Tyre Pressures
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The whole point about tyre pressures is that if they are overinflated then wear is on the centre of the tyre and the reduced footprint gives less grip. If under inflated then wear is seen on the corners of the tyres. All leading to a premature MOT failure.
When towing, a caravan will surely add more pressure to the rear wheels and less to the front thus needing an adjustment to tyre pressures so as to correct the imbalance and increase safety?
I adjust pressures every time to be on the safe side.
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That's what I have been saying that putting a caravan on a towball adds 100kg max to the rear of the car which is not a massive weight so why add air. If I filled my tank I would be adding more than the caravan would be adding and I don't add air when I fill the tank and deflate when tank is nearly empty.
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Agree DD. Incidentally, the Tyrepal system does provide tyre temperature readings as well as pressure and I have found it to be fairly accurate as compared with the air temperature reading in my car. Having suffered a blow-out on a boat trailer being towed by my Disco, some years ago - and I didn't even know it had happened - I am now a big fan of TPMS systems on trailers.
After returning from the dealers with our new caravan, I was unfortunate enough to get a nail through one of the tyres which caused a slow puncture. The TPMS alerted me and I was able to drive slowly for the remaining 5 miles to home, without doing any damage - which probably wouldn't have been the case if the system hadn't been fitted.
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Sorry, I know I am a bit thick but if I weigh my tow hitch on a scale then that must be whatever it says. I know the pivot point is the axle but how can the stated weight be different, 100kg 10 foot away from the pivot point is the same as 100kg 20 foot from pivot point. Please explain as the way you say it is multiplied so 100g 10 foot away equals 1000kg seems very wrong.
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Increasing the tyre pressures when towing, where the vehicle maker states doing so, is most unlikely to be due coping with the modest weight increase from the noseweight.
It is much more likely to be to increase the lateral stiffness of the vehicle to better control towing instability. The tyres being both a major contributor to this desirable feature, and the only one you can influence.
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Isn't it vehicle and tyre specific though? and the club can't be experts in every car and tyre combination, and I suppose the advice would be to follow what they say.
My previous car had differing pressures for various passenger and load combinations (though we never did) where as my present is the same no matter what.
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On our car, VW Touareg, the addition of 100kg on the towball will add about 138 kg to the rear axle load and reduce the front axle load by 38kg. The rear axle load is therefore increased by about 10 to13%, depending on other loads in the car. So yes we increase the pressure when towing, mainly to save the sidewalls of the tyres. A 12% increase in the tyre pressure will keep the footprint of the tyre the same as when not towing. The footprint is the area of tyre in contact with the road and is proportional to the load the tyre carries and inversely proportional to the tyre pressure.
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The rear axle loading calcs for the Disco4, using their European detachable bar, indicates a 100kgs noseweight yields 141.2kgs, 7.67% of its load rating. This is very slightly higher with the "fixed" bar.
Interestingly, only in the Australian market is it stated the tyre pressures be increased to maximum when towing, but there much greater bar weights are typically mandatory.
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The noseweight of the caravan is about a couple of big passengers plus luggage. inflate to suit and that is that. the small amount of travelling when away won't wear your tyres out, but return to normal if you wish. my inflator is a mains powered Aldi product, with tools and gauge. Not seen them since and that was long ago.
The 12volt inflators are OK for normal car pressures but caravan tyres are usually way above that and the inflator gets hot. You wait a while and gain another couple of pounds, then let it cool off again. That was my experience at any rate, hence my Aldi purchase!!!
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Hi everyone,
October is actually ‘Tyre Safety Month’ so this thread is very timely!
For tyre advice we would recommend you visit www.tyresafe.org/campaigns/tyre-safety-month-2019/tyre-safety-information/
We also have information and advice on our website here: Taking care of your outfit/caravan tyres and wheels
To help monitor your tyre pressures we have negotiated discounts on the following products:
Additionally, we have recently teamed up with National Tyres and Autocare who offer a FREE safety check (including tyres) and provide members with a 5% discount on new tyres: Member Offer National Tyres
I hope this helps!
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Thanks Ro, as you say timely advice.
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The 12volt inflators are OK for normal car pressures but caravan tyres are usually way above that and the inflator gets hot. You wait a while and gain another couple of pounds, then let it cool off again
Works fine for me and rarely need more than 1 or 2 extra psi anyway. Some pumps are rated higher than others
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Like most things, tyre pressures don't matter significantly until you realise that they significantly matter. Then its usually too late.
A few examples:
My last car my much beloved Shogun recommended increased the tyre pressures for towing, but then I could have been towing a 3.5T trailer with 150kg on the ball.
My current Santa Fe does not need any adjustment but then it is a very big heavy beast and runs on pretty sturdy high load rated tyres anyway.
The point is that the recommended pressures and loads are calculated by smart people who are trying to keep you safe whilst avoiding litigation.
In many cases the weight is not the primary concern, it is the lateral distortion of the tyre when you get a wobble, this can reduce the tyre contact to a tenth of what you need to keep your shiny side up.
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