In brief
The energy carried by compressed air in truck and earthmoving tyres is large; a lock ring flying off a multi-piece rim, or the sidewall of a tyre run underinflated tearing open, can cause severe injuries. The basis of protection is inflating the tyre in an inflation cage with a remote inflation set-up, standing outside the trajectory, fully deflating a damaged or underinflated tyre before removal, and never heating the rim.
How does an explosion happen during tyre inflation?
The difference between a passenger car tyre and a truck or earthmoving tyre is not only size. A large tyre works at both a higher pressure and a much larger air volume, and the energy stored inside increases accordingly. When this energy is released uncontrollably, the tyre, rim parts and air are thrown at great speed towards the person inflating it. Tyre fitter accidents therefore usually result not in a crush injury or cut but in severe blunt trauma. This is also why a tyre inflation cage is not an option for large tyres but a basic measure.
There are two separate mechanisms:
- Rim explosion: Especially on multi-piece rims, if the tyre is inflated before the lock ring or side ring is fully seated, or if the parts are mismatched, the ring flies off under pressure. The ring usually flies outwards from the side face of the rim, that is, towards a person standing opposite that face.
- Tyre blowout: The wires in the sidewall of a steel-belted tyre that has been run underinflated or overloaded weaken. When the tyre is reinflated, the sidewall can tear open around its circumference like a zip. Overinflation, impact damage and heat are also causes of blowouts.
The inflation cage and remote inflation set-up are the common answer to both mechanisms: if an explosion occurs, the cage absorbs the energy, and the worker stands outside the trajectory.
Risky tyre and rim types
| Tyre or rim | Why is it risky? | Specific measure |
|---|---|---|
| Multi-piece rim (earthmoving machinery, some older trucks) | The lock ring can fly off under pressure | Matching and seating of parts is checked; inflation only in a cage |
| Single-piece truck rim | High pressure and large air volume | Inflation in a cage or behind a barrier, remotely |
| Earthmoving machinery tyres | Very large volume; changed on site | Cage or barrier suitable for the site, tyre manipulator |
| Tyre run underinflated | Invisible damage to sidewall wires | Full deflation before removal from the vehicle, detailed inspection |
| Corroded, cracked or bent rim | Can break apart under pressure | Remove from service |
| Rim that has been welded or heated | Material structure is damaged; flammable gas can form inside the tyre | Remove from service; the rim is never heated |
On multi-piece rims, do not mix parts of different types and manufacturers. A lock ring that seems to fit can come out of its groove under pressure.
Tyre inflation cage and remote inflation
Under Art. 4 of Law No. 6331 on Occupational Health and Safety, the employer identifies the risks in tyre changing and inflation through a risk assessment and takes the necessary measures. A source frequently referred to in international practice is the US Occupational Safety and Health Administration standard OSHA 1910.177. This standard sets the following basic rules for servicing large vehicle rims:
- For inflating tyres on multi-piece rims, the employer provides a restraining device, that is, a cage, rack or similar equipment.
- Large vehicle tyres on single-piece rims are inflated only while in a restraining device or behind a barrier.
- The air line has a clip-on chuck, an in-line valve with a pressure gauge or a presettable regulator, and enough hose length between the chuck and the valve.
- Workers stand outside the trajectory during inflation.
What this arrangement means is that, once the clip-on chuck is attached to the valve stem, the worker controls inflation not by bending over the tyre but from the valve a few metres away, watching the gauge. Pressure is not checked by kicking the tyre or pressing it by hand.
Truck tyre changing step by step
The safe sequence for a truck tyre change carried out in the workshop is as follows:
- Secure the vehicle: The vehicle stands on level ground, the handbrake is applied and the wheels are chocked. Lifting is done with a jack, and no one works under or beside the vehicle until it is set on stands. We explained the rules for jacks and stands in our article on OHS in car repair workshops.
- Deflate before removal: If the tyre has been run underinflated, or damage to the tyre or rim is seen or suspected, the tyre is fully deflated by removing the valve core before the wheel is taken off the vehicle. OSHA 1910.177 states this rule explicitly for multi-piece rims, for tyres run at 80% or less of the recommended pressure.
- Before separating the rim from the tyre: Confirm that the tyre is fully deflated with the valve core removed.
- Inspection: The rim is checked for cracks, corrosion, bending and damage to the lock ring groove; the tyre for sidewall cracks, bulges and exposed wires. Defective parts are not used.
- Fitting: The tyre bead and rim are lubricated with suitable mounting paste. No flammable substance, fuel or spray is used.
- Inflation: The tyre is placed in the cage, the clip-on chuck is attached, and the worker inflates from outside the trajectory using the valve and gauge. The pressure does not exceed the value specified by the tyre manufacturer.
- Check: After inflation, the seating of the tyre and lock ring is checked visually. Parts of an inflated multi-piece rim are not struck with a hammer to seat them.
Layout of the inflation area in the workshop
The cage alone is not enough; the area around it must also be arranged with an explosion in mind. When planning the workshop layout, pay attention to the following:
- Separate inflation area: Place the cage in a corner away from the workshop's walkways and other workbenches. The area in front of the cage and opposite its side faces should be marked on the floor as a zone where no one stands during inflation.
- Valve position: The remote inflation valve and gauge should be fixed at a point outside the worker's trajectory from which the cage can be seen. The hose should be long enough to reach this point comfortably.
- Customers and drivers: Drivers and customers waiting for tyre changes should be kept away from the inflation area, with a separate waiting place designated.
- Walls and ceiling: There should be no windows, glass partitions or easily broken materials right next to the cage.
- Noise: Impact wrenches and air release produce high noise; for choosing hearing protection, see our article on choosing hearing protection and SNR.
Tyre changing at the roadside and on site
Tyre changing outside the workshop carries two additional risks: traffic and the absence of a cage.
- Traffic: A worker changing a tyre at the roadside is unprotected against passing vehicles. If possible, move the vehicle to a safe area separated from the main road, set up a warning triangle and signage, and wear a high-visibility vest. For drivers' road risks, see our article on company drivers and motorists.
- Inflation without a cage: If there is no cage on site, the tyre is inflated without removing it from the vehicle, from behind a barrier or the vehicle body, using a remote inflation set-up; no one stands opposite the side face of the tyre.
- Earthmoving machinery tyres: Because of their weight they are not handled manually; a tyre manipulator or suitable lifting equipment is used. Our article on the earthmoving machinery operator guides the daily check of the equipment.
Checking the compressor, hoses and equipment
The reliability of the inflation set-up also depends on the air supply:
- Compressor tanks are pressure vessels and, under Annex III of the Work Equipment Regulation, are subject to periodic inspection once a year. See our article on pressure vessels and compressor tanks for inspection details; you can plan the inspections through our periodic inspection service.
- Make sure the gauge on the inflation line reads correctly; do not inflate with a doubtful gauge.
- Check hoses and fittings weekly for cracks, swelling and looseness.
- Set the regulator so that it does not exceed the maximum pressure of the type of tyre being inflated.
Training, PPE and after an accident
A worker who changes tyres receives at least two hours of face-to-face, practical induction training before starting work; this training should demonstrate cage use, the trajectory and the deflate-before-removal rule on site. Impact-resistant glasses or a face shield, hearing protection, work gloves and steel-toe safety shoes are used as personal protection. Personal protective equipment does not replace the cage and remote inflation.
Injuries after an explosion are often severe trauma: call 112, do not move the casualty, and bring bleeding under control. For first aid in crush and limb injuries, see our article on first aid for amputation and crush injuries. A work accident is reported to the Social Security Institution (SGK) within 3 working days of the accident.
For fleet maintenance workshops, logistics companies and sites with earthmoving machinery fleets in Bursa and the surrounding provinces, Bursa Sistemer OSGB prepares the tyre changing instruction to suit the business's equipment as part of our OHS specialist services. Our approach to the logistics sector is on our logistics and warehousing page; inspection dates for compressors and lifting equipment are in the OHS calendar tool.
Frequently Asked Questions
Is a tyre inflation cage mandatory?
Under Law No. 6331, the employer is obliged to assess the risks and take the necessary measures. For truck and earthmoving tyres, a cage or barrier with remote inflation is the basic measure accepted in international practice; we recommend making this measure the basis of your risk assessment.
What is the difference between a rim explosion and a tyre blowout?
In a rim explosion, the lock ring or side ring of a multi-piece rim flies off under pressure. In a tyre blowout, the tyre itself tears, usually at a sidewall weakened by running underinflated. In both cases protection is the cage, remote inflation and standing outside the trajectory.
Why is a tyre that has been run underinflated dangerous?
At low pressure the tyre sidewall flexes too much and the steel wires inside it weaken. This damage may not be visible from outside. When the tyre is reinflated, the sidewall can suddenly tear; this is why such a tyre is fully deflated before removal and inspected in detail.
Is a cage needed for passenger car tyres too?
Passenger car tyres have lower pressure and air volume; OSHA 1910.177 also limits its scope to large vehicle rims. Even so, the tyre changer's instructions should be followed, the pressure specified by the manufacturer should not be exceeded during bead seating, and no one should inflate while leaning over the tyre.
Can a rim be welded with the tyre fitted?
No. A rim is never heated or welded under any circumstances. Heat can cause an explosion by generating flammable gases inside the tyre and weakens the rim material.
A certified specialist matched to your hazard class: site inspections, approved logbook, training plan, annual plan and report follow-up.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.