August is when trailers earn their keep. Second cut silage, grain carting, bales and muck, all of it moving on tyres that have spent most of the year parked in a yard.
That combination is exactly why trailer tyres fail at this time of year. The tyre sits idle for months, then goes straight to maximum load on warm roads with no run-in period. A blowout mid-harvest costs you a day you cannot get back.
Here is what to check before it happens.
Tread depth: know the actual number
For road use in Ireland, the minimum permitted tyre tread depth is 1.6mm, and for safety reasons it is recommended that each tyre should have at least 3.0mm. Most new tyres have 8.0mm. It is the central three-quarters of the tread pattern that must be greater than 1.6mm to be legal for road use.
The same 1.6mm limit applies in the UK and Northern Ireland, and it covers light trailers with a maximum gross weight of 3,500kg or less. Penalties are not trivial: towing a trailer with tyres that do not meet the requirements could lead to a fine of up to £2,500 and 3 points on your licence per tyre.
A quick field check: run a €1 coin along the centre of the tread. In the UK, the 20p test does the same job.
This gets missed more than people think. DVSA research found 50% of light trailers were failing to meet road safety standards.
Age matters more than mileage
A trailer tyre can look nearly new and still be finished. Trailer tyres usually carry more weight and stay stationary for longer periods than car tyres covering the same distance, and that combination puts stress on the casing.
What to look for:
- Fine cracking in the sidewall or at the base of the tread blocks
- A hard, glazed look to the rubber
- Flat spots from sitting loaded in one position all winter
- Bulges or blisters, which mean the casing has gone and the tyre needs replacing immediately
Check the date code on the sidewall. Four digits give you the week and year of manufacture. If you are replacing on age rather than wear, our full trailer tyre and wheel assemblies range ships as a matched unit, which saves fitting time in the middle of a busy week.
Pressure is the blowout risk
Underinflation is the most common cause of a trailer tyre failing under load. A soft tyre flexes more, flex builds heat, and heat is what destroys the casing on a warm August road.
Check pressures cold, before the trailer moves, and check them against the load you are actually carrying rather than the last job. A trailer running empty and a trailer running full are two different requirements.
Do not forget the spare. It is usually the oldest tyre on the unit.
Load rating and ply
If you have moved to bigger bales, a heavier body, or a higher capacity tank, the tyres that suited the old setup may not suit the new one. Check the load index against your loaded axle weight, not the trailer's empty weight.
Fitting a tyre with a lower rating than the job requires is the quickest route to a failure at the worst possible moment. If you are working heavier ground or running implements alongside the trailer, our agricultural tyres and agriculture wheels and tyres ranges cover the higher load ratings.
The parts people forget
- Valves. Perished valve stems leak slowly and are cheap to replace while the tyre is off.
- Rims. Check for rust pitting at the bead seat, which causes slow leaks that never quite go away. Replacements are in the wheel rims and assemblies range.
- Wheel nuts. Retorque after the first loaded run.
- Bearings and hubs. A running-hot hub will take the tyre with it.
- Jockey wheel. If it is seized or the tyre has collapsed, hitching gets harder and slower all season. Hubs, axles, hitches and jockey wheels are all in trailer parts.
Replace in pairs, on the axle
If one tyre on an axle is worn or perished, its partner has usually done the same work in the same conditions. Replacing both keeps the load shared evenly and saves you doing the job twice.
If your existing trailer tyres are Kenda and you are looking for a like-for-like replacement, we have set out the direct alternatives in our guide to Kenda tyre equivalents for ATV, quad and trailer.
Parnells stock trailer tyres, wheels and complete assemblies, trailer parts and trailer kits, with our own in-house team of wheel and tyre experts to help you match the right tyre to the load.