Hi Neil
How's the spring over coming on?
The Haystee springs were designed for left hand drive vehicles so are not handed as only right hand drive vehicles require this. On left hand drive vehicles the weight of the driver, steering column, steering box, Panhard rod mount, pedal box and dash and insruments are on the left so offset the weight of the Battery and offset drive train on the right so the vehicle is more evenly balanced side to side, hence the reason the spring rates are equall. Right hand drive vehicles, as the Daihatsus were originally designed, carry all this weight on the right and not a lot on the left hence the need for handed springs so that the higher rated springs carry the extra weight at the same height as the other side. The Belton springs I run on my Trak which are made in Malaysia (right hand drive) are handed and sat evenly to start with but two years hard use on lean heavily to the right, still work brilliantly though! To produce handed springs increases production costs and is never going to happen for vehicles with limited sale volumes, EG Fourtrak.
Paul Haystee's springs are as good as you can get, The quality control is second to none. I have dealt with him since 2002 when I bought a set of his new J40 Landcruiser parabolic springs for my 1982 FJ45 Landcruiser, neither he or I knew at the time that the rears were different on the long wheelbase model so I worked with him to develop the rears, both sets are still on the vehicle today. My FJ is a LHD model so the springs are spot on but if fitted to RHD have the same issues as the Fourtrak. The springs have to be made in Batches of 50+ pairs to maintain costs so small production runs such as RHD Fourtrak are not viable. Haystee springs used to be imported for series landrovers but were always fairly expensive however there are a lot of cheaper copys of his series landrover springs being sold in the UK nowadays but like most things they are made to a price, whilst the expensive Haystee springs will last for years the cheaper copys, whilst great to start with, soon wear out and sag badly. I have been in touch with him several times over the last couple of years with regard to supplying his product in the UK but the exchange rate has up to now has made them too expensive.
Parabolic springs, much like coils, are far more sensetive to static weight than multi leaf springs but I have seen how ingeniously some of the 4x4s are prepared in Indonesia in the Borneo challenge and other such events on the web so would suggest, if you can, altering the weight distribution of your F75. For example shift the battery across, store recovery gear and spare wheels on the left, carry any tools or passengers etc with a bias to the left and this may help, you could even fit slightly longer shackles to the right hand side but lower the bump stops to match as the Parabolic springs are designed with a very specific performance perameter and are more easily damaged than multi leaf springs if allowed to be overly compressed.
Hope this helps
Best regards
Dave
www.bloodredoffroad.com