MOT defect file
Tyre load index or speed rating below requirement
Last updated
Quick answer
The tyre is not rated to carry the weight or run at the speed the manufacturer specifies for this vehicle. It usually follows a cheap replacement, or car tyres fitted to a van.
- Typical cost
- £80–£320 per axle
- DIY viability
- Garage job
What you might notice
- A sidewall code with a lower number or letter than the plate in the door shoulder or the handbook specifies
- Tyres that squirm and feel vague under a full load or with a trailer, while the car drives normally when empty
- Sidewalls running noticeably hot to the touch after a motorway run
- Nothing detectable in ordinary driving — this is a paperwork-and-sidewall check, not something you feel at 30mph
What causes it
- Passenger car tyres fitted to a van or a heavy estate, where reinforced or commercial ratings are required
- A cheap replacement chosen on size alone, with the load index and speed symbol never compared to the original
- Winter tyres of a lower speed rating fitted and then left on year-round
- A trailer or caravan tyre, or a part-worn of unknown history, fitted to a passenger vehicle
Advisory or failure?
A tyre whose load capacity or speed rating is below the manufacturer's requirement for the vehicle is a major defect and a failure, and so is a tyre that is not of a suitable size or type for the vehicle. The tester reads the sidewall markings against the requirement rather than measuring anything, so this is one of the few tyre defects with no grey area and no advisory route. The ratings sit at the end of the size code — in 205/55 R16 91V, the 91 is the load index and V the speed symbol — and a higher rating than specified is perfectly acceptable, only a lower one fails. Vans and light commercials are where this bites most often, because a reinforced or C-rated tyre is frequently required and an ordinary car tyre in the same size will physically fit.
Can you fix it yourself?
Garage job
The check is free and takes minutes: find the manufacturer's plate, usually in a door shoulder, the fuel filler flap or under the bonnet, and compare the size, load index and speed symbol printed there with what is actually on each sidewall. Do it before you buy, because the fitting itself is machine work and nobody refunds a tyre you have already had mounted. Two traps catch people out. Reinforced tyres are marked XL, Reinf or C rather than by a bigger number alone, and a lower speed rating is not made acceptable by promising to drive slowly — the test compares markings, not intentions.
What it costs
Correctly rated budget tyres for one axle are £90 to £150 fitted, with mid-range and premium at £160 to £320. Van and commercial C-rated tyres cost noticeably more than the visually identical car tyre in the same size, which is precisely why the wrong ones get fitted. There is no labour saving available here and no repair path, so the cost is almost entirely parts. If all four are wrong, buy two axles' worth in stages by all means, but start with the driven axle and do not mix ratings across a single axle in the meantime.
What happens if you ignore it
Load and speed ratings describe how much heat the casing can shed before it starts to come apart, so an under-rated tyre is a tyre running closer to its limit every time the car is fully loaded or driven at motorway speed for an hour. Failures of this kind arrive as a sudden deflation rather than a slow one. The legal position is the same as any illegal tyre — up to £2,500 and three penalty points per tyre — and insurers can reasonably treat a knowingly under-rated tyre as a material change to the risk, which matters more than the fine.
Common questions
- What do the numbers and letters at the end of a tyre size mean?
- They are the load index and the speed symbol. In 205/55 R16 91V, the 91 is the load index, describing how much weight the tyre is rated to carry, and the V is the speed rating. Both have to meet or exceed what the vehicle manufacturer specifies on the plate fitted to the car.
- Is the wrong tyre speed rating an MOT failure?
- Yes. A tyre whose load capacity or speed rating is below the manufacturer's requirement is a major defect, and so is a tyre that is not of a suitable size or type for the vehicle. The tester reads the sidewall markings rather than measuring anything, so there is no grey area and no advisory route. Correctly rated budget tyres are £90 to £150 an axle fitted.
- Can I fit tyres with a higher speed rating than my car needs?
- Yes. A rating higher than the one specified is perfectly acceptable and is not recorded as a defect, because only a lower rating fails. Fitting a better tyre than standard is therefore never a problem, while saving a few pounds on an under-rated one can cost you the test and a second fitting bill.
- Do vans need different tyres from cars?
- Often yes. Vans and light commercials frequently require reinforced or commercial tyres, marked XL, Reinf or C rather than by a higher number alone, and an ordinary car tyre in the same size will physically fit the wheel. Commercial tyres cost noticeably more than the visually identical car tyre, which is precisely why the wrong ones get fitted.
- Can I leave winter tyres on all year round?
- There is no seasonal rule in Britain, but many winter tyres carry a lower speed rating than the car was specified with, and if it falls below the manufacturer's requirement that is a major defect whatever the time of year. Promising to drive more slowly makes no difference, because the test compares markings, not intentions.
This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.
Has this been recorded on your car?
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