Each system for final drives has its own merits and drawbacks.
What is the best: shaft, belt or chain drive? Of course, we realize each has advantages and disadvantages and what kind of riding you do has a lot to do with what final drive option you may prefer. But, for the sake of argument, let's break them down.
Not all that many years ago, I will admit to having a healthy skepticism about belt drive systems. Growing up with snowmobiles in a time where even the supposed high-strength racing belts didn’t last very long, I had my doubts about drive belts for motorcycle final drive systems. For a long time I referred to them as “rubber band” final drives.
What I didn’t take into account was the stark difference in the mode of operation between the variable ratio torque converter drive of a snowmobile, which puts much more stress and wear factor on a drive belt than the simple linear drive forces the belt handles as a motorcycle final drive. Another factor I wasn’t considering was the major improvement in materials available for drive belt manufacture and improved designs.
Belt drive systems are simple, quiet and remarkably reliable—but dirt ground in or a rock caught between the pulley and belt can cause premature failure.
Drive belts actually have about the longest history in motorcycle final drives, with some of the earliest examples being riveted leather belts. Metallic chains became more prevalent as bike development continued and power increased, but shaft drive systems were used early on as well, some appearing as early as WWI.
Contemporary drive belts have remarkable durability and strength. High-tech aramid and carbon fibers now in use hold up well even on today’s high output machines and have long service life requiring minimal maintenance and tension adjustment. Of course, following manufacturer’s instructions for belt maintenance, cleaning, alignment and tension maximizes service life.
I have two belt-driven bikes, both of Harley-Davidson manufacture. I have to admit they have changed my skeptical view of belt final drive. I’ve been riding the first belt-drive Harley I own since 2006 and have yet to replace the drive belt it came equipped with. In fact, the belt has never required adjustment between tire changes.
Harley-Davidson Belt System
Keeping the drive belts clean—grit can work its way into the belt and cause premature failure—and checking the tension before each ride is about all I’ve had to do. Belt drive systems in proper alignment, tension and condition are quiet and very low maintenance and I’ve found them to be reliable, as well.
On the other hand, while the belts have been reliable on both of my belt-drive bikes over the years, I still hate the thought of having a belt failure and I have yet to get a straight answer on recommended belt change intervals and expected service life. Of course, service life is highly affected by how hard the bike is ridden and under what conditions, but even a general statement of “under normal riding conditions” would be nice.
Depending on the bike make and model, the cost and complexity of belt replacement can range from “ouch” to “you gotta be kidding” depending on whether the bike’s design requires the swingarm to be removed to change the belt. I’ve never had to pay for it yet, but I’m not looking forward to it and it’s not a project that is easily done on a roadside somewhere.
After growing up on motorcycles with chain drive and then owning Yamahas and Hondas with shaft drive, I became a real fan of shaft drive systems. Eliminating chain cleaning, lubrication, adjustment and eventual pricey replacement of chain and sprockets by going to a system that is no-muss, no-fuss, high reliability and low maintenance seemed to me a no brainer for nearly any type of riding.
In addition to low maintenance and high reliability, shaft drive systems provide a clean look—but extra weight.
I mention reliability because the other thing that can happen with a chain is breakage, which can result not only in getting stranded someplace, but also in damage to the bike. I’ve never had a chain break on any of my bikes—something of a miracle, because I haven’t always been as diligent about chain maintenance as I should be—but it is a possibility. This isn’t to say shaft or belt drive systems can’t fail; of course they can, but if you think of the odds being multiplied by the number of moving parts, a chain falls under the old saying of being “only as strong as its weakest link.”
I’ve owned at least one shaft drive bike continuously since 1983 of one make or another. They include two 1981 Yamaha XJ750RH Secas, a 1982 Honda GL500 and CX500, 1985 Honda VF700C, 1982 Yamaha XV750 Virago, 1984 Honda VF1100S Sabre and a 1998 Honda VT1100 Shadow ACE. Combined miles covered on all these shafties are in the tens of thousands of miles.
Virago and Seca shafties
The shaft drive system on each was given its hypoid gear oil change each time the regular engine oil and filter change took place. Those models with zerk fittings get greased at the same time. Of course, maintenance schedules and requirements vary, so if you drive a shaftie, it’s a good idea to follow manufacturer’s recommendations. Among all those bikes, I never had to replace a driveline part or got stranded on the roadside by a final drive problem. For overall reliability, ease of maintenance and low cost to operate/maintain, it’s tough to beat a shaft drive system. Of course, if there is a failure of some type, that “low cost” part is subject to substantial change.
There are some disadvantages to shaft drive, too. It's heavier than belt or chain and has higher cost to manufacture. They are also less adaptable in terms of the range of swingarm travel that can be accommodated and ease of alteration of final drive gear ratios. Some test riders have described an “up-and-down torque reaction” from shaft drive bikes. Try as I might, I have never detected it. It may be more pronounced on some bikes, but I’ve never even felt it to a slight degree, so if it is a disadvantage at all, it would be a minor one.
Shaft drive systems have come into most common application in touring and some sport-touring bikes, but they have been used on conventional and adventure bikes, as well.
Metallic chain is by far the most prevalent type of final drive system for motorcycles and a lot of other types of powersports vehicles, as well. It's light, tough, relatively inexpensive to use in motorcycle manufacture and adaptable to varying riding conditions and final drive ratio needs.
Chains come in various sizes and can differ in several dimensions, which must be taken into account when replacing the chain and sprockets.
Probably the most common knocks on chain final drive systems are the maintenance required for cleaning, lubrication and tension adjustment and the rooting around down low and mess that goes with all that. There also tends to be a range of opinions about what the best cleaning and lubrication agents are and what the optimal service interval is. As is so often the case, there are any number of options that work and different manufacturers have recommendations that can vary quite a bit across their product line, depending on the application.
V30 Magna - Chain Drive
Indeed, shopping for a new chain can get pretty technical—and done right, you’ll also usually be in the market for a new set of sprockets at the same time, if you’re replacing a worn out final drive set. Chain size range includes 420, 428, 520, 530 and 630 and O-ring and X-ring chain is wider than standard roller chain—a factor that must be considered when upgrading some older bikes due to potential clearance problems at the drive sprocket.
Metallic chain with O-ring or X-ring design can have long service life, but regular maintenance and adjustment is key.
O-ring and X-ring chain designs available today last far longer than standard roller chains in common use some years back, but they still require regular maintenance, adjustment and eventual replacement.
Motorcycle chain sizing is numbered 40, 50 and 60 as is standard implement roller chain. Typical chain sizes are as follows:
40 class = pitch is 0.5”, roller width is 0.312”, roller diameter 0.306” or 0.335.”
50 class (520 & 530) = pitch is 0.625”, roller width is 0.250” or 0.375”, roller diameter 0.400.”
60 class (630) = pitch is 0.750”, roller width is 0.375”, roller diameter 0.469.”
Dimensions such as pin diameter, link plate thickness and height, color, finish and tensile strength vary across products. Sprockets must be sized not only based on the number of teeth, but to match up with the chain size, as well.
O-rings and X-rings seal lubricant inside the chain and are made out of neoprene or other flexible material, but an O-ring has a cross-section that is circular in shape. An X-ring has an X shaped cross-section in an effort to create greater sealing area against the plates than an O-ring can provide.
Advantages To Each
Each final drive system has its own merits and drawbacks. In general, when we’re riding none of that comes to mind, as long as everything works the way it’s supposed to. It’s probably when things don’t work right that the differences matter the most.