Are Reversing 4 link bars good?
Are Reversing 4 link bars good?
(OP)
I have a few questions that in another forum http://streetsourcemag.com is an extremely heated arguement between this is ok, and not ok to install and daily drive with.
In the custom truck world using air ride (air bags) and laying the truck on the ground and lifting up for driving. The fad in the past 5-10 years have been using 4 links with the top 2 bars triangulated "V". Now the issue is due to the gas tank being in the way with the top bars, so the easy way out has been simply facing the top bars backwards on the frame. Meaning they mount where the spare tire used to be. The air bags are mounted on each side of the solid axle. Which more and more are doing this due to simplicity and not having to move the factory gas tank. What are the pros and cons to this setup and what saftey measures are gained or loss from this type of setup?
The other question is the same as above, but reversing all 4 bars. What are the pros and cons and saftey measures gained or loss from this for a normal daily driving setup?
There are alot of people that swear to these reversing bars setups for years with around 50K+ miles driving from coast to coast and no problems. Stating that by the book the design has alot of flaws and should not work, but they do work, and more and more people are doing them... By designers and engineers what are your ideas, points, and explinations to these types of setups?
In the custom truck world using air ride (air bags) and laying the truck on the ground and lifting up for driving. The fad in the past 5-10 years have been using 4 links with the top 2 bars triangulated "V". Now the issue is due to the gas tank being in the way with the top bars, so the easy way out has been simply facing the top bars backwards on the frame. Meaning they mount where the spare tire used to be. The air bags are mounted on each side of the solid axle. Which more and more are doing this due to simplicity and not having to move the factory gas tank. What are the pros and cons to this setup and what saftey measures are gained or loss from this type of setup?
The other question is the same as above, but reversing all 4 bars. What are the pros and cons and saftey measures gained or loss from this for a normal daily driving setup?
There are alot of people that swear to these reversing bars setups for years with around 50K+ miles driving from coast to coast and no problems. Stating that by the book the design has alot of flaws and should not work, but they do work, and more and more people are doing them... By designers and engineers what are your ideas, points, and explinations to these types of setups?





RE: Are Reversing 4 link bars good?
Reversed 4-links put the link bars in more compressive loads, when hitting bumps, curbs, etc. I would think under acceleration, the torque would tend to lift the rear of the truck too. Instant center could be really odd.
I think of a reversed 4-link, like trying to push a rope.
-Dave
http://www.moslerauto.com
RE: Are Reversing 4 link bars good?
This is to provide enough lift with channeled/body dropped trucks to lay flat on the ground with large wheels, and have enough lift to clear the wheels for daily driving. So what would this gain and loose with the half reversed bars and full reversed bars?
RE: Are Reversing 4 link bars good?
RE: Are Reversing 4 link bars good?
RE: Are Reversing 4 link bars good?
Do the drawings, study the arcs and the effects of suspension movement on wheel, axle and pinion motion and alignment.
Consider the direction and magnitude of the forces involved and run the numbers.
eng-tips, by professional engineers for professional engineers
Regards
pat
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Are Reversing 4 link bars good?
A reversed 4-link...look at the instant center, its someplace behind the truck.
Try this once...take a push broom, the handle represents the 4-link bars, and the broom head is the axle. Now pull it around the room, and over some bumps, even over your couch. See how it follows you? Now put the handle against your stomach, and push it around the room, and over that couch. See how when it hit the couch, it transferred the load back into your stomach, aka frame? it also put the handle/bars into compression. On a car/truck, these compression loads are going to want to push that axle to the side.
A reversed 4-link also pulls the axle away from the transmission as the suspension is lifted, which slides the drive shaft farther out of the tranny, and if it goes too far...
I suspect the reason you don't see much literature on these setups, is because they were found to be inferior, not because its new and revolutionary. In my opinion, even though it may work, its far from the best way to do it.
-Dave
http://www.moslerauto.com
RE: Are Reversing 4 link bars good?
Another issue is the rigidity of the chassis as measured between the front and rear suspension linkage attachment points. Having the rear bar chassis side attachment points aft of the axle means some extra length of frame rail and added flexibility due to the bends necessary to clear the axle.
To get the same geometry would likely involve longer (read: either less rigid or heavier) brackets for the lowers, which in turn increases the load to the frame rails themselves.
It's not that you can't get it to work; obviously it can physically be done. It's just that there are more efficient solutions available. And isn't that one of the hallmarks of good engineering?
Norm
RE: Are Reversing 4 link bars good?
I think most have covered the problems of all 4 links facing rearward. Although I think I've seen this concept used in the front axle on old race cars(like old Indy 500 cars).
RE: Are Reversing 4 link bars good?
Regards
pat
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Are Reversing 4 link bars good?
I meant if you always run it at full height (20").
Otherwise it should run straight about halfway between the min and max run heights considering travel while running.
You should also consider that it should be as straight as possible in the most common drive position.
On the above two points, you will need to set a compromise
Regards
pat
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Are Reversing 4 link bars good?
Norm
RE: Are Reversing 4 link bars good?
RE: Are Reversing 4 link bars good?
The thing I keep in mind is just because you can get away with it does not always make it the best soultion.
how many low riders have you seen with terrible suspension geometry and bad bump steer?
all suspension designs are a compromise but I wouldn't mount my bars based on the location of the fuel tank, decide what will work best and truely customise it.