Don Madge Posted August 7, 2008 Share Posted August 7, 2008 A very useful link from the Caravan Club, it confirms approximately the tyre pressures that I've been running at rather than what Fiat state in the vehicle handbook. Also thanks to PJ. http://www.tyresafe.org/data/files/motorhome%2008.pdf Regards Don Link to comment Share on other sites More sharing options...
Itexuk Posted August 7, 2008 Share Posted August 7, 2008 Does not list my tyre size: 225/75/R16 CP 116R Not sure if it correct but I'm using 60psi front and rear. Link to comment Share on other sites More sharing options...
Don Madge Posted August 7, 2008 Author Share Posted August 7, 2008 Itexuk - 2008-08-07 1:11 PM Does not list my tyre size: 225/75/R16 CP 116R Not sure if it correct but I'm using 60psi front and rear. Does not list mine either. 205/70 R15C Don PS. Don't ask, I guessed 8-) Link to comment Share on other sites More sharing options...
fred grant Posted August 7, 2008 Share Posted August 7, 2008 don u is gettin fuzzier my the minute my biddy. cant u go to a proffessional and get it sorted?? alice Link to comment Share on other sites More sharing options...
panagah Posted August 7, 2008 Share Posted August 7, 2008 Don Madge - 2008-08-07 9:45 AM A very useful link from the Caravan Club, it confirms approximately the tyre pressures that I've been running at rather than what Fiat state in the vehicle handbook. Also thanks to PJ. http://www.tyresafe.org/data/files/motorhome%2008.pdf Regards Don Thanks for that Don, I run mine at 70 and it appears right. Link to comment Share on other sites More sharing options...
Mel E Posted August 8, 2008 Share Posted August 8, 2008 Don, I agree that this is a most useful list. Being a pedant, however, I would recommend that anyone who runs their tyres at a different pressure from that recommended by either the base vehicle manufacturer or converter writes a brief letter 'for the record' to their insurer attaching the evidence and checks that they have put the letter on file. There was a case posted on this forum some time ago by a man tussling with his insurance company because his vehicle was a write-off after a blow-out and the other tyres were above recommended inflation levels and the underwriter was rejecting liability. You cannot be too careful! And this applies especially to anyone with a van conversion rather than a coach built, because insurers will see no reason why a van conversion needs different pressures - it's a loaded van after all! Mel E ==== Link to comment Share on other sites More sharing options...
davenewellhome Posted August 13, 2008 Share Posted August 13, 2008 Many thanks for this Don, it has at last enabled me to get the correct pressures for my tyres (budget brands so not easy to contact manufacturers for advice). Weighed the 'van yesterday fully loaded to go to the Malvern show and still got 200 KGs to play with (although only 60KGs spare capacity on rear axle). Anyway, from the chart I've established that 40 psi front and 57 rear is more like it than the 40F 45R that I had been running. May even get better fuel consumption now too ;-) . D. Link to comment Share on other sites More sharing options...
cwmgiedd1 Posted August 13, 2008 Share Posted August 13, 2008 I have an Ace Sienna with 215/70 R15CP Continental tyres. The sticker in my vehicle indicates Front = 5bar(73psi); Rear = 5.5bar(80psi). These seemed rather high to me, so I weighed the van laden (except empty water tank) and emailed the tyre manufacturer with the axle weights (Front = 1440kg; Rear = 1560kg) I had a reply today - Front = 3.25bar(47) Rear = 3.5bar(50). I am now in a quandary, bearing in mind the huge discrepancy! Link to comment Share on other sites More sharing options...
paul2 Posted August 13, 2008 Share Posted August 13, 2008 what am i doing wrong when i try this link all i get is a blank page? Paul Link to comment Share on other sites More sharing options...
tp002c784tp002c784tp Posted August 13, 2008 Share Posted August 13, 2008 I have done the same with my present van as I did with my last one, I weighed the vehicle loaded for Holidays full water tank, full fuel tank and emailed Michelin with the results. With my present van ( Fiat Lunar Roadstar 2.8jtd ) I have reduced with the results from Michelin, Front from 80psi to 50psi and rear from 80psi to 57psi I now carry this print out in my vehicle folder in case I am ever stopped I now feel that the vehicle has better road holding and is a much better ride. Terry Link to comment Share on other sites More sharing options...
peejay Posted August 13, 2008 Share Posted August 13, 2008 paul2 - 2008-08-13 6:29 PM what am i doing wrong when i try this link all i get is a blank page? Paul Apparently, it sometimes doesn't work if you try to download direct from a pdf link. :-S Try right clicking on the link then click 'save target as' and save it on your computer. That might work. PJ Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 13, 2008 Share Posted August 13, 2008 cwmgiedd1 - 2008-08-13 6:09 PM I have an Ace Sienna with 215/70 R15CP Continental tyres. The sticker in my vehicle indicates Front = 5bar(73psi); Rear = 5.5bar(80psi). These seemed rather high to me, so I weighed the van laden (except empty water tank) and emailed the tyre manufacturer with the axle weights (Front = 1440kg; Rear = 1560kg) I had a reply today - Front = 3.25bar(47) Rear = 3.5bar(50). I am now in a quandary, bearing in mind the huge discrepancy! It would have been better to weigh with full water, as the tank is heavy (1Kg per litre). Were the occupants all on board? Were the gas cylinders all present and full. Was the fuel tank full? If not, your results will be a bit suspect. Also note that if your waste tank is rear mounted any waste water will transfer more than its actual weight to the rear axle.Truth is, that the load in a motorhome continually varies as food, drink, waste, gas, fuel, and occupants come, go, and move/are moved around. I think it is a bit unwise to tailor the running pressures too closely to the weighbridge results, but it definitely worth treating the the new pressures as food for thought. Try re-weighing with everything on board and full, but get the weighbridge ticket recording the axle loads. Then, run those figures past the tyre manufacturer again, and ask for them to be confirmed back to you in writing. Add 5psi as a safety margin both ends (to allow for the above variations) and see how it feels to drive.Never exceed the recommended pressures, as the tyres will definitely be overinflated, and on no account go below the tyre manufacturer's figure based on axle loads. If you don't like the results, you can always go back to the recommended pressures. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 13, 2008 Share Posted August 13, 2008 cwmgiedd1: The subject of ultra-high tyre pressures being specified by motorhome manufacturers for vehicles fitted with 'camping' tyres has been discussed regularly on this forum. The practice appears to stem from when Michelin first introduced the XC Camping tyre pattern and advised that (I quote from Michelin's Technical Handbook) "for maximum load conditions when used on mainland Europe it is recommended that the rear tyres are inflated to a pressure of 80psi." According to a Michelin spokesman, this recommendation was based on surveys revealing that a large percentage of Continental motorcaravanners were running their vehicles at or above rear-axle maximum permitted weight limits. Unfortunately, "80psi in the rear tyres" (and a similar high pressure for the tyres fitted to front wheels) has become standard advice, with Michelin's "for maximum load conditions" wording being ignored. With a relatively lightweight motorhome the effect of using such high pressures is totally predictable - the vehicle's ride is bone-shaking. It would seem from your statement that Fiat/Ace now choose to specify high pressures for all 'camping' tyres irrespective of make. As Brian says, when weighing a motorhome with a view to seeking advice on tyre-pressures from a tyre manufacturer, you really need to ensure that the vehicle is in its 'full to the brim' loaded state. Either that, or you'll need to factor in an axle-load allowance for fuel, water, passengers, etc. that the vehicle might possibly carry before getting in touch with the tyre manufacturer, or suitably increase the pressure figures the tyre manufacturer provides to allow for the 'missing' load. Like Continental, Michelin will provide pressure recommendations based on a vehicle's static axle loadings as measured by a weighbridge, but will normally recommend a 10% increase in the front tyre figure to better deal with weight transfer under braking and when cornering. One thing's certain, you do NOT want to be running your motorhome's tyres under-inflated and (to compensate for the empty water tank) I'd be tempted to opt for 3.5bar(front) and 4.0bar(rear) initially and see how that feels. (This is just idle curiosity, but presumably your Ace has high-pressure tyre-valves - either the metal clamp-in type or a 'rubber' HP snap-in design?) Link to comment Share on other sites More sharing options...
cwmgiedd1 Posted August 17, 2008 Share Posted August 17, 2008 Dear Brian, Thank you for your advice. All occupants were on board; full fuel tank, luggage; one gas cylinder; empty water tank; empty waste tank. This is how I normally travel. Your idea of adding 5psi each end to the weighbridge figures is a good one. Meurig Watts Link to comment Share on other sites More sharing options...
cwmgiedd1 Posted August 17, 2008 Share Posted August 17, 2008 Dear Derek, Thank you for your detailed response. My Ace has metal type valves which I presume are high pressure valves. I shall experiment with 3.5 and 4.0 bar which seems a good compromise between Fiat/Ace figures and tyre manufacturer figures. Meurig Watts Link to comment Share on other sites More sharing options...
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