steveandlisa Posted September 3, 2016 Share Posted September 3, 2016 Hi folks, Our first time on here and a subject that's probably been aired too many times! We`ve just bought a new to us a 2007 Swift Bolero. The reason for asking the question of tyre pressures is its running non CP tyres but 215/70/15 109 commercial tyres. I understand its quite legal to use these non camping tyres provided they`re suitably rated for the axle loads. The tyre pressure guide on the door pillar states 5.5bar 8-) this is for CP tyres, can anybody recommend a more suitable tyre pressure for my tyres fitted? PS maximum permissible axle weights are F1850kg - R2000kg Regards steveandlisa Link to comment Share on other sites More sharing options...
Cy.G Posted September 3, 2016 Share Posted September 3, 2016 The tyres will have a max pressure written on them im sure someone will advise but dont under inflate as it will generate too much heat . Axel weights are max but..... They cannot both be at max see the overall max on you plate . If either is on its max the other must be reduced so that they add up to the total max allowed . Link to comment Share on other sites More sharing options...
colin Posted September 3, 2016 Share Posted September 3, 2016 The pressure you quote is also the recommended one for the tyres you have, this is based on max axle loads, the only way you might be able to reduce them would be if the actual axle loads are less than max. Link to comment Share on other sites More sharing options...
Robinhood Posted September 3, 2016 Share Posted September 3, 2016 Not an easy question to answer definitively, and it would be interesting to know the manufacturer of the tyres (since the Continental tables are easily obtained). The best way of determining the correct pressures it to visit a weighbridge in fully loaded condition and ascertain the real axle loadings. Then try enquiring of the manufacturer the recommended pressures. However, running the non-Camping tyres at 5.5 bar is a no-no (they are not designed for the increased pressure relevant to CP tyres), so a bit of advice might be welcome. Accordingly, reference to the Continental tables for the same sized, non-Camping tyres gives roughly 4 bar (58psi) for the F1850kg, and 4.5 bar (65 psi, and the maximum recommended for this tyre) for the R2000kg. Be aware that these figures are given in good faith, but are only indicative (since the actual tyres and actual loadings are unknown) and I won't hold any responsibility for them. Unless you are severely overloaded, the actual front axle loading is likely to be quite a bit lower than max, and the rear is also likely to be a bit under, so lower pressures might be possible after weighing. (If they are Continentals, I'll try to dig out a current download link). Link to comment Share on other sites More sharing options...
Keithl Posted September 3, 2016 Share Posted September 3, 2016 Hi, Not knowing the make of your 'white van man' tyres the best information I can offer is the TyreSafe MH tyre brochure... http://www.tyresafe.org/wp-content/uploads/2015/12/motorhome-leaflet.pdf If you look at the top table on page 5 unfortunately it does not list your tyre size but if you look at 225/70 R15 these also have a load index of 109 and for your max axle loads give max pressures of 3.30 and 3.75 bar. I must stress that this is a totally unscientific way of getting pressures but does confirm your thoughts that 5.5 bar is too high. What you will have to do is get weighbridge figures for front and rear axles separately when fully loaded and then contact the manufacturer of your particular tyres for advice. Keith. Edit. RobinHood replied while I was typing but I think we are both saying the same thing. And here is a link to the Continental tyres book... http://www.conti-online.com/www/download/transport_bg_bg/general/tech_info/download/technical_data_book_pdf_bg.pdf you'll need to look at pages 22 - 23 which seem to confirm RH's 4.0 and 4.5 bar figures. Link to comment Share on other sites More sharing options...
Robinhood Posted September 3, 2016 Share Posted September 3, 2016 colin - 2016-09-03 9:34 PM The pressure you quote is also the recommended one for the tyres you have, this is based on max axle loads, the only way you might be able to reduce them would be if the actual axle loads are less than max. Colin, I suspect the 'van left Swift with CP rated, reinforced tyres, for which the 5.5bar rating is valid (though I would personally run at lower derived pressures)... BUT it would appear that replacements have been fitted that are C rather than CP-rated, and (in general) these tyres are not rated for 5.5bar, so it would be dangerous to use this. There's been much discussion on here as to whether running standard commercial tyres is a good thing; I personally have no issue (my last coachbuilt came from the factory thus equipped), as long as maximum axle loading and the (generally lower) maximum tyre pressures are observed. Link to comment Share on other sites More sharing options...
Robinhood Posted September 3, 2016 Share Posted September 3, 2016 Keithl - 2016-09-03 9:48 PM Hi, Not knowing the make of your 'white van man' tyres the best information I can offer is the TyreSafe MH tyre brochure... http://www.tyresafe.org/wp-content/uploads/2015/12/motorhome-leaflet.pdf snip you'll need to look at pages 22 - 23 which seem to confirm RH's 4.0 and 4.5 bar figures. I went there first, Keith, as it is easier to read, but found that the size was missing. The Continental 225/70 R15 figures are aligned with the lower ones you quote, so I think for the OP's size, the 4.0/4.5 values (subject to no overloading) are probably the best interim ones, and then go the weighing route. Link to comment Share on other sites More sharing options...
steveandlisa Posted September 3, 2016 Author Share Posted September 3, 2016 Brill forum, Response outstanding and I`m finding the information extremely enlightening :-) Link to comment Share on other sites More sharing options...
colin Posted September 3, 2016 Share Posted September 3, 2016 Robinhood - 2016-09-03 9:55 PM colin - 2016-09-03 9:34 PM The pressure you quote is also the recommended one for the tyres you have, this is based on max axle loads, the only way you might be able to reduce them would be if the actual axle loads are less than max. Colin, I suspect the 'van left Swift with CP rated, reinforced tyres, for which the 5.5bar rating is valid (though I would personally run at lower derived pressures)... BUT it would appear that replacements have been fitted that are C rather than CP-rated, and (in general) these tyres are not rated for 5.5bar, so it would be dangerous to use this. There's been much discussion on here as to whether running standard commercial tyres is a good thing; I personally have no issue (my last coachbuilt came from the factory thus equipped), as long as maximum axle loading and the (generally lower) maximum tyre pressures are observed. Whoops, my bad. Yes page 78/79 should be 4.5bar max for those axle maximums. NOT 5.5bar as in my earlier post. Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 4, 2016 Share Posted September 4, 2016 May I also suggest that you check the valves that were fitted along with the C type tyres? It is not unknown for regular car tyre valves to be fitted. High pressure valves (snap-in type I would think, but if clamp in valves were fitted - or retained that would be a bonus) should be used for the pressures most motorhomes need. The car valves tend to fail prematurely, some blowing out of the rim, so it is a worthwhile check. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.