Trye Pressures Again!!

[AnnPaul]

Many of you may have read my last message re trye pressures on my Rapido 7087F.

 

Front axle weight 1600 Rear 1860

 

About a year ago I rang Michelin Tryes and asked what pressures my tryes should be 215/70 15C

 

They told me then they should be F55 and R60

 

Rang them last week to check again, they quoted F70 R80

 

Rang them today only to be told they should be F55 R80 !!!!

 

Who else can I check with? Can I trust the experts!

 

Did not inform them of the discrepancy but I will. But would like to here other peoples comments.

 

Thanks

 

Paul

[dikyenfo]

Mine had the same woolly pressures and fortunately Don Amot altered mine from 80 psi to 60 all round and it seems to give a good ride with no overheating of the tyres which is always a good idea to check whenever you stop.

[BrianR]

AnnPaul - 2009-04-09 12:17 PM

 

 

Who else can I check with? Can I trust the experts!

 

 

Paul

 

As has been said on this forum many many times, for something as important as tyre pressures you need to get the answer in writing, firstly, so that you have evidence, if things go wrong, and secondly, so that you know that the reply has been properly considered by the right people. The procedure is - weigh your 'van, front axle only then both axles together, first with the van fully loaded as for a trip, including fuel and all passengers. Repeat this procedure for the van lightly loaded. Take the total loading from the front axle loading in each case to give the rear axle loading. E-mail or post these axle loadings to your tyre manufacturer, with details of the tyres. They will then send you the recommended pressures for your tyres for your 'van. You can then interpolate the required pressure for any loading in between these two loadings. I.e., for a loading half way in between the two the required pressure will be half way in between the pressures they give you.

[Chudders]

AnnPaul - 2009-04-09 12:17 PM

 

Many of you may have read my last message re trye pressures on my Rapido 7087F.

 

Front axle weight 1600 Rear 1860

 

About a year ago I rang Michelin Tryes and asked what pressures my tryes should be 215/70 15C

 

They told me then they should be F55 and R60

 

Rang them last week to check again, they quoted F70 R80

 

Rang them today only to be told they should be F55 R80 !!!!

 

Who else can I check with? Can I trust the experts!

 

Did not inform them of the discrepancy but I will. But would like to here other peoples comments.

 

Thanks

 

Paul

 

I have had several conversation with Michelin. I quoted them axle weights and they e mailed me with pressure recommendations of 60 F and 65 R. This was for 216/75 R16 XC camping. I had heard that they have changed their information generally so I rang them this afternoon. I am now told that they have been advised by their head office and I believe he said having had consultation with VOSA that they have revised their recommendations. The front they are permitted to vary according to axle weight. The rear however will always be recommended at the maximum of 80PSI. I am given to understand that VOSA consider that the majority of motorhomes will be running at or near their max weight. (If not over) and that they will wxpect the tyre pressures to be as stated. This has all changed within the last 2 weeks as far as Michelin are concerned. I guess the rears will have to be 80PSI now. Thats what VOSA apparantley expect as a legal requirement and I bet that in the case of an accident the Insurance company will wriggle out of a claim if the tyres are not at manufacturers recommended pressures.

This seems to be the same info as mentioned in the above post from Paul. They recommended my front pressures to be 60PSI for the axle weight given and this included an allowance for weight transfer under braking and cornering.

I have pumped mine up and am off tomorrow so am expecting a harder ride. Taking the lap top so may post over the weekend.

Regards, Dave

 

[fred22]

There's a heck of a difference between some of the tyre pressures being quoted. I would have thought that if a tyre was meant to be run at 80psi it would be considered under inflated at 20psi less?

I am sure some of us have seen the tread of car tyres that have been run over inflated with wear to the centre section of the tyre with very little to the shoulders. This surely means your vehicle is only running with a portion of the tyre on the road. Not a condition you would want in a motorhome.

Are the tyres motorhomes run on constructed in such a way that this "balloning effect does not occur and are designed to remain with a "flat" profile to the road over a large range of pressures?

[AnnPaul]

So what pressure should I use????????????????????????????????????????? or what pressure would you use??????????????????????????????????????

 

Paul

[rupert123]

AnnPaul - 2009-04-10 2:52 PM

 

So what pressure should I use????????????????????????????????????????? or what pressure would you use??????????????????????????????????????

 

Paul

 

You have to go with what tyre maker is saying but as already been stated get it in writing or email.

[ron.]

As I have said elsewhere Michelin and VOSA are playing a safety game here just in case you overload the rear of your van. A tyre that required, say 65psi, last week cannot suddenly need 80psi this week. What's more they seem to be quoting 80psi no matter what the rear axle weight is!

 

What with overinflated tyres and our clapped out roads watch out if you have false teeth!

[Derek Uzzell]

AnnPaul - 2009-04-10 2:52 PM

 

So what pressure should I use????????????????????????????????????????? or what pressure would you use??????????????????????????????????????

 

Paul

 

If you've been using for a year the 55(F)/60® combination Michelin originally recommended and have not felt there was anything 'wrong' about the way your motorhome drives, or noticed that its tyres are wearing abnormally, then why seek to alter those pressures?

 

(If you HAVE noticed something odd, then you've taken a helluva time getting round to doing something about it!)

 

Me, I'd stick with 55(F)/60®, but I might have some concern about how close to its 3500kg MAM your motorhome seems to be.

[Vernon B]

If you do a search for "tyre pressures" on this forum (say over the last 12 months) you should find reference to website and a simple chart that will give you all the information you need. Sorry mine's in the van at the moment and not to hand.

 

V

[trooper]

I'm like derek, could'nt agree more , if you are happy with presant pressures , why change, commen sense is often the answer.

[Derek Uzzell]

The chart referred to by Vernon is probably the one downloadable from

 

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

[Mike Chapman]

Chudders - 2009-04-09 9:22 PM

 

I have had several conversation with Michelin. I quoted them axle weights and they e mailed me with pressure recommendations of 60 F and 65 R. This was for 216/75 R16 XC camping. I had heard that they have changed their information generally so I rang them this afternoon. I am now told that they have been advised by their head office and I believe he said having had consultation with VOSA that they have revised their recommendations. The front they are permitted to vary according to axle weight. The rear however will always be recommended at the maximum of 80PSI. I am given to understand that VOSA consider that the majority of motorhomes will be running at or near their max weight. (If not over) and that they will wxpect the tyre pressures to be as stated. This has all changed within the last 2 weeks as far as Michelin are concerned. I guess the rears will have to be 80PSI now. Thats what VOSA apparantley expect as a legal requirement and I bet that in the case of an accident the Insurance company will wriggle out of a claim if the tyres are not at manufacturers recommended pressures.

This seems to be the same info as mentioned in the above post from Paul. They recommended my front pressures to be 60PSI for the axle weight given and this included an allowance for weight transfer under braking and cornering.

I have pumped mine up and am off tomorrow so am expecting a harder ride. Taking the lap top so may post over the weekend.

Regards, Dave

 

Hello Dave,

 

The information you obtained from Michelin/VOSA is correct but for all Motor Caravans fitted with only the XC Camping and Agilis Camping tyres which allow a maximum pressure of 80 psi. This is for the rear axle only. They still recommend pressures by axle weight for the front axle. This appears to replace the pressures given in the Michelin Professional Guide which quotes pressures by axle weight. They will still quote pressures by axle weights for non Camping tyres.

 

My understanding is that the change is not just by Michelin but also all Tyre Manufacturers, who supply Camping versions of van tyres, for liability reasons.

 

There are several issues that need to be considered with these Manufacturers recommendations. Firstly the Camping tyres can be fitted to Motor Caravans with greatly differing configurations and Maximum Weights.

Michelin accept that running a lightly loaded van on Camping Tyres with 80 psi on the rear and say 52 psi on the front could in some circumstances cause instability with roadholding or when breaking on wet surfaces. They have not given a satisfactory answer to this question only that they stand by the recommendation of 80 psi for Camping tyres on the rear axle and the correct pressure according to rear axle weight for non-camping tyres which seems to me to be contradictory advice.

 

A point raised was that of a weight imbalance across a single axle.

 

The example given was a van with an uneven load across the axle of 825 kg nearside and 950kgs on the offside a total axle weight of 1775kg. This would lead to a recommended pressure of 58 psi for both tyres but the correct pressure should be based on 2 x 950kg total 1900 kg which would need a pressure of 65 psi for both tyres.

 

The practical problem is that of weighing individual wheels rather than the axle and ensuring that any load carried is evenly distributed across the axle. The tyre manufacturers recommendation is that the axle load should always be 2 x the heaviest wheel side. Remember that many of the roadside weighing stations use individual wheel weighing pads to get axle weight and weight distribution.

 

Something to think about.

 

Regards,

 

Mike.

 

[rolandrat]

My Auto-trail on a Mercedes chassis with Continental Vanco tyres run at 55psi rear and 50 psi front, she glides along without interior rattles and pothole bangs, I cruise along at a steady 65mph on the motorways and the tyres run cool, they are in my opinion the best tyres on the market.

[Derek Uzzell]

rolandrat

 

But which Auto-Trail model do you own, what are its axle-weights when you are operating it, and what 'pattern' and size of Continental Vanco tyres are fitted to the vehicle?

[Mike Chapman]

Further to the points concerning tyre pressures for Camping Tyres (Those marked as a tyre type of CP) and after further discussions with Michelin the following information from their Professional Guide Van Fitments and Pressures 2008 page 10 should be followed. For those who do not have this book the following is given as General Advice.

 

"Since 2003, the ERTO has recommended that tyres produced especially to equip motorhomes be marked CP as opposed to the conventional C for van tyres".

 

"The ETRTO state that in the case where such tyres (ie., CP) are used on a rear driven axle, they should be inflated to a pressure of 80 PSI (5.5 bar) instead of the normal 68 PSI (4.75 bar)".

 

"The use of metal valves is strongly recommended. The maximum load of the tyre must not, for any reason, be increased above it's limit ie., The load rating must be respected".

 

Having read thoroughly the above statement I noticed that the term "Rear Driven Axle" is used. I am waiting for a response from Michelin about whether this rule will also apply to trailing or non-driven axles. I will post the Michelin reply when received.

 

Regards,

 

Mike.

 

[rolandrat]

Derek,

the tyres are Vanco-8 Continental 225/70R 15c 112/110R

Front 3.5 bar 49 psi

Rear 4.2-4.8 bar 59-66psi

the motorhome is an Auto-Trail Cheyenne 634u on a Mercedes chassis powered by a 2.2 engine.

Some time ago I asked you if you would name the dealer you spoke to regarding the Fiat juddergate problem as a matter of interest but you didn't come back.

rolandrat.

[Derek Uzzell]

rolandrat

 

I recall saying a while back that I had spoken to a motorhome converter about the Fiat juddering thing, but I deliberately chose not to identify the company as the conversation was 'off the record'.

 

In fact I did mention it to a motorhome dealership a few days ago and was told much the same thing - that their understanding was that the problem was confined to X/250 Ducato-based vehicles with the 2.3litre motor. They said a couple of customers had returned their motorhomes complaining of vibration when reversing and (if I remember correctly) in both cases the driver's technique had proven to be a contributory factor.

[Mike Chapman]

I have spoken to Michelin this morning and there appears to be confusion. The information that they are referring to is contradictory in that their documentation states "Rear Axle" on one document and "Rear DRIVEN Axle" on another. They are investigating this to establish which or if both apply and the recommendation also for tag axle vehicles.

 

Having spoken to the Technical Department at Continental Tyres they state that they are quoting tyre pressures by axle weight for all van tyres including those marked with a type of CP (Camping Tyres). Pirelli take the same stance so the information that I was given that all tyre manufacturers are following the ETRTO recommendation is inaccurate and should therefore be ignored.

 

Continental thought that using a blanket pressure of 80 psi for CP tyres no matter what the weight at the vehicle rear axle is incorrect and could in some circumstances be dangerous.

 

After searching the ETRTO and the VOSA website databases and finding no relevant information I spoke to VOSA as it had been indicated that VOSA roadside tests would check for correct inflation according to tyre type. Their statement was that they do not use tyre pressure gauges to test tyre pressures at roadside tests and are only interested in seriously under inflated and/or badly worn tyres and vehicle overloading.

 

Until I can get some offical ruling on this in writing or in an official document I shall continue to follow the recommendation of the tyre manufacturer and operate my vehicle with the pressures recommended by axle weight.

 

If anyone wants to follow up the advice of VOSA please contact technical assistance on 03001 239000 option 1 and ask for technical assistance.

 

Regards,

 

Mike.

[Brian Kirby]

Mike Chapman - 2009-04-15 1:39 PM Further to the points concerning tyre pressures for Camping Tyres (Those marked as a tyre type of CP) and after further discussions with Michelin the following information from their Professional Guide Van Fitments and Pressures 2008 page 10 should be followed. ...................

Mike

Many thanks for following up on this. 

Two questions:

1 For those with Michelin tyres on their vehicles (Camping or otherwise), can you say where copies of this booklet may be obtained?  That is to say, is it available on demand from Michelin, or only to "Trade" sources?

2 Are you aware if other tyre manufacturers publish similar booklets, what they are called, and where/how these may be obtained? 

My reason for asking the second question is this: our van is on Vanco 8 Tyres 215/75 R 16 C, but I know some of the Hobby Vans were supplied on Vanco Camper (CP) tyres of the same size.  The (Ford/Hobby) recommended pressures (which are the same whichever tyre version is fitted) result in a harsh ride, and some loss of adhesion at the front, due to the van's inherent rear heavy weight bias.  I therefore consulted Continental in 2007, when we got the van and had weighed the axles laden, and obtained revised pressures.  However, the front axle load was only 1,190Kg, which suggested a pressure below 3.0 BAR (probably 2.7 BAR) was appropriate.  To my surprise, my informant at Continental said they had no load/pressure figures below 1,300Kg/3.0 BAR, so he was unable to recommend any pressure below 3.0 BAR.  Thus the rear is now being run at pressures suited to the rear axle load, but the front tyres are being run at 3.0 BAR, which is OTT relative to load, and feels so at times with some tramlining and some scrabbling on hill starts.  If there is something in print, to which I can refer, I should at least like the benefit of seeing, and trying, what it quotes.

[Keithl]

Brian Kirby - 2009-07-03 1:29 PM

My reason for asking the second question is this: our van is on Vanco 8 Tyres 215/75 R 16 C. However, the front axle load was only 1,190Kg, which suggested a pressure below 3.0 BAR (probably 2.7 BAR) was appropriate.  To my surprise, my informant at Continental said they had no load/pressure figures below 1,300Kg/3.0 BAR, so he was unable to recommend any pressure below 3.0 BAR.  ...but the front tyres are being run at 3.0 BAR, which is OTT relative to load, and feels so at times with some tramlining and some scrabbling on hill starts.  If there is something in print, to which I can refer, I should at least like the benefit of seeing, and trying, what it quotes.

Brian,If you download the TyreSafe Motorhome tyre info sheet we will find that they quote a pressure of 2.50 bar for an axle load of 1376 kg for your tyre size. This is considerably less than the 3.0 bar that Continental quote so may be worth a try. The figures quoted are not for a particular make but are for Van tyres not Camper tyres.Keith.

[Brian Kirby]

Keithl - 2009-07-03 2:28 PM

Brian Kirby - 2009-07-03 1:29 PM

My reason for asking the second question is this: our van is on Vanco 8 Tyres 215/75 R 16 C. However, the front axle load was only 1,190Kg, which suggested a pressure below 3.0 BAR (probably 2.7 BAR) was appropriate.  To my surprise, my informant at Continental said they had no load/pressure figures below 1,300Kg/3.0 BAR, so he was unable to recommend any pressure below 3.0 BAR.  ...but the front tyres are being run at 3.0 BAR, which is OTT relative to load, and feels so at times with some tramlining and some scrabbling on hill starts.  If there is something in print, to which I can refer, I should at least like the benefit of seeing, and trying, what it quotes.

Brian, If you download the TyreSafe Motorhome tyre info sheet we will find that they quote a pressure of 2.50 bar for an axle load of 1376 kg for your tyre size. This is considerably less than the 3.0 bar that Continental quote so may be worth a try. The figures quoted are not for a particular make but are for Van tyres not Camper tyres. Keith.

Thanks Keith

I'm afraid my original post doesn't help, since I typed 1,300Kg as the minimum load Continental said they recognised, when I should have typed 1,590Kg!  The load pressure/chart you refer to does, indeed, quote lower loads and pressures, and corresponds closely with the information I had from Continental for loads above 1,590Kg.  I'll have another go, referring them to the chart, and see if they still give the same answer.  Thanks again.

[duetto owner]

on my transit hitop I have used full weight recommendations in the ford booklet and a much better ride [F55 R68]

 

when collected from the dealer they were [F55 R55]

[Mike Chapman]

Brian Kirby - 2009-07-03 1:29 PM

Mike Chapman - 2009-04-15 1:39 PM Further to the points concerning tyre pressures for Camping Tyres (Those marked as a tyre type of CP) and after further discussions with Michelin the following information from their Professional Guide Van Fitments and Pressures 2008 page 10 should be followed. ...................

Mike

Many thanks for following up on this. 

Two questions:

1 For those with Michelin tyres on their vehicles (Camping or otherwise), can you say where copies of this booklet may be obtained?  That is to say, is it available on demand from Michelin, or only to "Trade" sources?

2 Are you aware if other tyre manufacturers publish similar booklets, what they are called, and where/how these may be obtained? 

My reason for asking the second question is this: our van is on Vanco 8 Tyres 215/75 R 16 C, but I know some of the Hobby Vans were supplied on Vanco Camper (CP) tyres of the same size.  The (Ford/Hobby) recommended pressures (which are the same whichever tyre version is fitted) result in a harsh ride, and some loss of adhesion at the front, due to the van's inherent rear heavy weight bias.  I therefore consulted Continental in 2007, when we got the van and had weighed the axles laden, and obtained revised pressures.  However, the front axle load was only 1,190Kg, which suggested a pressure below 3.0 BAR (probably 2.7 BAR) was appropriate.  To my surprise, my informant at Continental said they had no load/pressure figures below 1,300Kg/3.0 BAR, so he was unable to recommend any pressure below 3.0 BAR.  Thus the rear is now being run at pressures suited to the rear axle load, but the front tyres are being run at 3.0 BAR, which is OTT relative to load, and feels so at times with some tramlining and some scrabbling on hill starts.  If there is something in print, to which I can refer, I should at least like the benefit of seeing, and trying, what it quotes.

Hello Brian,In answer to your questions:-1. The "Michelin Professional Guide Van Fitments and Pressures 2008" is available to the public and normally costs £10. However I have always been able to obtain a free copy from Michelin Technical Tel: 0845 36615352. Other manufacturers such as Continental, Good Year, Pirelli, Dunlop etc., do produce Technical Data Sheets for each tyre model but these are for the trade and can be difficult to obtain. They contain Technical Data by tyre size and tread pattern and this includes inflation pressure by axle load. I have always found it easier to talk to the manufacturers technical department or a local tyre dealer directly. In the case of Continental their Technical Department Telephone Number is 01895 425900. It would be worth calling them and asking if they could send you a Technical Data Sheet for the Vanco 8.Taking your Vanco 8 size 215/75R16C at 1190 kg I would expect the pressure to be quoted at 2.5 Bar and at 1590 KG the pressure quoted at 3.5 bar. This would be dependant however on Continentals recommendation for minimum pressure which may well be 3.0 Bar, as you were quoted. I have found that the tread shape on Continental Vancos have a much sharper defined tread edge and seem more prone to tram-lining especially in the Road Grooves on the M6 on the Lancashire section. I have never really noticed such a bad effect as this with Goodyear and Michelin Van tyres.If I can be of any further assistance please let me know.Regards,Mike.

[Brian Kirby]

Many thanks Mike, I'm presently awaiting Continental's response.

In the meantime, it strikes me as odd that the BTMA should publish the Tyre Safe publication without qualification, if certain of their members do not agree with its recommendations.  However, we shall see what Conti say, as I have referred them to the Tyre Safe booklet and asked if they subscribe to the recommended pressures for 215/75 R16 C 113/111 Vanco 8 Tyres.  If they don't, it seems to me that someone needs to say so!

Another puzzle is that Hobby Vans have been supplied with both Vanco 8 tyres, and Vanco Camping tyres.  I know this as mine has Vanco 8, and I have seen Vanco Camping on other Vans.  With reference to your post above, it does strike me as odd that both types of tyre are fitted, and that both have the same recommended pressures front and rear (3.5bar front: 4.75bar rear - the Hobby and Ford handbooks both agree).  Yet, on the basis you report, Continental would only be willing to recommend reducing pressures on the rear axle for the  Vanco 8 tyres, the Vanco Campers having to stay at 4.75 bar.  It then gets even odder, since both handbooks also say that if Michelin XC Camping tyres (of the same size as the Contis) are fitted, the rear pressures should be upped to 5.5bar!  All this with a rear axle limit of 2250Kg, for which the Tyre Safe booklet agrees (interpolating a bit) 4.7bar, including for the CP tyres.  Somehow, something doesn't quite seem to gel!!  :-)