Thoughts on running without front sway bar with air shocks? (1 Viewer)

[Dave 2000]

Drive the truck for a while and avoid the temptation to modify anything. You'll find a stock fzj80 will do just about anything you ask it to. Including wearing 34" tires and any type of "expedition" wheeling you'd like to do. Once you're familiar with it's capabilities and made sure it's all good maintenance-wise, then consider spending money on upgrades. A lot of people here (myself included) have spent boatloads of money on upgrades only to take them off and go in a different direction later. Maybe spend some time with the truck and let your experiences determine the direction you want to go before you buy anything.

Probably one of the best statements I have seen on MUD in a long while.

Regards

Dave

 

[malteserunner]

Actually it doesn't, one just has to look a level or two deeper into how this works. Traction between rubber and a road is not a linear function of weight applied. It's actually a quadratic relationship. With heavy vehicles and hard compound tires we are in the diminishing part of the curve. This means as the truck is leaning the traction on the outer wheels while increasing is doing so at a slower rate than the force is increasing. Conversely, light vehicles which sticky tires are in the part of the curve that increased faster than weight is applied hence why hyper sports cars can pull over 1G on a skid pad.

Thought experiment: The truck is going into a turn, the weight is transferring to the outer wheels. Ideally, the front axle roll stiffness his higher than that of the rear axle. This increases the weight, which is going up with increase cornering load, increase on the front wheel faster than weight is increasing on the rear wheel. This pushes the front farther into the diminishing range of the traction curve and encourages the front end to push/plow. Thus, it is not that the 80 overcomes its sway bars on the trail that matters, it is the difference in roll stiffness, which is heavily impacted by the sway bar, that matters here. We can't play tricks with camber, cambering in the rear and out the front, so roll stiffness is all we have to play with when it comes to designing in or preferably out oversteer.

Another way to visualize this and is a real possibility, is the truck goes into a turn, leans, the front being more compliant keeps the axle square with the ground, the rear with more roll stiffness lifts the inside rear wheel. This is bad, very bad. The rear is riding on the outer edge of the outer rear wheel and oversteer is eminent. I found this out once playing with sway bars the hard way. I didn't wreck, I had given myself lots of room, but it make for a high sphincter tension situation.

Many years later after becoming an ME I took on a side project to design a chassis and did a lot of reading on this subject and had one of those "ah ha" moments when it explained in technical terms what I had experienced years earlier.

Frank

All the science is proven in real world, on this matter. You have a whole lot of valid points here. So, on a track car, race truck, sports car, etc., the sway bar setup will be very important.

With the 80 series, specifically, the front suspension is so much less flexy than the rear suspension, that when the front sway bar is removed, the difference is negligible. If the front were linked and flexy, we wouldn't even be having this conversation.

 

[bwakeling]

With stiff springs and shocks I dont notice removing the front or the rear.

 

[elripster]

All the science is proven in real world, on this matter. You have a whole lot of valid points here. So, on a track car, race truck, sports car, etc., the sway bar setup will be very important.

With the 80 series, specifically, the front suspension is so much less flexy than the rear suspension, that when the front sway bar is removed, the difference is negligible. If the front were linked and flexy, we wouldn't even be having this conversation.

These principles are already in place on the 80 from the factory as well as every other vehicle and have been for decades.

One will not really notice the impacts of, for example, removing a front sway bar, until one attempts an avoidance maneuver and pushes the vehicle to its handling limits. That is of course the worst time to find out the rear is swinging ahead of front and you are about to rubber side up. Very stiff springs will also add roll stiffness and by themselves could increase roll stiffness beyond what the production spring/bar combo provided. Still, it's the difference in roll stiffness that is key and reducing front end roll stiffness is temping fate especially in a truck with a high CoG. Track cars might not handle well if roll stiffness is mismatched but they will likely slide before they roll.

If anyone here has the means to see if the impact of sway bar removal is negligible, great, if not, I suggest going by rules of thumb so to speak and keep the front bar if you are going to run just one bar. Removing the rear might let the truck lean more but it will probably reduce oversteer tendencies.

All I can do is provide the information. Whether or not one chooses to use it is up to them as is the liability.

Frank