Marc Parnes Wheel Balancing Adapter for Single-Sided Swing Arms

Changing tires at home is a dirty, sweaty ordeal and usually involves much swearing and gnashing of teeth. Specialized tools can greatly reduce the hassle factor, but outfitting a garage with such equipment means incurring significant startup costs. On the other hand, having this work done at a shop can also be expensive and time-consuming, once you’ve paid for all the parts and labor and either dropped off/picked up your bike or hung around for hours waiting on it. Doing the job yourself allows you to buy your tires from the cheapest source and change them at your convenience. If you replace your tires often, you’ll save a lot of time and money in the long run using your own elbow grease. Once you’ve mounted new rubber, you still need to balance the resulting wheel/tire combo. A single-sided swing arm may ease wheel removal, but it can complicate the balancing process.

When your bike has a single-sided swing arm, you can’t just throw your rear wheel on a static balancing stand, since the hole in the wheel’s center is much larger than any of the axle rods that typically come with such a stand. You’ll need an adapter to reduce that hole to a standard size. A variety of such adapters are available at wide-ranging price points, but the one from Marc Parnes (not a made-up play on my name!) occupies the low end of that range and works perfectly; there’s no reason to spend more.

You may already know about the Marc Parnes Portable Wheel Balancer, an elegantly engineered alternative to traditional static balancing stands. Eliminating the heft and bulk of a stand, the basic version of this minimalistic device is comprised of a tool steel axle rod with high-quality shielded ball bearings at each end and two moveable 1.45” cones to center and hold the wheel in place between them on the rod. Said cones slide into a regular wheel’s bearings from each side, their conical shape providing a secure interface with multiple bearing sizes. The user then supports the wheel/balancer assembly with whatever is handy—a pair of jack stands, chairs or even stacked blocks. (Some have been known to use milk crates. —Ed.) Because the balancer is functionally self-contained, its supports are irrelevant as long as they’re of equal height. This means the balancer itself can be stored or transported far more easily than a regular balancing stand. I would definitely own one of these if I didn’t already have a static balancing stand when I first came across the Marc Parnes variant; it’s brilliant! However, its adjustable cones are no more adequate for the gaping maw of a wheel from a single-sided swing arm than are the rods of a typical stand. Those using a Marc Parnes balancer will still need an adapter for such wheels.

Instead of a pair of cones, the adapter is a short cylinder machined from 6061-T6 aluminum billet to precisely fit the contours of the wheel’s center opening. It slips into place from the drive side and is then held there by a pair of wing screws with hard nylon sleeves. These sleeves abut the wheel opening’s edge on the opposite side and get snugged down gently by hand. Very little pressure is required to secure them, since the forces they’re subjected to during balancing are negligible, and the material won’t mar painted surfaces. Once mounted, the adapter then slides onto the rod just like a conventional wheel. There’s nothing special about the subsequent balancing process; the adapter’s weight is symmetrical and has no effect. (See my how-to article on static wheel balancing at https://www.bmwownersnews.com/2021/09/wheel-balancing/; you’ll find an embedded video from another MOA member, Doug Christensen, demonstrating the Portable Wheel Balancer there, too.)

Like many static balancing stands, mine came with a large assortment of rods for use with different sized wheel bearings; I simply choose the one matching the diameter of the wheel’s original axle. The selected rod is then cradled by a pair of bearings atop each of the stand’s upright supports. The Marc Parnes adapter takes a half-inch rod (the portable balancer’s axle size). Note the importance of selecting the proper adapter. While they all feature the same half-inch internal diameter axle hole, their external shapes and dimensions differ greatly, depending on the wheels they are designed to fit. Many modern BMW models, including my 2020 R 1250 RS, use the 62mm external diameter BA12 adapter pictured, but check proper fitment for your bike when ordering. As a safeguard against error, you may be asked to confirm its make, year, model, and wheel type (cast or spoke) prior to shipping.

The BA12 adapter costs a mere $40, with other adapters ranging from $25-70. If you haven’t already purchased a static balancer, the portable model described above can be ordered as a kit including the specific adapter(s) required for your motorcycle, rather than in its basic “universal” configuration ($105), saving the purchaser several bucks on the complete setup. The BG12 kit for my bike runs $140. If I needed only a half-inch rod with my adapter (e.g., if my existing stand lacked that axle size), the combination would cost $60. All prices include shipping to a US address.

A special message for those with an R 1250 RS like mine: Believe your owner’s manual when it says you must remove the exhaust canister prior to pulling off the rear wheel. Just eyeballing it, you might think there’s enough room to maneuver the wheel and tire out from between the swing arm hub and the exhaust, and you’d almost be right. However, you will discover a tad more clearance is needed to get past the brake caliper, and trying to wiggle the wheel free will only gouge the surprisingly delicate paint on your rim. (Of course you know how I learned this.) Removing the exhaust canister is a quick and simple affair involving just three easily accessed fasteners. Also, fully support the wheel while removing/installing its mounting bolts, as the hub ledge on which it rests is quite narrow. These warnings probably apply to other BMW models, as well.