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I'm sure this is pretty simple but I can't get my head around it!
I'm getting a spring assister kit fitted to my van, partly to improve the handling but mainly to raise my towbar so that my twin axle trailer rides level and doesn't keep grounding on uneven ground.
My van has a 3300mm wheelbase, and a 1800mm rear overhang. I need to raise the towball 50mm. How do I calculate the height required at the rear axle to achieve 50mm at the ball?
The manufacturer told me to jack the towbar up to the required height and then measure the axle to chassis distance to determine how much the springs need cutting down. (with an allowance for load) When I tried this the axle to chassis distance only increased from 170mm to 185mm (15mm) to raise the ball 50mm, but I think the tyres unsquishing/chassis flex as I jack up is messing up the distance. I was expecting an increase of 30-35mm to achieve 50mm at the ball.
There must be a simple method involving dividing overhang/wheelbase etc but I'm not good at working it out!
To do it the manual way I think I would need to put the jack between the axle and chassis to keep the suspension weighted but this is easier said than done!
sack of spuds on the bonnet?
So there's only 1300mm between wheel centres? With two meters behind rear wheel centre? That can't be right!
If you can work out the weight of spuds required then I will be impressed Cheez0. The front overhang is 60mm...
Paul, no, 3300mm (3.3m) between wheels, and I just adjusted the overhang down from 2000mm to 1800mm as I had guestimated 🙂
What's the current tow ball and axel height from ground?
Towball height = 430mm.
Distance between top of axle and chassis = 170mm.
Distance from ground to top of axle = 350mm.
Total distance ground to chassis = 520mm.
My wife is stumped 🙂
I reckon 33.11mm extra in fixed length, I basically used a right angled triangle starting from the front axel, through the rear axel and the right angle under the tow bar, then worked out what the right angled height would be at the rear axel. I then done the same for the higher towball, and worked out that the the right angle height at the rear axel would be 33.11 higher.
A proper engineer will be along soon to tell me I'm wrong though.
Using pythagoras i get 32mm lift at axel using your dimensions
Which i guess is what you did.
How ever if its anything like my van the axel doesnt move in a straight line. Piece of crap.
Thanks guys...I can't quite follow how pythagoras is used to work it but I am happy that your figures have come close to what I expected to measure before crawling under the van 🙂
I'm going to play it safe, plump for +35mm and then if its too high I just need to drag the angle grinder out and cut them down a bit to adjust the ride height.