A tractor tyre needs between 4.6 and 12.25 litres of OKO Original Off-Road, depending on its size. A common 540/65 R28 takes 6 litres, an 18.4-38 rear takes 8.75 litres and a large 710/70 R42 takes 12.25 litres. Because the dose depends on width, sidewall height and rim diameter together, check your exact size in the OKO dosage calculator before you fill.
Tractor tyre sealant doses by size
These are standard doses of OKO Original Off-Road for one tyre, taken from the OKO dosage calculator. Sizes are listed from smallest dose to largest.
| Tyre size | Rim | Width | Aspect ratio | Dose per tyre |
|---|---|---|---|---|
| 14.9-24 | 24" | 14.9" | 100% | 4.6 litres |
| 13.6-28 | 28" | 13.6" | 100% | 4.8 litres |
| 420/85 R30 | 30" | 420 mm | 85% | 5.75 litres |
| 540/65 R28 | 28" | 540 mm | 65% | 6 litres |
| 16.9-30 | 30" | 16.9" | 100% | 6.5 litres |
| 480/70 R34 | 34" | 480 mm | 70% | 6.75 litres |
| 460/85 R38 | 38" | 460 mm | 85% | 8 litres |
| 18.4-38 | 38" | 18.4" | 100% | 8.75 litres |
| 600/65 R38 | 38" | 600 mm | 65% | 9 litres |
| 710/70 R42 | 42" | 710 mm | 70% | 12.25 litres |
Fronts and rears are usually different sizes, so work out each axle separately. If your size is not in the table, the calculator covers it.
How the dose scales with tyre size
OKO works by coating the inside of the tread. As the wheel turns, the liquid spreads into an even layer, and when a puncture happens air pressure pushes it into the hole. A bigger tyre has more tread to cover, so it needs more sealant. Three parts of the size drive the dose:
- Rim diameter. Two tyres with the same 65% profile show it clearly: a 540/65 R28 takes 6 litres, while a 600/65 R38 takes 9 litres.
- Width. On the same 38" rim, a 460/85 R38 takes 8 litres and a wider 600/65 R38 takes 9 litres.
- Sidewall height. Older-style sizes such as 18.4-38 have a tall sidewall (the calculator treats them as 100% aspect ratio), which is why an 18.4-38 needs 8.75 litres.
The practical point: do not guess from a neighbouring size. If you are not sure how to read the markings on your sidewall, our guide on how to read a tyre size walks through metric, older-style and earthmover formats.
How much to buy
OKO Original Off-Road comes in 1250ml bottles, 5 litre cans and 25 litre drums. Some worked examples using the doses above:
- One 540/65 R28: 6 litres, so a 5 litre can plus a 1250ml bottle, with a little left over.
- A pair of 18.4-38 rears: 17.5 litres in total.
- Four 540/65 R28 tyres: 24 litres, which fits inside one 25 litre drum.
- A pair of 710/70 R42 rears: 24.5 litres, again within one 25 litre drum.
If you are treating more than one or two tractors, the 25 litre drum with the Metallic Application Pump for 25L Drums is the practical route. The pump delivers up to 250ml per stroke, so a 6 litre dose is 24 full strokes.
Getting the dose into the tyre
Apply OKO to new or fresh tyres for the longest protection. It goes in through the valve stem once the valve core is out. The OKO Cap on the 1250ml bottle has a valve core remover built in, and the drum pump works against tyre pressure of up to 60 psi (4.1 bar), so you do not need to jack up the wheel and fully deflate the tyre. After filling, refit the core, inflate to the correct pressure and drive a short distance so the sealant spreads around the tread. Our step-by-step guide on how to put sealant in a tyre covers bottle, injector and pump in detail.
Running inner tubes? OKO Original Off-Road works in tubes as well as tubeless tyres, but the largest puncture it can seal is smaller in a tube. See using sealant in inner tubes before you decide.
What that dose does for you
Once it is in, OKO Original Off-Road seals multiple tread punctures of up to 12mm as you drive. It stays liquid inside the tyre for the tyre's whole life, does not corrode rims, and can add up to 20% to tyre life. It is built for slow-moving machinery; for limited road work it is suitable up to 80 km/h (50 mph).
For large, high-load tractor tyres, OKO also makes OKO Premium Tyre Care Lifelong. It is a conditioner, not a sealant: it cuts pressure loss, heat build-up and rim corrosion, and can extend tyre life by up to 30%. Its doses are higher, for example 14 litres for an 18.4-38 and 20 litres for a 710/70 R42.
Quick answers
How much sealant does a 540/65 R28 tractor tyre need?
6 litres of OKO Original Off-Road per tyre, at the standard dose.
How much sealant does an 18.4-38 tractor tyre need?
8.75 litres of OKO Original Off-Road per tyre, at the standard dose.
Can I use OKO in tractor tyres with inner tubes?
Yes. OKO Original Off-Road works in both tubeless tyres and inner tubes, but the largest puncture it can seal is smaller in a tube than in a tubeless tyre.
Do I have to deflate the tyre to add sealant from a drum?
Not fully. The Metallic Application Pump for 25L Drums injects sealant against up to 60 psi (4.1 bar), so you avoid jacking up the wheel and fully deflating the tyre.
Enter your exact tyre size in the OKO dosage calculator to get the dose for every axle, then order OKO Original Off-Road. Our online shop delivers in the UK only; elsewhere, buy through your local OKO distributor.
