Time damages a motorcycle that stands still. Metal rusts and oil goes bad, and rubber ages in a way that is easy to overlook. Rubber is on every safety system of the bike: tyres, brake hoses, seals, fork seals. If you buy a classic that has been in storage, or if you own one that you do not ride often, these are the parts to check first.
Tyres
Reading the date
Every tyre has a code after "DOT" on the sidewall. The last four digits are the week and the year of manufacture: 2418 means the 24th week of 2018. Check both tyres. If the code has only three digits, the tyre was made before 2000 and is far too old to use.
How old is too old?
Rubber hardens with age, and a hard tyre grips less, especially in the cold or in the wet. Many tyre manufacturers advise replacing tyres that are about ten years old, whatever the tread, and having them inspected every year after the fifth. A tyre that looks new may still be old.
What to look for
- Cracks in the sidewall or between the tread blocks.
- Flat spots from long standing, and a tyre that has deformed.
- Bulges, cuts or embedded objects.
- Uneven wear, which may point to a bent wheel or worn bearings.
Choosing replacements
Use the size and type specified in the manual. Many classics have narrow rims and were designed for bias-ply tyres of a certain profile. A wide modern tyre can change the handling and may not fit. Look for tyres sold for classic use, and ask your owners' club which brands are used on your model. Fit new tubes and rim tape with new tyres on spoked wheels. Take the first miles gently: a new tyre needs a little distance to wear off its moulding release agent.
Pressures
Use the pressures in the manual and check them with a gauge that you trust. Old pressures are for old tyres, so if you fit a modern construction, ask the maker.
Brake hoses
Rubber hoses perish from the inside out. A hose can look sound and still bulge under the pressure of hard braking. Check for cracks, swelling, chafing and weeping at the fittings. Many owners replace rubber hoses when the bike has been standing for years, and braided stainless-steel hoses are a common upgrade that does not change the look much. Buy the right length and the right end fittings for your model.
Brake fluid
- Glycol-based fluids (DOT 3, DOT 4, DOT 5.1) absorb water from the air. Water lowers the boiling point and causes corrosion inside the master cylinder and the calipers.
- Many manufacturers recommend replacing the fluid about every two years. Check the manual.
- DOT 5 is silicone-based and cannot be mixed with glycol fluids. Use the type specified for your bike, and do not mix.
- Dark brown fluid, or fluid in a reservoir with a cracked diaphragm, should be replaced.
Disc brakes
- Check the thickness of the pads. Replace them before the backing plate touches the disc.
- Check the disc for wear, scoring and rust. A minimum thickness is often stamped on the disc.
- If the lever feels spongy, bleed the system. If it continues, the hose, the master cylinder or the calipers need attention.
- After a long period of standing, pistons in the calipers may be seized with corrosion. A rebuild kit with new seals is available for many models.
Drum brakes
- Check the thickness of the linings and the condition of the drum surface.
- Check that the shoes move freely and that the cable or rod is lubricated and adjusted.
- Take care with brake dust on an old bike: older linings may contain asbestos. Wear a mask, do not blow the dust out, and wet it or use a vacuum designed for fine dust.
- A drum brake needs correct adjustment more than power. Do not expect it to stop like a disc.
Other rubber parts that age
- Fork seals and dust covers.
- Fuel hose and carburettor O-rings and floats. Modern fuel can harm old materials: see what ethanol does to a classic fuel system.
- Engine and handlebar mounts, footrest rubbers, gaiters.
- Seat foam and covers.
- Seals in the master cylinders and the clutch.
A routine that works
- Before the first ride of the season: check the tyre pressures, the tyre dates, the brakes by hand, and the hoses.
- Every year: check the fluid, the pads or linings, and the wheel bearings.
- Every two years: replace the brake fluid.
- After storage: do the first ride at low speed and test the brakes before you need them.
See also waking up a bike from storage and the buying checklist.
