Are Lighter Wheels Better?

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If the marketing kitsch is to be believed lighter wheels are better in every way shape or form. So, we’re going to take our 848 and we’re going to replace the cast wheels with a set of forged wheels.

What’s the difference? Well, a cast wheel is when they take molten aluminum and they pour it into a mold cast the wheel into the shape. They tend to be a little bit heavier and not quite as strong because with the casting process you might end up with inclusions or little bubbles in the material.

A forged wheel is when they take a big giant block of billet aluminum under heat and they pound it, like with a hammer, forge it into the shape of a wheel, and then use a mill to cut out the spokes. This results in a much stronger and a much lighter wheel. Is it any better? We’re gonna find out, but that’s not why we started down this road with the 848.

When we started looking for these forged wheels we were trying to solve a completely different problem. Starting this year, Pirelli changed the sizes of their race tires. I can no longer get a race slick to fit on the back of the 848. What happens is the tires are getting so big the tire hits the front of the swing arm. Now I’ve already modified the swing arm several years ago to allow the eccentric to move back further, which gave me a little bit more space at the front of the tire between the tire and the swing arm for a tire warmer.

Space for the tire warmer between the tire and the swingarm

I have to take my modification to the next level. I now have to put a six inch width wheel, where the bike came with a five and a half inch wheel, so I can move up to a 190 size rear tire. Now it would have been easy just to go pick up any set of Multistrada wheels, or whatever, slap that on the back, and bob’s your uncle. I could have kept going but freaking Kory at Moto Station said, You know, Dave. Those champagne colored wheels that came on the Streetfighter S and the old Tri-Colore 1098? Those would look fantastic.

I was like, you know what? They would look fantastic and how hard would they be to find that bike has been out of production for 10 years. The world is littered with those things. But they were impossible to find. it took me all summer long hunting for a set of forged champagne Marchesini wheels.

The cast front wheel with the rotors removed is 4.4 kilograms. The forged front wheel 3.27 kilograms. That’s a 1.2 kilogram difference, or two and a half pounds lighter. The rear cast is 4.6 kilos, and the rear forged 3.6 kilos. One kilogram different, or two pounds different.

Honestly, I was surprised with these results. The difference between the cast and the forged wheels was greater than I anticipated. I was especially surprised at the rear wheel. Going from a 5.5-inch cast to a 6-inch forged; the 6-inch forged wheel is bigger, yet it still came in a full kilogram lighter.

Why do light wheels make a difference? What’s the theory? There’s actually two ideas. The first is we’ve reduced the sprung mass of the motorcycle. Sprung mass is everything that’s below the spring. That would be the wheels the tires the axles the rotor. That’s all unsprung mass. Everything above the spring is sprung mass. That’s the chassis and you.

That’s not going to make much of a difference, at least not anything that is going to be discernible in any way shape or form.

The other, however, should because we’re dealing with rotational forces. And with lighter wheels it’s what’s called the moment of inertia. It’s basically how much energy is required to get the wheel spinning, to slow it down, to get it to change direction… We’ve reduced the weight by over two kilograms, just under five pounds, and that should make a noticeable difference.

I was not really positive that would make a big difference but I gotta’ say, every single aspect of the motorcycle is now better. It shifts better, it accelerates better it, brakes better, but most dramatically it changes direction better! Through the tight chicanes, the bike just moves from side to side with so much less effort. I gotta’ say, if you’re gonna make one upgrade to your motorcycle, and I can’t believe I’m saying this, is skip the exhaust system get light wheels. It is astonishing the difference it made.

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