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Brilliant biking inventions…Cast Motorcycle Wheels

Motorcycles are a balance… no less a luminary than James Whitham once said that – the likes of the Yamaha RD350LC – was ‘just right’ as if it had any more power, the chances are the chassis would be tied in knots.

We’ve said it before (and we will say it again!) but race machines hold the key to road bike development and progression.

Today, we’re talking about cast wheels. Now, wheels, brakes, forks, frames, swingarms and tyres are all at the mercy of the motor. It’s all linked…

During the saucy 1970s the motors of grand prix 500cc machines crept up from 100 to 110, 120 and even touched around 130bhp… Frames had to go from double cradle or twin-loop steel to ally beam frames to cope. Tyres became slicks and then (OK in the early/mid 1980s) slicks became radials. Wheels – which had traditionally been ‘spoked’ also had to adapt and it was during this decade that they finally did.

1975 was an important year for grand prix racing for a number of reasons. Firstly, it was the first two-stroke 500cc world title, secondly it was Yamaha’s first 500cc title, thirdly it was Giacomo Agostini’s final 500cc title and last but not least, by the end of the year, Ago’s title-winning Yamaha OW-23 featured cast wheels towards the end of that season. This was a bit of a first…

The shift from four-stroke Grand Prix 500s to two-stroke (the last four-stroke win for some time would happen at the 1976 West German GP, again won by Ago) meant that power was heading crazily north. And this meant that all the various elements of chassis and tyres had to try and keep up.

Both wheel size and design had to change. The-then traditional spoked wheels needed checking on both road and race bikes. You ran an inner tube, you had to ensure the spokes were free from rust and that the inside of the wheel rims were free from rust also. The spokes had to be tight… From the very start, cast wheels were tougher and maintenance free. And aluminium cast wheels soon changed to ‘mag’ or magnesium wheels.

Marvic developed and built their three-spoke mag wheel in 1983. These weighed much less than even ally cast wheels which meant less unsprung weight, which meant the suspension didn’t work as hard. It also meant quicker turning, too.

The same happened on road bikes. The 1975 Laverda Jota had cast wheels, 1978’s Kawasaki’s Z1-R also used cast wheels and who can forget the ‘Italic’ cast wheels on the RD-LCs: not only were these wheels lighter and lower maintenance but they were stylish, too!

That’s not to say they were without fault: early cast ally wheels on both two and four-wheels sometimes had a problem with leaking. Many blamed poor casting of the wheels where, literally, the metal was porous and air would leak out. Sometimes we would run inner tubes as well…but things soon improved and by the mid-1980s, new materials and new methods of making wheels came along, so that by the time we were running our extruded-rim ComStars on our Hondas things were much better. And of course on off-road machines, we’ve never really used cast wheels as they are more likely to get damaged…

Today we need to be careful… cracks and issues mean older alloy wheels can have serious issues, but many people offer an X-ray service or you can check for cracks with a special paint. Either way, we have a lot to thank those early cast wheels for. Some may say that they don’t look as nice as a set of chrome-spoke wheels, but they have a use and style all their own.