barge1914
Full Member
- Posts
- 1,918
- Likes
- 3,264
Certainly agree on M+S on all 4 wheels...and the spare.By "stiffened" sidewall I would think that that means extra reinforcement to be able to take the higher maximum pressure specified.
The rubber of the tyre being basically a bladder, it gets its shape and structure and strength from the strength of, and way that, the plies are laid up inside. And the higher the pressure inside the stiffer it becomes.
I suspect that say a van tyre running at 65 psi would be similarly "stiff" to a camper tyre run at 65 psi, rather than 85.
85 is 30% higher than 65, so the tyre must surely be significantly more strongly built to withstand this, when you consider the overall pressure on the total area of the sidewall it is enormous. All held in by just two windings of polyester strands in the ones in the picture above. Perhaps those plies are much stronger ones, or more tightly wound ?
Since Dethleffs specify 65 rear 60 front, and fitted van tyres originally, not camping ones, from new, and my weighbridge tests show that both axles are comfortably within their plated weights, that's good enough for me.
Besides, when I replaced the originals I uprated them to the wider ones that the Fiat handbook show as correct, there are two options given for the same wheels, and the wider, slightly lower profile ones have a higher load rating, so I have more margin.
But that's just my setup, and I do realise that some motorhomes with pitifully small payload allowances are sometimes run heavily overloaded because the owners, even the dealers, pay no attention to this and just pile stuff in and add stuff on, as long as there is room for it and have never visited a weighbridge to check, or just prefer not to know. So perhaps that's when a stronger constructed camper tyre, run at maximum pressure, would withstand the abuse much better.
If the manufacturer fitted camping tyres originally it would be sensible to keep on choosing them, they may have anticipated them being run overloaded and chosen them as a prudent precaution.
Just my speculation,
By the way, I like to have M+S all round, I wouldn't want them only on the front drive wheels. In poor conditions with the rears giving far less grip (and under the heavier load) the tail could slide out unpredictably and suddenly, you won't get much warning from e.g steering feel, and no amount of electronic driver aids will help if basically the rear end is no longer stuck to the road.
I have run my present van (of similar weight to the new one) for the last 5 years on Vredestein all Season tyres at 4.7 bar, as recommended by Vredestein, to no ill effect and with much improved grip in winter. Previous Continental campers at 5.5bar as recommended by Fiat were like driving on concrete wheels and slipped like mad on grass; when I reduced to the lower pressures recommended by Continental the ride improved considerably. Continental reckoned Fiat doesn’t know how the base vehicle will be loaded when they send them to the converters so they play safe and recommend the max pressure...which is over top for all but the heaviest vans.
The fact remains that there is no purpose made camper tyre that qualifies for winter use in Germany. Hence in Germany and other Alpine countries the use of all season commercial van tyres such as Agilis Crossclimate is common on motorhomes, as indeed it is on commercials.