Carbon-fibre materials lighten the load, but at a weighty cost

  • Choosing a car at dealership. Thoughtful grey hair man in formalwear leaning at the car and looking away

Weight reduction has become the focus of engineers across many industries. But do they sometimes go a bit too far?

From air to water and ground transportation, it is all about making things lighter and more efficient. Most of the work has been driven by material engineering, including the integration of carbon fibre.

Both Boeing and Airbus have incorporated a lot of carbon fibre in their latest 787 and A350. Car companies have started using these composite materials in their vehicles ? starting with race and super cars and slowly moving down the price chain. And, of course, carbon fibre has become the material of choice for the bicycle industry.

But I wonder if we go a bit too far in deploying weight-reduction tactics that could compromise product integrity, while only producing marginal benefits for the end user. Things that are great for marketing and PR are not always the most sensible in terms of pure engineering principles.

Related: Jim Kenzie takes stunning 2013 McLaren 12C Spider for a spin

For example, the interior of the new McLaren P1 is made of carbon fibre. Dashboard, floor, headliner, doors and centre console are all made with this material.

On the surface, it is a formidable idea: lightweight, strong and great looking. But the components lack the top clear coat that is usually applied to carbon fibre for protection and durability.

McLaren?s idea was not to save costs, but to save weight. The lack of a clear coat reportedly saves 1.5 kg in the car?s overall weight. But considering the car weighs 1,490 kg, this is a reduction of just 0.1 per cent.

From my experience on the bicycle side, I know raw carbon fibre without a clear coat tends to have a very low scratch resistance, making it quite unpractical for everyday use.

So the question is whether the benefits of a 0.1-per-cent weight reduction are worth the possible deterioration of long-term durability?

Granted, this is not about structural integrity, but given the $1-million-plus price tag of the McLaren, I would certainly want mine to remain like new for as long as possible. And I would certainly intend on driving it!

This scenario happens all the time in the bicycle industry. Have you ever read ads proclaiming that this frame set is the lightest in the world? Or that by slightly altering a component, about 10 grams were saved?

Considering that any bicycle raced on the pro tour cannot weigh less than 6.8 kg (as dictated by the Union Cycliste Internationale), 10 grams is close to negligible ? just 0.15 per cent of the total weight (although quite a bit more in relative terms than the McLaren example).

Beyond the marginal weight reduction of a seat clamp, rear derailleur hanger or even a stem or handlebar, there are some engineering solutions that carry much more significance than others when it comes to performance.

For example, saving 150 grams on the rims will have a much greater impact on performance than 150 grams on the frame (or one of the non-moving parts attached to it).

The former is a dynamic mass, the latter a static one. Weight loss is important; weight loss for any moving part generally more so, because it will elevate the level of responsiveness of the system.

Driving a sports car or riding a high-performance bicycle is about one thing: the ride experience.

And I am pretty sure the P1 would not feel any different if the carbon fibre was protected by a top clear coat. I am also positive that a lighter seat clamp won?t make you a faster rider.

If you prefer the look of an unfinished carbon fibre surface or the style of a non-operating component, fine. But don?t pretend they have any impact on ride experience, and consider the ramifications they have on other facets of engineering: durability, ease of maintenance, functionality, etc.

In the end, good engineering is always about making the right compromises; those that truly make a difference. I?ll order mine with clear coat and some very light wheels.

Wheels bicycle columnist Julien Papon is the president and founder of Vitess Bicycle Corp. His column appears every two weeks during the summer.

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