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BA FRONT STRUTS/SPRINGS AWESOME ON AU. 

 

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Posted: Wed Jun 06, 2007 11:14 am 
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xpression wrote:
as taken from whiteline.com.au

Quote:

Why don't I just cut my existing springs?

1. Many aftermarket lowered springs are designed to be just captive (held in place) with the wheel at full droop. This is a legal requirement throughout Australia. Cutting off a portion of the coil will reduce the free height (length of the spring out of the car), possibly to the point making the spring loose at droop.

2.Most springs are designed to a fairly tight tolerance of material volume to load carrying capacity. That is, the amount of steel used in the spring is just enough to hold up the car over the life of the vehicle with normal use. Chop off some coils and you've dramatically reduced the amount of material, which almost always will lead to an overstressed coil that will sag prematurely.

3.A reduction in ride height is normally coupled with a proportionate increase in rate to offset the reduced bump travel. We need to slow down the compression of the spring enough to make sure we don't punch through to the shock at high velocity. A properly designed lowered spring will have a rate increase sufficient to offset this bump travel reduction.

4.The cutting method can also be a problem. Generating heat is not so much a problem as reduction in the heat afterwards. That is, heating the material beyond its temper and then rapidly cooling it will affect the composition of the material.Iirrespective of what tools you use, its not good practice overall.


How much spring do you plan on cutting?

Number 1 is s**t. Ever removed a coil over strut from a falcon? I wouldn't dare undo the top of the strut without spring compressors keeping the spring in check. Full droop when the spring is installed in the car has less spring extension as a coil over completely removed from the vehicle. If its snug in the coil over when its outside of the car its more than enough for when its installed.

Number 2 may or may not be s**t. I'll let you know when I do some creep and fatigue analysis next year. But since he is using a stiffer spring as a replacement then this point will be taken as marketing s**t untill proven for this case. In other words you prove to me that a slightly cut down BA/BF spring will sag more than a standard height standard duty AU spring when they are loaded with the same load. I look forward to seeing the results.

Number 3 is only a problem if you use an oxy. But if you know what you are doing then its no problem. Spring stiffness is determined from the bulk modulus of the steel, coil diameter of the wire, second moment of area of the wire (depends on if the wire is round or rectangular), the effective radius of the spring.
Use a grinder properly and the area you are trying to cut will not even get close to hot enough to affect the bulk modulus of the steel when it cools down. Even better, use a cold saw.

In regards to accellerated piston travel due to a shorter spring, that is complete s**t for a snug fitting linear spring or a progressive rate spring that has had the soft side (bottom) trimmed but yet still fits snug. Do you want me to mathematically prove it to you?

Engineering guideleines are designed to protect the stupid and stop the wreckless from endangering lives whilst also insulting the intelligence of the responsible.
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Posted: Wed Jun 06, 2007 11:52 am 
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I won't go as far as to defend cut springs, cause they are teh illagelz, and we dont want to defend tee illagelz thingz.
But I will say if done with half a brain, they are no more dangerous then any other lowered spring.
In fact, I'd rather be in a car with cut springs and konis or similar GOOD quality shock, then a car with superlows and monroe GTs.

Also, xcabbi, weakness man, you can undo that nut with any spring in there, the spring flying around and decapitating your children is a myth, worst case the nut launches and hits your mate in the balls, +humour.

 

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Posted: Wed Jun 06, 2007 1:03 pm 
Getting Side Ways
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I dunno. The ammount of tension I had to apply to the spring compressors when I last changed the shocks in the cab was substantial enough to have me worrying about what would happen if I just undid the nuts without compressing the springs.
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Posted: Wed Jun 06, 2007 1:15 pm 
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your not wrong about the tension on them, but theyre no worse than alot of over coil overs i've changed hey...
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Posted: Wed Jun 06, 2007 1:23 pm 
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richard williams wrote:
Oh grow up everyone. There have been thousands of springs cut over the years including mine I think by a professional suspension business. So long as your struts support the spring there is no danger. If you have worn standard struts then there is definitely a danger. Since modern springs are variable rising rate then you will find it best to replace with new ones of the height you require. Old cars eg Kingswoods didn't have rising rate springs and the simple swap was to fit cut down V8 springs to 6cyl cars to improve handling and appearance.


lol

so what, its illegal, end of story. Doesnt matter how safe they are, how tight they are or how much anyone knows about cars, its illegal - which makes it bad

When it comes to a pivotal part of the safety of you and your family is 300 odd bux really worth the risk?

 

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Posted: Wed Jun 06, 2007 1:25 pm 
Getting Side Ways
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But, having said all that, I wouldnt mind to try a set of those BA/BF coil overs the T2TE50 suggested in the first post (minus the cutting)

T2TE50 - what brand are these units anyway that are std on the BA/BF?

 

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Posted: Wed Jun 06, 2007 1:31 pm 
Getting Side Ways
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SpuDTE wrote:
richard williams wrote:
Oh grow up everyone. There have been thousands of springs cut over the years including mine I think by a professional suspension business. So long as your struts support the spring there is no danger. If you have worn standard struts then there is definitely a danger. Since modern springs are variable rising rate then you will find it best to replace with new ones of the height you require. Old cars eg Kingswoods didn't have rising rate springs and the simple swap was to fit cut down V8 springs to 6cyl cars to improve handling and appearance.


lol

so what, its illegal, end of story. Doesnt matter how safe they are, how tight they are or how much anyone knows about cars, its illegal - which makes it bad

When it comes to a pivotal part of the safety of you and your family is 300 odd bux really worth the risk?


The reason they are illegal is because it something that can not be regulated and have a close eye kept on it. I could say something here about preferences but I don't want to drag this thread through the mud.
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Posted: Wed Jun 06, 2007 1:39 pm 
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So your saying they just made a blanket rule to cover all bases? Yeah can see how that works.

I just wouldn't do it cos they make the ride too stiff.

As the original topic says tho (in an attempt to get back on topic) it looks like an interesting idea. If they really are a straight swap over and at a fraction of a price of aftermarket units then maybe they are worth a lookin. Depends I suppose too if you are happy with the standard ride height they offer or if you are after something a bit lower

 

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Posted: Wed Jun 06, 2007 2:16 pm 
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xcabbi wrote:
I dunno. The ammount of tension I had to apply to the spring compressors when I last changed the shocks in the cab was substantial enough to have me worrying about what would happen if I just undid the nuts without compressing the springs.

Whack a blanket/towel/friend over it, and point away from face.

It's ALL about keeping the spring captive, and having shocks that have enough damping to control the much stiffer spring.
Ultralows with s**t shocks are just as dangerous as cut springs with s**t shocks.
So, in conclusion, less worry about springs, more worry about quality of shock absorbers.
Oh, and cut springs = illegal, but not dangerous if done right.

 

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Posted: Wed Jun 06, 2007 4:16 pm 
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SpuDTE wrote:
But, having said all that, I wouldnt mind to try a set of those BA/BF coil overs the T2TE50 suggested in the first post (minus the cutting)

T2TE50 - what brand are these units anyway that are std on the BA/BF?


Sorry dude bu you need to cut them or otherwise you'll be driving a 4WD. standard the BA XR's are taller in the front end then an AU, couple this with the AU's considerably lighter front end and you'll be shocked.

ie: I don't recommend reseting them because it just softens the spring and just defeats the purpose.

The xr6t/xr8 coilovers are distinguised by a blue sticker down the bottom of the strut with the number 5. The lesser model struts have a red sticker with the number 4, the piston rod is also alot narrower if you look closely.
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Posted: Wed Jun 06, 2007 8:07 pm 
Getting Side Ways
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What about using a slightly shortened shock to keep your AU ride height?
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