operator’s livery colours?
No, the Disc-Lock Safety Wheel Nut will NOT operate effectively if painted, as paint can work itself between the two rising cam sections of the wheel nut thus rendering the unique locking design of the Disc-Lock Safety Wheel Nut ineffective. Disc-Lock Europe would strongly advise operators against painting wheel nuts.
According to the Code of Practice for the selection and care of tyres and wheels for commercial vehicles issued by the British Standards Institution (BS AU 50: Part 2: Section 7a) "where wheel and hub surfaces mate they should be clean, free from surface protrusions and preferably free of paint."
17. Will the Disc-Lock Safety Wheel Nut save maintenance time
Regular maintenance programmes should always be carried out. However by fitting Disc-Lock Safety Wheel Nuts savings will be made on down-time costs, repairs and overtime caused by lost wheels.
18. How is the Disc-Lock Safety Wheel Nut fitted?
An M22 Disc-Lock Safety Wheel Nut (most common size) is fitted with a six point M38 socket which must be placed over the entire wheel nut when fitting or removing. An instruction leaflet is provided with each order of Disc-Lock Safety Wheel Nuts or can be obtained from the Disc-Lock office free of charge (email info@disc-lock.com).
19. Do you need to re-torque the Disc-Lock Safety Wheel Nuts after installation?
Yes. This is very important. All wheel nuts require re-torquing after approximately 80km/50 miles or 30 minutes standing time to ensure the torque tension relationship is maintained.
20. Do you need a torque wrench when fitting Disc-Lock Safety Wheel Nuts?
Yes, when fitting any wheel nut a torque wrench should be used to check that the axle manufacturer's recommended torque settings are achieved (or Disc-Lock’s recommended torque of 700 Nm / 515 ft lbs).
21. Can an air-gun be used when fitting Disc-Lock Safety Wheel Nuts?
The use of an air-gun
when fitting wheel nuts is not recommended by the Institute of Road Transport
Engineers. However, should an air-gun be used: "Final tightening (of wheel
nuts) must be with a calibrated torque wrench set to the vehicle manufacturers'
torque value. Air impact tools and extensions to wheel braces should not be
used for final tightening." - IRTE Guide to wheel security.
(Also see Code of Practice for the selection and care of tyres and wheels for
commercial vehicles issued by the British Standards Institute, ref: BS AU 50:
Part 2 - Section 7.)
22. Can an air-gun be used when removing Disc-Lock Safety Wheel Nuts?
Yes, an air-gun can be used when removing the Disc-Lock Safety Wheel Nut, but it is essential to undo the nuts first with a bar first. In addition, it is important to remember to place the air-gun socket over both hexes of the wheel nut. If the air gun is not placed over the entire Disc-Lock Safety Wheel Nut (both top and bottom sections) it could damage the nut by pulling it apart.
23. How can one maintain Disc-Lock Safety Wheel Nuts in good condition?
To maintain Disc-Lock Safety Wheel Nuts in good condition and to prevent potential cracking caused by careless fitting methods or incorrect use of an airgun it is important to follow the following procedures:
a Wheel nuts can be run up with a Windy Gun, but NOT UP TO TORQUE. Be aware, guns without regulators have been found which give well over 1224 Nm (900 ft lbs).
b When using air-guns it is important that the six-point hex socket of the air-gun is placed over the entire Disc-Lock Safety Wheel Nut (both top and bottom hexes). If this recommendation is not followed the air-gun could damage the Disc-Lock Safety Wheel Nut by pulling it apart or crushing the rising cams.
c Final turns and torque must be applied with a calibrated wrench.
d If nuts have to be removed, then they must be undone with a bar first, not with an Air Gun.
24. Should the wheel stud be lubricated with oil before fitting the Disc-Lock Safety Wheel nut?
Yes, two drops of oil should always be added to the wheel stud before fitting the Disc-Lock Safety Wheel Nut. This not only prolongs the life of the threads, but also helps to achieve the proper torque tension relationship.
25. Does the Disc-Lock Safety Wheel Nut need a UK Vehicle Inspectorate (Department of Transport) Modification Certificate?
No, the UK Vehicle Inspectorate has examined the Disc-Lock Safety Wheel Nut and stated in writing, dated 21st June 1994, that it does not require a notification certificate. (Copy of letter on request from Disc-Lock Europe).
26. Is the Disc-Lock Safety Wheel Nut acceptable for use on aluminium wheels?
Yes, experience in the U.S. and Canada indicates no problem with galvanic corrosion between the Disc-Lock Safety Wheel Nut and alloy wheels. The Disc-Lock Safety Wheel Nut is fully approved in all sizes for use with alloy wheels providing the wheel nuts have been fitted correctly and the recommended torque has been applied.
27. Is wheel loss really a problem?
Yes. In 1991 Disc-Lock Europe commissioned a report which estimated that 2,000 to 3,000 wheels were lost in the UK from moving trucks, trailers and buses. As a result 5-10 people were killed and millions of pounds were paid out in insurance claims. It was estimated at that time that an average insurance claim resulting from a lost wheel was £26,500. Every week in the UK alone, the Disc-Lock Europe office receives reports of lost wheels from moving commercial vehicles and buses.
28. Has the Disc-Lock Safety Wheel Nut a British Standard seal of approval?
No, because the Disc-Lock Safety Wheel Nut is a unique product and is patented world-wide. There is no British Standard for this particular style of locking nut.
The Disc-Lock Safety Wheel Nut received the German TÜV Approval - Certificate Number 57 8703/01 - which is recognised in Europe in 1994. (An English translation is available on application to the Disc-Lock Europe office.)
The Disc-Lock Safety Wheel Nut was also endorsed by leading Lloyd's commercial motor insurer - the Crowe Insurance Group in 1997
29. Do vehicle manufacturers fit Disc-Lock Safety Wheel Nuts as standard?
Not yet. However, manufacturers will fit Disc-Lock Safety Wheel Nuts if specified by the customer.
30. Will the fitting of Disc-Lock Safety Wheel Nuts affect axle manufacturers' warranties?
No. As far as Disc-Lock is aware axle manufacturers, including BPW, Gigant, GKN Dana, Granning UK, Hendrickson, Meritor ROR (formerly trading as Rockwell ROR) and SAF have inspected the Disc-Lock Safety Wheel Nut and have given no indication that the fitting of the wheel nut will affect their warranties.
31. Is the Disc-Lock Safety Wheel Nut patented world-wide?
Yes, the Disc-Lock Safety Wheel Nut is patented world-wide in all metals.
32. How can I order Disc-Lock Safety Wheel Nuts?
Disc-Lock Safety Wheel Nuts come in boxes of 80 (minimum order) and are available through appointed Disc-Lock distributors.