M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Suspension => Topic started by: Chalino on January 27, 2010, 11:57:54 AM
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I know that "the way to go" is to buy a set of lowering springs but please listen to me. I read on IX registry of an actual engineer "modifying" his front springs on this IX by cutting of a coil. Acording to the guy, these are dead coils that do NOT affect the spring rate. I'm happy with how the back end looks and I'm just looking to lower the front a tad. Does anyone have personal experience with cutting STOCK springs and having adverse effects? Keep in mind I've heard all of the "don't do it", "ricer", "buy lowering springs"....
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Have you researched heating them and then applying weight to lower them? Have seen an e30 with this and it looked good and the ride was still fine. Just another option and sorry if it does not answer your question.
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The coils aren't parallel on the rear. There's a lot of area on the perch & swing arm, but I'd be worried about the coil squirming around on the mount. I have seen a lot of successful lowering jobs with a coil or two cut off. If it's done right I see no problem with it.
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I know there is a fairly old post on here from a guy who did cut his own front springs. Seems to me it was titled "want an even ride height" or something to that effect. He was happy with the results. I did a couple of quick searches but didn't find it immediately (never can) but do a little digging and it will show up.
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Thanks for the quick replies guys! Yes, I really just want to lower the front end since the wheel gap is about 3" higher in the front. I'd be a bit more worried about heating the springs since it's kinda hard to apply the same amount of heat throughout the process and then there's the whole weakening deal....Not saying cutting is fool-proof but it seems a bit more "safe" lol
The rears won't be touched so I'm not worried about non-parallel coils. the front seem to be straight so I feel I can cut a coil or two and have the spring sit correctly on the perch.
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I cut exactly one front coil. The front drop is about 1.5in. Drives much better and looks right. reset toe when done. Cutting does increase the spring rate by about 18%+-, or so.
91 IS, Mike Ogren /Protech
Dont heat them, cut them quick. with a hot ass torch. Heating and lowering is bad for the springs, the heat goes way too far around the coil and it coilbinds at less compresion.
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I heated & cut both front and rear but i went way low, 2.5 coils as I can remember(on 17'' u couldnt see the tires on the rear) I ll c if i still have a photo or so ,the ride was too hard for my taste,and when I replaced it with HRs after a year or so I found both rear springs cracked :rolleyes:
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Cutting a coil was a common old school trick on 2002s. I bought a tii that had cut coils and the look was great, but the ride was surprisingly harsh. I switched to H&Rs. Big improvement.
You might also think about first removing the rubber pads at the top and bottom of the spring. I did this front and rear to my 318is along with M3 springs and really like the stance. I cut up one of those heavy plastic rock salt bags to create a liner to replace the pads just so it wasn't metal on metal. No problems after 4 years this way.
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DON'T DO IT!!. I seriously can't believe people are encouraging this.
Here is what happens. Your spring is designed to compress X". By cutting the springs, they don't get stiffer, They stay at the same rate. Now they still travel X' and you have less spring length.
Do what you want, but get yourself some or several spare lower oil pans. I bought a car that had cut springs in the front. Went through a few pans before I got around to picking up some E30M3 ST springs.
But seriously, this is a stupid idea. If you crack the pan and don't catch it immediately, you'll be buying the correct springs and another motor.
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DON'T DO IT!!. I seriously can't believe people are encouraging this.
Here is what happens. Your spring is designed to compress X". By cutting the springs, they don't get stiffer, They stay at the same rate. Now they still travel X' and you have less spring length.
Do what you want, but get yourself some or several spare lower oil pans. I bought a car that had cut springs in the front. Went through a few pans before I got around to picking up some E30M3 ST springs.
But seriously, this is a stupid idea. If you crack the pan and don't catch it immediately, you'll be buying the correct springs and another motor.
I repsect your opinion, as it seems that you have first-hand experience in the subject. With that said, busted oil pans are a risk when lowering these cars regardless of method. Shit, the pan is low enough at stock height let alone lowered any tiny but; but it's a risk most of us are willing to take.
Controversial topic to say the least...
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I have extremely stiff coilovers. When at full drop I can't lay a pack a cigarettes flat and slide it underneath the pan. I haven't cracked one yet. Here in Hawaii, I am spun all the way up because the roads are a nightmare. I have roughly 2.0" to 2.5" of clearance with no issues.
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Cutting the springs does increase spring rate. Do more research. Thanks, MM
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Cutting the springs does increase spring rate. Do more research. Thanks, MM
Rarely, but more often then not, they stay the same or drop. If they do go up, it's very minimal. But not near enough to compensate for the extra travel. When you buy lowering springs, you typically don't get a shorter spring, with the same spring gap. You normally get a shorter spring with just as many or more coils and they are wound tighter. It's simple physics, i just don't want to write a book.
If you absolutely have to cut, run more, and stiffer bump stops.
I tell people the rate drops to discourage this type of stupidity
And rates are irrelevant. Click here (http://m42club.com/forums/showpost.php?p=86070&postcount=10)
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I have cut the 2 front springs on my E30 318is only 1 coil and the ride and handling has not changed at all
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cutting springs is a old old trick. ive cut a few down before. i didnt use a torch i used a big ass band saw i have at the shop. i supose if you wanted to keep the heat factor down a plasma would be the way to go.
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i bought a 89 cabrio once it had cut springs on the front the ride was rough and it didnt feel better than stock....and it made so much noise...
i recently bought a 318is and it has h&r lowering springs and honestly i wouldnt go lower than this i have trouble with the pan it scrapes occasionally
i wouldnt go too low....at the end its your decision :)
(http://img.photobucket.com/albums/v256/ooinreverieoo/IMG00032-20100103-1558.jpg)
its lower than it seems cause it has tiny tires
and this thing had cut springs and driving it sucked!
(http://img.photobucket.com/albums/v256/ooinreverieoo/IMG00297-20091103-0805.jpg)
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If the coils are evenly spaced the spring rate is constant per inch of compression regardless of length.
If they are a progressive rate spring, IE have tight coils at one end and loose coils at the other the rate goes DOWN if you cut a tight coil and UP if you cut a loose coil.
Stock BMW ti springs are progressive. The Race springs from H&R are not.
Just my little old free opinion...
BTW if you cut the springs the cap coil will not grip the perch as well unless you re-bend the coil to fit correctly.
Remember this is a strut not you 62 Impala with big buckets for the spring to sit in...
Dave
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If the coils are evenly spaced the spring rate is constant per inch of compression regardless of length.
If they are a progressive rate spring, IE have tight coils at one end and loose coils at the other the rate goes DOWN if you cut a tight coil and UP if you cut a loose coil.
Stock BMW ti springs are progressive. The Race springs from H&R are not.
Just my little old free opinion...
BTW if you cut the springs the cap coil will not grip the perch as well unless you re-bend the coil to fit correctly.
Remember this is a strut not you 62 Impala with big buckets for the spring to sit in...
Dave
This was my concern; it seems like it wouldn't be way off but it probably wouldn't sit correctly as you stated.
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You cant decrease spring rate by cutting coils. That is not correct info.
Think of it like this. Place one end of a 4ft rod in a vise. Twist the free end with a pair of visegrips. Moves real easy. Now twist it at the 3 ft mark,much harder to twist.
Go to 2ft, 1 ft etc. At 6in the rod will twist very hard and depending onthe actual size of the rod, maybe not at all.
A coil spring is a twisting rod of steel. Cut off some of it and it will twist less , with
the same force. That just how it is.
For the actual calculations please see ;http://www.eatonsprings.com/atqCuttingCoilSpringsCalculations.htm TIA. MM
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That would just be leverage exerted at the fulcrum.
(http://blog.lifebeyondcode.com/wordpress/wp-content/uploads/the_fulcrum_effect.jpg)
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From your link....
The longer the wire is the lower the spring rate. As the wire get shorter, such as when cutting the coil, the spring rate increases.
This is true on a piece of straight rebar for example. But only due to the lack of leverage that can be exerted. Not because the bar is magically stronger.
Take the same bar and crush it flat with a hydraulic press. It doesn't matter if the rod is an inch or a foot long. It will take the same pressure to flatten the bar.
Maybe those years I spent engineering for race teams I was wrong all along. Glad nobody got killed.
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And allow me to quote one of the greatest suspension engineers/experts in the world and a mentor to me, Allan Staniforth
Spring rate is meaningless as it is totally modified by two things: the sprung weight of the vehicle and the leverage exerted by the suspension.
In the end, it's the OP's decision.
I'm done here.
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My spring dyno doesn't lie.... :) Usually.....
I've ruined a bunch of springs screwing around and according to my tester I'm right.
Progressive springs have a rising rate per inch as they are compressed, linear springs dont. Taking the stiff end off makes a softer spring at full compression, cutting the soft end off makes a harder spring at full compression.
I agree with the last post though, its the whole package that affects handling as much as the spring rate ,, within reason..
Dave
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Sounds like you guys know what you're talking about. My initial thought was to cut ONE coil and live with the "shitty" ride but now I'm wondering if it's safe...it probably is, right?
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If you put an E30 M3 spring next to a 318i spring, you'll realize that the M3 spring is identical, minus 1 coil. Same wire thickness, same coil spacing. Go ahead and cut 1 coil. You'll basically end up with stock M3 springs. The whole cut springs = bad myth starte with ricers that cut their springs in half to get that special-ed slammed look. Cutting 1 coil won't hurt a thing and the spring will be slightly stiffer.
(http://farm4.static.flickr.com/3350/3344866044_24b816d930_b.jpg)
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tjts, you make a good point. I'm cutting mine this weekend.
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tj as allways you cut thru the bullshit. good on you man! im gonna hack up a pair of junkyard coils this weekend. if nothing else spring steel is great to forge drifts and punches out of :)
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o and on that note dont buy h & r racing springs they are crazy low i snap a pic of how low my 318is is i belive its close to a 3" drop....speed bumps put great fear in my heart....o and funny ass quote 4 banger!
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I would like to chime in too, hopefully without sounding like an arrogant know-it-all. On Efunda.com, they lay out the equation for calculating spring rate.
k = spring rate
G = shear modulus
d = diameter of the wire
D = diameter of the entire coil
na = number of active coils
k = (G*d^4)/(8*D^3*na)
Ignoring the complicated stuff, the bottom line is that spring rate (k) increases as the number of coils (na) decreases.
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I cut mine and have had no problems and I am well happy with the ride height and the handling
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Do you cut off the top or bottom coil of the spring?
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I cut the top on mine
But a friend cut top on one and the bottom on the other and the side he cut the bottom the car sat lower :eek: