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Damage Control

The inside story on repairing damaged alloy and steel rims.

By Michael Knowling

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Imagine you're blasting up your favourite stretch of blacktop in your modified streeter with your mates egging you on to go faster-faster. Everything's going hunky-dory and you're threading the car through corners as if you're a true racing driver. But then you lapse concentration just for a moment, get it all crossed up and screeeeeech - crack! In a blink, you've just clouted the gutter at high speed. You get out to check the damage and sure enough, you've buckled to hell your new aftermarket rim, and the tyre's deflated and hanging off. It's a sad sight. Don't feel too badly though, it's a common story of woe for those with a taste for speed. The good news is that you can return that sorry-looking rim back to virtually good-as-new condition.

We took our cameras and the rest of our journo junk along to Adelaide Wheel and Rim Works, who showed us step-by-step how they can save your bacon. The rim that we followed through the process was a customer's 15 x 6.5 inch ROH Ritz that had struck a gutter heavily. Each major city has similar rim repairers available.

Inspect the Damage

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The very first step in determining whether or not your rim can be repaired is to thoroughly inspect the damage. Rims that have been bent level to near the centre section are repairable, but beyond this it's likely that the entire wheel has been buckled - which means you'll have to replace it with a new one. In most cases, the lip that extends outward from the rim and forms its outer edge is the part that gets bent first. Steel rims are simple to fix - they're simply bent back into shape.

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For an aluminium rim, damage like this is generally repairable so long as it has only been bent in by around 45 degrees or less (depending slightly on the radius of the bend). Over and above this 45 degrees it is likely that the aluminium has been finely cracked. This can usually be identified by a "scaley" surface appearance - and if this is the case, it's advisable to replace the wheel. Essentially, steel rims can be repaired in all but the most severe cases, while alloys are prone to cracking if they've been subjected to major stress. Most of the time though, damaged alloy rims remain crack-free and so can be fixed.

Rehab Step 1

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The first hands-on step in restoring a rim to its former glory is to lever it back into its general shape. Steel wheels can simply be held in a press and bent using a lever bar, but both forged and cast alloy wheels require pre-heating prior to bending. How much heating is required depends on how hard the rim material is. The pre-heating of an alloy wheel is achieved by applying a heating torch to the affected area and steadily warming it to around 60 degrees celsius. It gets tricky here because different alloys require slightly different amounts of heat, and it's important not to over-heat it or excessive brittleness will result. Another trap for the uninitiated is any alloy wheel that contains magnesium should not be heated at all. Those alloys that have been heat treated also become discoloured in the heated area, but this all gets shaved off later so it's no problem at all.

Hammer Time

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This step takes the rim visibly much closer to its original shape, and it is sometimes referred to within the trade as the "panel beating" stage.

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Using a jig equipped with a dial gauge, the rim is examined for high and low spots through its rotation. To remove high spots, it is then struck from the outside with a copper/hide dolly hammer and various service tools. The reasoning behind the use of the soft copper/hide hammer is to prevent further denting and scratching the rim. For maximum precision, this process is often performed with one hammer held underneath the rim, with the another striking the other side from above. If alloy rim has had time to cool during this process and has become difficult to shape, it can again heated with the heat torch and the process started again.

Major low spots are filled in by either MIG or TIG welding. Note that welding an alloy rim is only performed for cosmetic reasons - it is not recommended as a structural measure intended to hold the wheel together! Steel rims don't mind being welded, though. TIG is the preferred weld type of the two, as it doesn't place as much heat into the aluminium (which might cause brittleness or distortion). The rim may look a little daggy after this step, but the excess weld is removed in the next stage. After a few of minutes of this treatment, the rim should look about three-quarters of its way back in shape.

Put it in a Spin

This is where the wheel goes for a ride on a lathe. There are two reasons for putting it on a lathe 1) to make the wheel round, and 2) to restore it cosmetically.

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Depending on the damage, the rim can spend quite a few minutes mounted on the lathe where it is continually measured for run-out with a dial gauge - both laterally and radially. The lathe operator also has to work the diamond tip on both these axes simultaneously, in order that the correct contours of the rim are matched. This is a tough challenge indeed. Adelaide Wheel and Rim Works said it was technically possible to do this work on a computer CNC lathe, but the time consumed programming it would be too prohibitive for just one wheel.

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In the case of our demo ROH rim, only a few of thousandths of an inch had to be removed - well short of the approximate limit of around 20 thou. Some rims require the removal of quite a lot of material, in which case it is a good idea to then have all four wheels machined to match. This will hide the fact one wheel has been fiddled with. After the diamond tip tool has done its job, a scraper (which is basically a very sharp knife) is then used to gently contour the stepped angles that may have been caused by the lathe bit.

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Running a rasp and a strip of fine emery cloth against the rim while it's spinning can also perform further fine shaping and tidying up. The discolouration that is caused by the pre-heating of an alloy rim is usually removed by the time the face has been made flush.

Home Stretch

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This is how the rim looks after it has come off the lathe - it's essentially as good as new. At this stage it is only the customer's choice of cosmetic finish that remains on the job card. This particular rim had to be lacquered to match the other three in the set - the lacquer offers a high level of protection for the bare alloy surface. Alternatively, some rims are polished, painted or powder coated - it depends on what the customer wants the rim to look like. Hinging on the type of finish required, this final step might be sent out to a specialised tradesperson.

The Final Product

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Adelaide Wheel and Rim Works say the strength of a properly repaired rim is virtually the same as it was when it left the factory. The very fine amount of material that is removed means there is an absolutely minimal loss of structural integrity. Most aftermarket wheel manufacturers have their own specified tolerance level, which is the point to which the wheel can be machined without weakening it beyond their specifications. So long as the wheel meets this requirement, there are absolutely no safety or legal issues.

In case you're wondering about hardening and X-raying after a rim repair, you can always get this done as well. But we've been advised that the cost for a proper X-raying report on its own might be over A$100 - which means you have to weigh up whether it's worthwhile buying a completely new rim.

What's the Damage? To Your Wallet that is...

Adelaide Wheel and Rim Works tell us the usual charge for straightening an alloy rim is around A$60, with the final cost depending on the sort of finishing required. The lacquer lick our demo ROH will receive will cost about another 40 bucks. The job takes anywhere from about half an hour to simply roll an alloy rim, up to around 1½ hours for a fully completed surface-finished wheel that's ready to go.

So if you're ever unlucky enough to bend a wheel, take it in for surgery and you'll probably save yourself a heap of cash!

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