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Discussion Starter #1
ok first off i'd like this to say on topic, not looking to start a debate about the possible cons of cutting a coil spring. i've read up a lot on this and know the proper way to cut the spring without harming the temper of the steel. with that being said i've decided to switch from the bilstein pss's im running now to a set of koni sports. i already have a set of front eibach lowering springs i'll be using. though i need a similar drop in the rear. frankly im just not looking to spend anymore than i have to and being i have two sets of stock e39 m5 springs i figure why not just cut a set down a bit. so my question is how much should i cut off the spring to achieve a similar drop as the front? thanks.
 

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with so many options theres no reason to cut springs, if this was a car with little options for lowering yea cut away. where people get into trouble with cutting springs is cutting way to many coils off and not flattening the end to seat in the purch properly.

cutting a half a coil off is not a big deal but you have to then flatten out the rest of the coil to match how it was before you cut it in order for it to seat properly.
 

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Discussion Starter #4
its about i already have probably $1800 into a bilstein pss kit that i'll be lucky to see half of that back when i sell it. i want this next suspension swap to be as cheap as possible. and again please, as i said im not looking for a discussion on why it shouldn't be done, please stay on topic. i know how to cut the spring correctly, finish the end, and rust proof it. if you look at the top coils on a rear m5 spring the last few do very little as they are completely compressed when loaded. im not looking for a 3in drop, just enough to match the front, around an inch. just need to know how much to cut off, ie one coil, half a coil etc.
 

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Can you regroove the perch on the konis instead of cutting the spring?
 

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Unless someone chimes in saying they've done this to the rear of an M5 it's going to be a guessing game. It's too bad the rears are such a pita to do, but then again you wouldn't be putting everything back together until it was where you want it anyway. I would just get out a measuring tape and check coil thickness and go from there. My guess is you will want a full coil, but probably start with half and see how much change you get.
 

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Discussion Starter #8
Unless someone chimes in saying they've done this to the rear of an M5 it's going to be a guessing game. It's too bad the rears are such a pita to do, but then again you wouldn't be putting everything back together until it was where you want it anyway. I would just get out a measuring tape and check coil thickness and go from there. My guess is you will want a full coil, but probably start with half and see how much change you get.
i have to do some more research but i think im gonna start with one coil. i have two sets so if i screw up i have an extra.
 

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ok first off i'd like this to say on topic, not looking to start a debate about the possible cons of cutting a coil spring. i've read up a lot on this and know the proper way to cut the spring without harming the temper of the steel. with that being said i've decided to switch from the bilstein pss's im running now to a set of koni sports. i already have a set of front eibach lowering springs i'll be using. though i need a similar drop in the rear. frankly im just not looking to spend anymore than i have to and being i have two sets of stock e39 m5 springs i figure why not just cut a set down a bit. so my question is how much should i cut off the spring to achieve a similar drop as the front? thanks.
Before I get the wrong idea? Because you know or have read what to do??? So you are going to cut the spring detemper the top or bottom and reform it to be the same as it was before? IE so that the spring has the same shape as it did to fit the seat?
If you just cut it you will only have an inch or two bearing in it's seat and the spring will rotate on ever compression and wear thru the seat in no time.
The top and bottom of the spring have been flattened that profile must remain because of the overall design of the suspension. If you can do that you should be OK. If you can't... then you should not. You could likely do it by using a spring shop as they will detemper reshape and then retemper. My bet is it will only cost twice as much as a spring.
 

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I've done exactly what you want to do, a few months ago. Brand new Koni yellows and all associated hardware, H&R kit up front, and I cut 2/3 of a coil off the rears. From what I've read, because I'm certainly no susp expert, removing coils ups the spring rate a bit to help match the new springs up front. I adjusted the Koni's per Dinan recommendation, and they were spot on for the rears. I had a bit of bounce out front, but dialed that out with another half turn on the adjusters. Cutting the rears got me very close to even, and the extra 3/16th's lower the front sat was remedied by lifting the strut housing in its pinch bolt. After some camber plates and a mildly aggressive aligment it handles perfectly. I can get you an exact measurement of the height in the back from the centercap to the fender lip if you need it. I say go for it, if I didn't like it I certainly would not have been afraid to switch it up.
 

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Would custom springs not be an option?

I know you are not specifically asking for them and at first glance it would seem they would be an expense you are trying to avoid but they really aren't that expensive and will have been properly manufactured re: ends formed and tempered etc.

These guys are UK based but ship internationally and are well reknowned in the UK at least and amongst the rallying/motorsport fraternity.

Perhaps a quick call or email would leave you in a position to see if its worth pursuing or not.

Suspension springs for the Motorsport Industry | D Faulkner Springs LLP

At a quick glance springs are about £30 each depending on length and lb'age. About $100 in for a pair isn't too bad IMO
 

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It's been a while, but OldRanger "fixed" the Eibach front spring only '60s drag racer rake issue this way with excellent results. Andy spent a good bit of time and thought on the progression that led to this step. Here's the link to his thread. This is one of those "d**m, can't believe this was 9 years ago moments again.
 

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Discussion Starter #13
I've done exactly what you want to do, a few months ago. Brand new Koni yellows and all associated hardware, H&R kit up front, and I cut 2/3 of a coil off the rears. From what I've read, because I'm certainly no susp expert, removing coils ups the spring rate a bit to help match the new springs up front. I adjusted the Koni's per Dinan recommendation, and they were spot on for the rears. I had a bit of bounce out front, but dialed that out with another half turn on the adjusters. Cutting the rears got me very close to even, and the extra 3/16th's lower the front sat was remedied by lifting the strut housing in its pinch bolt. After some camber plates and a mildly aggressive aligment it handles perfectly. I can get you an exact measurement of the height in the back from the centercap to the fender lip if you need it. I say go for it, if I didn't like it I certainly would not have been afraid to switch it up.
thank you, exactly the info i was looking for. i measure ride height from the bottom lip of the wheel to the fender, if you can get me that spec i would appreciate it. apparently Oldranger did exactly what im planning on doing, even ran the same springs i have for the front, the h&r 29441's. if you read his thread on the matter even Lscman advised that you can cut a bit off the top of the rear spring with no ill effects. that guy is like the e39 suspension guru so if says its ok im going to tend to believe him.
 

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on an expensive car like this, why cut up perfectly good springs?

just do the old "use nuts as spacers trick" for that perfect sick drop.



Height is adjustable in increments of 1 nut - go as crazy as you want!



You might have to cut your rear shelf though (or maybe even remove rear glass), to allow the tops of the struts to come up far enough.
 

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One full coil will be way to much.

It is unseemly seeing M5 owners trying to cut corners because of money :( It makes those of us who aspire to the heights of M5 ownership question our quest :eek:

:rofl:



PLEASE NOTE THAT I DO NOT OWN AN M5 AND THIS POST IS NOT INTENDED TO BE ARROGANT. PLEASE READ THE IMPORTANT REVISED DISCLAIMER THAT APPLIES TO THIS POST
 

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on an expensive car like this, why cut up perfectly good springs?

just do the old "use nuts as spacers trick" for that perfect sick drop.



Height is adjustable in increments of 1 nut - go as crazy as you want!



You might have to cut your rear shelf though (or maybe even remove rear glass), to allow the tops of the struts to come up far enough.
Are those pics from your personal collection? You could have at least spray painted the nuts!
 

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Discussion Starter #18
guys im not rich by any means and dont take this the worng way but i can order a set of dinan etc springs, throw em in the trash, order another set, throw them in the trash, then get another set and install them, and it wont brake my bank. my issue is i already spent way too much on my previous suspension which im going to take a beating on when i sell it. im just pissed off and dont want to throw any more cash into the next setup that i have to. its well documented already that two people have already done this mod with no issues.
 

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I just left half a coil in the toilet. I must say I am sitting pretty good right now.
 

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well if ordering expensive springs 3 times in a row won't break the bank, certainly you can afford to buy a set of brand new BC coilovers for under $1000 for all 4 corners and then set your ride height (and damping) to exactly what you want, as many times as you want.

There is no exact science to cutting springs. People give you flak because it's a silly idea - it changes not only ride height but also the spring rate, and in turn the handling characteristics. Just cut off half a coil, see how it looks, rinse and repeat if necessary. Good luck.
 
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