Recently, we attended the National 4×4 & Outdoors Show in Brisbane. We were thrilled with the turnout and very happy to meet the 4WDers who braved the torrential downpour to come out, say g’day and get the technical advice they needed for their vehicles.
We were astounded though by the regularity of the request people had to “level off” their vehicle in one way or another. The most common request was for the Toyota Hilux 2005 on, we had a number of people telling us that they had seen sellers in the market offering a three inch front and two inch rear lift for the vehicle to level the car off.
This worrying trend is something we want to try to educate people about because the reality is that levelling off a vehicle is one of the worst things that could be done when it comes to 4WD suspension.
Rake is the term used to describe how much of a difference there is between the front and the back of the vehicle, or how much nose down, or nose up attitude the vehicle is sporting. We measure rake from the chassis to the ground at a part of the chassis that is the same at the front and the back (there’s no point measuring from a dent or a mounting plate). The rake of the car is the difference between the front and the back of the car.
Ideally, we want between 10 and 15mm “nose down” attitude in the vehicle. For anyone who has ridden a motorbike or a pushbike, the importance of keeping the weight slightly forward when braking and turning will ring true. The same applies in a 4WD, we want to keep the weight in the car in a position where under braking and turning, the weight transitions forward.
So, if we attempt to set up in a level stance, the moment that even the lightest of light loads is put in the rear, the vehicle will no longer have good weight transition and will suffer in cornering and braking performance.
We have lost count of the frequency of the request for ‘Heavy Duty’ springs for vehicles. Heavy Duty, is a term that marketing teams and advertisers have bandied about far too liberally, and the true meaning has been lost. Heavy duty means the ability to last a long time, and be reliable even in situations that demand the most out of a product. Because that is the case, all Tough Dog product is tried, tested and proven to be ‘Heavy Duty.’ Of course, heavy duty is not the same as heavy load carrying, and that’s where the majority of the mix up occurs.
Tough Dog make (for most vehicles) three rear springs; a 0-300kg, a constant 300kg, and a constant 500kg. And too many times the constant 300 and 500kg springs are used when the user wants something heavy duty. The end result, when the weight is not on the car, it has a stance like a dragster from the 1950’s, and has achieved 30mm or more of forward rake! This is just as bad as not enough rake, but now the car looks ridiculous as well. This set up will cause a world of problems and premature bushing failure. Most people respond by increasing the height of the front, instead of correcting the actual problem… the rear height. Now all of a sudden the possibility of CV joint problems, front strut problems and wheel alignment difficulties are all brought into play.
For more information, check out our video on selecting spring rates here, remember, what applies to the front spring selection is just as relevant in the rear.
The answer is a simple one, the rake in a car should be 10mm approximately and with regards to spring selection… put simply, select a spring based only for the weight that is constantly on the vehicle, not the weight that is removable.