UK law requires trailer tyres to carry at least 1.6mm of tread across the central 75% of their width all the way round.
The legal minimum
The DVSA and Highway Code set out the tread depth rule for trailers: a minimum of 1.6mm must be visible across the central three-quarters of the tyre's width, measured at all points around the circumference. This is the absolute legal floor. Any tyre found below this depth during a roadside check or pre-purchase inspection will fail, and you must not tow with it.
The 1.6mm standard applies to both cars and trailers. It is checked using a tread depth gauge - a simple tool costing very little that any garage or tyre fitter can use in seconds. Some tyre shops will check your trailer tyres free of charge when you bring it in for maintenance.
Why wet weather matters more
Although 1.6mm is legal, grip drops noticeably in wet conditions once tread falls below 3mm. Wet roads are common in the UK, and a trailer with shallow tread will lose contact with the road surface more easily, increasing stopping distance and the risk of skidding. Professional hire companies and operators often replace tyres well before the legal limit to maintain performance and reduce liability.
If you are hiring a trailer, check the tread depth on arrival. Poor tyre condition is one of the quickest ways a hire agreement can be disputed, and you may be charged for premature wear if tyres were already worn when you collected the unit.
How to check tread depth safely
Checking tyre tread is straightforward. Insert a tread depth gauge into the groove - aim for the central 75% of the tyre width and test at least three points around the circumference. If you do not have a gauge, some tyre fitters will do it for you. A quick visual check is not reliable enough; always measure.
Before hitching up any trailer, walk around it and inspect all four tyres. Look for signs of damage, bulges, or uneven wear as well as depth. Our full guide to trailer tyres covers sidewall markings, mixing tyre types, and load ratings - all things that affect safety and legality alongside tread depth.
Other tyre rules you must know
Tread depth is only one part of trailer tyre law. Cross-ply and radial tyres must never be mixed on the same axle. Each tyre's sidewall must display a load index and speed symbol that match or exceed your trailer's rated specifications. Mismatched tyres or underrated ones can cause failure under load and invalidate your insurance.
Check the tyre age as well. Even if tread depth is good, tyres older than ten years should be considered for replacement. Rubber hardens over time, and an old tyre may look sound but perform poorly in an emergency.
Before you hire
When looking for a trailer to hire, ask the supplier about tyre condition and age as part of your pre-hire checklist. Reputable companies maintain their tyres well and will have records of replacements. If you are hiring locally, trailer hire companies in your area should be able to show you documentation and allow you to inspect the unit before payment.
GetBrent.co.uk connects you with local trailer hire, sales, and removals firms across the UK. Check your trailer's tyres carefully on collection, report any defects immediately, and keep evidence of the condition in case of dispute later.
