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Is this safe?

Is this safe?

(OP)
Hello everyone.

We recently had the (double) rear wheels stolen on both sides of our Transit twin wheel 14 seater minibus. We have obtained four second hand wheels and tyres but having fitted them inside edge of the inner wheels foul the brake calliper, not by much, but enough to be audible and to leave a deep score around the inner edge of the rim.

Another person obtained some washers and put them between the wheel and the hub flange, one 2mm thick washer on each stud was enough to provide sufficient clearance. However I’m not happy with it and recommending it isn’t used until new correct wheels are obtained.

My concern is based on the following theory. The wheels on the Transit get their concentricity by being a close fit over the machined flanges on the hubs. They get their lateral support (ie resistance to sideways forces caused by cornering loads) by being clamped (via the wheel nuts) to the machined face of the hub. My fear is that with washers between the inner wheel face and the flange face we no longer have 100% face to face contact. Instead, the washer becomes a fulcrum and with a vehicle weighing several tons multiplied by a G factor during cornering this will permit movement of the wheel laterally, resulting in either disintegration (crushing) of the washer, shearing of the wheel stud or loosening of the wheel.

Am I be over cautious? What do you reckon? Is it a valid theory?

Thanks for eading this.

RE: Is this safe?

You shouldn't be cornering hard or carrying payload on the wrong wheels.

Mike Halloran
Pembroke Pines, FL, USA

RE: Is this safe?

The wheels need to be centered correctly by the flangre on the hub. If this is not the case there is quite a risk of imbalance which to some degree might be acceptable but the far more dangerous thing is that the wheel bolts will see a different case than the one they were designed for. Usually the bolts are designed for a sheer load only and should never see a lateral load (which causes bending) that can lead to a failure mode.
Adding the extra spacers implies another risk. The 2 extra surfaces of the spacer will "set" when the wheel tightening torques are applied and since these 2 extra surfaces were not considered in the original calculation for the wheel torque there is also a risk that after a certain time the wheel nuts will get loose. I think you are doing the right thing to not use them.

dynatune, www.dynatune-xl.com

RE: Is this safe?

You are correct in not wanting to use this arrangment. I have personally seen a situation in which the lug nuts worked loose due to the flexural action of the rim not being seated properly against the wheel flange.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

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