Hi Paul, on our two DS's I kept the tyres at the higher pressure all the time mainly because we use our vehicle to 90% for towing. I can't honestly say that I noticed excessive tyre wear on either nor for that matter on our current Evoque.

 

There are of course legal requirements which can invalidate your insurance.

Because your tyres play such a vital role, there are some very important and specific legal requirements relating to their condition and maintenance:

Tyre must be fit for purpose and be free from any defects which might damage the road or endanger any person.
Tyres must be correctly inflated to the vehicle manufacturer's and the tyre manufacturer's recommended pressure.

 

In the case of towing with a DS increasing the tyre pressures (mainly on the rears) improves stability. The high load pressures are exactly the same as for a fully laden vehicle with passengers and luggage.

 

I alway adjust the tyre pressures to max load requirements when towing. However, when not towing I always put them back to normal load requirements as the ride is awful on hard tyres with no load.
Also agree with Barnsh and the comments on legal requirements. I'm not a legal person but suspect that should an 'incident' occur, incorrect tyre pressures could be considered contributory.

 

Yes, having higher pressures on the back will induce oversteer if the car is under normal load. Although in practice, as the car is effectively front wheel drive in normal circumstances, oversteer would be easy to correct.

 

Hope you don't mind if I disagree partially on this, I would have thought it depended upon what and whom are in the car in addition to the towball weight.
Light load: Up to 4 persons Front 35psi and Rear 31psi
Heavy load: 5 + 2 persons + luggage Front 37psi and Rear 41psi

We tow extensively in Europe, two of us plus about 60kg on the back seat and approx 85kg noseweight. I understand the noseweight is to the rear of the axle but even then with a car GVW of 2660kg, a kerbweight of approx 1800kg that gives a car payload of over 700kg.
Two persons, items on back seat and noseweight adds up to around 300kg, not what I would call a heavy load.