E31 Suspension Gurus Needed! Custom springs.

[MJ DOOM]

I have Bilsteins with stock springs. Top of wheel well to ground is 27 inches front, 26 inches rear. I want to drop the front 1.5 inches and the rear .5 inches.

Bilsteins specs are:

PE3-B009 (F)
Compression @0.52m/s: 1000
Rebound @0.52m/s: 3400

BE5-A809 (R)
Compression @0.52m/s: 1100
Rebound @0.52m/s: 3000

Is is possible to make a custom spring set to match the Bilsteins, give the drop I want and have a proper Spring Comparison %F-%R?

Through my research there are alot of guys on the board that know the suspension on our cars very well so its kinda strange I couldn't find anything like this done before. It seems it should be possible. I found a lot companies that make compression springs and it seems I just would need a spec to give them.

So asking the suspension gurus or anybody could you give a me spec for some custom springs that matches what I want, if possible? Or some info to lead me in the right direction.

Thanks,
Doom

[Max Lumens]

If I get ambitious, I'll build you a set of springs like that. No cutting, will shorten them on the barbecue. Should leave you with a slightly softer spring, which should be a good match for the slightly too-firm shocks. What could go wrong? Interested?

I'm kidding about the barbecue, would use a kiln. Not kidding about this means of adjusting springs, tho. A DIY solution waiting to happen IMHO. Anyone can do it, just go pester a potter and stink up their kiln. I haven't worked out the details on heat, nor figured the best way to arrive at the calculated length. You could install spring compressors and crank them to your desired length, ie 1.5" shorter, then heat them till there's no pressure on the compressors. Or heat and then compress. You could compress the whole spring or just a section, guessing at what this would do for the rate. Throw them in the hot tub afterward to freshen up the temper? Toss some powder coat on them when the temp is right? I think it's time to boldly go for it; plenty of stock springs around, and you should be able to adjust them repeatedly till you get what you want. FWIW

[MJ DOOM]

Thanks for response. Honestly I'm not much of a DIYers when comes to mechanical stuff. Just looking for set to made to my specs and give them to my Indy and be done with it.

[Max Lumens]

Contact me offline after the holidays, "max@finemotoring.com". I have a kiln, been meaning to figure this out for a while, maybe 2013 is the year.

[MJ DOOM]

Cool, thanks.

[toomanyparts]

Bill,

I'm not a materials engineer, but are there any side effects from heating the spring?

[legoman67]

Id imagine if you were to put them through multiple heat cycles they were start to get brittle and break easily.

[Max Lumens]

Google on "harden, temper, and anneal". I doubt you'd have to get them very hot to get them to compress, and temp would be low enough that it would simply re-temper the steel a bit. I'd be more concerned about making them softer, ie lower spring rate after shortening.

[MJ DOOM]

Is it possible for me to just send the stock springs to a spring manufacturer to give them a base to work with and asked for a duplicate set with custom lowering and a spring rate to match the bilsteins?

[8eights]

Bill,

I'm not a materials engineer, but are there any side effects from heating the spring?

Yes, You'll ruin them and the car will eventually float like a 76 Coupe De Ville with bad shocks, Horrific and unsafe outcome!

[Max Lumens]

Yes, You'll ruin them and the car will eventually float like a 76 Coupe De Ville with bad shocks, Horrific and unsafe outcome!

Have you done it? If so, what did you do and what happened? I've cut coils with a torch, never tried heating the whole thing. Why doesn't it work?

[Kralik]

Max Lumens, if you heat the whole spring for example up to 350°C and then cool it down naturally in the air, then it will be probably softer it. There is a big BUT. You do not know the original iron structure. You do not even know the percentage of the carbon in the iron (exact material), you do not know the springs "tempering" cycle in factory... So, at the end you are not able to predict how your DIY "heat" treatment will effect the material from pure material and mechanic perspective Basic diagram with temperatures and iron structures for all enthusiasts & professionals is Iron-Iron Carbide Phase Diagram = Fe / Fe3C.
PS: Max, you do great 8er related stuff, that is amazing!

[bcain79]

I used to help design suspension systems for armored vehicles. We would always have custon springs made to meet our specs. You just tell them what you want and how much your vehicles weighs and they do the rest. We paid $250 a pair. For what its worth we used Benz Springs in Portland, OR.

[tvjake2]

I used to help design suspension systems for armored vehicles. We would always have custon springs made to meet our specs. You just tell them what you want and how much your vehicles weighs and they do the rest. We paid $250 a pair. For what its worth we used Benz Springs in Portland, OR.

Thanks, that's good info.