Agricultural tyres

The mainstream rear and front fitment on 100 to 300 hp tractors. The rear carries the drawbar load and the tractive effort; the front carries the loader and the front weight block and does the steering, which is why fronts are usually the first pair to be replaced on a loader tractor.

Keep the front and rear in ratio. A mechanical front-wheel-drive tractor needs the front axle turning slightly faster than the rear — typically a small percentage lead — and that ratio is set by the rolling circumference of the two tyres, not by their nominal size. Change one end to a different size, or to a worn set, and you can put the transmission into wind-up on hard ground. Our rolling circumference calculator checks the pairing before you fit.

Metric and inch are the same tyre. 520/85R42 is 20.8R42, 420/85R28 is 16.9R28 and 380/85R24 is 14.9R24. Customers with older machinery will ask in inches and read the invoice in millimetres, so quote both.

Narrow, tall sections for inter-row work in beet, potatoes and vegetables. The design job is to fit between the rows without touching the crop while still carrying full axle load, so row crop tyres run tall diameters and high pressures relative to their width.

Because the section is narrow, the load has to come from pressure rather than footprint. That is exactly the case where IF or VF construction earns its cost — it lets a narrow tyre carry the load at a pressure the soil can tolerate. Note that the 90 and 95 series designations carry inch equivalents too: 380/90R46 is 14.9R46.

Row crop sets are usually a second set of wheels rather than a replacement, so check the machine’s approved fitment list and the rolling circumference against the standard set before quoting. A row crop pair that does not match the drive ratio of the rears will wind up the transmission the same way a mismatched standard set will.

Sprayers are the hardest case in the sector: heavy when full, light when empty, working on soft ground, and asked to travel between fields at road speed. The tank empties through the pass, so the axle load at the headland is not the axle load at the far end of the tramline.

Two sets is the standard answer — narrow row crop tyres for in-crop work and wide flotation tyres for early-season and travelling. Where the customer only wants one set, specify against the full tank at the working speed. Provide the applicable pressure settings from the manufacturer’s load-and-inflation table for each operating condition.

This is the strongest case on the farm for VF. A VF casing lets the sprayer carry the full tank at a pressure that will not compact the seedbed, and the yield argument usually pays for the tyres well before the tread does.

Grain trailers, slurry tankers and chaser bins spend half their life at road speed and half on soft ground, which is the hardest brief in agriculture. On the road they need pressure and a speed rating; in the field they need footprint and low ground pressure.

Road transport and field work can require different pressures. Provide the manufacturer’s load-at-pressure settings for both speeds and explain when each applies. Always maintain the required pressure for the load and road speed; under-inflation during transport creates a risk of heat damage.

Watch the speed symbol on this application in particular. A D-rated flotation tyre is good for 65 km/h; an A8 is good for 40 km/h and is out of specification behind a 60 km/h tractor.

Balers, mowers, tedders, trailed sprayers and drills. Check implement tyres for ageing, under-inflation and damage after standing loaded through the winter, as well as for tread wear.

Many implement sizes are still cross-ply and marked with a ply rating rather than a load index — a 400/60-15.5 14PR, for example. The hyphen instead of an R is the tell: it is a bias tyre, it will run hotter and deflect less than a radial of the same size, and its ply rating is a strength class rather than a count of the layers in the casing.

The 15.3 series is specific to implement and trailer running gear. 10.0/75-15.3 means a 10 inch section at a 75 per cent aspect ratio on a 15.3 inch rim, and it does not interchange with a 15 or 15.5 inch rim.

A combine on full grain is one of the heaviest axle loads on any farm, carried on four tyres, on unprepared ground, in a short and weather-dependent window. Casing capacity and heat tolerance govern the specification, and availability governs everything else — order the size before harvest, not during it.

Combines are the classic case for cyclic field operation. The machine is at its heaviest for a fraction of the working cycle and much lighter for the rest, and the standards recognise that with an additional low-speed load allowance for tyres marked accordingly. That allowance applies in the field, at low speed, only. It is not a road rating and it is not a licence to run the machine heavier all the time.

Steering axle tyres on a combine are smaller, carry a surprising proportion of the load when the tank is full, and are the pair most often found under-inflated.

Farm telehandlers and loading shovels work on hard yard surfaces as much as on soil, so a pure agricultural lug tread wears quickly and rides badly. An industrial R-4 block pattern lasts far longer on concrete but gives away traction on wet grass and in a silage clamp.

Sizes here overlap the construction range — a 460/70R24 is fitted to both farm and site machines, and 460/70R24 is the metric form of 17.5L-24 — so establish whether the machine is doing farmyard or site work before choosing between an agricultural and an industrial pattern. See also our construction range.

Compact tractors, yard scrapers and small utility machines on smallholdings, estates and equestrian yards. We hold more than 1,000 compact agricultural tyres, for compact machinery and utility applications.

The choice on a compact tractor is between an agricultural lug that will pull on wet ground, an industrial tread for yard work and a turf tread that will not tear grass. For machines carrying out different types of work, a second wheel set may be worth considering. Turf and grounds care fitments are covered on our forestry and grounds care page.