Disc-Lock FAQs

Frequently Asked Questons - Disc-Lock Safety Wheel Nut

  • 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.
  • Where are Disc-Lock Safety Wheel Nuts manufactured?
    Disc-Lock Safety Wheel Nuts are manufactured under license in Taiwan and Detroit, Michigan, USA.
  • How does the Disc-Lock Safety Wheel Nut Work?
    Unlike a standard two-piece wheel nut, the Disc-Lock Safety Wheel Nut is split into three sections, comprising a nut, a hexagon-flanged washer and a flat faced cup washer. These sections are joined together to form a one-piece assembly with an O/ring.

    The top two sections (the hexagon-flanged washer and the flat faced cup washer) have interlocking rising cams. When subject to road shock or vibration, the most common causes of wheel nut loosening, the interlocking cams of the Disc-Lock Safety 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 a wedging action takes place and the Disc-Lock Safety Wheel Nut locks and will not come loose, thus maintaining the clamp load and keeping the wheel on the axle.

    Click here for the Disc-Lock Safety Wheel Nut brochure.
  • 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.
  • 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.
  • 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.
  • What about conical wheel systems?
    The Disc-Lock Safety Wheel Nut cannot be used on conical wheel systems or the DIN spherical system.
  • 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.
  • Does the Disc-Lock Safety Wheel Nut require a different torqueing 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 (515ft lbs) on M22 and 7/8" nuts in order to achieve optimum clamping force.
  • 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.
  • 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, 7/8" x 14 UNF and 7/8" x 11 BSF.
  • 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 28-32 and coated with Geomet®
  • 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 – Geomet® – which has passed a 720 hours salt spray test.
  • Is the Disc-Lock Safety Wheel Nut corrosion resistant?
    Yes, the Disc-Lock Safety Wheel Nut exceeds industry standards for corrosion resistance.
  • 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."
  • 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.co.uk) or download here.
  • Do you need to re-torque the Disc-Lock Safety Wheel Nuts after installation?
    Yes. This is very important. All wheel nuts require re-torqueing after approximately 80km/50 miles or 30 minutes standing time to ensure the torque tension relationship is maintained.
  • 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).
  • 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.)
  • 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 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 or grinding down the cams.
  • 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 air-gun 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 1200 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.

    Click here for Disc-Lock Safety Wheel Nut Installation Guide which can be downloaded.
  • 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.
  • 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).
  • 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.
  • 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.
  • Will the fitting of Disc-Lock Safety Wheel Nuts affect axle manufacturers' warranties?
    No. As far as Disc-Lock Europe 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.
  • Is the Disc-Lock Safety Wheel Nut patented world-wide?
    Yes, the Disc-Lock Safety Wheel Nut is patented world-wide in all metals.
  • How can I order Disc-Lock Safety Wheel Nuts?
    Contact Disc-Lock Europe. Telephone +44 (0) 1303 884762 E-mail: info@disc-lock.co.uk

Frequently Asked Questons - DISC-LOCK Washer

  • Who developed the Disc-Lock Washer?
    The Disc-Lock Washer was developed by Disc-Lock International, California, USA.
  • Where are Disc-Lock Washers manufactured?
    Disc-Lock
    Washers are manufactured in California and Taiwan.
  • How does the Disc-Lock Washer work?
    The Disc-Lock principle consists of two washer shaped pieces that have inclined cams on one side and a series of ridges on the other. The greater the rise angle of the Disc-Lock cams along with the non-slip ridges work together to prevent loosening caused by shock and vibration.  The result is a fastening system that is vibration proof according to Military Standards*.

    United States Military MIL-STD-1312, Test 7. Vibration Test Results data available upon request to info@disc-lock.co.uk
  • What are the chances of a fastener loosening if Disc-Lock Washers are fitted?
    None.  When applied and installed properly Disc-Lock Washers will ensure the fastener remains secure.
  • Can Disc-Lock Washers be used under the head of cap screws in blind hole applications?
    Yes.
  • Can Disc-Lock Washers be re-used?
    No.
  • Does a fastener fitted with a Disc-Lock Washer require a different torque setting from conventional washers?
    No, just use the recommended handbook torque.
  • In what sizes is the Disc-Lock Washer available?
    Fifteen sizes ranging from 5mm to 38mm in metric and from 3/16 to 1-1/2” in imperial.
  • What material is used in the manufacture of Disc-Lock Washers?
    Standard Disc-Lock Washers are made from 1010 Carbon Steel. Disc-Lock also stocks washers manufactured in 316 stainless steel – from 5mm to 16mm or 3/16 to 5/8” inclusive. Disc-Lock can also make special, exotic materials on a custom basis.
  • Does the Disc-Lock Washer have a special coating?
    Standard coatings are as follows:  Zinc plated per A.S.T.M B633-98, Trivalent Chromate (NO Hexavalent Chrome) and baked to prevent hydrogen embrittlement. (Disc-Lock Washers are not suitable for hot dip galvanising)
  • Are Disc-Lock Washers susceptible to hydrogen embrittlement?
    No, as they are baked after coating.
  • Is the Disc-Lock Washer corrosions resistant?
    No, the standard Disc-Lock Washer is not corrosion resistant.  However, our stainless steel washers are corrosion resistant.
  • Is the Disc-Lock Washer heat-treated?
    Yes, they are case hardened to between 40 to 50 on the Rockwell C scale, in a rotary furnace, in a carbon nitrite environment.
  • What is the maximum temperature in which Disc-Lock Washers can be used?
    Standard Disc-Lock Washers (made from 1010 carbon steel and case hardened) can be used for applications in environments up to a maximum temperature of 300° Fahrenheit.

    Stainless Steel Disc-Lock Washers can be used for applications in environments up to a maximum temperature of 1,150° Fahrenheit.

    Note:  To convert Celsius into Fahrenheit multiply C degrees x 1.8 and add 32.  Eg.  500° Celsius = 932° Fahrenheit  (500 x 1.8 = 900 + 32 = 932)
  • Is the heat treat hardness of Disc-Lock Washers checked?
    Yes, by micro hardness testing at independent testing laboratories.
  • Are lot numbers for checking on quality control maintained?
    Yes.
  • Will the Disc-Lock Washer save maintenance time?
    Yes, nuts and bolts fitted with Disc-Lock Washers do not require retightening.
  • In which type of applications have Disc-Lock Washers performed successfully?
    Disc-Lock Washers have out-performed all other types of loose, washered, threaded or pinned systems in a wide range of high stress, corrosive and vibration sensitive applications including heavy equipment, bus and truck fleets, oil drilling rigs, public utilities, railroads, logging and mining equipment, pipelines, military and many more.
  • How is the Disc-Lock Washer fitted?
    Simply mate the cams together and place between the nut and the joint material.
  • Do you need a torque wrench when fitting Disc-Lock Washers?
    No.
  • Can an air-gun be used when fitting Disc-Lock Washers?
    Yes.
  • Is the Disc-Lock Washer patented world-wide?
    Yes.