maximum lift height for 4x4 vehicles?

[custom4x4]

Hi, I'm new to this forum, so I apologize if this has been covered before or is posted in the wrong place.

I am currently building a 1973 toyota landcruiser fj40, rego on hold with a declaration for a 350 chev and 3 speed auto. I am doing all the normal rust repairs, new hoses, bushes and tires as it has been off the road since about 2006. I thought because I have to replace the tires i may as well go bigger, I am hoping to put 35/12.6/15's under it. I have widened the guards and done a 50mm suspension lift using Ironman 4x4 uprated lift springs, anti inversion shackles and big shocks. It does have enough clearance now but I am planning to do a fair bit of ugly off road work in it so I would like some more, so i want to do a 50mm body lift. my question is: Is there a maximum height that you can lift to? I know that I will need certification for it, but I am also fitting power steering and converting the rear to disc brakes to cope with the bigger wheels, so that's no worries for me. original tire size is 205/75/15, which is about 28", so with suspension/body and tire height change truck would be about 190mm taller than original. rim offset and extra tire width has made the truck about 150mm wider, does this compensate for any change in height as far as stability goes? 

also, because the roof on the fj40 is removable and not particularly strong, I would quite like to fit a 4 point cage behind the seats to give me a bit of protection if i flip it, and I thought it would make sense to mount the top seatbelt mount to it so that if i get the urge to take the roof off on the track i can still have functional seatbelts. does this put the cage in a whole different category, or as long as the mounts and seatbelt ancorages are a decent size can i do it myself? 

cheers in advance,

Blair

[Leon]

Good morning,

There isn't a specific number for how tall a lifted vehicle can get, because what might suit a Nissan Safari probably won't suit a Suzuki Jimney.

You'd be getting towards the high end of what's going to be safe to drive on the road if you're doing a 2 inch spring lift, 2 inch body lift, and then a big tyre increase. You might end up having to back off the tyres to get it to where a certifier is happy that it is going to be stable enough for ordinary road use. The proof is going to be in how it drives though.

Maybe start working with your certifier now, and he can advise you what he has passed on FJ40's in the past. Which might save you from doing mods, and then having to undo them to get through cert.

If you follow the recipe for seat belt anchorage frames when you're building your roll hoop (tube diameters, straight backstays etc) then having a roll bar that is a seatbelt upper anchorage point is no problem, and reasonably common. Note that means you'll not be able to have rear seats in the vehicle with a roll bar in nearly all cases.