Thread: Tyre pressures when towing?

Originally Posted by Dante

John,
I have tried the method to do it by feel, but had to stop it because my tongue always ended up being black and the taste wasn't too greate either.

As you darn well know, I meant I use my hand, not my tongue!

As for the difference in load between front and rear ... not sure how that would make a difference, you can have different pressures front and rear.

Yes, the temperature/pressure method will automatically increase/decrease the pressure according to the load. But handling/ride may require a different pressure difference, for example to give less sway when heavily loaded than a proportional pressure increase in the back gives.

As for feel and handling ... I (that is me personally, just for me) wouldn't be using the tyres to accomodate handling and steering. Unless where circumstances require it (the usual spots where you let your air down ... eg sand, off roading, etc).

Most people would require handling to be a major consideration - and a lot would also put ride quality above tyre life!

The method above is obviously only any good if you travel speeds > 30km for longer than 30 mins.

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But coming back to the original question, method above is more or less useless for trailers as their axle is not driven.
I think the meassuring approach goes back to seeing the axle of the trailer as the 3rd axle of your truck and therefore you should try to match the characteristics of the trailer tyres to the charasteristics of the rear tyres. Pressure again will depend on the load, so that is how the length of pattern comes into play.
I believe that this is only valid if you are using same or similar tyres on your truck as on your trailer. We had on our trailer the bolt pattern, rims and tyres changed to be identical to the one on the car. More spare tyres ;-)

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Can't argue about the desirability of having the same tyres on the trailer, as you say, more spares

While there is good reason to have the same tyre track on a trailer as the towing vehicle, I am not sure that (apart from the spare question) there is any real reason to have the same or even similar tyres on the trailer, especially if it is unbraked. The four wheel drive towing vehicle is driving on all wheels, but the trailer is not, and furthermore, in most cases, the load on each tyre will be very different from either the front or rear of the towing vehicle. If the trailer is unbraked, the tyres have no need for any sort of mud grip, and would be better with a pure road tread. Even if braked, circumstances where better grip than given by a road tread is needed will be very rare - most heavy braking happens on hard surfaces, and the less aggressive tread will give better mileage and lower costs on hard surfaces. But there are real advantages in having the same tyres on both the towing vehicle and trailer from the point of view of spares, so this is usually the best way to go if you can, particularly if really offroad.

John

Having the trailer the same track as the vehicle may be desireable when on rutted road or sand but is not always possible, as you may need a wider trailer.
I do a lot of long trips with a large trailer, about 1100kg, and as I have a very accurate pressure gauge( don't believe servo ones) and a pyrometer to use on my race bike, I did some tests of car and trailer tyre temperatures and pressures. I found the trailer's left side got hotter, either due to my large tool box or road camber pushing more weight on that side, so I tried more pressure in the left. It seemed to work, but I don't know if everybody would approve of different pressures on the same axle.

I usually run 36psi front, 60 rear and 55 right and 60 left on the trailer.
My LR has Michelin X and the trailer Yokohama 14" light trucks.

Jeff