Pneumatic or solid ?

[FrintonMike]

Earlier in the year I changed the jockey wheel to a pneumatic one as they seem to be better on grass and gravel.
I am thinking of changing back to the solid one as the pneumatic one gets squashed and almost comes off the rim when I use the mover to make a turn. I make sure before I use the mover that the tyre is pumped up to the max 30psi shown on the tyre and after use it is still at 30psi.
Has anyone else had this problem. I have used pneumatic tyres on s/a caravans but now have a t/a. Is a t/a too heavy for a pneumatic tyre ?

 

[WoodlandsCamper]

I have used pneumatic tyres on s/a caravans but now have a t/a. Is a t/a too heavy for a pneumatic tyre ?

The down force on a jockey wheel is nearly the same as the nose weight. Surely there isn't much difference between between nose weights of s/a or t/a? :huh:

 

[ProfJohnL]

Hello Mike,

From what you tell us, the tyre is not losing air, so if it's getting squashed to the extent you tell us then it certainly suggests the loads being applied are high.

The effect you describe is quite possibly another symptom of the geometry and interaction of the two sets or suspensions on the the axles. You may recall that I have suggested much greater care needs to be taken when measuring nose loads on TA's as only relatively small changes in the height of the hitch can make quite dramatic differences in the actual nose load applied to the towing vehicle.

The jockey wheel of course takes the place of the hitch to support the caravans nose when its being manouvered, so it will experience changes in its load also corresponding to height of the hitch. But in addition, because the position of the jockey wheel is closer to the caravan axles than the hitch coupling the actual loads it has to carry will greater. Exactly how much is difficult to predict without taking measurements, but it could easily be 10% or more.

In simple terms, the area of tyre that makes contact with the ground will be determined by the load on the tyre, divided by the pressure within the tyre. Consider your nose load + 10% to account for the shorter distance to the jockey wheel and you could easily see 90kgs load on the jockey wheel. That is 198Lbs divided by 30PSI gives a tyre contact area of 6.6 square inches. And this figure can increase well beyond that if the attitude of the caravan changes whilst starting to go up a or down a slope. For a small diameter tyre to handle this sort of load, it's hardly surprising the tyre squashes and squirms quite a lot.

As you are finding it a problem, you might be better reverting to a solid tyre.

 

[Dustydog]

Hi Mike.
I had the same problem..The Prof's point is very relevant. My TA has the mover fitted on the front axle. To partially relieve the tyre scrub I lower the jockey wheel as far as possible without fouling the chassis.Th8s the load on the jw increases.
I went back to good wide solid wheel. Never had a problem.

 

[ProfJohnL]

I have used pneumatic tyres on s/a caravans but now have a t/a. Is a t/a too heavy for a pneumatic tyre ?

The down force on a jockey wheel is nearly the same as the nose weight. Surely there isn't much difference between between nose weights of s/a or t/a? :huh:

Hello Woodlands,
On flat hard concrete I would agree with you, but you may have seem my other reply in this thread. Another point to consider is that to lift the hitch off the coupling you have to raise the hitch higher. With a single axle the load will actually lighten, but for a TA, with its dual suspension, and depending on how its loaded, the hitch load could actually increase or decrease, and the rate of change with hitch height will be far greater than with a single axle.

 

[ProfJohnL]

Hi Mike.
I had the same problem..The Prof's point is very relevant. My TA has the mover fitted on the front axle. To partially relieve the tyre scrub I lower the jockey wheel as far as possible without fouling the chassis.Th8s the load on the jw increases.
I went back to good wide solid wheel. Never had a problem.

Hello Dusty,
Adjusting the jockey wheel will certainly help reduce tyre scrub, and in your case it seems you had enough forward loading to allow your hitch to drop and keep the jockey wheel in contact with the surface. :cheer:

I have moved a wide variety of TA's, and some will not drop as yours does. Its yet another example of interaction of the TA'a suspension and loading.

 

[WoodlandsCamper]

I'm glad my van is single axle, life is soooo much easier :lol:

 

[Phil.Q]

I fitted one to our Coachman Pastiche 520/4 fitted with a mover and whilst it was on the drive it was very very good.
The problem was anywhere else and it came off the rim. I stupidly thought this was a problem with the tyre / rim and after several times of re inflating and trying different pressures I threw it away and bought another.
Needless to say i got exactly the same problem.
Never again for me.

 

[Craigyoung]

I'm with Woodlands , solid jockey , single axle , light enough to manoeuvre - within reason - and I'm good at reversing with it !