Steve Burke has seen it all in his 30+ years in the tyre industry. In his role as Toyo Tyre Australia’s Tyre Technical Manager he’s responsible for carrying out quality assurance testing on new tyres arriving in Australia, as well as ongoing product development and technical enquiries. In his first guest blog, Steve explores the unique demands that caravans and camper trailers place on tyres, and common mistakes to avoid.
Tyre Inflation Pressures
Inflation pressures are one of the things I constantly see people get wrong - they’re often underinflated on sealed roads, or over-inflated off-road leaving them exposed to punctures. The simple fact is that correct inflation pressures will extend tyre life and most importantly avoid an in-service tyre failure - the most common of which is due to under-inflation (that is, the inflation pressure is too low for the load carried by the tyre).
The first step in determining the correct tyre inflation pressures for your van or camper trailer should be determining what it actually weighs. I highly recommend that you have your van or camper weighed in a loaded condition, less the tow-ball weight. With this information we will know the actual load supported by the tyres on your caravan or camper, from which your tyre manufacturer can provide accurate inflation pressure recommendations.
Why don’t we use the GTM as shown on the compliance plate? The GTM (Gross Trailer Mass) shown on the compliance plate is the maximum loaded weight recommended by the manufacturer, less the weight on the tow ball. The GTM is the maximum weight the tyres on your van or camper should be carrying. The actual loaded weight of your van or camper (less the tow-ball weight) can be less or more than what is stated on the compliance plate, and when it comes to determining accurate inflation pressure recommendations, we need to know the actual loads the tyres are being subjected to.
As well as determining the correct inflation pressures, it’s a great way to ensure your van or camper is legal regarding its loaded weight, and does not exceed the GTM or other maximum loads shown on the compliance plate. This article is about tyre safety, but weighing your van or camper when loaded can allow you to identify where there are compliance issues relating to weight so they can be addressed. Toyo Tyre Australia recommends using your van or camper trailer within the maximum capabilities specified by the manufacturer.
While you are weighing your van or camper, it is highly recommended you weigh your tow vehicle at the same time, for the same reasons. For the tow vehicle, front and rear axles will not load-share, therefore should be weighed separately so accurate tyre inflation pressures can be determined. Mobile weighing services can also measure the tow-ball weight to ensure it is within the manufacturer’s specifications. The correct tow-ball weight is essential for stability of your van or camper.
Where to weigh?
Your local public weighbridge can provide this service, keeping in mind not all weighbridges can provide separate axle weights for the tow-vehicle. Here is a comprehensive directory of public weighbridge locations all around the country:
https://www.industry.gov.au/national-measurement-institute/trade-measurement/weighbridges-used-trade/find-public-weighbridge
It’s also worth checking your local directories for mobile weighing services, which are now common. I’ve listed one for Sydney and Melbourne metro areas, but a quick search should uncover your closest provider:
Your Weigh
Sydney Metro, Wollongong and Southern Highlands
Phone: 0419 473 397
https://www.facebook.com/MobileVehicleWeighing/about
Downunder Weighing and Repairs
Melbourne Metro area
Phone: 0492 184 495
https://www.facebook.com/Dwnunderweighingandrepairs/about
Tyre Age
Due to slow wear rates and the seasonal use of vans and campers, their tyres usually outlive their safe service life before they wear down to the tread wear indicators. Therefore, only checking a van or camper’s tyre health by measuring the tread wear and overlooking the tyre’s age only tells us half the story.
So what is old?
A common industry standard is that when tyres are 10 years old from the date of manufacture, it is recommended they are replaced or removed from service regardless of the remaining tread depth or appearance.
The origin of this standard is advice from JATMA (The Japan Automobile Tyre Manufacturers Association). JATMA also recommends that all tyres be inspected after 5 years of service by a qualified tyre service person to identify any visible signs the tyres are not safe for continued use.
Tyre age from the date of manufacture can be determined by the last 4 characters (which will always be numbers) of the tyre’s serial number. For example, using the fictitious serial number ‘CXE31NH3718’ we can use the last four characters to decipher the week and year of manufacture. Our example tyre was produced in the 37th week of 2018.
Visible signs of ageing indicating tyres need replacing are:
- Large cracks in the tread grooves. Keep in mind some tyres will have small cracks between the blocks, which are normally safe for further use. If you are not sure, consult your local Toyo Tires Dealer
- Small cracks on the sidewalls
Other signs indicating tyres need replacing can include:
- Tyres are worn to the tread-wear indicators on any part of the tread
- Any cuts that expose cords or damage cords
- Circumferential or radial cracking on the lower sidewall or bead area. This indicates structural damage caused by under-inflation
- Bubbles / bulging above the bead or on the sidewall. This indicates structural damage caused by under-inflation or impact damage.
- Bulges in the tread area which may indicate a separation.
If you are not sure regarding the condition of your tyres, consult your local Toyo Tires Dealer.
Are Tyre Pressure Monitoring Systems (TPMS) Worthwhile?
In short, absolutely! We mentioned in our opening paragraph how important tyre pressures are to the performance and longevity of your tyres, so it should be no surprise that an accurate TPMS is a great investment.
A TPMS allows you to check your tyre pressures in real time, just by looking at a screen inside your vehicle. In the instance of a tyre losing pressure for whatever reason, a TPMS will allow you to identify a leaking or damaged tyre before it suffers a total failure. Especially in the instance of a camper trailer or caravan where the tyres on the rearmost axles might be difficult to visually inspect in the vehicle’s mirrors, a TPMS gives you critical data which improves the safety of your vehicle, van or trailer combination.
Replacing Your Original Equipment Tyres
For caravans and camper trailers, the compliance plate will specify the legal tyre requirements for your caravan or camper trailer. All compliance plates will include the manufacturer’s recommended tyre size. Some compliance plates include load and speed ratings. All compliance plates will include a statement regarding the tyres fitted being rated to carry the axle loads specified.
The tyre load ratings indicated by the maximum axle loads are the minimum requirements for your caravan or camper trailer.
It is highly recommended that the tyres fitted to your van or camper have a load carrying capacity that is at least 10% greater than GTM, however exceeding this 10% margin is always advisable.
Running a tyre too close to 100% of it’s load capacity doesn’t allow for extenuating circumstances, where load shift or road conditions might place stresses on the tyre that cause it to be loaded beyond 100% of it’s maximum load capacity. In isolation, these occurrences may not be catastrophic but constantly stressing your tyres in this way will lead to fatigue, and often failure.
To help shoulder these loads, the tyres will need to be run at their maximum cold tyre inflation pressure, which increases transmitted noise, vibration and harshness through the tyres and on to the vehicle’s suspension. Especially for those traveling on remote sealed roads or off-road, the transmission of an irregular road surface through your tyres and suspension can cause premature fatigue of your tow vehicle or van.
Switching to tyres with a greater safety margin between their maximum load capacity and your caravan or camper trailer’s GTM means your tyres can be safely run at lower inflation pressures, and provided that your trailer’s spring rates and dampers are appropriately matched to the load, can result in a smoother more comfortable towing experience, and less wear and tear on your ‘van or camper.
