nigee Posted September 3, 2012 Share Posted September 3, 2012 Hi i have 215/70/R15 CP on the front and 225/70/R15 CP on the rear is this normal , the plated wieght is 3700kg GMV can any one shed some light on this thanks :-D Link to comment Share on other sites More sharing options...
colin Posted September 3, 2012 Share Posted September 3, 2012 Make and model might help anyone replying. I would say it's fairly unusual, I have a vehicle with different size tyres front and rear but I don't think major manufacturers like doing this. Link to comment Share on other sites More sharing options...
Keithl Posted September 3, 2012 Share Posted September 3, 2012 Hi Nigee and welcome to the forum, Without more details I would guess that a previous owner has increased the plated weight (possibly from 3,500 kg) and has had to increase the load carrying capability of the rear tyres to do so. Changing from 215/70R15 to 225/70R15 changes the load index from 109 to 112 (at least for Conti Vanco's). This will increase the load carrying capacity of the rear axle from 1854 kg to 2016 kg (according to the Tyresafe MH leaflet). What the person who changed the tyres should really have done would be to have changed all 4 (or 5) tyres, not just the rears. BTW What size spare do you have? (If you have one that is) As using odd size tyres on the same axle is illegal (as well as dangerous and possible damaging to your drivetrain). Keith. Link to comment Share on other sites More sharing options...
nigee Posted September 3, 2012 Author Share Posted September 3, 2012 Hi thanks for replying i have a 2004 Autocruise Starblazer 3.700 KG GVM 1st axle 1,750 kg 2 nd axle 2,240 kg , the fronts are both 215/70r15 the rears are 225/70r15 the spare is 215/70r15 the payload is 530KG , they are all Michlens camping , thanks N Link to comment Share on other sites More sharing options...
Keithl Posted September 3, 2012 Share Posted September 3, 2012 You are running your rear tyres at their absolute limit for load at 2,240 kg axle loading! To support this they must be inflated to 5.5 bar (80 psi) and this ONLY applies to Camping tyres (CP marked) (Info from Tyresafe MH leaflet - Sorry but I only have a copy not a link). From the same source the recommended Max axle loading is as I quoted earlier, 1,854 kg at 4.82 bar (70 psi). Also be warned that it will be dangerous to use your spare on the rear as it will potentially be overloaded beyond it's individual limit of 1,030 kg to 1,120 kg (again only at 5.5 bar). I would advise changing it for a 225 section as whilst still illegal it will at least have the correct higher load rating for the rear (but again it must be a CP tyre). As said before the best option would be to change spare AND fronts for 225 section CP tyres then you will remain safe and legal no matter what. I'm sure others will follow with more advise but this is my opinion only. Keith. Edit, Found a Link to the Tyresafe MH leaflet I keep referring to! Link to comment Share on other sites More sharing options...
nigee Posted September 3, 2012 Author Share Posted September 3, 2012 Many thanks for your reply , just checked my rear tyre pressures and they were both 65 psi , i will go to the garage tommorow first thing to put the correct pressure in, then ring the salesman up to ask why he sold me a motor home with the wrong tyres .cheers N Link to comment Share on other sites More sharing options...
George Collings Posted September 3, 2012 Share Posted September 3, 2012 Before blowing your tyres up suggest you check their sidewalls for recomended maximum inflation pressure. For most it will be 65psi. Check with the tyre manufacturer if in doubt. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 4, 2012 Share Posted September 4, 2012 The normal tyre size for a 2004 Peugeot Boxer-based motorhome with a 3500kg chassis would have been 215/70 R15. Like Keithl I thought that nigee's Starblazer's tyre-size difference might have been the result of a previous owner uprading the vehicle's maximum overall weight, but a contemporary copy of "Which Motorcaravan " magazine quotes 3700kg as the standard 'chassis weight' for a Starblazer. If nigee's motorhome has been replated to have a rear-axle maximum permitted load of 2240kg, then 225/70 R15 tyres will be needed at the rear to meet that (potential) load. I can think of one instance on this forum where a forum-member did exactly what seems to have happened here - uprating the rear-axle maximum weight limit and going from 215/70 R15 to 225/70 R15 tyre size. As far as I'm aware this is perfectly legal, so nigee may have difficulty convincing the person who sold him the motorhome that it has "the wrong tyres". Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 4, 2012 Share Posted September 4, 2012 I don't know how old the tyres are (though from the description, I suspect possibly several years old) but for maximum safety and versatility, it would be wise to do three things. First, and most important, take the van, fully laden, to a weighbridge, and check not only the actual overall weight, but also the load on each axle. Don't forget to do this with both driver and passenger aboard! This is a van with a large "garage", and a very long rear overhang, meaning all loads behind the rear axle will add more that their self-weight to that axle, reducing the front axle load correspondingly. That rear axle will be very easy to overload, even with the added margin provided, at 2,240kg. If that gives an acceptable result, look closely at the tyre date marks and if any are 5 years old, or older, but especially if around or over 7 years old, take to van to a reliable tyre specialist and ask them to check for cracks etc. IMO, it would make sense to replace the two front tyres, plus the spare, with the higher rated tyres, fitting the two new tyres at the rear, bringing the best of the two existing rears to the front, and relegating the less good rear tyre to spare duty, inflated to 80psi. Then, as stated above, if you have the misfortune to get a flat, you can legally fit the spare on any axle without fear of overloading it, and will be able to continue your journey in safety once the pressure is adjusted. That should give complete peace of mind. If in doubt, "Google" tyresafe and, once onto their website, enter motorhome tyres into their search box and look for the .pdf download tyre safety information sheet. In that, you will find all tyre sidewall markings explained, and an idea of the pressures appropriate for various axle loads and tyre ratings/profiles. It would still be wise, however, to contact the tyre manufacturer's technical department to verify that they fully agree the Tyresafe information. On this van, as it seems likely to be rear heavy, I would definitely stick with CP rated tyres, and have the new ones at the rear. In practical terms, that is likely to mean Michelin Agilis Camping tyres, since AFAIK, Continental's Vanco Camping is not available as 225/70 R 15, and the Pirelli Camping seems almost unavailable in UK. You may find the Michelins difficult to source, and may have to resort to the internet for suppliers. If so, I have previously found Camskill Tyres excellent, though getting someone to fit customer supplied tyres can also be a bit of a problem. Hey, ho! :-) Finally, I would then check the appropriate tyre pressures for the actual tyre size and axle loads with the manufacturer. It is probable you will need to run the rears at, or close to, the maximum pressure, because that garage, when laden, will load the rear axle very heavily. However, that simply means the front axle will run light, meaning the front tyres are liable to be somewhat over-inflated for their actual load. Not dangerous, but makes for a hard ride, rapid wear in the centre of the tread band, less efficient braking, and possibly an exaggerated tendency to "tramline" over road irregularities. Once off road, be very cautious about driving onto soft ground. Tail heavy FWD vans very easily get stuck on soft, slippery ground, as the front tyres cannot develop enough traction to drag the rear off. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 4, 2012 Share Posted September 4, 2012 There are a number of on-line adverts for 2004 Autocruise Starblazers and these confirm the 3700kg maximum overall weight figure. Referring to a 2004 Hobby handbook, the maximum axle-weights of a Ducato/Boxer 3500kg 'non-Maxi' chassis using 215/70 R15C tyres were 1750kg(front) and 2000kg(rear). The axle-weights total of 3750kg indicates that a 3700kg overall weight would (just) be acceptable, though unusual. This advert http://www.becksmotorhomes.com/vehicle/2004-autocruise-starblazer shows that a 2004 Starblazer advert has a long rear overhang and rear garage - a recipe for potential rear-axle overloading. I don't believe Autocruise will have originally fitted bigger tyres on a Starblazer's rear axle, so it's probable that nigee's motorhome started life with 1750kg(F) and 2000kg® maximum axle-weights. If that's so, and the vehicle's rear-axle capacity has been uprated from 2000kg to 2240kg at some stage to combat rear-axle overloading, the vehicle's weight-related data-plate(s) may reveal evidence of this. Link to comment Share on other sites More sharing options...
Keithl Posted September 4, 2012 Share Posted September 4, 2012 Brian Kirby - 2012-09-04 11:55 AM If in doubt, "Google" tyresafe and, once onto their website, enter motorhome tyres into their search box and look for the .pdf download tyre safety information sheet. In that, you will find all tyre sidewall markings explained, and an idea of the pressures appropriate for various axle loads and tyre ratings/profiles. It would still be wise, however, to contact the tyre manufacturer's technical department to verify that they fully agree the Tyresafe information. Derek, I did post a direct Link to the Tyresafe leaflet in an earlier post. :-D Keith. Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 4, 2012 Share Posted September 4, 2012 That was me Keith, not Derek! :-) My apologies, I missed the link in your post, but it is indeed the document I was referring to. Link to comment Share on other sites More sharing options...
nigee Posted September 4, 2012 Author Share Posted September 4, 2012 Many thanks for all your comments and advice , the rear tyres are marked 04 and 05 , as for the front ones i cant find a date stamp , i have found the certificate for the suspension upgrade which included Kuhn air suspension ,it states front tyres 225/70R15 rear tyres 225/70 R15 , i will now have to buy four new tyres and keep the best 225 for the spare , the spare is a brand new 215/70R15 which the dealer fitted on the day of purchace hope fully they will swap it for the correct tyre , cheers all Nigel Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 5, 2012 Share Posted September 5, 2012 Nigel There have been a few earlier forum threads relating to Autocruise and the company's use of a Kuhn air-assistance on the rear axle to upgrade a motorhome's load-carrying capability. http://www.outandaboutlive.co.uk/forums/search/query.asp?action=search&searchforumid=all&keywords=kuhn&author=&days=&Submit=Search There's also a mention here http://www.motorhomefacts.com/ftopic-58460-days0-orderasc-0.html I fully expect you are aware of this, but it may be worth highlighting that Autocruise's uprating exercise will have (or should have!) placed your Starblazer in Vehicle Excise Duty (VED) Tax Class 10 (Private HGV) currently charged at £165 annually. The 3700kg weight also has driving licence implications (a minimum C1 entitlement will be needed). Link to comment Share on other sites More sharing options...
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