The system Lords of the caravan world

[Jim.M_5040716]

For a number of months I have been reading through many of the items on this channel, As there are many subjects covered. there seems to be a group that make regular appearances, I will call them the System Lords.Such as Lord John L and the kangaroo's that pop up every day. I recently made the mistake of transgressing into Lord John's domain, he has a DUTY to put me right.Forgive me Lord John, as my qualifcations are approved by The D.o.T which is the highest in the UK. But I forgot that the GODS are all knowing, and therefor better qualifed than me a mere mortal.

Anyway I must say that many of the questions and answers have been very entertaining over the past few months. Keep it up it is good fun

Jim M

 

[ProfJohnL]

Do I detect a non believer? Is there treason amongst the mortals? I will crush this rebellion without mercy. BOW DOWN TO YOUR GOD! - and while your down there please check the tyre pressures.

Sorry Jim.

Jaffa Kree!

 

[Lol1]

They were great in that attle against the Darleks!

 

[Lol1]

They were great in that attle against the Darleks!

Battle, I meant Battle! Sugar, thats another spoiled post!

 

[CaptainKangaroo]

Battle, I meant Battle! Sugar, thats another spoiled post!

Have you posted one that hasn't been sploit?

 

[Pete4]

I thought I'd get a mention. I try to put people right too!

 

[Lol1]

For outright tenacity, you deserve it bud.

 

[Jim.M_5040716]

Do I detect a non believer? Is there treason amongst the mortals? I will crush this rebellion without mercy. BOW DOWN TO YOUR GOD! - and while your down there please check the tyre pressures.

Sorry Jim.

Jaffa Kree!

Lord John Hi good buddy.

Joking aside, I dont think the issue of tyre pressures was resolved. Let me give you the Info I have, Five years ago I bought a new swift, on delivery I said to the dealer that the tyres looked a bit soft he infomed me that they were check on pdi however the service man was called to reasure me that all was well and to prove it he checked them to let me see that it was correct which according to them read 35psi. I was still not convinced as on the way home there was quite a lot of bounce. At home I looked at service book to check, a figure of 40-60psi is given, so confusion, I then rang Swift they could not explain the differential of figures, but sujested that I should stick to 40psi, I tried this and did a 50mile road test there was still quite a lot of bounce with the van, dealers explanation was as a new van it would need to be run in and that it would settle down. to put it mildly I have not heard such rubbish. Given my previous expreiance of towing of all sizes of trailers this did not make sence, so I checked the pressure rating on the tyre it is rated at 55psi. I then contaced the British tyre Assoiation They told me that if a tyre is rated at 55psi ect then that is what it should be run at, simply because at lower presures a tyre will run to hot as heat is the worst enemy to a tyre, as heat disapation is very poor, The constrution of the tyre is the same as for a transit van and nobody would run a transit at 35 psi, so on theyr advice I have run at 55psi it imediatly cured the bounce. they also run much cooler. I did mention to BTA that I had been told this by the maker he said we have had this problem for some years they cover themselves by quoting a wide range of pressures and hope that you might pick the right one.

The most important thing is not to go higher than the rated pressure.

This has also proved that niether dealer nor manufacturer can be trusted to give correct information, I found this on many other issues over the past 40years.

So John I hope this explains my previous staement.

anyway keep on trecking

Jim M

 

[ProfJohnL]

Do I detect a non believer? Is there treason amongst the mortals? I will crush this rebellion without mercy. BOW DOWN TO YOUR GOD! - and while your down there please check the tyre pressures.

Sorry Jim.

Jaffa Kree!

Hello Subjet Jim,

You can get up now, but dont let your head rise above mine! Just geneflect two or three times a minute.

Seriously, Thank you for the added information, I have to say I'm not convinced by your quote from the BTA, which implies that all tyres should be run at thier maximum stated pressure.

It is my understanding, that most tyres are desined to run with a prescribed area of contact with the road.

Provided the tyre is run with this area of contact, it automatically means that the tread will have even wear, the walls will support the tread, and the tyre will handle surface water and maintin grip correctly.

If you under-inflate for the given load, the tyre will deform more to bring more surface area into contact with the road. The increased deformation generates more internal heat through friction. It also allows the pre-stress shaping in the tread width to cause shoulder wear.

Conversley, over inflation will stiffen the tyre and the tyre will deform less for the given load. As the profile becomes more circular, less tyre will be incontact with the road surface. The internal pressure will overcome the treads pre-stressed formation and cause it to become convex, result is incresaed centreline wear.

The tyre pressure should be matched to the imposed load. If the load is less than the tyres stated maximum, then the pressure should be less than the stated maximum.

If we consider a fairly typical car in towing configuration, the tyre pressures are likely to be about 30psi (sorry I'm still old school in many ways) That will typically support about 400Kg per wheel (total 1200Kg) Most caravans area about 1000Kg or more so each tyre will be expected to carry 500Kg or more. That is at least 25% more than the car tyres.

So I would expect a caravan tyre to need at least 30+25% psi (37.5 psi). These figures are of course ficticous and don't take acount of tyre width and diameter, but they do give an indication of what might be required.

May I suggest that you seek further clarification from the BTA or an actual tyre manufacture.

Kind regards

John L

 

[Icemaker]

Hi jim and john and all others, in the 7 years i have been caravvanning i first had a swift challenger that did not have a owners manual, i rang swift to enquire as to the tyre pressure and they quoted 56 psi for the van (520/4, my next van a coachman pastiche 520/4 was new and the manual quoted tyre pressures at 54 psi as was my next van a coachman vip 520/4, when we changed this van for a coachman laser 590/4 the pressure was quoted by the dealer (the van was new but somebody had stolen the manuals from the dealers)as 38 psi. i adviced that all my other vans had been in the 50- 60 psi area and was told that twin axles where lower due to double the wheels, we ran at 38 psi with no problems. i now own an ace jubilee celebration 590/4 another twin axle and the book quotes tyre pressure at 33 psi or 2.3 bar whichever you prefer. it would appear from my experiance that most single axle vans are somewhere between 50 - 60 psi and twins are round about 33- 40 psi. we found after returning our pastiche to the dealer twice due to stability problems that the pressure was only 50 psi the dealer inflated to 54 and the van was completly different, towed like a dream 4 psi made a hell of a difference.

 

[WatsonJohnG]

You seem to be under a lot of pessure no wonder you shout your name !!!!!

 

[Icemaker]

My english teacher taught me to use capitals for names, I would have thought that was obvious. I am only under the correct pressure and was only giving advice that was asked for, see above.

 

[WatsonJohnG]

My english teacher taught me to use capitals for names, I would have thought that was obvious. I am only under the correct pressure and was only giving advice that was asked for, see above.

Its just the first letter that your English teacher should have told you to use.In computer speak capitals are shouting.

At least you have acknowledged me at last !!!

 

[Jim.M_5040716]

Hello Subjet Jim,

You can get up now, but dont let your head rise above mine! Just geneflect two or three times a minute.

Seriously, Thank you for the added information, I have to say I'm not convinced by your quote from the BTA, which implies that all tyres should be run at thier maximum stated pressure.

It is my understanding, that most tyres are desined to run with a prescribed area of contact with the road.

Provided the tyre is run with this area of contact, it automatically means that the tread will have even wear, the walls will support the tread, and the tyre will handle surface water and maintin grip correctly.

If you under-inflate for the given load, the tyre will deform more to bring more surface area into contact with the road. The increased deformation generates more internal heat through friction. It also allows the pre-stress shaping in the tread width to cause shoulder wear.

Conversley, over inflation will stiffen the tyre and the tyre will deform less for the given load. As the profile becomes more circular, less tyre will be incontact with the road surface. The internal pressure will overcome the treads pre-stressed formation and cause it to become convex, result is incresaed centreline wear.

The tyre pressure should be matched to the imposed load. If the load is less than the tyres stated maximum, then the pressure should be less than the stated maximum.

If we consider a fairly typical car in towing configuration, the tyre pressures are likely to be about 30psi (sorry I'm still old school in many ways) That will typically support about 400Kg per wheel (total 1200Kg) Most caravans area about 1000Kg or more so each tyre will be expected to carry 500Kg or more. That is at least 25% more than the car tyres.

So I would expect a caravan tyre to need at least 30+25% psi (37.5 psi). These figures are of course ficticous and don't take acount of tyre width and diameter, but they do give an indication of what might be required.

May I suggest that you seek further clarification from the BTA or an actual tyre manufacture.

Kind regards

John L

Hi there John

I have not been on line for a few days as at weekends I am off with van,have van will travel, it is what it is for, since joining the ski club I dont have much time these days, dont no where it goes.

Anyway I concur mostly of what you say, I did also check with the tyre manufacturer which is India tyres They confirmed that for that type of tyre it was ok to run at that pressure, it is only when this pressure is exceded that crown runing will occur, I think that it wil depend what type of tyre is fitted as all makes are different, as long as the correct presure is used for that tyre., I use a digital gauge with a .01 variance.

After an average of 3000 mile a year for 5 years with no significant wear I think it's very good.

keep on trecking

Jim M

 

[ProfJohnL]

Hello again Jim,

It seems your more of a trekkie than a Gater, so is it Classic, TNG, Voyager, or Enterprise? The nearest thing I can come up with to a univerasl God is 'Q' So I might consider renamimg my self.

Thanks for the further info on the tyres, it seems we do really agree on the subject.

Anyway I'm just about to go off on holiday, not with caravan but on the Canals, so I'll have to check the pressure of the fenders, and I hope the old Carver SB1800 will still work (actually they did do a marine version!).

On my return I few weeks before having to contemplate major heart surgey, so my postings may be deminished. I hope I can leave my kingdom in safe hands of Jim.M, Lutz etc.

It seems even Gods needs help sometimes.

Have fun.