- May 16, 2021
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- Autotrail
Your comment on the Autotrail 634 sat down even when empty is interesting, as I would think your Apache 634 and my Cheyenne 635, both at 3500Kg would have near identical weight distribution.
But where as yours is flat on the springs, mine is anything but (as can be seen by the photo posted to illustrate) and pretty well echos your experience with the Bolero with its uprated springs, even when loaded close to capacity on the rear axle.
The springs were updated before my ownership - and replaced from the standard due to a breakage. And the previous owner decided to avoid a repeat by going for the VHD triple-spring (from Jones Springs, if interested?). I have not come across anyone who has the VHD springs fitted let alone airbag/spring uprate combo.
Pressures and "Motorhome" tyres are a tricky one.
As most know, If you run Michelin Aglis CP Camping Tyres, they only have one permitted rear pressure - 80PSI. Much higher than other tyres (including their other Aglis ones) would be specified at. The Aglis Camping tyre does have a different construction, so maybe that 80PSI stipulation IS required as a feature of safely running the tyre and trumps other desires? Something to consider as there must be a reason why they demand 80PSI on that tyre and not their others?
I recently did a check (using Tyresafe I think?) on pressures after my weight uprate and I am set at 67PSI rears and 56PSI fronts on my Michelin Aglis Tyres - however I am not running the CP Campers, but the C Cross-Climates due to wanting better all-season & colder temperature ability than the Summer focussed Campers.
I try to drive my Motorhome on a weekly basis however rather than being stored and stationary for months though.
I think your above comment mirrors my experience to a fair degree. Because the Uprated Springs increased the gap from the bump stop position to the axle, by the time you have inflated the airbag enough for it to have any compression resistance (if that makes sense), the pressure it will be set is probably too high to provide that compliance and control that the airbag is meant to provide.
The airbag clearly can have some advantages over an uprated spring, being adjustable. My previous camper was a 4.6t Minibus I converted, with the suspension fitted accordingly as standard. When the van was stripped out ready to start the conversion, the ride was incredibly bouncy due to so little weight at the rear.
I would not recommend Airbags for anyone who already has VHD uprated springs simply as it does little as normally installed. I guess you could have some kind of block added to the Airbag so that it starts to take effect at a lower pressure? That could have a good effect thinking about it, but could well change other characteristics and not a project to be undertaken lightly.
I spoke to VB Suspension about the combination of Uprated Springs and their Air Assist system before I installed it and they couldn't really comment as had no experience of using the two togethr either.
I would need to drive a similar motorhome to mine, but fitted with Airbags and standard spring to know the answer vis-a-vis Airbags vs VHD Springs (maybe we need to try a drive in each others motorhomes?
)If I needed to get extra assistance at the rear and had to chose between Air Assist or Uprated Springs, I would go Air Assist if I was also wanting to get a weight uprate - so that decision based on getting the right paperwork more than anything else.
If I didn't need a weight uprate, I think it is much less clear-cut. Springs are the more agricultural but cheaper and more reliable solution for sure, but the techie in me likes the idea of adjustable rear air suspension (which is why I was disappointed at the end result on my own van).
So a lot of words to say "no, I don't know either"
