Single-Sided Swingarm vs. Double-Sided Swingarm
Is life better with one arm?
By Motorcyclist Staff: Spenser Robert
Whatís with single-sided swingarms? Like forks, clutches, front brakes, and other major components on motorcycles, thereís 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. Thereís 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 thatís accomplished with a traditional, double-sided swingarm. And in itís simplest form the double-sided swingarm is little more than
some rectangular steel sections welded togetherósimple, cheap to manufacture, and totally effective. Some bikes, however, have a single-sided swingarm, and this setup does have some advantages.
First of all, thereís style. Thereís 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 bikeís
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 donít 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 theyíre 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, itís not the kind of tool the average home mechanic is
going to have on hand. And unless your bike has a center stand youíll 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. Thatís 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 itís 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
And that brings us to handling advantages. There are none, at least none that are significant enough that youíre going to notice. So when it comes down to it single-sided swingarms are sexy and offer easier wheel removal
and chain maintenance, but thatís about it.
Copyright © 2000 NTNOA All rights reserved.
Revised: April 06, 2017