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Monday, 21 January 2013

Winter Tyres - Part 3. Buying and using the tyres

Having checked various suppliers, locally and on the Internet, for availability for our size and load rating of tyre, the decision narrowed down to a choice between the Continental Vanco Four Seasons or the Michelin Agilis Camping. At the time the Vredestein All Season wasn’t readily available in our size and load rating. As I found, just because a website lists a certain tyre, it doesn’t necessarily mean that it is in stock or even quickly sourced. 

The choice eventually narrowed itself down to the Michelin, simply because they were available next day, whereas I would have to wait 10 days for the Continentals. Though I was hankering after the Vanco’s, I did have some reservations about their Euro noise rating and in the end, the price differential was negligible, so I settled for the Agilis Camping, and as a safe bet. 

Happily, Xpress Tyres in Falmouth, Cornwall, gave us a telephone quote, including fitting, which beat all others, outdoing even the Internet firms when delivery and fitting was included.

Xpress tyres beat even the best internet quote I had - for fitted tyres

GPS: 50.1543 N, 05.0942 W

Other sites to try:

The old, the very old, spare - note the long split in the top tread!

And the new, not just a better tread, but a better compound

The crucial - to comply with the law in certain countries - M+S mark

How did the new tyres perform on the road?

Instantly we drove off, a radical change was apparent. Compared to the old Michelin Camping XC’s these were quiet, seriously quiet. A low, almost discernable rumble, that I had taken to be transmission noise, totally disappeared on smooth roads.
The removed Camping XC’s were old, too old, but the van now also felt more surefooted in both cornering and braking in the dry. A great start.

It wasn’t until we were in Germany and coming down a steep hill in the rain into a corner, that I suddenly realised how much more confidence I had in the handling of the van. Obviously new tyres should give a better performance than old, but this was better than the XC’s had ever been. The newer technology in the Agilis is a quantum leap over the old.

The acid test was still to come however – how would they perform in ice and snow? When we arrived at the Wohnmobil park in Xanten there was still a layer of ice and snow on the rising gravel track, but first we had to manoeuvre in and out of the snow covered service bay. It was well below freezing and the snow was crusty but we accomplished both movements without a moment’s slip or hesitation – something we would have never done on the old tyres. Optimistically, they were looking good.

Another test came in Wernigerode, in a super little stellplatz just on the edge of the old town. We were late arriving and only had the option of a muddy corner near the barrier. I reversed in without a hint of wheel spin. A week or so later we had to leave to get some more Autogas. It had rained incessantly for days and our muddy little corner was now awash in places, we would have to drive out through a puddle. 

As I eased out the clutch the van faltered and I thought, “here we go, not as good as I hoped”. Then there was a bang and the rear brake pads, which had lain and rusted under the handbrake, snapped away from the disc. The van then moved forward through the mud as if nothing had tried to hold it back. Now, I was well impressed. 
I got out to photo the track, and was intrigued to see the imprint that the deep side cuts had made in the mud. With the old tyres, we would have had to inch our way forward, strip by strip on the grip pads, never mind having the grip to snap free the seized brake pads!

 Enough grip to snap off the seized rear brake pads!

Note the imprint of the deep side cuts

At the elevated Rosstrappe hotel, there is a large sloping terraced car park to accommodate the walkers and mountain bikers that enjoy the area. This was empty apart a solitary car, and I used it to do a sweeping three-point turn on a few centimetres of loose snow. Not a glimmer of a slip or spin, something that the old tyres would never have done, I probably wouldn’t even have attempted it without putting the chains on.

A quick three-point turn? No problem.

The tyre that did the business!

At Altenbrak-Wendefurth, on a deserted stellplatz by the forbidding wall of a huge reservoir we stayed the night at minus 6.5°. The thermometer hadn’t moved at all when we left amidst flurries of fresh snow. I pulled off smoothly with no worries and even succeeded in accelerating without spin. Showing off, I managed to get some brief spin accelerating from standstill.

Even managed to acclerate in this stuff! (minus 6.5 °C)

Finally, in a campsite in Walkenried we had a functional loss of grip. Trying to pull the van forward up a single ramp at the rear to level it out, the differential gave up and the wheel on the same side of the ramp spun, but this trick can be difficult to do on the best of surfaces. But, reversing up the same ramp was accomplished with ease. Will I ever need the chains again?

Reversing up the ramp? - no problem.

What have we learnt?

This article all started when I got asked the question: “Does the Law in Europe require you to fit winter tyres?” I answered by saying (incorrectly) that I didn’t think so and that we just managed with snow chains when we needed to. 

In some countries winter tyres are still only a recommendation, but the reality as I see it now is: “You would be nuts not to fit at least an all-season tyre, even a full winter tyre, not only to protect yourself from the long arm of the law, but for the sheer benefit of having mud and snow capable wheels on your van” 

Our new tyres (in comparison to the old Michelin Camping XC’s) have been a revelation, not only for their performance in the mud and snow, removing virtually all concerns about manoeuvring in those conditions - and the hassle of chains, but also for their surefootedness in wet conditions and their quietness, which is exceptional.

If you can satisfy yourself as to your load ratings, I see no reason not to fit an “all season” tyre with the M+S mark. The Euro label ratings show the Continental Vanco and Vredestein Comtrac offerings to be slightly noisier than the Michelin Agilis Camping, but we have found the Agilis to be so quiet, that may not bother you. The all-season tyres may even have the edge on grip over the Camping, but I am now inclined to believe Michelin’s claim that their rubber compound is more flexible than a standard summer tyre.

We have just watched pictures of cars and vans skidding all over the place in the UK, on slushy roads that wouldn’t now give us a moments hesitation with these new tyres. It seems a bit of sick joke that so much expense and disruption is going on, all for want of some modern tyre technology. We are late to the party, but ”by, heck” we are converts!

In order to buy your new tyres, you need to know exactly what you are asking for. This appendix below covers sizes and terminology, plus the all important load ratings.

How are tyres specified? 

Motorhome tyres and wheels, generally come under Light Truck or LCV (Light Commercial Vehicle) sizes and ratings, which can limit the range of tyres available, particularly at the high load ratings specified for some motorhomes.

The stream of code on the tyrewall is known as the “Tyre Size and Service Description” and for our original motorhome tyres reads: 215/75 R16C 113/111 Q, where the R stands for Radial and the C for Commercial or Camper (depending on your source!) and Q is the speed index, in this case, up to 100 mph.

 "The Tyre Size and Service Description"

What do you actually need to know to order new tyres?

For the common motorhome built on a Fiat Ducato, Ford Transit, Mercedes Sprinter, Renault Master, etc. the rim size is the first criteria and for most vans will be 15 or 16 inches. Our van has 16 inch rims.

Next to be specified is the nominal tyre width, for our van, 215mm. Quoted next to this, normally with a forward slash between, is the nominal aspect ratio - the tyre height as a percentage of tyre width. For our van it is 75, it is 75% as high in section as it is wide.

Additional to this will be a load rating – a number to indicate the maximum safe load per single tyre in kg. For our van it is 113/111, indicating, from the appropriate tables, a safe load of 1090/1150 kg.

Armed with this data it is possible to specify and search for a suitable tyre on the Internet or from your local dealer. The speed index is not really relevant as any suitable tyre is likely to have a rating in excess of the speed your motorhome is likely to travel at, but the load rating is very important. 

For safe tyre loading it is recommended by the UK tyre industry that the maximum all up weight or “maximum technically permitted mass” (MTPLM) - as shown by putting your van on a weighbridge - does not exceed 90% of the tyre load capacity as indicated by the tyre load rating.

Theoretically, for a fully loaded standard 3.5 tonne van, the load on each tyre should be 3500 kg divided by 4, that is, 875 kg. The maximum recommended load on each tyre would thus be 875 x 90%, that is, 787.5 kg. 

From the tables, the nearest load rating to 787.5 kg is 800kg, equating to a tyre load index of only 100, but our tyres have a 113 rating? The reason for this is to take into account the fact that most vans will be more heavily loaded at the rear - particularly motorhomes that tend to spend life fully laden to the gunwales!

Most weighbridges will only give axle loads, front and rear, (unless of course you meet one of those friendly policemen with their portable load cells that fit under each wheel) so it probably makes more sense to take the tyre load index as a starting point. 

For a 113 index tyre, the theoretical maximum loading per axle will be 1150 kg x 2, that is, 2300 kg. The maximum recommended loading, however, would be 2300 x 90%, that is, 2070 kg. 

Maximum all up weight for both axles would thus be 2070 x 2 = 4140 kg, a good safety margin for a 3500 kg van. The bottom line of course, is that the rear axle load limits are not exceeded!

When you are inspecting your tyres, old or new, another important marking is the four digit number used to indicate the batch production code and thus the date of manufacture, e.g. 2212 would indicate the 22nd week of 2012. Check this before your new tyres are fitted, if they are more than a year old you might wish to reject them as the rubber compound will have already aged and hardened slightly. Five years is generally considered to be the safe working life of a tyre from an age point of view, but as long as the tyre is inspected properly each year, its life may extend depending on the conditions and use it has been subjected to.

Lastly, but not least, is the maximum indicated inflation pressure. Some  “Camper” tyres may have higher maximum pressures than light commercial tyres because of the anticipated hard life they will lead. For example, many LCV tyres have a maximum pressure of up to 66 psi (4.5 bar), but a camping specific tyre may allow pressures to be set up to 90 psi (6.2 bar). It’s very unlikely that you would want or need to run at such high pressures though - at 90 psi, the tyre casing would be very rigid, giving a very hard ride, and increased wear and tear to the fabric of the motorhome.

There are tables available that indicate the appropriate pressure for the individual tyre loads, and again the only way to correctly establish them is to put your van on a weighbridge, when you are fully loaded with your normal kit, and get those axle loadings!


Tony Roberts said...

Do you need to fit winter tyres on all wheels or just the driving ones? We have a tag axel motorhome so six winter tyres would be rather expensive!

Ian and Sue said...

Hi Tony

I am not a tyre expert, I just read everything I could find on winter tyres before I wrote the articles. I am afraid that the answer to your question based on that is yes, you probably should. The logic given is that the last thing you want is the tail of your vehicle swinging out of control – that is likely to be more destructive/traumatic than reduced braking effect going ahead. Therefore your best tyres should be on the rear wheels, even with front wheel drive. Presumably you have brakes on the extra axle, therefore you would not want to reduce the grip on that axle because of the risk of a skid. A mis-match of tyres is similarly not recommended because of unpredictable effects.

Personally, I have found the extra grip of the winter tyres to be a revelation in slippery conditions. If you shop around and can cut a deal (should be even easier with six tyres!) you shouldn't pay that much more than for a regular tyre. Once bought you will only have to replace the front tyres every two years of so, depending on your mileage, as the rear hardly seem to wear at all.

Hope this helps, and good luck. Happy travels!