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This is a car repair that can’t wait

Hi Rob.

While washing my car recently, I noticed a crack on one of the aluminum rims, extending all the way around the spoke.

I will not be able to get it to a shop for a few days. Is it safe for a few more days of city driving? Can this normally be repaired?

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Thanks, Jake

Bad news Jake is that you need to have the wheel repaired now – with urgency! In most major cities, you will find aluminum alloy wheel repair shops, usually located in industrial parks or near auto recyclers.

Alloy is a catch-all term used to describe the additives that individual wheel manufacturers use in their proprietary mixtures that provides necessary boosts to the qualities of the base metal, aluminum. Aluminum is used for its light weight and availability.

A good friend of mine had OEM (original equipment manufacturer) aluminum alloy wheels on his pick-up.

He was motoring along the freeway one day, when one of his aluminum wheels exploded. It threw him off the road. Luckily he wasn't injured. An investigation afterward revealed an old crack in the wheel – where the spider meets the rim.

The crack was identified as old because the surface of the crack was two shades of grey. A shiny surface in a crack is an indication that that part of the crack is new. If the crack has been there for a while, the metal will have had time to oxidize, turning it to a dull, darker grey.

So my buddy had been unknowingly driving around with a cracked wheel. He was so rattled that he replaced the old aluminum wheels with steel wheels. Aluminum doesn't withstand much abuse if the casting (or forging) is compromised. He chose steel based on its load-carrying capacity, which pound for pound usually out-performs alloy in this department for wheels at the same price point.

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Please do yourself, your passengers and the motoring public a favour by taking off the cracked wheel, installing the spare for the time being, and have the wheel repaired or replaced.

A note on terminology, Jake. The word "rim" is a commonly misused term used to describe a wheel. A rim is actually a part of the wheel assembly. A wheel is constructed with a centre section called the disc, and the rim, which is what the tire is mounted on. Together they form the wheel assembly.

This assembly will only be as strong as its weakest link – in your case, a very weak link. Time to Google "Aluminum + Wheel + Repair + Shop" – quickly.

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About the Author
Globe Drive columnist

As associate dean of Motive Power programs at the British Columbia Institute of Technology, Rob MacGregor has nearly three decades' experience in training the province's automotive technicians. He has written extensively on car mechanics, appears regularly on television and is a member of the Autotmobile Journalists Association of Canada. More

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