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Tyre and Motor mover puzzle

Question

Posted

OK we had new tyres fitted and noticed whilst we were away that the mover wasn't as effective as it should be

On checking the gap between the tyre and mover roller was 21mm - it should be 17-19mm

First check was that the tyres were correctly inflated the caravan plate says 39PSI the tyre sidewall says 49PSI

with the tyre at 42 PSI as said above the gap on one side was 21mm

with it inflated to 49PSI the gap decreased to 18mm

Now to be honest the tyres circumference should NOT be affected by pressure

The motor mover works perfectly on both sides with the tyre inflated to THEIR stated pressure

Can anyone help me with advice before I contact the tyre supplier

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Posted

I wonder if the tyre circumference decreases as the pressure increases as the side walls will start to bulge out more? Is the 49psi the tyre max pressure? What does your handbook say the pressure should be? Were the tyres the same make, as it may be possible that softer side walled tyres may be affected by pressure which in turn would affect the tyre circumference?

Only a few thoughts.

Graeme.

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Posted

Spoke at length with my service guy

The 49lb PSI is the tyre max

the Caravan handbook say 39lb PSI

my guy says reduce the pressure down to the 39lb PSI and then move the motor mover to 19mm from the tyre all the extra pressure has done is put the tyre under an increased risk of deformity at speed especially under a light load when the caravan will bounce more

SO when my back feels better the caravan is coming back out of the shed and I will sort the mover out so that I will have the speed and grip we need for the curved sloped drive

AND If I need he will come and sort it out for me (at a cost of just £60 )

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Posted

........all the extra pressure has done is put the tyre under an increased risk of deformity at speed especially under a light load when the caravan will bounce more

Perhaps he could explain?

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Posted

These are Reinforced tyres so although they state a maximum pressure above 42psi, it is not to be considered the correct pressure at the tyres stated maximum load, (as is otherwise the case with different construction tyres), ie, all reinforced tyres carry their maximum load at 41 or 42psi and not the 49psi stated in this case.

I would not agree about deforming the tyre at 49psi, it would though not be suitable for anything other than a specific reason and probably at a very slow speed. On the otherhand then, using 49psi in storage will IMO stop the tyre deforming unduly while carrying their load in one spot, the extra also likely preventing deflation below the correct pressure for towing and only needs adjusting down and your ready to go

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Posted

Hi all,

My tyres on Hymer Nova are set to 4.5 bar = 62 psi.

I have had to adjust a mover in the past when tyres were changed ( even being the same size ).

If the mover is fixed to a point on the chassis and has a travel of say 100 mm, it should and will travel the same each time until adjusted, the changing of tyres will affect the performance ( in some instances ) of the mover.

Happy caravanning, indoors.

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Posted

Anyway guys ALL fixed now

deflated the tyres and got pressure to the chassis stated 39lb PSI

Then using a form of wood to 19mm (advised to go from 17-21mm so took the middle) reset the motor mover myself

Blooming difficult but our drive is a steep slope so with the caravan on the flat at the top of the slope brakes on and wheels chocked the from of the caravan jacked up until the rear of the caravan rested on a thick blanket on the ground (to prevent damage)

with Stephanie helping we adjusted both sides of the mover which is surprisingly simple just five bolts each side - four on the clamps and one on a slide stop

Once done and I had been helped back up and rested we got the caravan back on to it's jockey and moved it around without problems - no more slipping

Shame it took me three days to recover and get my pain levels back down (but I didn't tell Stephanie how bad I was although I think she sussed me out from the way I got told off later)

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