Car tyre pressures when towing

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In nearly 4 decades of towing, I have always raised rear tyre pressures. My current LR Discovery Sport handbook gives two pressures for the rear tyres, one for lightly loaded and one for fully. I use the latter when towing and just put up with the slightly harder ride when driving around solo while we are away

I tow with a Volvo XC70 and the recommended economy pressures (38psi) are the same front and back no matter what the load. 

I am quite particular about this.  The 'normal' tyre pressure on my Touareg is 33psi all round but under heavy load increases to 44psi for the rears - which is a big difference.  I always increase the pressure for towing - and - once on site - reduce them to the 'normal' pressure.  Two reasons - main one is safety - but also I am also conscious of increased tyre wear if the correct pressures aren't adhered to - and at just under £200 a tyre, I'm keen to get as much mileage out of them as possible.

It only takes about five minutes to get the pressures right - so no great hardship, really.

Tyre loadings are calculated at specific pressures for the loading of that tyre. The caravan manufacturers cant be bothered to rate their tyres correctly for each van and just state the max pressure for the tyre.

The car manufacturers calculate the correct pressures for the loading and (by law) stick a sticker on the drivers door pillar or inside the petrol flap.

They do this for a reason, the lateral forces on a towing vehicle are far higher than a non towing vehicle. The non towing pressures give the best comfort ride when not towing, the towing pressures give the safest pressures when towing.

Running at highest pressures stated on the info sticker has little effect on tyre wear, handling or safety but does give a poor ride as it is harsher and more noisy. Riding on lower pressures when towing is dangerous. 

Ditto

"Running at highest pressures stated on the info sticker has little effect on tyre wear, handling or safety"

I beg to differ - running on over-inflated tyres (for the load) will increase wear in the centre of the tyre and also reduce grip, especially during cornering or braking.

I totally agree but running on the manufacturer recommended tyre pressures you are not overinflating the tyres. The tolerances shown on tyre inflation label is recommendation to optimise the handling and comfort but does not give overinflated tyres.

With two VW Tourans over 13 years, I always inflate my tyres to maximum pressure when towing.  There are just the two of us, but the car is also loaded with chairs, awning, etc.  Pressures are dropped to normal when on site and car unloaded.  Inflating is not a chore, since I have a Ring heavy duty 12-volt inflator, and is very quiet in use so does not annoy others if used late evening or early morning.

We are just in the process of changing to a VW Caravelle, so will not know until next week if tyre pressures need to be increased for towing.

Keeping the tyres at the correct pressures when loaded is important, since an under inflated tyre will suffer more sidewall flexing and thereby increase the amount of heat generated in the tyre.