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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Re-tempering springs (heating the coils) to lower Eibach Pro Kit springs slightly



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      11-01-2010, 07:39 PM   #1
3X3=5
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Re-tempering springs (heating the coils) to lower Eibach Pro Kit springs slightly

Hold on, before the WTF replies start, let me explain. I currently have ST (like KW V1) coilovers on my sedan. I like them a lot except the ride is still a little rough on crappy Seattle streets. So I'm switching to Koni FSDs and Eibach Pro springs this week. I really like where my car is sitting right now - fenders just over the tires, very little wheel gap. This is slightly higher than when I had H&R sport springs, but I'm pretty sure the Eibachs will be even higher than this based on what I've seen. Here's my car right now, I like where it's at:

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Now, the reason I would even consider posting a flame-worthy topic like this is that it was suggested by a very reputable local suspension shop. By their "BMW guy" in fact. I mentioned that I'd be swapping to the Eibachs, but I think it'll be a little high for my taste. He said you could re-temper the springs without any compromise in comfort or handling as long as it's a minimal change, which it would be. We'd be talking about maybe .25-.4" depending on where my car ends up sitting. Basically they heat the coil using a precision technique and allow the weight of the car to compress it slightly. It sounds ghetto as hell, but he assures me they've done this on plenty of cars before and it's fine.

Here are a couple of pics I found of sedans with Eibachs. There's a variance in how low they get. This drop looks pretty good to me, similar to where I'm at now and I'd be happy with this (note this car has 19" style 162 reps).

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This guy also has Eibach pros, but there's way too much wheel gap for me. If my car ends up like this, I'd consider re-tempering the springs to close that wheel gap. But I'd like to hear from other drivers if anyone has tried this before I risk it.

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      11-01-2010, 07:55 PM   #2
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How do you do this with the car loading up the spring? I thought you had to heat and quench to properly retemper springs, and fairly precisely, what am I missing.

edit: doing this wrong could fail in so many ways, and not immediately either. Could take many compression cycles and then one big bump, springs fail. You'd really want someone to know what they're doing. Like a blacksmith for race cars.
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      11-01-2010, 08:19 PM   #3
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Sounds like a bad idea IMO.
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      11-01-2010, 09:24 PM   #4
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I don't know the exact process, but I'd guess one corner at a time, wheel off with something under the hub? It doesn't sound reliable to me either, but Tru-Line Seattle has a great rep and said it will work no problem. I have a hard time taking their word - that's why I'd like to hear from anyone who has actually done it.
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      11-02-2010, 02:03 AM   #5
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It will work, but it will make the steel less strong. I never did it on my car, but my brother and a couple of his friends have done it to their cars way back in the day before height adjustable coilovers were even available. The cars seemed none the worse for wear, but re-heating steel to let it sit at a more compressed state I'm sure would affect long term durability.

Other factors to consider - if they do it w/ the springs still on the car, it may affect the shock/strut as you will need to warm up the coils pretty hot for them to droop. Do they use a heat shield to prevent stuff like the strut housing, piston and shock boot from being messed up?

FWIW, from my experience messing around w/ suspensions, most of the complaints of poor ride quality comes from lack of suspension travel. Do you know if Koni FSDs are shortened? If not, and you take eibach springs and drop them even further, you may reduce your suspension travel to such a minimal level that the ride would still end up feeling pretty crappy.
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      11-02-2010, 07:11 AM   #6
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I wouldn't do it. Eibachs already have problems with long term reliability and cracking of springs. This will only add to the problems.
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      11-02-2010, 10:44 AM   #7
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Quote:
Originally Posted by 3times3 View Post
I don't know the exact process, but I'd guess one corner at a time, wheel off with something under the hub? It doesn't sound reliable to me either, but Tru-Line Seattle has a great rep and said it will work no problem. I have a hard time taking their word - that's why I'd like to hear from anyone who has actually done it.
Nah, to do a heat and quench cycle properly you have to put the whole spring into an oven, then after it heats to a certain color (uniformly) you deform it to whatever your spec is, then drop it into a water bath (quench). I can't see how you'd do that to just a part of a spring with a torch or whatever while on the car & loaded up without seriously messing up local properties of the steel. And anyway you'll burn off all the powder coating.

See if any guys who drive race cars a lot are comfortable with this technique in cars they drive. I doubt it.
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      11-02-2010, 11:09 AM   #8
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if you're gotta be ghetto, I'd rather cut the springs instead of getting them heated.
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      11-02-2010, 12:25 PM   #9
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my advise is to go with a different brand, eibachs are different on every car ive seen. i have sportlines and they are higher then any photos ive seen, pro kit or sportline. i wouldnt even bother with eibachs at all. my car sits higher then the blue one with pro kit springs. i have not measured yet but it looks like i got a half inch front and back over stock sport, so you would have to drop another inch all around and imo that would be to much to risk it with your method.
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      11-02-2010, 01:47 PM   #10
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Wow, that's with the Eibach sportline springs? Something isn't right there. That's more wheel gap than I had stock - do you have an Xi? The pics I posted above are both Pro Kit drops, much lower than what you have.

My other option of course is to do H&R sports over the Koni FSDs but I already did the H&R sports once and found the ride to be too rough, probably more than the FSDs could correct. Also, the H&R sport is a pretty low drop and may be more than advisable for the FSDs (I know Gizmo335 is running this combo and likes it, but longevity could be an issue). So that really only leaves me with the Eibachs. Guess I'll just hope for a good drop, and if not I'm stuck with it.
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      11-02-2010, 05:04 PM   #11
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the photos are immediately after install, they have settled since(about two weeks). i just measured today and i have one inch to the top of the tire in the front and a touch over a half inch in the back, so they are settling. im going to get 10mm wider tires with the same ratio so that should make up a little of the gap. but over all i love the way it rides so im not going to change anything. also i do not have an xi and it was about a half inch lower then my sport suspension but not at all what i expected.
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      11-02-2010, 05:18 PM   #12
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custom springs dont really cost that much do they...?
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      11-02-2010, 05:20 PM   #13
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You can lower the front a bit by using a perch kit....It will lower the front end about 1/4 inch.

I wouldn't re-temper them....cut a bit off? Maybe....
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      11-02-2010, 08:54 PM   #14
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Brock - I just installed the rear Eibachs and FSDs on my car today (getting the fronts done at a local shop this week since they're way more of a PITA). I have a similar gap to your pics, maybe a little bit less. I hope it settles more, maybe .5" would be perfect I think. How much did yours settle?

Custom springs, haha, if I wanted to spend that much I'd probably just go with KW street comforts. I thought about using those from the start, but it's just not worth the money to me - I don't drive nearly enough to justify $1600 coilovers.

As for using the lowering perch kit, the thing is I won't know if I like the drop up front until it's done. And if I do want more of a drop I don't think it's worth it spend $250 on labor and $100 on perches just for an extra .25" drop. I've decided I'm not going to cut or re-temper the coils, just hope it sits close enough to where I want it when it's done.
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      11-02-2010, 09:45 PM   #15
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its hard to say exactly how much it settled since i never put a tape to it till today. also the angle of the pic can make the car look lower then it is my photos are right there up in the wheel well, my other pics of the full car make it look lower. and i have 18 inch wheels almost all the photos ive seen on this site have 19s im sure that makes a difference as well. if i had to guess i would say in the two weeks it settled a half inch, if you would like i will snap a shot tomorrow. eibach recommends to shave the rear bump stop an inch, i put brand new bump stops in and did not trim them so im thinking the bump stops may be holding the car up, that may sound stupid but i cant think of any other reason the car sits so high. it just rides so nice that im not going to change anything.
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      11-03-2010, 12:21 PM   #16
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here are pics from today, after comparing it may not be a full half inch difference but it definitely settled in the two weeks, still hoping for more. i have my alignment next week.
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      11-03-2010, 11:10 PM   #17
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Quote:
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its hard to say exactly how much it settled since i never put a tape to it till today. also the angle of the pic can make the car look lower then it is my photos are right there up in the wheel well, my other pics of the full car make it look lower. and i have 18 inch wheels almost all the photos ive seen on this site have 19s im sure that makes a difference as well. if i had to guess i would say in the two weeks it settled a half inch, if you would like i will snap a shot tomorrow. eibach recommends to shave the rear bump stop an inch, i put brand new bump stops in and did not trim them so im thinking the bump stops may be holding the car up, that may sound stupid but i cant think of any other reason the car sits so high. it just rides so nice that im not going to change anything.
I think if you were riding on the bump stops (which would raise the car up a bit) you'd know it. You wouldn't be saying "it rides so nice" if you were sitting on the bump stops. I know because I experienced this when I had H&R sport springs over OEM sport shocks which left no suspension travel. Hitting any bump was very jarring until I cut the OEM bump stops way down to allow some travel. And actually based on the height your car is at now, that looks like way too much wheel gap for their to be bump stop contact. It does make me wonder why it's so high though...

I installed my rear Eibach and FSDs yesterday, having a shop do the fronts tomorrow (this is already my 3rd suspension swap and I'm tired of dealing with compressing the front springs). Definitely not very happy with the drop - it seems about stock height - so I hope it settles a lot. It seems quite a bit higher than the pics I posted above, so I'm hoping for .5" of settling, but I think that's optimistic. At least the left and right sides are even height - I've read a few people had the driver's side .5" to .75" higher than passenger. Here are a couple of shots (this is on 19"s):

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I liked my H&R sport drop but unfortunately they're probably too low for the Koni FSDs (I've read most of the threads on this and some say it's fine while others said it doesn't allow the shocks to work properly leaving them constantly in "soft mode" resulting in a poor ride). I'm so tired of changing my suspension I don't want to chance it on the H&Rs with FSDs...
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      11-04-2010, 08:38 AM   #18
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im going to fill my gaps with rubber will post pics when i pick up my e60 18x8s with 245 40 tires. and as far as the bump stops im not so sure, the fact that i said it rides really nice is a matter of opinion. ive only had this set up for two weeks, yesterday i went on a forty mile highway journey, when i hit bumps its not any worse then sport suspension, but when there are dips and waves in the pavement the car violently bobs up and down to the point that i cant have a drink in my cup holder without it spilling.

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      11-06-2010, 12:56 PM   #19
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So I did the Eibach/Koni rears myself on Tues, shop did the fronts on Thurs. I'm much happier with the front drop, it looks just about right - riding just a bit above the tire (and I assume it will settle a bit more as I put some miles on). However the rear is pretty high, in fact I'd guess it didn't really lower the car at all (hard to say since it wasn't a direct OEM to Eibach swap - there were H&Rs, then coilovers and an upgrade to 19"s before I tried the Eibachs). But I compared the Eibach spring to the OEM spring and they were the same the height, the Eibach being maybe .25" shorter, maybe. The Eibach spring is a higher spring rate, so how could it lower the car?

There's still quite a gap in the back and it doesn't the front, giving the car a raked look. I'm wondering if the rears will even settle, it's been a few days and it hasn't changed. From the other posters I've seen with Eibachs the rear looks higher... What do you think? Sorry for crappy pics (rainy Seattle weather didn't give very good lighting for showing the wheel gap) and dirty car (again, rainy Seattle weather).

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Front drop:
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      11-08-2010, 05:08 PM   #20
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i just got off the phone with eibach tech support, my measurements are off by 3mm from what they have in their database. meaning my car sits 3mm higher then what they say it should, keep in mind that there is an error factor. that is enough to ease my mind that there is a problem with the install of my suspension. so my advise to others is if looks are more important go with h&r.
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      11-08-2010, 06:44 PM   #21
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Here's what you do.

Find out the spring rate of the Eibach springs. For example, if it's 200lbs/in, and you want to lower the car another 1/2", then put 100lbs of lead weight on the car on the side of the car you want to drop another 1/2". It's that simple.
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      11-08-2010, 08:13 PM   #22
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but the problem is the scuba weights are to heavy for the duct tape, it keeps falling off.
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