Tyre Tensioning: What is it and why do you need to know?

ByRV DailyOctober 6, 2020
3 MINUTE READ
Tyre Tensioning: What is it and why do you need to know?

After being on the road for three years, you would think we would have come across most things that could upset your day when using a caravan, particularly regards to tyres. Well, we are here to attest that we can add one more thing to the already-long list of things that can go wrong.

So, for your educational pleasure, I present problem number 999: Tyre tensioning when reversing. As you can imagine, after a few years of reversing our caravan into all types of weird and wonderful, not to mention impossibly tight spots, it’s a wonder we haven’t encountered this problem before. Obviously we have been very lucky.

The problem occurred when we reversed the van into a spot and didn’t pull forward to straighten out the van to the car. Like many times before the van was straight on the site but the vehicle was a little bit angled to the van. Not thinking anything of it, we didn’t bother straightening the car.

So, the unhitching checklist commences. Wheel chocks in – check. Handbrake on – check. Trailer-Mate block in position – check. People out of the way – check.

All good to go – or so we thought. We slowly lift the van off the hitch pin. Van comes up and then all goes south very quickly after that. The van leaps forward, missing the car’s rear bumper by millimetres, rolls off the block of wood, Trailer-Mate footplate digs into the ground and stops about 400mm in its new position. We all stand back, take a breath, scratch our heads and mutter, “What the bloody hell went wrong there?”

caravan tyres

Reversing a dual axle van on a tight turn can cause tension to build up in the tyres.

We each took a guess. Were the wheel chocks not in tight enough? Nope, two of us had kicked them in! Was the handbrake faulty? Nope, it had just been serviced! Was the site on too much of a slope?  Nope, fairly level as we didn’t need the levelling ramps. We searched for the answer, we double-checked with the caravan service agent about the handbrake, and then we sat down and wracked our brains. What we discovered blew our minds a little.

The issue was that the caravan tyres were still under too much load tension after reversing into the site. This in effect puts energy into the tyre and when you release it from the hold of the tow vehicle it has the chance to release this energy. Due to the weight of the van and nothing more than a handbrake and chocks stopping its movement, it explodes at a great rate, only stopping when the energy is expelled or it runs into something like the rear bumper of your brand-new tow rig. This is not confined to big vans either. Apparently it can even happen to box trailers and the like. The energy must be expelled if it has built-up –  much like kids after a long drive.

beachside camping

Blocks, chocks and little tension

Imagine, as we have seen many people do before, and are guilty of doing ourselves, that you are standing beside the drawbar. Caravan releases from the car and lurches to the side with such speed and force that the only thing stopping it is your leg. All I can say is, I hope your medical insurance is paid up and you are camped in a nice spot for six to eight weeks while your broken leg mends.

We were lucky though. No damage to property or legs, thank goodness. But it had the potential to be a lot worse.

Parking the van

It’s this alignment that caused us the problems

Travelling this great land we have had many a good thing happen to us and a couple of bad things and it is the good, and the bad, that we should all share with each other so we can get better at this travelling gig. To enjoy the good things we must learn from the bad.

So remember, tyres can be under a lot of tension when you reverse into a camping spot. Fix it by straightening the car with the van by moving forwards and reversing back into your site if possible. Look at the tyres too; you can actually see that one, or more, are turned in or out compared to the others. This is a sign that the tyre(s) is under tension and may cause you some grief when you remove it from the tow bar.

grassed campsite

Correct alignment, with no stored recoil potential

See, no matter how long you’ve been caravanning, there’s always something else to learn – and you really can teach an old dog a new trick.

Disclaimer: We set up the angles in a larger location for purpose of photography.

Words and images Four Hands in a Tin Can.

Read more: The essential guide to tyres for your 4×4, caravan or camper trailer.