Along with the hitchhead, your caravan's tyres are the only things that keep your caravan under control. With that in mind, you'd expect that they'd be regularly inspected as they are crucial to your outfit's safety on the road. The truth is, however, that many of us do little more than occasionally pump them up or run a sponge over them. Yet, careful checking could be the difference between a happy holiday and
a horrible accident.
Tyre inspector
The minimum amount of tread permissible is 1.6mm across the centre three-quarters of the tyre tread width, but that is barely relevant as caravan tyres don't generally wear out. They do, however, degrade with old age and poor storage.
The advice is that caravan tyres are replaced every five years. A tyre's age can be identified by the date code on its sidewall, usually with the word 'DOT' nearby, which stands for the American Department of Transport. It's a good place to start an examination.
Tyres made between 1990 and 1999 use a three-digit code followed by a triangle and indicate the month and year the tyre was made. The first digit indicates the month, while the second two digits indicate the year. Therefore a tyre code of 699 equates to June 1999. If your tyres have a three-digit date code, they really should be replaced, unless they have been stored meticulously, are regularly inspected and are in perfect condition.
From 2000, a four-digit code showing the week and year of manufacture is used. It takes a little more working out, but allows tyres to be dated to within a few days rather than a few weeks of manufacture. In this system, a code of 0402 indicates the tyre was made in the fourth week of 2002. A small number of tyres may not have the DOT designation, but the date code will appear somewhere on the sidewall.
The next thing to check is the tyres' physical condition. Any cuts, lumps missing or compression marks caused by wheel clamps are a cause for concern. If there is evidence of cracking on the sidewalls, they are scrap. Even if the sidewalls look good, there can often be evidence of radial cracking between the treads; the tyre will need to be removed to check on this. Whichever type of cracking is evident, the outcome is the same, new tyres.
What is much harder to detect, without removing the tyre from the van, is deformation. This usually appears as a bulge in the sidewall or the tread, and indicates the tyre's steel structure has begun to detach from the rubber outer and its failure is imminent. The tyre must be replaced immediately.
If a caravan tyre has gone flat while the van is in storage, it needs investigating. Tyres do not go flat without a reason and all the common causes will degrade
it further if not attended to.
A puncture caused by the tyre being pierced can usually be found. A slow puncture may be caused by a damaged valve, which is a cheap fix but requires a visit to the local tyre depot, or, on older vans, rusty wheel rims. When rust forms on the rim of the tyre, the seal can break down, allowing a slow escape of air from the tyre.
Choosing a caravan tyre
Many tyre specialists aren't familiar with the specifics for caravans, so it is useful if you understand the legalities, to ensure you are not sold something unsuitable. The tyre must be the correct size and type, and able to carry enough weight. The law states that if a vehicle was to operate outside the service description indicated on the tyre's sidewall (such as the speed rating or load index) the tyre is deemed unsuitable for the use and prosecution could follow. With a maximum penalty of £2500 and three penalty points per faulty tyre, it's not something you will want to get wrong.
Tyre size
The size of the tyre is the easiest thing to get right, and if your tyre fitter gets this wrong, you are shopping in the wrong place. It's not unheard of for unscrupulous fitters to try and sell you the wrong size because they have it in stock, or to say that tyres are "basically" the same size. The thing is, if it's not exactly the same size as the tyre on the other side of the van, it's not the same and it's not legal.
Check your caravan's handbook against the chassis plate and the tyres actually fitted. Not all chassis plates carry the tyre size and handbooks are often lost, but it's useful to know what was fitted and ensure they are fitted now.
A common caravan size is 175/13, and that's what we will use as an example. A 175/13 tyre refers to a tyre with a tread area that is 175mm wide with a 13in rim. It may seem strange, but this mix of metric and imperial measurements is the standard.
If the size is 175/70 13, that refers to the depth of the tyre's sidewall or profile. The '70' refers to the tyre wall being 70% of the tread width. In our example tyre, that would be a sidewall of 122.5mm, as this is 70% of 175mm. If there is no second number, the tyre profile is standard, which translates to 82%. Anything lower than 82% is considered
a low-profile tyre.
To be legal, the tyres fitted to the caravan need to be the same size at either end of the axle. If there is a size published on the chassis plate, the tyres fitted must match.
Tyre type
Establishing the type of tyre is quite involved. There is a distinction between commercial and car tyres. Both types are suitable for caravans, but you cannot mix commercial tyres with car tyres on the same axle, so you need to know which type you have.
The markings for a commercial tyre will say 175/13C, the 'C' suffix indicates that they are a heavier duty commercial type. You may also find '8-ply' or '8PR' marked
on the sidewall to indicate they are of heavier construction. If these markings are absent, it is
a regular-duty tyre.
The tyre specialist we spoke to said he always recommends commercial tyres for caravans as the extra strength, ease of availability and negligible cost difference between these and regular car tyres make it an obvious choice, and many popular caravan sizes are more readily available as commercial tyres.
A tyre's speed rating should also be noted. Typically, tyres of the correct size and type for a caravan are 'S' rated which makes them suitable for all speeds up to 112mph, which is more than enough for any caravan.
Load Index
Being a caravanner these days involves a little maths knowledge to work out your 85% ratios and so on, and it's important to do the same with your tyres. You need to know the MTPLM of your caravan. We'll use an example weight of 1450kg. You need to work out 110% of it. The easiest way to do that is to divide the MTPLM by 100 and then multiply it by 110. Now divide that number by the number of wheels on your caravan, excluding the jockey wheel. For our example caravan, that gives us a figure of 797.5. Armed with this, we can make sure that we get tyres with a suitable load index.
The load index is expressed as a numerical code on the tyre, with either two or three numbers. We've put some of the most popular sizes in the table above, but for our example, 797.5Kg corresponds to a minimum load index (LI) of 73. It's important to round up rather than down when choosing caravan tyres as this increases the safety margin. Often, the nearest matching LI rating will be considerably higher than is necessary. This is not a problem, but a lower rating is a safety issue.
Tyre care
Ideally, during winter, your tyres will be replaced by 'winter wheels' stands and stored, but storage sites don't like immobilised caravans and it's very time consuming to set them up. If you can keep the tyres indoors, stand them up on their tread or the sidewalls, moving them occasionally and keeping them away from solvents and bright sunlight. Ensure they are clean before they are put away, too.
For on-van storage, maintaining tyre pressures minimises the chances of sidewall damage and covering them with plastic will limit weather damage. Turn the tyre occasionally to prevent flat surfaces. Cleaning with a regular caravan shampoo will stop grime damaging the surface, but avoid using pressure washers directly onto tyres as the high pressure water can degrade the rubber and cause problems once on the road.
Our thanks to…
Northwood Hills Tyre and Battery, Tel 01923 840113
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