If you've looked closely at your caravan or trailer tyres, you may have spotted a "C" in the size, for example 165R13C. That one letter makes a big difference to how much weight the tyre can carry, and it's one of the most important things to match when you buy replacements.
This guide explains what the C means, how to read the load numbers that come with it, and how to check your tyres can carry the weight of your caravan or trailer.
What does C mean on a tyre?
C stands for commercial.
C rated tyres were originally designed for vans and other light commercial vehicles, which carry heavy loads. According to Michelin, C tyres have a reinforced carcass and a higher load index than conventional tyres of the same size.
That extra strength is exactly why they're so common on caravans and trailers, which put a lot of weight on a small number of tyres.
How to spot a C rated tyre
The C appears straight after the rim size in the tyre size on the sidewall. For example:
- 165R13C 96/94N is a C rated tyre for a 13 inch wheel.
- 155/80R13 84N is a standard tyre with no C, also for a 13 inch wheel.
C rated tyres usually show two load index numbers instead of one, which is another easy way to tell them apart.
What the two load numbers mean
On a C rated tyre such as 165R13C 96/94N, the two numbers are both load indexes:
- The first number (96) is the load index when the tyre is fitted as a single wheel. 96 means up to 710kg per tyre.
- The second number (94) applies when the tyre is fitted as a twin, with two tyres side by side. 94 means up to 670kg per tyre.
Caravans and most trailers run single wheels, so the first number is usually the one that matters. The letter at the end (N) is the speed rating. You can look up any load index or speed rating in the tables in our tyre size guide.
Why load capacity matters so much
The difference between a standard tyre and a C rated tyre can be significant. Here are some examples from our own range:
- 155/80R13 84N (standard): up to 500kg per tyre.
- 165R13C 96/94N (C rated): up to 710kg per tyre.
- 185/70R13C 106/104N (C rated): up to 950kg per tyre.
All three fit a 13 inch wheel, but the C rated tyres can carry far more weight. If a caravan or trailer needs C rated tyres and has standard ones fitted instead, the tyres could be overloaded, which increases the risk of a blowout.
How much load do your tyres need to carry?
Your tyres need to be able to carry the full weight of your caravan or trailer when it's loaded. For a caravan, that's the MTPLM (maximum technically permissible laden mass), which you'll find on the caravan's weight plate or in the handbook.
TyreSafe says the combined load capacity of the tyres must be enough for the MTPLM, and strongly recommends that the MTPLM doesn't exceed 90% of the tyres' combined capacity, to allow for uneven loading.
For example, on a single axle caravan with two tyres:
- Two 155/80R13 84N tyres carry up to 500kg each, or 1,000kg combined. Keeping to 90% suits an MTPLM of up to 900kg.
- Two 165R13C 96/94N tyres carry up to 710kg each, or 1,420kg combined. Keeping to 90% suits an MTPLM of up to 1,278kg.
These figures are just examples. Always check the tyre size and load rating your caravan or trailer manufacturer specifies.
Can you use car tyres on a caravan or trailer?
Some caravans and trailers are fitted with standard, non-C tyres from new, and that's fine as long as the replacement matches the size, load index and speed rating the manufacturer specifies.
What you shouldn't do is swap in a different tyre, such as a car tyre in the same size but with a lower load rating, without checking first. TyreSafe advises that any change in tyre size or type should only be made after seeking advice from the caravan or tyre manufacturer. It also warns that your car's spare wheel must not be used on your caravan, even in an emergency.
Tyres across the same axle should also match, with the same size, load index and speed rating on both sides.
Buying C rated tyres
We stock C rated trailer and caravan tyres from Kenda, GT Radial and Starco, in sizes including 155/70R12C, 185/60R12C, 195/60R12C, 165R13C, 175R13C, 185/70R13C and 195/50R13C. Browse our trailer and caravan tyres, or choose a complete trailer wheel and tyre with the tyre already fitted.
While you're checking your tyres, it's worth reading our guides to how old your caravan or trailer tyres are and checking your tyre pressures.
If you have any questions, see our FAQs or get in touch.