TJM Gold Edition or OME

[Izak]

Thanx Peter

Very well explained Peter, thanx a lot.



IJM

[ChrisAfrica]

Gents,

Got a Nissan petrol with the standard spring,coils and shocks. Have fitted a long range fuel tank (150l) and the car is petty loaded when we go camping as we are 2 adults + 4 kids with all our stuff on the roof.

I would like to fit the OME 971 and 981 ( I think that is medium -front and Heavy Duty in the rear).

My first question is, being very new to fitting mods, do I have to fit OME shocks, coils and springs or can I "reuse "the nissan springs?"


Second question, I only want 5' lift as I have heard that one can get problems with the steering, if the lift is more. Any advice would be appriciated

Chris
The Dane in Lagos

[Peter Connan]

Hello Chris
Here I go again, trying to explain stuff to people who probably understand it better than I do. Sorry if you already know all this.

An OME or similar quality lift kit should consist of the following items, and I will attempt to explain the function of each item as I go:
1) Springs. This is what determines the ride height of the vehicle, as well as how much it sags when you add load. The spring rate (strength expressed in N/mm or similar units) determine how much it sags if you add a certain load, while the length at which the weight is carried then determines the ride height. Therefore to reduce the sagging you need to fit "stronger" springs, and to lift the vehicle you can use either stronger springs of the same or longer length or springs of the same strenght which are longer.
2) Shock absorbers. Normal shocks have no effect on ride height at all. They control the frequancy of the spring movement. Shocks are the most important suspension element in determining ride comfort and safety. If you drive next to a car without or with worn out shocks, you will see it's wheels bouncing. The springs want to do that, but the shocks keep the wheels on the ground. Good shocks are very complex and the manufacturers save money by using relatively simple ones, while most of the better suspension kits use slightly better (but still not great) shocks. They also control how far the wheels wil go down when the suspension is unloaded, and therefore have an impact on wheel movement in cross-axle situations. Since OME shocks are generally longer, they give better axle articulation.
3) Suspension bushes (castor correction bushes). When the suspension is lifted, the angle of the leading arms holding the front axle changes, and this causes the front axle's angle to change. This in turn reduces the castor angle (the angle of an imaginary line drawn through the pivot pins in the hub bearings relative to the road when the car is seen from the side). The castor angle determines how strongly the steering returns to centre after turning. In other words, not fitting these will result in the car "wandering" across the road more.
4) Gearbox mounting. This mounting is slightly lower than standard, so that the engine and gearbox are kept in line with the propshaft to the rear axle. The reason for this is that if a u-joint (as is found at both ends of the propshaft) is driven through an angle, it loses power through friction and also it's output speed is not equal to it's input speed. If you draw a graph of the output speed of a twisted U-joint, the graph will form a sine wave, the average speed being equal to the input speed, and the greater the angle the worse it gets. In other words, during one revolution of the propshaft, the output will be at times faster than the input, and at times slower. This places extra load on all the driveline components.

So you can decide which parts of the kit you want to buy, but if you leave anything standard you will not get the best benefits.

With regard to how much to lift, this is a question you need to answer by considering the use you want to put the vehicle to. The more you lift it, the worse it gets on road but the better it gets under certain conditions off-road. It will have better approach, departure and ramp or break-over angles, but reduced side-slope abilities. I beleive a 5" (125mm) lift is probably excessive for normal overlanding use (unless you go to Baboon's pass every holiday), and most of us go with a 40-50mm (1.5"-2") lift, if at all. I beleive a patrol with a 5" lift will probably be risky at any speed over about 115km/h.

Because the steering angles change, and the car will roll over more easily (paricularly in avoiding an emergency) the whole behaviour of the vehicle is affected by such a high lift.

Another popular option is to keep the suspension standard but fit air helper springs inside the rear coils. These can be inflated to return the car's attitude to normal when loaded, or deflated when the car is empty. They can also act as anti-roll bars which may improve your car's stability on the road, but when inflated they will limit suspension travel unless you couple the bags together with large diameter piping with a manual or electric isolation valve.

Regards
Peter


Regards
Peter

[Traveler]

It is quite a painfull and slow process to choose.

In the end I am fitting TJM. It all comes down to a large difference in price. And the guys on Patrol4x4.Com seem to have had good experience with it.

My Hilux rolled on a Rancho kit for the Tacoma, having the ability to change damper settings by turning a little dial was a huge pleasure. Would have like to combine Rancho Coils and shocks again.