Issue with using wheel nuts with washers

[dchw1975]

Hi,

I am wondering if anyone else has solved an issue I have with the rear rub/drum/wheel fixing??

When competing in sevens there is often a requirement for using washers to prevent wheel loss due to pulling over the standard conical nuts. From my assessment of the standard configuration this it would seem that actually the conical nuts do multiple jobs (maybe why they can fail dramatically when highly stressed).

1) They hold the wheel to the drum
2) The cone on the inside of the nut also acts to hold the drum radially centered on the wheel stud (so that torque is not only transferred by the drum screws)
3) Finally the tip of the cone also reaches into the hub outer where the hole is also a larger diameter than the stud so allowing some movement when loose, locating the back of the hub to the front and the drum.

This means that with my tuned engine I am currently eating my way through drum retaining screws and probabaly will eventually have a failure due to this?

Cheers

David

Cheers

David

[Chris KC]

David, do your drums not have shallow 'dowels' keeping them in register with the wheels?

Other than that 3 large penny washers (slightly relieved to clear the wheel centre) and nyloc nuts done up tight should do the job. Never had a problem with anything slipping, but possibly I'm not pulling as much torque as you are?

[Erich]

David, there are conical washers available(one side flat) which allow the use of unlock nuts for wheel fixing. This makes the wheel well secured to the hub. I can't recall who has them...perhaps Jamie.

Erich in Seattle

[Bob Culver]

It is true the cones provide final centring but the dowells are near enough.
If the stud is not tight and thus stud is subject to fluctuating load, is liable to fatigue failure. The stud is likely to be tensioned to maybe 10 ton psi  which amounts to a clamp of a ton on each stud, enough to ensure the stud or dowells are not subject to bending.Thick paint and dirt or grease can be a problem, encouraging movement. The drum retaining screws must be distinctly below surface level. On many "modern" cars the drums are not separately retained.

The wheel pulling over fully clamping nut is another issue.

[spannerman]

I use the washers you use with rose
Joints for mine never have any problems?

[Ian Williams]

Sounds to me like you may have big seven drums which have no dowels but fitted on A7 hubs, Big seven hubs have a register to radially locate the drum and the hole on the drum is larger than an A7 drum. If you miss match them, as I suspect you have, then the three screws will be locating the drum radially as you describe. Like others have commented I raced for many years and never experienced a failure with correctly matched parts and wheels retained by lock nuts with washers.
PS, the stud holes in big seven drums are a closer fit on the studs than and A7 drum as well.

[Stumpi]

I have had this problem om my trials car,so i made some spacers to reduce the hole in the drum.
These were made from some stainless pipe fittings i had.They are a good fit on the studs and slightly less in thickness than the drum face.
Andy