Tyre Pressure, Wear and When to Replace

The sidewall number is not your pressure — and the date code matters as much as the tread.

Two things get this wrong more than anything else on a motorcycle. The first is reading the pressure off the tyre sidewall. That number is the maximum the tyre is rated for, not what your bike wants — the recommended pressure comes from the motorcycle, not the tyre. The second is judging a tyre purely on tread depth, when age and shape often condemn a tyre long before the tread runs out.

Tools

• A gauge you trust — a decent pencil or dial gauge beats a forecourt airline
• Tread depth gauge or a coin
• Torch
• Owner's manual

Where your pressure actually comes from

Your recommended cold pressures are on a placard on the bike or in the owner's manual, and they are often different front to rear. Take them from there.

Many models also specify a higher rear pressure when carrying a passenger or luggage. If you ride two-up at solo pressure the rear tyre runs hot and the bike wallows.

Check COLD — before riding, or at least a couple of hours after. A warm tyre reads high and you will end up letting air out of a correctly inflated tyre.

Check weekly. Tyres lose pressure slowly and continuously, and a slow puncture announces itself as "it seems to need air more often" long before it strands you.

Reading the wear, not just measuring it

SHAPE tells you more than depth. A rear tyre worn flat across the centre with sharp edges still has tread but has lost its profile — the bike will feel like it falls into corners and stands up under braking. That tyre is finished regardless of the gauge.

CUPPING or scalloped wear on the front, felt as a wobble or heard as a hum, points at suspension, wheel bearings or steering head as much as at the tyre.

UNEVEN WEAR side to side usually means the bike is being ridden on consistently wrong pressure, or something is out of alignment.

Wear indicator bars sit in the tread grooves. When the tread is level with them, the tyre is at its legal and practical limit — not approaching it.

Look for the obvious too: embedded stones and screws, cuts, bulges, and perished or cracked rubber in the grooves and on the sidewall.

Age — the part nobody checks

Every tyre carries a DOT code on the sidewall ending in four digits. Those four digits are the week and year of manufacture: "2319" is the 23rd week of 2019. Learn to find it — it takes ten seconds and it is the single most overlooked fact about a tyre.

Rubber hardens with age whether the bike is ridden or not. A tyre with plenty of tread on a low-mileage bike that has sat for years is not a good tyre; it is an old tyre with tread on it, and it will not grip like a new one, particularly cold or wet.

Check the date code on any NEW tyre before it is fitted. Tyres sit in warehouses, and you are entitled to know the age of what you are buying.

Replacement

Replace in pairs where you reasonably can. A new front against a worn, square-profiled rear gives a bike that steers oddly and inconsistently.

Match the type and construction to what the bike is specified for, and do not mix construction types front and rear. Fitment is not just about size.

Fitting motorcycle tyres needs the right equipment — it is easy to damage a bead or a wheel, and balancing matters at road speed. Removing the wheel yourself and carrying it to a shop is the sensible split for most people.

New tyres have a release agent on the surface from the mould. Ride gently for the first tankful and build lean angle progressively.

Parts for this job

Check fitment for your own model and year before ordering — add your bike and we will flag what fits.

Other Harley how-to guides

This guide covers procedure and judgement. Torque figures, fluid capacities, gaps and tension settings are specific to your model and year and must come from the factory service manual for your motorcycle — we deliberately do not print numbers we cannot stand behind for your bike. Independent aftermarket retailer, not affiliated with Harley-Davidson, Inc.