BS AU 50-3.7:1985 download free.Tyres and wheels Part 3: Valves — Section 7: Code of practice for the selection and care of tyre inflation valves for passenger cars (including caravans and light trailers).
7.1 Scope
This section of BS AU 503 gives recommendations for vehicle manufacturers on the initial steps to be taken in selecting valves for passenger car wheels (including caravans and light trailers) and recommendations on the care of valves for the user.
7.2 Valve selection by vehicle manufacturer
When selecting a valve for a wheel and tyre assembly it is important to ensure that the correct choice is made.
Basic factors which influence this choice are:
a) type of tyre (tube type or tubeless);
b) inflation pressure of the tyre;
c) type of wheel;
d) vehicle maximum speed.
The basic choice is between tube type and tubeless tyres. This would generally be decided by the vehicle design and performance requirements and the valve type is therefore predetermined.
7.3 Types of valves
7.3.1 (eneral
Valves are available in the following two basic types:
a) tubeless type valves, which can be either of the rubber snap-in or metal clamp-in types (see 7.3.2):
b) tube type valves (see 7.3.3).
7.3.2 Tubeless valves
7.3.2.1 Rubber snap-in c’ak’cs. Rubber snap-in valves are available in several different lengths and sizes and care should he exercised in selecting the correct size to suit the rim hole, and the most suitable length for ease of access so as not to be damaged in service.
The valve stem is threaded internally and externally for fitment of the valve core and valve sealing cap respectively.
It is essential that special care should be taken when fitting rubber snap-in valves, First the rim hole should be inspected to ensure it is dimensionally correct to an approved standard. is in good condition and free from burrs and sharp edges which can damage the rubber body of the valve. Then the rubber body of the valve should be lubricated with an approved lubricant for ease of fitting and inserted into the rim hole using a special valve insertion tool. To ensure that the valve is correctly located, it is essential that the moulded fitting line on the rubber valve body passes completely through the rim valve hole.
NOTE Thta type of valve is uitabIe for tyre inflaizon pressures up to a maximum of 475 kPa (4.7 bar or (39 psi).
7.3.2.2 Clamp-in calves. Metal clamp-in valves are available in a variety of sizes. It should always be ensured that the correct valve is fitted for the rim hole size and application. Clamp-in valves for tubeless tyres are clamped into the rim and an airtight seal is achieved by means of a hexagonal nut and rubber grommet. During fitting it should be ensured that the valve is correctly located relative to the wheel components to ensure ease of access for pressure checking and adjustment.
Metal clamp-in valves are strongly recommended for use with “V” or ‘VR” rated tubeless applications except where specific provision has been made by the vehicle manufacturers for the use of a rubber snap-in valve. It is essential that metal clamp-in valves are used where tyre inflation pressures exceed 475 kPa (4.7 bar or 69 psi).
7.3.3 Tube valves
These have rubber covered stems and are vulcanized to the inner tube. It should always be ensured that the correct valve is used for the rim hole size and application.
7.4 Valve fitting checks
Whatever type of valve is fitted it should always be ensured that the valve core has correctly sealed. Leaking valve cores should be replaced. It should not be attempted to cure a leaking valve by extra tightening, as this may damage the core seat.
It should be ensured that the valve hole in the rim is in good condition and is free from burrs which could
damage the valve and cause deflation of the tyre.
A valve cap of the type which has an additional air seal and which will protect the valve core from dirt, dust
and water should always be fitted.
7.5 Valve accessibility
Where access to the valve for inflation or pressure checking purposes is difficult, a valve extension may be used.
Valve extensions are attached to the valve cap threads and are available in different lengths and designs so it is important to ensure that the extension chosen is correct for the application. Valve extensions for passenger car valves carry an internal sealing mechanism, and inflation, deflation and tyre pressure checks can be carried out without removal of the extension from the valve. The sealing extension cannot generally be fitted with a valve cap.
7.6 In-service valve checks
New rubber snap-in valves and the rubber components of metal clamp-in valves should always be fitted when fitting new replacement tyres.
Rubber covered valves should be examined regularly for splits and cuts. Damaged valves should be replaced immediately.
All valves should be examined regularly for damaged cap threads andlor distorted valve mouth where the cap is fitted. The internal valve core threads should also be examined for cleanliness. If the valve mouth is distorted the valve should he replaced.
It should be ensured that the radiused valve mouth which contacts the cap sealing washer is smooth and without nicks and burrs which may scuff and tear the cap seal.
Damaged cap threads, internal core threads and valve mouths should he repaired with an appropriate and recommended repair tool.
7.7 Check list for care of inflation valves for passenger cars
(including caravans and light trailers)
The following check list should be used for care of inflation valves for passenger cars (including caravans and light trailers).
a) l)o ensure the valve and valve fitting is the correct Do not assume that any-old” valve or valve size and type for the wheels and usage, e.g. it is fitting is suitable.
essential that clamp-in valves are used for inflation pressures above 475 kPa (4.7 bar or 69 psi) and are strongly recommended for use on cars capable of very high speeds. 210 km/h (130 mile/h) or more, except where specific provision has been made by the vehicle manufacturer for the use of a snap-in valve.
b) Do regularly check on valve cores for leakage. Do not attempt to cure leaking valve core by
Replace damaged or leaking cores, over-tightening. Damage to core seat can
easily result.
c) Do ensure that valve caps are always fitted and Do not leave valve caps on the ground when
replaced after removal. Sealing type valve caps are servicing. They can become damaged or lost.
preferred.
d) Do ensure that the valve holes in tubeless rims are in good condition and the surrounding area free from rust, pits and burrs. Seek advice if in doubt.
e) Do ensure that after fitting a rubber covered snap-in tubeless valve, the indicating ring around the body is fully visible on the outside of the rim. This is an indication of correct fitment. Use an approved lubricant.
fi Do ensure that clamp-in type valves are correctly positioned and securely fitted.
g) Do examine regularly the valve’s rubber fitments or rubber cover for cracks or splits and examine the metal portions of the valve for distortion and the threads fcr damage. Ensure that valve mouth is round, smooth and without nicks or burrs which would hinder the sealing quality of the cap. If in doubt change the valve or appropriate fitment immediately.
h) Do ensure that new snap-in valves or clamp-in valve rubber fittings are fitted when replacing tubeless tyres.
i) Do ensure that if valve extensions are used they are the correct type and length for the application and they are securely tightened on to the valve.