The rover boys use them, they all appear to be 2 or 3 leaf parabolic springs - they use small spacers in the center of the pack to keep the leafs from rubbing, save for the very ends. They sound like a good idea....
I'm working on a project vehicle ('67 FJ40) right now and have wondered about the same question. To be honest I've never seen any discussions about parabolics outside of the Rover community. Do you know of a source for FJ40 parabolics?
I also have a long wheelbase Rover ('63 109) and am running parabolics on there. It's a significant improvement over the old springs both in ride quality and articulation. I have to admit though, that the old springs were very old and rusty, so it may not be an entirely fair comparison. The parabolics are also lighter than the old springs.
I'm running a two leaf spring in the front and three leaf in the rear. I originally had four leaves in the rear but it was way over sprung so I pulled one leaf out of the spring pak. There are 1/8" spacer plates between the leaves and a bend at the ends to keep the leaves separated and reduce friction. I've had them on the Rover for about 4 years now and have no complaints.
although primarily a Rover outfit, I met and talked with the guy running it and he said that they were starting to make or could make parabolics for the Cruiser. For what it's worth, there was another guy there while we were talking who had put a set on his FJ62 and he couldn't say enough positive things about the springs.
dogboy, that's one of the sites I've been checking out.
As far as I know the fj40 springs are two leaf front and rear, with 50mm lift. I wanted to see how they compared to OME both price wise and in terms of performance. There is heaps on the rover sites about them, and it seems hardly anyone has a bad thing to say about them. Maybe I'll just have to get a set and see.
Woody, the pics on that website are not too good as far as detail. I'll try to borrow a digital cam and get you some better installed pics off my Rover. That is the same brand that I have. You could also check out www.ticonsole.nl they are a european manufacturer that is real popular with the Rover gang. They have a slightly different different design from the Rocky Mountain Parabolic product. They also have better pics.
The primary difference most manufacturers claim for the parabolics is reduced weight and better compliance. They claim that the separation of the leaves reduces the inter-leaf friction that binds up or limits the traditional leaf spring design.
In LR's it's a geat ride and confort improvemnent. The www.ticonsole.nl parabolic springs are made in a factory in Portugal and they started to make parabolic's for Toyota Land cruisers but they had some problems because they made left and right springs equal and when installed in the cruiser the vehicle does't stay levelled (maybe because it's heavier in the left side). But as i know they are trying to solve the problem before putting it for sale. If i know any dates of starting sales i'll post it here