Tyre pressure

[Rikvater76]

Hi all,

I have recently purchased a 1993 Bailey SE Avallon. I am confused as to what tyre pressure to use, the tyres fitted are 175R13 LT 97/95R (8PR), Max load single 730kg dual 690kg at 450KPa (65psi) cold and the caravan has a MTPLM of 1048kg. Now the confusion is that the owners manual quotes 33 psi but I'm not convinced this is right as they look under inflated at that pressure, I have even emailed Bailey who have confirmed this psi. I have searched the internet but this has only confused me further as I'm getting quotes anywhere from 42psi through to 65psi (but this is the max psi quoted on the tyre). I'm hoping somebody on here could please shed light on this for me and point me in the right direction as I'm a newbie to caravanning and planning my first long journey in August and have read the importance of getting this right. Thanks in advance Richard.

 

[xtrailman]

I had the same issue with a 1979 Avondale, the tyres on that were also 33psi, and the tyres never looked right. That's assuming the tyres are the same spec as the originals.

I would stick to the 33psi especially as you have a Email confirmation, I always add a couple of psi anyway, same as I do with the car, its better to be over than under.

This chart may help.

http://www.tyresafe.org/images/campaigns/caravan_tyre_safety_leaflet.pdf

 

[WoodlandsCamper]

A good approximation is to proportion the max tyre pressure against the actual load (half caravan MTPLM per tyre). In your case 524 divided 730 times 65 equals 46 psi.

Edit - are the tyres fitted exactly the same as the specification in the handbook?

 

[JTQ]

A good approximation is to proportion the max tyre pressure against the actual load (half caravan MTPLM per tyre). In your case 524 divided 730 times 65 equals 46 psi.

Edit - are the tyres fitted exactly the same as the specification in the handbook?

I would agree with the rule of thumb approximations made here but more importantly it is indicating that at 33psi they are dangerously under inflated and at serious risk of heat damaging the sidewalls if run for any length of time.

 

[Gafferbill]

Hello Rikvater76 and welcome to the forum

There is a lot of poor advice about regarding your size of tyre fitted to caravans.......you are right to be cautious.
Nowadays they are not a common size and people just do not know what advice to give.
IMO the advice given in your Bailey handbook is incorrect...........misprints in handbooks have been known before!

If you caravan tyres are indeed designated 8 ply then the ambient inflation pressure should be 42-44 psi.
If they are a commercial tyre then the pressure for your caravan tyres should be 50psi.

Commercial tyres are far more common as replacements on older caravans as they are used on light vans...... they are designated with the letter C.......so your tyres would be 175R13C if you have them fitted.

I have researched this exact topic over many years as I have a 1995 Swift of 1150kgs MTPLM on the 13 inch rims.
It is doubly essential that you carry a good spare with your caravan, as a tyre of your size nearly always has to be ordered........especially if you go abroad.

 

[Rikvater76]

Hi,

Thanks for all the advice.

That formula is what I have been basing my pressure on. Hopefully getting the van weighed this weekend so that will help with the calculation.

I have been running them on 45psi as that was what was in when I purchased a few weeks back but when I read the manual I panicked.

Does the (8pr) on the tyre wall mean 8 ply?

Thanks again

 

[xtrailman]

I might add that I did own the Avondale for 7 years, and did use the 33psi recommended with the factory fit tyres, Avondale did say the tyres were a soft wall tyre and will look under inflated.

Obviously if the tyres have been changed to a different make the pressures will be different.

I had the same concerns as the OP as my previous caravan were at 42psi, my present are at 62psi, so it is a mine field.

 

[Rikvater76]

Yep tell me about it I've been going round and round in circles trying to figure this out.

I have emailed Bailey again to find out which tyres should be fitted because I do suspect the ones I have are different to the ones they are quoting the psi for. Had no response so far so watch this space

Thanks
Rikvater76

 

[Gafferbill]

Hi,

Does the (8pr) on the tyre wall mean 8 ply?

........it stands for 8 ply rating.

 

[Rikvater76]

Thanks for that so does that mean they are classed as reinforced tyres and not commercial

 

[Gafferbill]

Thanks for that so does that mean they are classed as reinforced tyres and not commercial

......from what you have written they are reinforced tyres.

I would also check the age of your tyres see here for how if you do not know

 

[JTQ]

Another point of view is that 8 plies hints at old technology being used in their construction, without the benefits of modern high performance synthetic materials and with laid up sheeting, rather than a purpose made woven donut reinforcement. You will notice that quality modern construction tyres feature fewer “ply” than tyres of yesteryear, for the same load rating, so aren't saddled with overly stiff sidewalls.
There seems to be a hang up with many caravan owners in seeking as many “ply” as they can find, rather than relying on the maker to design for the specified loading.

 

[Rikvater76]

The numbers are 4912 so does that mean 49th week of 2012?

Thanks

 

[xtrailman]

The numbers are 4912 so does that mean 49th week of 2012?

Thanks

Yes according to the data in the link I provided.

 

[colin-yorkshire]

hi welcome to the forum,
yes it does or it could be 4/9/12 either way they are only 18mths/2years old so no problem,
from the information provided I would say the correct pressure for these tyres is 42/46psi, given the axle weight, and they are not the original spec tyres but much stiffer ones.
how do I know well these are the exact tyres I have on my bailey, the original ones quoted at 33psi (on the weight plate near the door) relate to the much softer ones supplied by bailey which IMO were crap, as the van rolled about like it was running on jelly wheels.

 

[Gafferbill]

.........yes it does or it could be 4/9/12 .

No it coul'nt Colin......It means the 49th week of 2012 or 3rd -9th December 2012

......... these are the exact tyres I have on my bailey, the original ones quoted at 33psi (on the weight plate near the door) relate to the much softer ones supplied by bailey which IMO were crap, as the van rolled about like it was running on jelly wheels.

......and the wheels must have felt like hot jelly with the tyre side walls flexing to that extent!!

 

[Rikvater76]

So glad I posted now, thanks for all the info can now tow confidently.