Wheels may fall off more now but there is a solution - The Globe and Mail

I’ve been seeing media coverage recently about wheel separations owing to recent tire changes. The No. 1 assumed cause of this is that someone forgot, or insufficiently tightened their wheel nuts/bolts. There are many reasons why a fastener might come loose, but in my mind the lighter materials being used to reduce weight and save fuel play a key role.

In the early days of my career in the early 1990s, passenger car wheel separations were rare. I can only remember one time when a car was towed off the side of the road and a technician was at fault. Now, every dealership and independent facility has to try hard to implement procedures to avoid wheels coming loose.

When I was young and doing a dozen wheel changes in a day, I and all my coworkers used air impact tools. Accurately torquing wheels was only just becoming something that dealer staff paid attention to. Prior to that, no one cared and wheels were bolted on with air tools set to their maximums. The torque these tools were capable of would tighten fasteners at many times more than the amount specified by the manufacturer. A wheel fastener that required a torque of about 136 Nm (100 lb-ft) was quite often bolted on at a minimum of 542 Nm (400 lb-ft), meaning it rarely came loose.

These fasteners were more tolerant of this style of abuse. Now that brake and suspension components are manufactured with both cost and weight in mind, that exaggerated tolerance is gone. Overtighten a wheel today like we did three decades ago and either the fastener will break off in your hand or the brake rotors will warp prematurely. Now, wheel fasteners must be accurately torqued, quite often in the sub 136 Nm-range. Many contemporary passenger cars are in the 115 Nm-range. That is not very tight, and there is now no room for error.

The biggest problem I see is corrosion and oxidation between the wheel face and the mounting flange of the brake rotor and also in behind the brake rotor where it mounts to the hub.

When the wheels are unbolted and everything is disturbed, quite often rust is displaced. Sometimes that rust is easy to spot, sometimes it is located behind the brake rotors. Any tiny piece of flaked-off rust can now fall into areas that it shouldn’t. Mind you, this was true back then and also today. The difference is that smashing on wheels at 542 Nm obliterated and flattened every piece of foreign debris. Like I said previously, things were so tight that debris was a moot point. Now, when a piece of debris falls into an area of concern, 115 Nm is not enough to make it irrelevant, and sometimes that small piece of debris may cause a false reading when torquing wheels. A technician or DIY’er may think they have accurately torqued the wheels, but that debris may have caused the gap to increase ever so slightly and torque to be reached early. Drive the car around for a bit and a fastener may back off once that debris falls out of place.

Combating this is done by thoroughly cleaning all mating surfaces and re-torquing wheels after 100 kilometres of driving. You may notice on many repair invoices a disclaimer stating that the dealership or repair shop will not be held liable because of damages caused by a wheel separation if you do not return for a retorquing. It’s a thing, check it out, and get your wheels retorqued after every service where they are taken off.

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Your automotive questions answered

Hi Lou,

I have a 2018 Ford F-350 work truck with a 6.2-litre gas V8. It has 45,000 kilometres on it and was bought as a new cab chassis, which I added a custom service body.

Starting at 40,000 kilomtres and during last fall the check engine light came on three or four times. This resulted in many codes for misfires on more than one cylinder and particularly cylinder 8.

The Ford dealer repaired it under warranty, saying this was normal and might be my fault for buying gas at a faulty supplier. I disagreed and suggested there is a problem with the motor as I have two other F-350s with the same motor and both run fine.

The code went again immediately after getting the plugs replaced and also ignition coils. This time they said it was emissions and they ran a smoke test. They found a leak in the filler hose for the gas tank and said it was rubbing against the frame because of poor routing around the “aftermarket” service body. I paid to replace, and they say this was the possible cause of the misfire problems.

It all adds up and would be an easy fix, but can an air leak in a filler hose cause misfiring? Can’t air get in through the cap? Curious if you think this could be the explanation. The truck comes off lease in November and I can buy it out well below market value but don’t want to get stuck with a lemon motor.

Thanks, Dave B. - Guelph, Ont.

It is unlikely that a filler hose leak is causing a misfire. Also, one would think that you would be complaining of a fuel smell after filling the truck. If it’s leaking air, then more than likely it would also be leaking fuel. The idea of the problem being related to the fuel supplier is also a stretch.

The more common issue for this motor related to misfires is faulty engine valve springs. A power balance test should identify this issue and hopefully result in a repair that isn’t financially significant and restore your faith in the truck.

Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail globedrive@globeandmail.com, placing “Lou’s Garage” in the subject line.

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Wheels may fall off more now, but there is a solution - The Globe and Mail
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