parabolic springs vs leaf springs

[nugget]

I was not able to find anything using search, so wanted to bring up this topic, because I think they would be an excellent option for the MS on the rear of the generation 1's.  

I used to have a series 3 land rover and parabolic springs was one of the huge improvement mods that made the ride bearable versus bouncing all of the place, which is how the ride was on normal leaf springs at each corner.  

If you are unfamiliar with what they are, here is a link that explains them reasonable well.  www.loske.org/html/dusty/pinfo.htm 

I would like to know if anyone has done a setup like this, they would most likely have to be custom made, but something really worth looking into.  

[ES_97Sport]

Feb 21, 2016 12:10:28 GMT -5 nugget said:

I was not able to find anything using search, so wanted to bring up this topic, because I think they would be an excellent option for the MS on the rear of the generation 1's.  

I used to have a series 3 land rover and parabolic springs was one of the huge improvement mods that made the ride bearable versus bouncing all of the place, which is how the ride was on normal leaf springs at each corner.  

If you are unfamiliar with what they are, here is a link that explains them reasonable well.  www.loske.org/html/dusty/pinfo.htm 

I would like to know if anyone has done a setup like this, they would most likely have to be custom made, but something really worth looking into.  

I went all through this years ago. There used to be a bunch of stuff on this on Pirate some time ago. I expect its still there, but leaf technology is generally considered to be 'old' and 'outdated' so I don't think there's anything new. If you ask they're going to tell you "You're an idiot, you should just run a link suspension with coil overs. RTFM!" Kind of the 'Linux' bunch of the 4WD world.

The issue I ran into is that its hard enough just to get leaf springs. Never mind what kind. I talked to the former owner of Alcan about this many years ago. Yes there were benefits but the cost exceeded the benefits. Least-wise, that's what I was told.

I do know that it was cheaper to settle on a well built set of 'regular' springs, than even a generic set of parabolic springs.

KIM that springs are a disposable, wear item like brake pads. You don't build a set of springs and then you're done for ever and ever, amen. This is the same for coil springs like my Ford Bronco set or coil-over springs. I go through a set of leafs about every three years. Typically, even on a street vehicle that isn't used for towing, carrying loads or anything else stressful, leafs only last for 10-15 years.

Now, I get where you're coming from. The stock Gen 1 leaf springs are crazy stiff. It doesn't matter what they're on or what engine it came with. There's absolutely no difference between my '97 LS 3.0L, my two friends '98 LS 3.0Ls and my top of the line '99 Limited 3.5L. Its great if you're carrying a load but otherwise its kinda harsh.

The issue isn't the type of the springs, however, its the spring RATE and the anti-roll (sway) bar. (I'll get to the bar later.) I had the chance last month to do a apples-to-apples comparison between the OEM leafs in my '99 Limited 3.5L and my custom Alcan leafs in my big Sport with the 3.5L conversion. I had the tech leave off the anti-roll bar on the '99 since its going way here shortly and the big Sport doesn't have anti-roll bars so its possible to get a feel for the actual spring behavior without the interference of the anti-roll bars.

There is absolutely no resemblance between the two. The custom springs - while able to carry at least twice the weight of the OEM springs - are softer, more consistent, very smooth and flex a lot better than the OEM springs. There's nothing fancy or 'special' about my Alcan springs. They're just a better design than the OEM spring packs.

The other thing that contributes to the choppy, harsh ride in the back is the anti-roll bar. That thing is way, WAY too 'stiff'. I'm not sure what Mitsu was trying to accomplish with this. I suspect there's some Fed insane tip-over at 100 MPH while trying to make a 90 degree corner thing going on there. Whatever it is, that bar is really over the top. That was one thing I'd forgotten from more than a decade ago. When the tech pulled the anti-roll bar off the '99, about 1/2 the problem disappeared.

I AM NOT advocating removing the rear anti-roll bar! The OTHER thing I'd forgotten is what its like driving an OEM Sport with no rear anti-roll bar. That back end tends to have a mind of its own when it comes to corners.

Anyway, just my 2 cents worth.

Edward

[nugget]

Thank you Edward for your awesome explanation. Your knowledge and experience is always beyond my expectations and greatly appreciated.

[dclambertt]

I think that response was worth AT LEAST 4 cents Edward, maybe even 5.

[ES_97Sport]

Mar 14, 2016 13:43:32 GMT -5 dclambertt said:

I think that response was worth AT LEAST 4 cents Edward, maybe even 5.

I'll add one more cent ...

What would be REALLY cool would be a single leaf setup.

Mono Leaf Springs vs Multi Leaf Springs from Eaton Spring

I run a composite single leaf setup on my '68 'Bird. I THINK they came from Eckler's but its been so long now that I've forgotten where I got them from.

This would be insanely stupid to do on something like a SUV or truck. I run a 'military' wrap on the big Sport for good reason. I've broken almost every leaf in a spring pack, including two main leafs. The last main leaf I broke was on Flat Pass trail after coming off of Steel Bender outside of Moab. I was able to limp the vehicle - barely without body damage - back to Moab but only because of the wrap. The secondary leaf still kept things in position. I had maybe 4" of clearance left after PS dropped when the leaf broke. If there were anymore big obstacles, I would have been screwed. Its real handy getting springs from Alcan in Grand Junction. They're only about an hour from Moab. Turns out I had a secondary leaf broken in the DR side as well. A shop dropped both springs, I grabbed a rental and hauled them to GJ and Alcan repaired the springs in a couple hours. Drove back to Moab and the shop dropped 'em in. Out of a two week vacation I was only down for a day and a half.

ANYWAY, its amazing how nice a mono-leaf is vs a multi-leaf. There is a LOT - a WHILE LOT - more friction between leafs than most people would think and that frequently causes issues that are attributed to the rate of the spring. When a leaf spring pack compresses or extends, the leaves rub against each other. This is a problem that gets worse as the spring packs age. Rust, dirt, sand, and crud get between the leaves and increase the amount of friction.

There are several ways to work around this. Pads, liners, special low friction paint, but at the end of the day, they're really just band-aids. Necessary and definitely wanted band-aids, but still band-aids.

nugget: I've been around or involved in maintaining or building cars and trucks since I was born and I have a some background in mechanical engineering (which helps). I can't take all the credit. A lot of what I know has been passed on to me by people who are a lot smarter than I am. I've had a lot of really good teachers in a lot of fields over the years.

Edward