Tyre overloading: what happens when you exceed the load rating, and how to avoid it
What happens when a tyre is overloaded?
When a tyre carries more weight than its rated load capacity, the tyre structure undergoes greater deflection (more sidewall flex per revolution) than it was designed for. This excess flexing generates heat in the carcass — and heat is the primary mechanism by which tyres fail. A tyre running at 20% over its rated load generates approximately 30–40% more internal heat per revolution than a correctly loaded tyre. This heat accelerates compound degradation, weakens the belt-to-tread adhesion, and in severe cases causes tread separation or sudden tyre failure. Overloading also reduces the tyre's ability to respond to aquaplaning — a heavier contact patch requires more drainage capacity than the tyre was designed to provide.
- When a tyre carries more weight than its rated load capacity, the tyre structure undergoes greater deflection (more sidewall flex per revolution) than it was designed for.
- This excess flexing generates heat in the carcass — and heat is the primary mechanism by which tyres fail.
- A tyre running at 20% over its rated load generates approximately 30–40% more internal heat per revolution than a correctly loaded tyre.
FAQ
- What happens when a tyre is overloaded?
- When a tyre carries more weight than its rated load capacity, the tyre structure undergoes greater deflection (more sidewall flex per revolution) than it was designed for. This excess flexing generates heat in the carcass — and heat is the primary mechanism by which tyres fail. A tyre running at 20% over its rated load generates approximately 30–40% more internal heat per revolution than a correctly loaded tyre. This heat accelerates compound degradation, weakens the belt-to-tread adhesion, and in severe cases causes tread separation or sudden tyre failure. Overloading also reduces the tyre's ability to respond to aquaplaning — a heavier contact patch requires more drainage capacity than the tyre was designed to provide.
- What should I verify before using this information?
- Use TireFitLab values as a sizing reference, then verify the vehicle handbook, tire placard, rim compatibility, load rating, and physical clearance before fitting.
Try a load index
Type the number printed before the speed letter, such as 91V or 94W.
- kg per tire
- 615
- lb per tire
- 1,356
Reference-table value only. Always match your vehicle placard and tire sidewall markings.
Load index reference table
| Load index | Max load (kg) | Approx lbs | Typical vehicle class |
|---|---|---|---|
| 71 | 345 kg | 761 lb | Small hatchbacks and superminis (Volkswagen Polo, Renault Clio) |
| 75 | 387 kg | 853 lb | Compact cars (Ford Focus, Vauxhall Astra) |
| 80 | 450 kg | 992 lb | Mid-size family cars (Toyota Corolla, Skoda Octavia) |
| 84 | 500 kg | 1102 lb | Mid-size family cars (VW Passat, BMW 3 Series) |
| 87 | 545 kg | 1201 lb | Larger cars and small SUVs (Skoda Superb, Kia Sportage) |
| 91 | 615 kg | 1356 lb | Crossovers and medium SUVs (Toyota RAV4, VW Tiguan) |
| 95 | 690 kg | 1521 lb | Large SUVs and light vans (BMW X5, Mercedes ML) |
| 100 | 800 kg | 1764 lb | Full-size SUVs and 3/4-ton vans (Ford Transit Custom, Mercedes Vito) |
| 104 | 900 kg | 1984 lb | Large commercial vans (Ford Transit, Volkswagen Crafter) |
| 109 | 1030 kg | 2271 lb | Light trucks and dual-rear-wheel vans |
Note: The total rated load capacity of the vehicle is the sum of the four tyre ratings. A vehicle on 91-rated tyres (615 kg each) has a total tyre load capacity of 2,460 kg. The vehicle's GVM (Gross Vehicle Mass) must not exceed this figure — or more accurately, must not exceed the vehicle manufacturer's specified GVM as shown on the VIN plate.
What happens as overload percentage increases
| Overload amount | Heat increase per revolution | Tyre life impact | Failure risk | Typical cause |
|---|---|---|---|---|
| 1–5% over | ~3–8% more internal heat per revolution | Negligible in short term. Small accelerated wear over full tyre life. | Very low. Unlikely to cause immediate failure but contributes to premature wear. | Slightly overloaded with normal luggage + 4 passengers on a small car. |
| 5–10% over | ~10–18% more heat | Noticeable reduction in tyre life — estimated 10–20% shorter service life. | Low at low speeds. Meaningful risk at sustained motorway speeds, especially in hot weather. | Full boot + roof box + passengers. Frequently seen on holiday journeys. |
| 10–20% over | ~20–35% more heat | Significant life reduction (20–40%). Heat degradation of carcass begins. | Moderate. At motorway speeds in summer, risk of tread separation or blowout meaningfully elevated. | Van slightly overloaded with building materials. Car towing at rating limit with passengers. |
| >20% over | ~35–50% more heat | Severe. Carcass overheating — possible internal delamination even on short journeys. | High. Tyre can fail without visible warning — sudden tread separation or sidewall rupture. | Light van fitted with car-rated tyres. Overloaded commercial vehicle. Wrong tyre spec for vehicle. |
The relationship between load and pressure
Tyre pressure and tyre load are interdependent. Pressure is what supports the load — not the rubber itself. When a tyre is inflated, the air pressure inside supports the vehicle weight by pressing outward against the rim and the road. The rubber structure constrains the air and determines how much the tyre deforms under load.
Sidewall flex is the key variable. Every revolution of a loaded tyre causes the contact patch area to flatten and the sidewall to flex inward. This flexing generates heat through hysteresis — the rubber absorbs mechanical energy and releases it as heat. More flex per revolution = more heat = faster degradation.
| Scenario | Sidewall flex | Heat generation | Tyre behaviour |
|---|---|---|---|
| Correct load, correct pressure | Normal design deflection | Within design limit | Optimal performance — contact patch size, wear, and temperature all within specification. |
| Correct load, under-inflated | Excessive flex (both sides of carcass flex more than designed) | Elevated — can mimic overloading even at rated load | Accelerated shoulder wear, heat buildup. Combined with actual overloading, dramatically increases failure risk. |
| Overloaded, correct pressure | Excessive flex (tyre carrying more than design load, pressure cannot compensate) | Elevated proportional to overload amount | Harder ride. Visual bulging of sidewall under load. Progressive heat-related degradation. |
| Overloaded AND under-inflated | Severe — sidewalls may contact road at low speeds | Very high — rapid heat buildup | High risk of sudden failure. Most tyre blowouts on motorways involve this combination. Never drive with this combination. |
Common overloading situations
| Situation | Risk level | Detail | What to do |
|---|---|---|---|
| Passenger car with 5 adults + full boot | Low to moderate | Most modern cars have tyres rated to carry the maximum GVM of the vehicle. With 5 adults (averaging ~75 kg each = 375 kg) + 50–80 kg luggage, a compact car approaching its GVM may load rear tyres to 90–100% of their rated capacity. The tyre load index is chosen by the manufacturer to accommodate this — provided the correct tyres are fitted. | Check your vehicle handbook for tyre load index. If you have fitted lower-LI aftermarket tyres, you may be creating an overload situation. |
| Rooftop cargo carrier (roof box) | Low to moderate | A roof box raises the vehicle's centre of gravity and adds weight. At 50–80 kg, the contribution to individual tyre load is small (~12–20 kg per tyre). The greater risk is not tyre overloading but vehicle handling — roof loads shift the weight balance rearward and increase crosswind sensitivity. | Check the vehicle's roof load rating. Keep roof box weight under the roof load limit. Reduce motorway speed. |
| Towing a caravan or trailer | Moderate to high | Towing adds drawbar load (noseweight) to the rear axle. If the trailer noseweight is 75 kg, each rear tyre carries an additional 37.5 kg. Combined with a full load of passengers and luggage, rear tyres can reach or exceed their load rating. The trailer tyres are also often neglected — many caravans sit for months, then hit motorway speeds with tyres that may be at or near rated load. | Calculate total rear axle load including noseweight. Verify trailer tyre load index and pressure. Some vehicles require increased tyre pressure when towing — check the handbook. |
| Light commercial van (LCV) | High | LCVs — Transit, Sprinter, Ducato, Crafter — are most commonly overloaded of any vehicle category. Payload capacity is frequently exceeded by tradespeople who load by judgment rather than by weight. The legal payload limit is on the VIN plate in the vehicle door jamb. Tyres on LCVs are often C-rated (commercial) with higher load capacity, but may still be under-rated if the van was registered with passenger-car tyres or if aftermarket tyres with lower LI were fitted. | Weigh the vehicle if you regularly carry heavy loads. Ensure C-rated tyres with correct LI are fitted. Most LCV tyres require 4.0–4.5 bar (58–65 psi) when loaded — check and inflate before motorway use. |
| Wrong tyre fitted (lower load index than OEM spec) | High — may be illegal | Fitting a tyre with a lower load index than specified by the vehicle manufacturer creates a structural overload situation at normal vehicle loading. In most European jurisdictions, fitting a tyre with a lower load index than OEM spec is a road traffic offence. In the UK, it constitutes a tyre "in an unsuitable condition" under Road Traffic Act 1988. MOT failure is guaranteed. | Always match or exceed the OEM load index specification. If unsure, check the vehicle handbook or the tyre placard on the door jamb or fuel filler flap. |
How to check you are within the safe load limit
To verify your load situation, follow these steps:
- Find your tyre load index. Read the tyre sidewall. The load index is the two- or three-digit number after the tyre size, e.g., in "225/45 R17 94W", the load index is 94 (670 kg per tyre). Look up the load index in the table above or in our Load index chart.
- Calculate your total tyre load capacity. Multiply the per-tyre rating by 4. For LI 94: 670 × 4 = 2,680 kg total.
- Find your vehicle's GVM. This is on the VIN plate in the door jamb. It includes the vehicle's kerb weight plus maximum payload (passengers + cargo).
- Check the GVM does not exceed the OEM tyre specification. The vehicle manufacturer has already verified this for the original tyre spec — if you have aftermarket tyres with a lower load index than OEM, recalculate.
- Increase tyre pressure when fully loaded. Most vehicle handbooks specify a higher inflation pressure for full-load conditions (sometimes labelled "laden" or "max load"). This is typically 0.2–0.4 bar (3–6 psi) above the normal recommendation.
The legal position
In the UK, driving a vehicle with tyres of inadequate load index for the vehicle's GVM constitutes a tyre in an unsuitable condition under Road Traffic Act 1988. This is a three-point penalty endorsement offence per tyre. The same tyre would fail an MOT.
In Germany, fitting a tyre not approved in the vehicle type approval (Fahrzeugschein) is a §29 StVZO violation. Tyres must match the vehicle approval document — either the exact OEM specification or a tyre listed in an aftermarket approval (ABE or KBA number).
Across the EU, vehicles must not be operated above their type-approved GVM (ECE Regulation No. 54 covers tyres for commercial vehicles). Overloaded vehicles also void insurance in many cases — insurers can reject claims if the vehicle was overloaded at the time of the incident.
More tools
- Load index chart
- Tyre blowout guide
- Tyre pressure for heavy loads and towing
- Tyre load capacity guide
- Trailer and caravan tyre pressure guide
- Tire & wheel reference guides
Seasonal check
Planning a long summer drive?
Use the budget and running-cost tools before a trip, especially if the current tyres are worn or the replacement size changes diameter.
What changed
- Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.