Each spring is designed for two different things. One thing that is nice about the progressive coils is that as you articulate the axle it will progressively get stiffer keeping you from having harsh bottomings. In the past few years we have been seeing people adding the air bumps, which also as you compress get firmer to keep from having harsh bottoming. Progressive coils can also be engineered to provide a softer ride intially so that bumps aren't harsh, but at the same time you won't bottom.

If you plan on carrying a load in your Jeep the progressive coils won't sag as much as a liner spring rate. This also works as you add bumper, etc...

The bad part about progressives that a lot of people have is that they don't flex as well as a linear rate when the vehicle is not in motion. If a moving force is being applied then they flex as well, but when you get out to take the picture, you are no longer applying the moving force, and never will see the bumpstops hitting. Also they take a lot more work and engineering, and a lot of companies just get it wrong. This is a big reason why people tend to dislike them because company XYZ had them too soft initially so the softer portion collapsed, and now they are riding on the hardest part of the sping causing a harsh ride.

 

I understand that. But that's because the diameter has to change to clear the suspension. If the diameter has to change, then the coils must get tighter to retain the same rate. You still might be right, I don't know, but just because they get closer together doesn't necessarily make them progressive.

 

Thanks, Littlejon. That's a good explanation. I've just never thought progressive springs were really what a Jeep needs.

 

Such interesting stuff, I'm loving it.
I love how discussions pop up when anything from the AEV stable is mentioned.
It's awesome haha Keep posting guys, I'm absorbing it all into my cranium

 

I think it is just the purpose you have for your Jeep. For me oftentimes I tend to have to travel in our Jeep to go to many off roading locations, and so I will have a Jeep with a few hundered pound of gear and 4 people, and with a linear rate I will ride the bumpstops all day. This is where the progressives are nice. They aren't for everyone, but like anything we add to our Jeeps they do have a purpose for some people.

 

AEV isn't the only one doing the progressive springs. Rough Country has also done them. They both have had issues with getting the spring rate right with the weight transfered to the rear when the front is lifted. AEV went to a linear rate for the 2 door because of this (prior to releasing their kit), and Rough Country went to a linear rate on the rear of all Jeeps (after releasing the kit and recieving complaints). It really does take a lot of work and engineering to get them right.

 

Totally agree. Same story here. That's why I like the AEV lift. I realise it doesn't flex as much as other lifts, but I don't need super crazy flex, and I have lockers for when traction is scarce.

I think the most important thing is when discussing a product or part is to look at it from other peoples perspective as well. A product may be completely wrong and unsuited for you and as a result you don't like it and criticise it, yet it may be perfect for someone else and they love it.

Eg - I'm not a fan of Budget Boosts. I think if you are going to lift your Jeep you should make a considerable amount of change, otherwise why bother? That's entirely my opinion and I know many people will disagree with me. But at the same time I appreciate Budget Boosts and what they are. They do improve clearance etc and can be a great improvement to a JK, so why not? They're just not what I want and need for my Jeep. But I'm not going to go and criticise them because they don't suit me needs and wants..

K, I think I'm rambling on here. I'm going to be quiet now and enjoy a drink on this lovely Friday afternoon. Cheers guys!

 

I totally agree with littlejon facts and opinions.

 

Redneck I understand why you disklike progressive rate coils and I agree that most of them have poor performance, but the ones that are properly engineered (and I am not using the term loosely) do not suck.

Progressive coils like the ones from RC have given this type of coils a bad reputation. However, the stocks coils and the ones from AEV are examples of what a well designed and manufactured coil can deliver.

To say that progressive coils suck is akin to saying that progressive shocks suck which they obviously do not or Bilstein, King, Fox and all the other high end shocks would not have a market.

The challenge with progressive coils is that they require taking into account the dynamic behavior of a vehicle which requires much more sophisticated knowledge base, analysis and design software, simulation and testing than what is required for the pseudo-static design of constant rate coils. This is why the factory engineers or anyone that has worked on their team has an advantage over the rest. It's a simple matter of budget and resources.

Constant rate coils are a compromise of every operating condition by design, where progressive coils attempt to address different inputs with a different response. Ideally both coils and shocks would be computer controlled to respond to more conditions.

Progressive coils are also more sensitive to the design weight (preload) because the lower spring rate portion of the coils is designed to compress easily to absorb relatively minor road disturbances to provide a softer ride on the road. The challenge is that some of us run stock weight, some of us run even below stock weight by removing the top, doors, spare tire and everything else that is not firmly attached while still others load the Jeep up with armor like a tank. The RC coils are designed with a preload that is too low and the AEV coils are a bit stiff unless you carrying an extra 400 lbs of armor. But when you are on the target, where as linear rate coils are just a bit stiff no matter what.

The reality is that most suspension companies try to cover up the poor performance of the coils with the shocks and they don't even bother to match the shocks to the coils. If we were willing to pay $1000 for a set of coils instead of the usual $200-400 others would produce high quality progressive coils.

Like everything else, progressive coils are not for everyone, but it sure is nice to have a lot of options unlike the days of leaf springs on the YJ

 

I love it when Redneck gets on a rant.