Reverse 4 link

[bagged74]

Originally Posted by 70short/step

Just got my Air Ride Technologies catalog and this was in it!

that is talking about running two to the front and two to the rear. That does create a lot of pinion angle problems for sure.
Think about this for a minute...... people have been using 4 bar setups on the front of hot rods with straight axles for longer than most of us have been alive......this has the bars running forward and attached to the axle, no different that that rear setup, yet this is accepted as probably the best setup you can have for a straight axle....hmmmmm....
now, tell me why it wont work agian.....

[a squarecan]

Well the front axel is not driving the car; the rear wheels are. so if your pinion angle changes drastically while driving you are well.... SOL. The front wheels dont do anything but spin; there is no power to them. Also if you have 2 bars in front and 2 bars in the rear you limit your travel and if you do try to get much lift you just start to twist the axel in a forward or backwards motion depending on the upward or downward travel of the bags.

Keith

[70short/step]

[bagged74]

Originally Posted by a squarecan

Well the front axel is not driving the car; the rear wheels are. so if your pinion angle changes drastically while driving you are well.... SOL.

Keith

the pinion angle still changes whether the bars are to the front or the back. right? the arc is different, but the pinion angle still changes. the bottom line here is that that setup WILL work, is it the optimum sytem absolutely not.
I agree 2 to the front and 2 the the rear is possible the worst setup.

[dwcsr]

Originally Posted by bagged74

people have been using 4 bar setups on the front of hot rods with straight axles for longer than most of us have been alive......

Could you post a picture of a 4 bar on the front of a hotrod? I'd like to see what that looks like.

[darcane]

Originally Posted by dwcsr

this helps explain some of the problems with reverse setups
http://www.streetissuecustoms.com/reverse4.html
http://www.bagginit.com/research_paper.html

I'm not convinced that a reverse 4-link is an inherently bad design. Both of these imply that someone is simply taking a 4-link and installing it backwards so the instant center is behind the rear wheels. (Not surprising that both say this, since one cites the other). While this setup would undoubtedly be a bad design, I've never seen pictures of such a beast. Most of what I've seen are the reversed 4-bar setups like the picture in the first post on this thread. (Note: 4-bar normally means all four bars are parallel to each other and the instant center is at an infinite distance in front of the vehicle, while 4-link normally means that the bars are not parallel when viewed from the side of the vehicle and the instant center is in front of the rear axle.) A 4-bar will not have any effect on anti-squat, anti-dive, or pinion angle regardless of whether it is in front or behind the axle. So long as the rear of the bars are higher than the front, both setups should have acceptable bump/roll steer behavior. The only issue I can think of would be in an extreme lift situation the driveshaft could fall out of the tranny since the axle would move towards the rear of the vehicle. Not an issue for virtually every bagged vehicle out there.

I haven't seen any like this, but a reversed 4-link could be designed to provide anti-squat. Simply move the rear mounting points of the upper bars slightly upwards compared to a 4-bar setup. This would place the instant center in front of the axle where it should be. This would also change the pinion angle similarly to how a normal 4-link would. There may be some dynamic issues that I'm not considering here, but I don't see it as the inherently horrible design everyone seems to think it is.

[bagged74]

[bagged74]

not a very good picture but you can see the bars. I will find a better one.

[hotrodhomi]

nice car. I would drive it.

[70short/step]

Well since Air Ride Technologies has made quite a bussiness in the suspension department, I will believe what they say and that a "Reverse 4 Link" is a BAD BAD IDEA!
Until one of you who think it is a GOOD idea has a company and makes them and becomes one of the largest manufactures of suspensions, well maybe then I might think about it!

[valleycustom]

Originally Posted by bagged74

not a very good picture but you can see the bars. I will find a better one.

This would make a good point if the front had 10" of travel. If your running bags and you run a reverse setup you might have issues with the trans yoke pulling out from the trans. That would be bad because your car will become airborne when the driveline gets hung up on something.

BTW that's a bad A$$ car

[fastbagged68]

Also with a front end with a 4 link you have the nose dive effect when you slam on the brakes....causing the front to plant and the rear to lift. NOw if you have a reverse 4 link on the rear and you slam on your brakes the rear end will want to be pulled out from the rear....make sense?

[darcane]

Originally Posted by 70short/step

Well since Air Ride Technologies has made quite a bussiness in the suspension department, I will believe what they say and that a "Reverse 4 Link" is a BAD BAD IDEA!
Until one of you who think it is a GOOD idea has a company and makes them and becomes one of the largest manufactures of suspensions, well maybe then I might think about it!

That response from ART is refering to reversing just the top bars of the 4-link. This is a bad design, and I don't think anyone is saying otherwise.

Also just because ART is a large company doesn't mean they are always right. Keep in mind that it's likely a marketing team that wrote that response up there, not an engineer. Their job isn't informing the public on rear suspension design, their job is to lead people to buy ART products.

For instance, note this line: "With a normal 4 link, when you hit the brakes, the rear suspension geometry wants to lift the rear of the vehicle... therefore trying to plant the rear tires and assisting the braking action." This is flat-out wrong. The reason the rear lifts is due to weight transfer, not because of the suspension geometry. The 4-link will have some amount of anti-squat designed into it which, while accelerating, creates additional loading on the tires for more traction and pushes upward on the rear of the chassis. This will have the exact opposite effect during braking since the braking torque is in the opposite direction as the accelerating torque. So, there will be a downward force on the chassis and reduced loading on the rear tires. In cars that have a lot of anti-squat, the effect can be great enough that tire tires will lift off the ground causing brake hop.

[a squarecan]

Something else you need to think about is 95% of using doing or talking about these mods have bags. Dependning on set up you are looking at anywhere from 5-24 inches of lift. Ya you are going to cause some problems. On those old ford buckets if one decided to install a reverse 4 link they are most likely using coil overs. Nice ride; Yes! A lot travel? No! So that is something to consider, also fast bags is right about the pulling direction, but a lot of these old school buckets are mearly show cars/trucks. So backing out of the trailor or even driving a few blocks to the show usually will not cause any problems.

Keith

[bagged74]

Originally Posted by a squarecan

Something else you need to think about is 95% of using doing or talking about these mods have bags. Dependning on set up you are looking at anywhere from 5-24 inches of lift. Ya you are going to cause some problems. On those old ford buckets if one decided to install a reverse 4 link they are most likely using coil overs. Nice ride; Yes! A lot travel? No! So that is something to consider, also fast bags is right about the pulling direction, but a lot of these old school buckets are mearly show cars/trucks. So backing out of the trailor or even driving a few blocks to the show usually will not cause any problems.

Keith

have you ever even seen what i am talking about? coilovers??? on the front?? with a straight axle??? no i dont think so. And for show only??wtf?? there are plenty of those cars that log many many miles. I agree that the amount of travel will make a difference. But the braking problems are nonexistent. I'm not trying to say this is the ideal setup by any means, I'm just saying that it will work. Until you have driven a truck with a reverse 4 link daily for about a year, dont tell me about how it wont work and it will have all of these problems. I am telling you that it will work i have used it on my own truck, and I have actually installed one a truck for a buddy. Once again is it the ideal setup...NO, does it work better than some of the other option that you have on certain vehicle?....YES.

[a squarecan]

Hey bagged74,

Sorry for the miscommunitcation; I was speaking about the rear when I was talking about coil overs. I posted that right after I woke up this morning and was not all there. I agree with you it does work it is just not ideal.

Keith

[dwcsr]

I came across this link on 4 links and what happens in each of the install types we were discussing

http://www.illconformity.com/videos/linkvideo.wmv

[darcane]

That's a decent video, it illustrates how the suspension moves pretty well. And in the reverse 4-bar you can see that the only difference in movement compared to the regular, 4-bar is that the driveshaft could get pulled out of the tranny as previously mentioned

But...

The suspension travel he is showing is rather extreme, which is better for illustration purposes, but doesn't translate to reality. The links on my rear suspension are 30" long IIRC. If they were able to move 45 degrees up and down, that would give me a total travel of ~42". The reality is that I get a total of about 8-10" of travel with my airbag setup. That translates to up to ~9 degrees of angle up and down, and the differential would move fore-aft less than 0.5". Nothing to get too worried about, even in a reverse set up.

[dwcsr]

It is a very exaggerated travel. When I saw it my thought was that with a plywood cut out of the axles housing and some 2x4’s you could do a actual size mock up to get an idea of what would fit and what the clearances look like and estimate the C notch.