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Location:
Melbourne
Registered:
March 2003
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 Chopped springs
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Tue, 18 January 2005 14:01
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Before you come down on me like a tonne of bricks let me state that :
NO I AM NOT GOING TO CHOP MY SPRINGS
now that that is sorted i have a question reguarding the effects of chopped springs.
My mates a mechanic and he had chopped springs in his comodore (now replaced with kings superlows) and he said that it made the car much much stiffer.
How is this so? I read this thread about progressive rate springs http://forums.toymods.org.au/index.php?t=msg&t h=6729&rid=2211&S=53d231e43b8378846ff53cde cf84f307&pl_view=&start=0#msg_55305
so it sort of makes sense, but then why would the car bounce? Wouldnt this be due to inadequate shocks or because the spring rate is too low... or too high.
Right now i'm under the impression that chopped springs will leave hte spring with the same spring rate as though they were unchopped but the travel of the spring is reduced but i have a feeling im wrong so what is it?
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Location:
Brisbane
Registered:
May 2002
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Re: Chopped springs
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Tue, 18 January 2005 14:40
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The stiffness of a spring is a function of wire thickness, coil diameter and number of coils. Less coils means a stiffer rate, so yes chopping your springs makes it stiffer. The problem is people tend to chop way too much, and while the spring rate increases it doesn't increase enough to counteract the decreased spring travel. On top of this, most people who chop their springs don't replace the shocks so the valving is all wrong, hence bouncy-bouncy.
Note that chopping a spring can be a legitimate modification in some circumstances, but only if done in moderation (eg removing a single coil). Problems occur when dodgy bastards go nuts with the angle grinder, which accounts for 99% of chopped springs out there unfortunately.
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Location:
South-West Sydney
Registered:
February 2004
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Re: Chopped springs
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Wed, 19 January 2005 14:45
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i always thought the stiffness was due to riding on the bumpstops in addition to shocks being used to a point they were not designed for.
thanks for the detailed explaination, norbie
-strober
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Location:
brisbane
Registered:
October 2004
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Location:
Adelaide
Registered:
September 2003
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Re: Chopped springs
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Thu, 20 January 2005 10:14
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A chopped spring will always be stiffer as you have shortened the effective length.
Think of it by unwinding the spring into a straight peiece of wire. The shorter you make it, the harder it is to get a set amount of twist.
As Norbs said, the stiffness of a coil is controlled by the no of coils, wire dia, temper, and material
Cheers
MB
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Location:
Kilsyth, Melbourne
Registered:
September 2004
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Re: Chopped springs
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Fri, 21 January 2005 10:28
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my brother and my cousin both hav cars with chopped springs in them and they are both fine. they handle better look betta and don't bounce. i know it is not the rite thing to do but if u can't afford new springs and u don't want ur car to look like shit then cut away
(preper to be bagged out sompletely  )
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Location:
Melbourne
Registered:
March 2003
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Re: Chopped springs
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Fri, 21 January 2005 10:46
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actualy i've had a look at the formula that defines the spring rate, and if you do it correctly you can actualy have chopped springs that perform much better than the stock springs would. Its just that most people go about chopping them incorectly and go nuts and cut out way too many coils
Spring rate = (G*d^4)/(8*n*D^3)
It'd be pretty dman hard to figure out though because most cars would have progressive rate springs in them stock
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Location:
perth
Registered:
January 2005
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Re: Chopped springs
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Fri, 21 January 2005 12:15
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| bbaacchhyy wrote on Thu, 20 January 2005 21:14 |
A chopped spring will always be stiffer as you have shortened the effective length.
Think of it by unwinding the spring into a straight peiece of wire. The shorter you make it, the harder it is to get a set amount of twist.
As Norbs said, the stiffness of a coil is controlled by the no of coils, wire dia, temper, and material
Cheers
MB
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Dude, if you (sorry your brother or cousin) can't afford lowered springs, then you can;t afford for your insurance company to not cover you if/when you have a crash, because tires, suspension and brakes are the three main safety components in EVERY car, therefore the first thing they will check in a 'modified' car.
if the truth hurts, put standard springs back in, I'm sure you can get them for free or bugger all in the trading post/ local newspaper.
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Location:
Vic, AU
Registered:
September 2004
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Re: Chopped springs
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Fri, 21 January 2005 23:41
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| hokey wrote on Fri, 21 January 2005 21:28 |
my brother and my cousin both hav cars with chopped springs in them and they are both fine. they handle better look betta and don't bounce. i know it is not the rite thing to do but if u can't afford new springs and u don't want ur car to look like shit then cut away
(preper to be bagged out sompletely )
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Yeah, seriously.. What the other guy said. Lowered springs are about $100 a set. Can't afford that?? That's a couple of slabs. Lay off the booze for a weekend and you'll be able to afford it. 
Chopped springs are primarily bad because they don't have the same captiveness (is that a word?) as the original spring/shock combo. eg. At full expansion, the shock will travel further than the spring, possibly causing it to come loose from the strut and cause damage when the shock start compression again... Not a good thing. 
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Location:
Brisbane
Registered:
May 2002
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Re: Chopped springs
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Sat, 22 January 2005 08:39
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That dude's cousin says chopped springs are all good, so I must have been wrong all this time. 
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Registered:
December 2002
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Re: Chopped springs
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Sun, 23 January 2005 05:57
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If nothin else that chopped springs are dangerous, one of my mates chopped his springs in his ae86 seca, handled like a dream... UNTIL goin 150 down a country road and OH *%#@ Cattle grate... all 4 corners smashed bumpstops and 3 out of 4 wheels overextended the length of the spring and they lost the seating on the strut... not fun!!! they drove 60kms on bumpstops...
In summary chopping springs is a cheap option, But how cheap is your ride to replace when you write it off because your goin faster than u should due to your fully sick racing suspension package you just installed???
The cops don't make it illigal to ruin our fun they do it coz its bloody dangerous!!!
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Location:
Kilsyth, Melbourne
Registered:
September 2004
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Re: Chopped springs
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Sun, 23 January 2005 11:19
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poppy cok  i hav been in a car wit no springs and that handled like a go kart till u hit a bump in a corner and the car would bounce over a metre or two  . i know that chopped springs is dodgy but i think u guys are makin them sound worse than they are
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Location:
brisbane
Registered:
October 2004
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Chopped springs
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Mon, 24 January 2005 23:30
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Without advocating chopping coil springs, how is a pair of "King Lows" any more captive than a cut spring.
Really fellas, get off the band wagon and say something constructive.
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Location:
Terrigal
Registered:
May 2002
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Re: Chopped springs
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Mon, 24 January 2005 23:43
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Yeah the kmac springs i have in the AE86 at full droop you can easily pull them put they are that much uncaptive.
Same with the RA28 lowered king springs (not superlow ones). These were uncaptive until I moved the shock mount lower on the diff so now they are captive.
Most people are running around with uncaptive brand name lowered/uncut springs and probably dont even realise it.
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Location:
Kilsyth, Melbourne
Registered:
September 2004
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Chopped springs
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Tue, 25 January 2005 00:00
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that's just dodgy!! they shouldn't be able to sell springs like that.
to keep them captive they either need a progressive section, designed to keep it captive, or for coil-overs, a helper spring which does the same...
reasons i don't like cut springs.
a) unless you know what you are doing, you will have an unknown spring rate, which may be far too hard, leading to the "fooly sik bouncies" (ie most cars on george st on fri/sat nights)
b) usually, cutting changes the profile of the end of the spring, and as such does not sit neatly on the spring perch, leading to increased point loading at the end of the spring.. depending on the cutting process, the heating may have reduced the temper of the spring so the end may be able to deform to the perch, but thats not a good thing to bet on.
over time, 1/4 of car weight focused on a small point = broken spring perch.
c) non-captivity. point taken that some aftermarket springs are not captive, but it is always a good idea to keep the mechanical parts of the car in the position and shape that they are designed for... you would sure as hell be worried if your camshaft or diff was not captive
d) you can get any spring of any size with any rate made up for not that much, if you just ask.
Cya, Stewart
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Chopped springs
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Tue, 25 January 2005 00:04
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| hokey wrote on Tue, 25 January 2005 10:54 |
Turbo ra28- u say that u moved ur shock mount lower, does that mean that the shock is at full extension before the spring???? if so that is very bad. u could wreck ur shox Instead of using ur shok as a retainer for the springs u should get some retension straps which will b very cheap and u won't damage ur shox.
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what keeps a spring captive if not for the shock? (LOL at shox.. reminds me of shazza and dazza ).
the only thing that limits the full droop travel of either front or rear suspension is the shock.
droop straps, are not exactly the best idea since you will suddenly change the rate of the suspension (well.. i guess so would a shock when it reaches full travel)
anyway, a car with straps to limit suspension movement will look like the car to the left, when it hits a bump or a curb
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Location:
Melbourne
Registered:
January 2005
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Re: Chopped springs
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Tue, 25 January 2005 01:25
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Hey, can I have a go at this?
1. You can "chop" a spring if:
a) You understand the existing and new specifications of the spring after the cut as outlined by Norbie and others above, not just the fooly sic factor (emphasis on the fooly).
b) You perform the cut while controlling the temperature (typically done while immersed in an oil bath), else you will alter the metallurgy and risk snapping the spring during operation, most likely at an inconvenient time (see wrecked BMW above and add death & injury to you, your occupants and others)
c) You increase the bump and rebound damping rates in the corresponding shock absorbers, else your car will "pitch" (increased spring rate with no corresponding rebound shock rate will cause the car to over-correct the wheel movement causing the car to "bounce". If you watch your headlight line (assuming halogens or better) at night you will see it bouncing up and down even on a relatively smooth road - often called a "jiggly" ride.
d) While modifying the shocks, you will need to change the shaft length to adjust for the new operating lengths, else at a minimum you will need to wire in the springs to the top hat and base mount plate to ensure the spring does not demount itself on full extension. Most cut springs will be shorter than the full extension of the shock.
e) You modify the bump stop in the shock absorber to ensure you have sufficient travel for the new spring to operate. Hitting the bumpstop regularly will typically break the foot valve in the shock with a similar outcome to b). Also makes a good lap time impossible. Man, you should try driving around the Calder Thunderdome at 230kmh in a standard Group A GT4 Celica. Turn into the banked corner, the suspension compresses onto the bump stops, yours eyes jiggle so bad you can't see and the ripple across the road surface near the exit point throws the car 5 metres to the left - into the wall if you're not careful.
OR
2. Take your car to someone who knows what they're doing...
Nuff said.
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Location:
Terrigal
Registered:
May 2002
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Re: Chopped springs
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Tue, 25 January 2005 01:34
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Yeah my shock keeps the spring captive, like Oldcorollas said what else would hold it captive?
I dont like chopping springs either.. They are not expensive to purchase, even custom made ones to your specs.
But yeah kings and kmac off the shelf springs especially for the rear of the ae86/ra28 are not designed correctly to be captive anymore. They are still progressive springs though and not linear.
In the front of mine with the coilovers i put some helper/keeper springs in to keep captive at full droop.
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Location:
Vic, AU
Registered:
September 2004
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Re: Chopped springs
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Tue, 25 January 2005 06:44
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| gold28 wrote on Tue, 25 January 2005 10:30 |
Without advocating chopping coil springs, how is a pair of "King Lows" any more captive than a cut spring.
Really fellas, get off the band wagon and say something constructive.
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Well, FWIW, the set I installed in the XT130 struts fitted JUST without springs compressor. The spring was very much captive though..
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