The drive chain or belt and the tires are where a motorcycle's power meets the road, and they wear with every mile. They also give plenty of warning before they fail, as long as someone looks. A short inspection on a regular schedule, and before any long trip, covers all of them. Slack specs, wear limits, and tire pressures vary by model, and the owner's manual or a sticker on the swingarm lists the numbers for your bike.

Checking chain slack

Chain slack is the up-and-down free play in the lower run of the chain, measured at the midpoint between the sprockets. The manual tells you how the bike should be positioned for the measurement, whether on the side stand or upright on a stand, with or without a rider, and the reading changes depending on which. Chains rarely wear evenly, so roll the bike forward and check slack at several points, then set it at the tightest spot.

A chain that's too tight does more harm than one that's slightly loose. As the swingarm moves through its travel, the distance between the sprockets changes, and a chain with too little slack can go taut when the suspension compresses. That puts heavy load on the countershaft bearing and the rear wheel bearings. A chain that's far too loose can slap the swingarm or jump a sprocket.

After adjusting, check that the rear axle is square. The alignment marks on the swingarm adjusters aren't always accurate, so many riders measure from the swingarm pivot to the axle on each side and compare. Tighten the axle nut to the torque in the service manual, and recheck slack afterward, since tightening the axle can shift it.

Lubrication and chain wear

Most street motorcycles use sealed chains, sold as O-ring, X-ring, or similar designs, with grease locked inside each roller by small rubber rings. The lube you apply protects the outside of the rollers and keeps the rings supple. Clean the chain with a chain cleaner or kerosene labeled safe for sealed chains, then apply a lube rated for them to the inner side of the lower run, ideally while the chain is warm from a ride. Lube every few hundred miles, after riding in rain, and after washing the bike, and keep pressure washers, harsh solvents, and stiff wire brushes away from the chain, because they can damage the rings.

Chain wear shows up as stretch. The pins and bushings wear, the pitch grows, and the chain no longer meshes cleanly with the sprockets. Service manuals give a wear limit measured over a set number of links or pins, and some bikes carry a wear indicator label at the chain adjuster. Other warning signs include tight or kinked links that don't straighten as the chain rolls, rust between the plates, missing or damaged O-rings, and a chain that needs adjusting much more often than it used to.

Look at the sprockets as well. Teeth that have become hooked or pointed, like a breaking wave or a shark fin, are worn out. Replace the chain and both sprockets as a set, because a new chain on worn sprockets wears quickly and a worn chain chews through new sprockets. A chain that breaks at speed can lock the rear wheel or punch through the engine cases, so don't run one past its wear limit.

Inspecting a drive belt

Belt final drives, common on Harley-Davidson and Indian cruisers and used on some other bikes, need no lubrication and stretch very little, but they still need regular inspection. Check tension with a belt tension gauge at the force and deflection the service manual specifies, since tension that's off in either direction shortens belt life. Then rotate the wheel slowly and look over the full length of the belt for cracks across the teeth, missing or damaged teeth, frayed edges, and stone damage.

A small stone caught between the belt and the rear pulley can punch a hole through a belt in a single ride, so check the pulley teeth and the inside of the belt guard too. The Harley-Davidson maintenance article covers belt checks on those bikes in more detail. Shaft-drive bikes skip all of this, though the final drive housing holds gear oil that needs changing on the schedule in the manual.

Tire pressure

Check tire pressure cold, before the bike has been ridden more than a mile or two, with a gauge you trust. The correct pressure is in the owner's manual and often on a sticker on the swingarm or chain guard, and many bikes list a higher pressure for riding two-up or with luggage. The figure molded into the tire's sidewall is the maximum the tire can hold, and it isn't the pressure to run.

Tires lose air slowly, so low pressure creeps up on riders who don't check. An underinflated tire flexes more, builds heat, wears at the shoulders, and makes the bike slow to turn and vague in corners. Off-road machines run far lower pressures that a standard gauge can't read accurately, which the ATV and UTV maintenance guide explains.

Tread, damage, and age

Motorcycle tires have tread wear indicators, small raised bars at the base of the grooves, and a small triangle or the letters TWI on the shoulder show where to find them. When the tread is flush with the bars, the tire is done. Legal minimum tread depth is set by each state, and wet grip drops as the grooves get shallow, well before a tire reaches that minimum. Look for uneven wear too. A rear tire with a flat strip down the center from highway miles turns in less predictably, and a front tire with scalloped or cupped wear can point to a suspension or pressure problem.

Run your hand and your eyes over the whole tire, sidewalls included. Cuts, bulges, embedded nails or glass, and cracking in the sidewall or between the tread blocks are all reasons for a closer look or a replacement. Tire makers set their own rules on repairs. Many limit or discourage repairs on motorcycle tires, and those that allow them often call for a combination patch-plug installed from inside the tire, sometimes with a speed limit afterward, so treat a roadside plug as a way to get home.

Rubber hardens with age even when the tread looks fine. The last four digits of the DOT code on the sidewall show the week and year the tire was made, so 2223 means the 22nd week of 2023. An old tire can grip noticeably less than a fresh one with the same tread depth, so check the tire maker's guidance on age before trusting old rubber, especially on a bike that's been sitting. The spring check in storage and spring startup includes this step.

Wheels and bearings

With the bike on a stand and a wheel off the ground, grab the tire at the top and bottom and rock it. Any clunk or play points to worn wheel bearings, or on the front, possibly the steering head bearings, and both should be checked further before the bike is ridden hard. Spin the wheel and listen for grinding or roughness. On spoked wheels, tap each spoke lightly with a small wrench. A tight spoke rings, while a loose one makes a dull sound and should be tightened to the manual's spec before the spokes around it loosen too.

Specs in this guide are general. Fluid grades, capacities, torque values, and service intervals vary by model and year, and the owner's manual or factory service manual for your exact machine takes priority.