Tyre Pressure/contradiction

[terryW]

My Autoroller has the correct tyres as specified in the Fiat handbook and the tyre pressures are as stated both in the fiat handbook and on the cab door pillar.

 

However the tyre wall states a lower pressure then these; I have contacted Autoroller and they inform me that the markings on the tyre walls are not relevant to the UK.

 

Anyone know if this is true and if so how do I know the maximum inflation?

[euroserv]

They are talking out of their derrieres. The markings are relevant to the tyre, not the market. That tyre could have ended up in any european country and others further afield.

 

This is wrong. Not the first time I have seen this either.

 

What make of tyre is fitted? The majority of X250's have shipped with Continental 16" or Bridgestone 15" tyres.

 

Nick

[terryW]

My thoughts exactly, they are Continental 215/70 R15 CP and the side wall states 69 lb the handbook states 79.5 lb!

[Randonneur]

The only way that you will be able to get the correct tyre pressures is to go to a weighbridge and get all weights and then send in an email to the tyre manufacturers, they will then give you the correct pressures. When you receive their email keep it with you in the van in case you have to produce it if you are stopped as this will be the evidence that you have the correct pressures.

[terryW]

Thanks I will try that, I have a friendly local business with a weighbridge.

 

many thanks for every ones your replies

[Robinhood]

terryW - 2010-10-06 5:52 PM

 

However the tyre wall states a lower pressure then these; I have contacted Autoroller and they inform me that the markings on the tyre walls are not relevant to the UK.

 

 

This is in fact likely to be true:

 

Many tyres are shipped with a pressure and load marking that is specific to the N American market, and (I assume) aligned to some local legislation there.

 

AFAIK, they are not generally shipped with such markings specifically applying to the UK.

 

The manufacturers state that these figures specifically DO NOT apply to the European Market, and whilst I can't vouch for your specific tyres, I have certainly seen tyres in use in the UK at pressures in well excess of the NA sidewall markings. (From experience and observation, I would expect the tyres you quote to be capable of handling those pressures, but I'm not an official expert).

 

BUT, and as posted elsewhere on this thread, as long as you are running within legal axle loading, if you use a weighbridge to ascertain real weights, I would expect Continental to recommend pressures well below those in the handbook/on the pillar (and an improved ride will result).

 

For background on both above items, dowload the motorhome tyre safety leaflet from:

 

http://www.tyresafe.org/tyre-safety/

 

HTH

[flicka]

Randonneur - 2010-10-06 6:31 PM

 

The only way that you will be able to get the correct tyre pressures is to go to a weighbridge and get all weights and then send in an email to the tyre manufacturers, they will then give you the correct pressures. When you receive their email keep it with you in the van in case you have to produce it if you are stopped as this will be the evidence that you have the correct pressures.

 

Then when contacting Continental get them to confirm the Maximum pressures also.

So, if you are stopped you will have the manufacturers advised pressures & that they are within the Maximum the tyres are designed for.

[Derek Uzzell]

Robinhood - 2010-10-06 6:49 PM

 

terryW - 2010-10-06 5:52 PM

 

However the tyre wall states a lower pressure then these; I have contacted Autoroller and they inform me that the markings on the tyre walls are not relevant to the UK.

 

 

This is in fact likely to be true:

 

Many tyres are shipped with a pressure and load marking that is specific to the N American market, and (I assume) aligned to some local legislation there.

 

AFAIK, they are not generally shipped with such markings specifically applying to the UK.

 

The manufacturers state that these figures specifically DO NOT apply to the European Market, and whilst I can't vouch for your specific tyres, I have certainly seen tyres in use in the UK at pressures in well excess of the NA sidewall markings. (From experience and observation, I would expect the tyres you quote to be capable of handling those pressures, but I'm not an official expert).

 

BUT, and as posted elsewhere on this thread, as long as you are running within legal axle loading, if you use a weighbridge to ascertain real weights, I would expect Continental to recommend pressures well below those in the handbook/on the pillar (and an improved ride will result).

 

For background on both above items, dowload the motorhome tyre safety leaflet from:

 

http://www.tyresafe.org/tyre-safety/

 

HTH

 

The tyresafe document actually says

 

"Note: The loads and pressures moulded on the sidewalls of many tyres are a North American requirement and do not apply in the UK and Europe."

 

It definitely used to be the case that this fact was made clear on the tyre's sidewall, but I think that may no longer be so. Nevertheless, I believe the tyres fitted to modern European-built motorhomes will normally carry some form of words indicating the tyre's maximum designated load-carrying capability and the appropriate inflation-pressure required to support that load.

 

I've yet to see a tyre where the maximum load (in words) did not tally with the tyre's load-index. For example, for a Continental VancoCamper 215/70 R15CP tyre the load index is 109, indicating that the tyre's maximum designated load-carrying capability is 1030kg. This limit will be repeated (in words and also showing the 'in lbs' equivalent) on the tyre's sidewall, together with the inflation-pressure (in psi and kPA) necessary to support that load (apparently 69psi in this instance). Similarly, the tyre-pressure advised will be the maximum beyond which the tyre should not be inflated.

 

Now, I've been down a slightly similar road to TerryW's. My 2005 Ford Transit-based Hobby's cab door-pillars carry Ford data-plates advising that an inflation-pressure of 79.8psi/5.5bar be used for the rear tyres. However, the tyres (Continental Vanco-8 215/75 R16C) carry sidewall markings indicating a maximum designated load-carrying capability of 1150kg at an inflation-pressure of 70psi.

 

When I contacted Ford(UK), warning them that data-plates being fitted to Transit FWD motorhome chassis with Vanco-8 tyres were advising an inflation pressure 10psi above the pressure shown on the tyre's sidewall, I got told the same story as TerryW - that the tyre sidewall markings weren't 'relevant' in Europe. It was suggested that I contact Continental about this. I said I had - Continental had told me that the 70psi figure was a maximum and warned me that it should not be exceeded.

 

Ford(UK) then argued that as the Hobby was a) a motorhome, b) a German-built motorhome, c) a German-built LHD motorhome, they couldn't easily access data about it via their databases. It was suggested that, as I was worried about the 79.8psi/70psi conflict, I should contact Hobby. I replied that I wasn't worried as I knew that the data-plate was wrong, but, as the plate carried the Ford logo and was plainly fixed on the vehicle in Ford's Turkish factory, I would have thought that Ford might want to explore the discrepancy further as recommending a tyre-pressure 10psi beyond the tyre manufacturer's designated maximum was surely a safety issue. I heard no more from Ford(UK), though I later learnt that it was eventually admitted that the data-plates were incorrect and replacement plates were provided to owners of affected vehicles (though I never got any!)

 

The reason for the Ford 'mistake' was that, when Transit FWD platform-cab motorhome chassis were introduced in 2004 they were all fitted as standard with Michelin XC Camping 'camping-car' tyres. These tyres did have a design capability of being inflated to 5.5bar - in fact Michelin themselves advised that this was the appropriate inflation pressure for XC Camping tyres on motorhome rear wheels. So the Ford data-plate's 79.8psi recommendation was OK safety-wise when the motorhome had XC Camping tyres. However, from mid-2005 these chassis began to be fitted as standard with Continental Vanco-8 'white van' tyres, with a 70psi maximum, but the Ford data-plate information wasn't altered to reflect this change.

 

When Michelin was the only manufactuer of 'camping-car' tyres, it was difficult enough for a motorcaravanner to obtain informed advice about tyre pressures. From TerryW's comments it seems that Continental (at least) is taking a different stance to Michelin reqarding its "CP" tyres. Continental appears to be considering its VancoCamper tyres as if they are 'white van' tyres, advising 'white van' maximum inflation pressures and marking the tyres accordingly. Michelin (I believe) continues to advise (and mark) high maximum inflation pressures for its camping-car tyres.

 

Fiat (and some motorhome manufacturers) used to recommend two sets of inflation pressures - one when the vehicle was fitted with ordinary 'white van' tyres and another (higher) set when the vehicle had (Michelin) camping-car tyres. In the latter instance, pressure recommendations of 80psi were the norm rather than the exception.

 

It's hard to see how this issue can be resolved as long as Michelin continues to actively recommend 80psi for its camping-car tyres (and marks the tyres thus), while Continental evidently acts differently. One things certain, if a tyre shows a particular inflation pressure on its flanks, then advice from the vehicle or motorhome manufacturer to use a higher pressure should be vigorously challenged.

[lennyhb]

My van has Continental 215/70 R15 CP tyres and above the Max inflation pressure 5.5bar it clearly states ""Due to the special service conditions of motor caravans it is permissible to increase the inflation pressure"

 

 

[Robinhood]

lennyhb - 2010-10-07 9:32 AM

 

My van has Continental 215/70 R15 CP tyres and above the Max inflation pressure 5.5bar it clearly states ""Due to the special service conditions of motor caravans it is permissible to increase the inflation pressure"

 

 

As far as I can tell from the technical documentation on the Continental site (It's reasonably clear, but you have to line two PDF pages up to get tables to match), this (5.5 bar) is the maximum pressure quoted for this CP-rated tyre, and the associated load table aligns directly with that contained in the "Motorhome Tyres" download I mentioned above.

 

Nonetheless, I believe Continental will advise lower pressures if actual (legal) axle weights are quoted to them, and it is worth doing that as a better ride is likely to ensue.

 

Picking up on Derek's point about non-camper tyres - my recently purchased Hobby has Continental Vanco (non camper) tyres fitted, and the "Ford Sticker" pressures for these are what I would expect for non-camper tyres (i.e. somewhat lower than previous vehicles with CP rated tyres) and in line with the recommendations for such non-camper tyres in the downloaded leaflet. They've obviously made the appropriate production-line adjustments. :-)

 

BTW, it occurs to me that the wording on the tyre defines a maximum *load* at a given pressure (i.e. that the maximum load is safe at that pressure), but *doesn't* define a maximum *pressure*. AFAIK the whole principle behind CP (camper) rated tyres is to allow for higher pressures to be used to allow for the particular usage patterns of camper vehicles.

 

I certainly wouldn't choose to exceed the quoted maximum load, but the above would explain the pressure question.

 

(Edited to add last two paras)

[terryW]

Just to short update as a thank you to all those who contributed. I have supplied my max axle loads as per the vehicle plate (Front 1750/rear 1900) and Continental have replied:

 

"Thank you for your recent query. It certainly is a popular question!

 

The pressures you require are as follows:

 

Service description: 109/107R

Front: 3.75bar - 54psi

Rear: 4.25bar - 62psi

 

Service description: 109R

Front: 4bar - 58psi

Rear: 4.5bar - 65psi

 

Regards

 

Craig Sterry

 

Product Support Engineer"

 

In short by following the handbook/vehicle plate my rear tyres were 1 bar over pressure.