Towing advice please for E400d Estate

[GavinP]

I tow a twin axle touring caravan, of 1,950 kg with an E400d Estate. Car has run flats all round, front are 245/35 R20 Michelin Pilot Sport3 and rears are 275/30 R20 Pirelli PZero.
Towing ratio is 85-87%.

I am trying to find qualified advice on how much to increase rear tyre pressures by when towing - the hand book for the car only offers either 39psi (2 adults) or 49psi (4 adults + luggage).

The noseweight limit on the car is 84kg which I always set by re arranging things in the caravan. I do appreciate this a static, not a dynamic, value.

However, a 10 psi increase seems overkill to my untrained brain!

Looking on the internet I see some saying add 3-5 psi, others say don't increase at all, leave

I am starting to think the rears are wearing in the centre - a sign of over-inflation I believe?

Any ideas please?

G

 

[ALFAitalia]

That's a lot of weight behind a 1995kg car..... towing at close to 100 % is not something would recommended to my customers to be honest. As far as tyres are concerned as long as the car itself is not fully loaded with people and gear then leave the tyres at the pressures for normal load. There is only 84kg extra downforce on the car.... which will get less the faster you go..... like having one slimmish extra passenger....not enough to worry about. And 84kg nose capacity is also not really enough for a 1950 kg van... the recommended neing between 5 and 7%....so 100 minimum really. But of course most vans have a 100kg hitch limit anyway.
Out of interest what make/model of van is it?

 

[W1ghty]

Does the caravan club or similar have online charts or info on that ?

 

[BTB 500]

The guideline always used to be to use the maximum plated pressure (passengers + luggage) for towing. But I'm pretty sure this was simply to increase stability (higher pressure stiffens the tyres and would reduce sideways flex, resisting snaking). If the car handbook doesn't specifically tell you to increase the tyre pressures for towing then I wouldn't bother (I haven't done this for 20 years or more). Modern outfits are generally more stable to start with thanks to advances in tyres/suspension/stability control systems/etc.