Post by mudgrip4 on Dec 1, 2006 9:35:54 GMT 11
Had an interesting nite last week when my Canterbury 4wd club went to a 4x4 shop which offered free use of their ramp to test articulation on vehicles. We had 22 or so trucks of all makes and setups and all went through the process. Some results as expected but also a few surprises. Big range of results reading from 188 to 700 points.
Highest ramp index figure came from a modified cruiser mwb at about 700 points followed by an old Rangerover - also fairly modified - at about 690. In the 600s were an assortment of Safaris and cruisers with the beam axle front. Quite pleased that the two bighorns came in at about 9th and 10th out of the 22 trucks at 546, and about 530 points for mine. Behind us were an assortment of cruisers, terranos, surfs and various makes down to 188 points.
The 88 bighorn and the 93 bighorn - both swb - scored well and ahead of most of the non beam axle trucks.
Big surprise and a warning for everyone was a seriously lifted, lockered and well modifed 1989 cruiser MWB which should have measured about 650 on the ramp but came in 2nd last at just 273 points - approximately the same articulation as a Morris Minor.. Turned out the owner had just had a spring job and fitted new stiffer springs plus an extra leaf - which totally killed his truck's articulation, cut it by 60%. His new springs look great and sit the truck up quite high but they are about as flexible as railway girders. Same issue with a 93 beam axle prado which only scored about 460.
This is something we know can happen, and is a real warning for those who follow unqualified advice re spring jobs, when planning to modify your truck. You can completely ruin articulation which is so imortant offroad. The only time one should do a spring job is after alot of checking that the spring people really know their offroading. Go to experienced offroaders, not spring shops. And often better to keep slightly saggy but flexible older springs and simply put on longer shackles, rather than get stiff new leaves fitted.
A benchmark figure for acceptable offroad articulation is about 550 points. So both isuzus pretty good. You can often improve articulation up to another 100 points (as a surf did on the nite - from 388 to 475 points) by disconnecting all sway bars - and more by lowering tyre pressures to about 15lbs. The isuzus were not disconnected but mine was partially disconnected with James' system. Full disconnection and a bit of tweaking could see the isuzus round the 600 point mark, which is good.
So some possible lessons from of the night:
- only use expert experienced 4wd advice re spring alteration
- avoid extra leaves if possible
- only use shocks which do have long travel
- longer rear shackles may be better than new springs
- full disconnect of swaybars can add 25% to
articulation for some trucks
- lowering tyre pressures to maybe 15lbs can improve articulation by maybe 10%
And of course it was pleasant surprise to see isuzus do quite well in an area that is their weakness - Independent Front Suspension articulation. Seems rear articulation is very good. (The most effective offroad cure for IFS limited articulation is a front lokka.)
Another club with seriously modified trucks had results up to 800, and the highest the bloke had seen on his ramp was a truck which read 1200 points - I don't think that was for driving to work today.
Might be a good idea to have an isuzu club nite there also and do some experimenting with sway bars, tyre pressures etc.
Mike.
Highest ramp index figure came from a modified cruiser mwb at about 700 points followed by an old Rangerover - also fairly modified - at about 690. In the 600s were an assortment of Safaris and cruisers with the beam axle front. Quite pleased that the two bighorns came in at about 9th and 10th out of the 22 trucks at 546, and about 530 points for mine. Behind us were an assortment of cruisers, terranos, surfs and various makes down to 188 points.
The 88 bighorn and the 93 bighorn - both swb - scored well and ahead of most of the non beam axle trucks.
Big surprise and a warning for everyone was a seriously lifted, lockered and well modifed 1989 cruiser MWB which should have measured about 650 on the ramp but came in 2nd last at just 273 points - approximately the same articulation as a Morris Minor.. Turned out the owner had just had a spring job and fitted new stiffer springs plus an extra leaf - which totally killed his truck's articulation, cut it by 60%. His new springs look great and sit the truck up quite high but they are about as flexible as railway girders. Same issue with a 93 beam axle prado which only scored about 460.
This is something we know can happen, and is a real warning for those who follow unqualified advice re spring jobs, when planning to modify your truck. You can completely ruin articulation which is so imortant offroad. The only time one should do a spring job is after alot of checking that the spring people really know their offroading. Go to experienced offroaders, not spring shops. And often better to keep slightly saggy but flexible older springs and simply put on longer shackles, rather than get stiff new leaves fitted.
A benchmark figure for acceptable offroad articulation is about 550 points. So both isuzus pretty good. You can often improve articulation up to another 100 points (as a surf did on the nite - from 388 to 475 points) by disconnecting all sway bars - and more by lowering tyre pressures to about 15lbs. The isuzus were not disconnected but mine was partially disconnected with James' system. Full disconnection and a bit of tweaking could see the isuzus round the 600 point mark, which is good.
So some possible lessons from of the night:
- only use expert experienced 4wd advice re spring alteration
- avoid extra leaves if possible
- only use shocks which do have long travel
- longer rear shackles may be better than new springs
- full disconnect of swaybars can add 25% to
articulation for some trucks
- lowering tyre pressures to maybe 15lbs can improve articulation by maybe 10%
And of course it was pleasant surprise to see isuzus do quite well in an area that is their weakness - Independent Front Suspension articulation. Seems rear articulation is very good. (The most effective offroad cure for IFS limited articulation is a front lokka.)
Another club with seriously modified trucks had results up to 800, and the highest the bloke had seen on his ramp was a truck which read 1200 points - I don't think that was for driving to work today.
Might be a good idea to have an isuzu club nite there also and do some experimenting with sway bars, tyre pressures etc.
Mike.
