Help I Broke My Wheels! - Overdrive
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Help I broke my wheels!

11 Apr 2014  /  13
Editor two wheelers

It seems the internet is abuzz with the fact that the alloy wheels on people’s motorcycles are breaking. The resulting hue and cry usually heads straight to the point where the breakage is blamed on the manufacturer or OE supplier, “They’re cheating us with substandard parts.” Is this really the case?

Wheel design

Motorcycle wheels, like all other engineering projects, are result oriented. With all things that involve performance, the trade-off is the same. It is always strength and resilience versus lightness. The easy way to get both is to employ exotic materials which is great for a high-priced performance item but will usually be out of everyone’s reach. When you’ve decided to stick to a budget, the exotic metals are out. Then begins the process of taking away metal to create a light design and keeping metal to create a strong, impact-resistant design.

The decision to use a light wheel or a strong wheel is a matter of the role of the motorcycle. Off-road motorcycle wheels that have to, by design, survive big impacts will favour strength where as sports motorcycle wheels have to be light because unsprung weight’s effect is magnified. Every gram saved pays back tenfold in performance.

Which motorcycle are we talking about

Shine-and-Twister.jpg

Bikes which are relatively slow, their wheel designs favour strength and don’t mind the extra weight that brings

That’s crucial. You’ll rarely hear of Unicorn or Shine wheels breaking. That is because first, steel wheels bend but tend to not break and second because the bikes are relatively slow and their wheel designs favour strength and don’t mind the weight that brings. When you switch to a performance motorcycle where a lot of work goes into preserving and enhancing the power-to-weight ratio, the design will favour lightness over ultimate strength in the face of a massive impact. If you search across the internet in fact, you will find that most big sportsbike also suffer broken wheels from impacts. The problem is simply that while 10,000 owners who don’t have broken wheels tend not to come online and discuss the non-event, the three owners who do suffer a broken wheel almost always will. The breakage ratio is low but the reporting of the break is much more common leading to the perception that wheels are breaking left right and centre.

Why do the wheels break

Motorcycle wheels have a finite resistance to impacts. When you add soft tyres to the mix β€” crucial for performance β€” the chances of a bump compressing the tyre momentarily rises. And if you hit hard enough, the thing causing the bump will impact the rim directly leading to a crack or a break. This is one of the reasons why ensuring the tyre is correctly inflated is critical to riding a faster, lighter machine.

What did you hit?

Ceat-riding

Accelerate gently through a pothole so that the extended suspension has a better shot at absorbing the impact and saving the wheel.

Not all potholes are born equal either. Potholes with sharp rims tend to be the wheelbreakers. As I’ve written earlier, your reaction to the pothole can add to the damage you’re suffering. In short, the right way to handle this is to slow down as much as possible before the wheels encounter the pothole. And then accelerate gently through it so that the extended suspension has a better shot at absorbing the impact and saving the wheel. When you hit the rim of the pothole while still on the brakes, what happens is simple (and catastrophic). Your suspension is fully compressed and the wheel fully weighted. Which means at the moment of impact, the rim is literally sandwiched between a rock (the pothole rim) and a hard place (fully compressed suspension). You can easily generate such hefty front-end loads from braking that you can break your rim at relatively low speeds. If you imagine a pothole as a negative (as in hole in the ground), then even a positive irregularity (like a sharp crest) can be troublesome β€” fortunately, the way to tackle both obstacles is the same. You always brake before you arrive at the obstacle and then accelerate gently through it.

How effective is this technique?

KTM-200-Duke

Keeping the throttle open helps greatly when you find a pothole suddenly

In 14 years of testing, I’ve only bent two sets of rims. The CBZ X-Treme rims went when I hit a open (square) manhole at top speed. I had no acceleration left to help the motorcycle and both rims bent enough for the tubeless tyres to deflate within 300m of the impact. I then bent my KTM 200 Duke rims hitting a pothole at about 40kmph right outside our office. I was distracted at the time and when I noted the pothole, I closed the throttle and ended with a dent each. I’ve on other occasions, hit potholes at three-digit speeds two-up, jumped street and performance bikes, and worse without ever damaging a wheel β€” I find keeping the throttle open helps greatly.

Fine, now I’ve got a set of broken wheels, what to do next?

Your vehicle warranty does not cover wheel breakage – this is not restricted to motorcycles either. Manufacturing defects in wheels are relatively rare (we understand the failure rates are below 1 per cent), so chances are warranty claims will not work.

The right way to tackle the cost is to file an insurance claim, same as you would in the case of an accident – which in fact, the wheel breaking incident is. Most insurance companies will honour this claim without fuss. Sometimes, the insurance investigator can deny your claim because he will not find any damage outside of the wheels on the machine. In this case, speak to your service centre, they will usually speak to the insurance people and help you as much as they can.

How do I avoid a broken wheel, but?

Ride more carefully. If you’re riding something fast, be aware of its speed. Every additional kmph that you bring to an impact magnifies the forces that are in play. Ensure your tyres are correctly inflated and whatever happens, do not continue to brake into the impact.



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