Single-Sided Motorcycle Swingarm vs. Double-Sided Swingarm

Is life better with a single-sided motorcycle swingarm?

What's with single-sided motorcycle swingarms? Like forks, clutches, front brakes, and other major components on motorcycles, there's some variation when it comes to how things are done, in this case, how the rear wheel is attached to the bike.

The swingarm has to support the rear wheel, pivot so the suspension can do its thing, and deal with some pretty major loads. There’s the weight of the bike and the rider, but engineers also have to consider lateral loads encountered while cornering and the twisting forces imparted by the drivetrain.

To handle all that stress, a swingarm has to be stiff and strong. Most of the time that’s accomplished with a traditional, double-sided swingarm. And in it’s simplest form the double-sided swingarm is little more than some rectangular steel sections welded together—simple, cheap to manufacture, and totally effective.

Some bikes, however, have a single-sided swingarm, and this setup does have some advantages.

First of all, there’s style. There’s no doubt the styling department has a lot to do with selecting a single-sided setup, but besides good looks this swingarm offers easier chain maintenance and wheel removal.

With a traditional swingarm, you have to remove the axle, get your hands greasy putting the chain aside, and deal with the sprocket, spacers, and rear caliper just to remove the wheel. With a single-sided swingarm the axle, sprocket, and chain, all stay where they are, while the wheel just slides off the axle.

Fast wheel changes are a huge benefit in endurance racing, which is where single-sided technology first became popular. In racing, a single-sided swingarm also allows the muffler to be tucked in closer to the bike’s center line for steeper lean angles and mass centralization, while on the street it makes it easier to mount larger, close-fitting side cases.

Another advantage is chain adjustment and alignment. With a single-sided arm the alignment is fixed from the factory, so you don’t have to futz with vague hash marks on the chain adjusters.

However, there are a few drawbacks. For starters, you usually only see single-sided swingarms are higher-end bikes because they’re more expensive to make. Remember all those loads and forces I mentioned? A single-sided swingarm is at a bit of a disadvantage since it only has one arm, and to accommodate that the design has to be more complex. And with complexity comes cost.

Removing the wheel from a single-sided swingarm setup involves fewer steps, but may entail a monster socket or even a special proprietary attachment. In either case, it’s not the kind of tool the average home mechanic is going to have on hand. And unless your bike has a center stand you’ll need a special paddock stand to support a single-sided swingarm bike. That being said, some bikes, like BMWs, have automotive-style lugs holding the wheel in place (plus a center stand), so popping the wheel off really is simple and easy.

Speaking of BMWs, the majority of them have single-sided swingarms. Same goes for scooters. That's because the manufacturer is already designing a big, strong assembly to house the driveshaft and gears or the pulleys and belt on a scooter, so it's just a little more work to have the assembly double as the support for the rear wheel.

And as with our discussion of upside down versus right-side up forks, weight, specifically unsprung weight, is a hot topic of debate with swingarms. A lighter swingarm would be advantageous, but which style is lighter really depends on the bike. There is no hard and fast rule that says one setup weighs less than the other.

And that brings us to handling advantages. There are none, at least none that are significant enough that you’re going to notice. So when it comes down to it single-sided swingarms are sexy and offer easier wheel removal and chain maintenance, but that’s about it.

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