LATEST FEATURES...

 

Sticking the knife in forks

Funny front ends? You must be joking

Twenty one years ago BMW launched the R1100RS with a Telelever front end. It's gone on to be fitted to the most popular bike of the 21st Century, BMW's GS. Yet still – apart from BMW's other forkless system, Duolever – conventional telescopic forks survive on all other bikes, including MotoGP. Why?

Life is one big drag

The high (and low) pressure world of aerodynamics

A road cone is more aerodynamic blunt end forwards (if you fill the hole in first). Same goes for a bullet. And most cars – if you geared them to suit you'd get better fuel economy driving in reverse.

Intuition says, aerodynamically, a sharp, pointy front end is more important than a sharp, pointy back end. For you Ferrari and Lamborghini owners, sadly, this is wrong. A falling raindrop points us, literally, in the right direction: pointy at the back. It's seven times more aerodynamic than a pointy wedge. If you cut the 'nose' off a raindrop, its drag increases by 6%. If you cut its tail off...

Engines are a waste of energy

Given the amount of work petrol does, it's amazing your motor uses so little to go so far so fast

It takes just 100cc of unleaded mixed with 800 litres of air – or two and a bit Tequila shots in four large garden water butts – for your engine to accelerate you from a standing start to 150mph under half of a mile away in around ten seconds. And it's even more impressive when you consider...

Sticking with aluminium

CCM's 450 Adventure frame is the first to be held together by glue

Compared to engines, suspension, brake systems and electronics, a bike frame seems relatively simple. It must be rigid enough to hold a swingarm and forks in place, resist the efforts of a rider, an engine, the ground and physics to twist, bend or deflect it, and be durable for the lifetime of the bike. Ideally it's also light, easy to process in production, cosmetically pleasing and cheap.

But as long as the first two requirements are met, different bikes have different priorities and thus there is no single perfect frame design, which is why we get anything from round, oval, square or rectangular tubes, pressed sections, extrusions, cast or forged sections, usually in combination and made from steel or aluminium alloy (although titanium, magnesium, carbon fibre and even fresh air have been used – the German Windhoff in 1927, 1976 Quantal Cosworth Norton and 1992 Britten V1000 were frameless, with the engine connecting headstock and swingarm. And, arguably, Ducati's Panigale, BMW's flat twins and hub-centre bikes like Bimota's Tesi and Yamaha GTS1000 are frameless). With hundreds of frame permutations over the years, it's rare to hear of a new one.

But a Lancashire's CCM is doing something different: the new GP450 Adventure, MCN's group test winner, has a frame held together by glue (although they prefer 'adhesive', and call the process Bond-lite).

Gluing metal-on-metal isn't new. The idea came from...

Forcing the issue

So we've got all the power we can use. What do we do now?

With traction-controlled streetbikes making more power than a ten-year old World Superbike, and with pressure to reduce emissions and fuel consumption, where do engines go from here?

One answer is more torque. For a given size of engine it could be just as powerful as a bigger engine but at lower rpm, thus cleaner and more efficient – more time to fill the cylinders, longer burn, better scavenging, lower mechanical losses. Be nice to use, too.

But since modern bike engine architecture was established in the mid-80s, the peak torque from a given capacity has remained static. A 1992 Suzuki GSX-R1100 N made...

Holding back the gears

The relationship between gear ratios, torque, thrust and 'retuning' is never an easy one

Honda's new CTX1300 is, at first glance, technically unremarkable. It is, essentially, a stripped-down, half-faired Pan European with sharper steering, a wider rear tyre, a stereo and, somehow, more weight. It has the same 1261cc transverse 90° V4, 'retuned' for more midrange.

But the spec shows this is more, or less, than a retune: a stock Pan makes 125bhp at 8000rpm and 92 lb.ft at 6000rpm. Honda say the CTX makes 83bhp at 6000rpm and 78 lb.ft at 4500rpm. That's a massive 40% less peak power and 16% less peak torque!

Doubtless the curves are reshaped, but it's still a big deficit. Why Honda has done this will be revealed...

Clearance approved

Why it’s important to have room at the top, especially if you’re a valve

MCN reader Ron Smithson emailed with two questions: “Re: Honda’s CB500 range having a 600-mile valve clearance check; imagine the furore if a new Honda Civic (30,000 miles) was the same? Why’s a bike engine different?”

The second question has a straightforward answer...

Going off at a tangent

Why steering geometry is never a straight ahead subject

Indian’s new Classic, Vintage and Chieftain share engines and frames, differing only in trim and styling. Yet while the Classic and Vintage have identical chassis spec, the Chieftain has different numbers: 61mm less wheelbase, 4° steeper rake angle and 5mm less trail. If you were to judge which Indian was sportiest on spec, you’d say the Chieftain. Which is odd, because...

Syndicate content