where to get 4kq springs??????
Jason K Gray
jason510 at att.net
Tue Jul 1 10:24:02 EDT 2003
I do not dispute that GCT front springs may in fact be stiffer than 4Kq
springs. I have never tested or measured a GCT spring. Does not suprize me
that the more sporty GCT would be offered with more suitable perfromance
springs. The 4Kq in my opinion was factory set-up to provide cushy smooth
ride, not at all for performance driving. The cornering body roll on a stock
4Kq is aweful. The selection of stock spring rates for the 4Kq is anything
but locigal from a performance standpoint. I do not defend audi's selection
of stock spring rates, just passing on what I have firsthand measured with
scientific means (not just an uncalibrated butt-o-meter). I suggest that any
doubters at least go out with a set of calipers and verify for themself that
the stock rear 4Kq springs DO in fact have significantly thicker wire
diameter than the front springs. (you can do this with the springs still on
the car).
Springs are very simple and predicatable devices. They are not endowed
with majical pixie dust properties by being painted a certain color and sold
with labels such as "sport", "performance" or even "coilover". The formula I
used to calculate the spring rate comes right from the book "HOW TO MAKE
YOUR CAR HANDLE" by Fred Puhn.
http://www.amazon.com/exec/obidos/tg/detail/-/0912656468/104-8745155-0244760
?v=glance
This book is an excellent introduction to chassie handeling dynamics and
adjustment. Despite the fact that the book is 25 years old, the formula for
determining spring rate still has not reached its expiration date.
As I said, I confirmed the calculated rate by measuring actual physical
compression of the springs. The stiffer rear 4Kq springs were verified by
measuring the springs from two different cars. Whenever you are considering
changing springs, I would think it vitaly important to first know the spring
rate of both your old and new springs in order to make the correct rate
selection (unless you are buying into the aftermarket pixie dust theorys).
Any perceived improvement in the handeling of a 4Kq by installing softer
front springs in the rear could well be due to factors such as the
correction of suspension geometry obtained when the sagging ride height is
restored, from the addition of other components (stiffer rubber isolaters,
shocks, additional (rear) sway bar?) or perhaps from the placebo effect of
working under your car for 4 hours to change the springs and then
"expecting" an improvement when you go out for that first test drive. You
have to push a car pretty hard (autocross type conditions) and have a solid
understanding of chassie dynamics in order to validly evaluate the tuning
effects of chassie handeling.
Jason K Gray
Anchorage Alaska
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where to get 4kq springs??????
passat TS passat_ts at hotmail.com
Tue, 01 Jul 2003 14:18:24 +0000
Jason,
I can't discuss your findings, since I have not background to do so.
and please I'm not disputing anything, this is just IMHO.
However, my old friend common sense tells me:
1. 4k has the weight distribution moved a bit to the back due to the 016
transmission, prop shaft, rear diff, rear suspension, etc.
2.4K even with the new weight distribution still have the engine in the
front. which I believe makes the front heavier than the back, but lighter
than a CGT.
3. The CGT is nose heavy as hell, with the engine and 093 transmission
concentrated around the front "axle", and nothing on the back.
My conclusion sorting from the higher spring rate to the lower is:
CGT Front
4K Front
4K Rear
I personally don't have a 4K, and have never done the suggested change, but
I can quickly recall 5 people using this set up, or 6 if you count a fellow
lister that responded.
Have you considered a minor mistake or a wrong spring?
Please this is not a flame, and I'm sure you need clearance (and a
funtioning heater) were you live.
Cheers,
Carlos.
>From: "Jason Gray" <jason510 at att.net>
>To: <quattro at audifans.com>
>Subject: Re: where to get 4kq springs?????? Date: Mon, 30 Jun 2003 22:58:40
>-0800
>
>I measured the spring rates myself, they were same from two different 4KQs
>that I checked.
>
>The formula for spring stiffness is =(1,500,000(#/in^2)*W^4)/(N*D^3)
>
>where W is the wire diameter in inches (raised to the 4th power)
>N is the number of free spring coils
>D is the diameter of the overall coil spring (raised to the 3rd power),
>measure across coil from middle of the wire
>The 1,500,000(#/in^2) is a constant that comes from the inherent properties
>for spring steel. (same equation could be used to calculate stiffness of
>wooden springs (or whatever) if you had the right constant for the
>material.
>
>For front springs,
>W= .504"
>N= 6
>D = 5.28"
>
>For Rear Springs
>W= 0.528"
>N= 5
>D = 5.26"
>
>The coil diameter (D) is a bit smaller at top and bottom of the springs,
>making these sections of the spring slightly stiffer (progressive). This
>would result in a slight error if you were comparing to truye linear
>springs
>but since both front and rears are wound the same way, the difference is
>negligile when compairing them to eachother. The major effect of the
>stiffness here is the diameter of the wire (because it is raised to 4th
>power in the equation for spring rate). The small increase of the wire
>diameter for the rear springs really boost their stiffness. I confirmed the
>calculated spring rate by compressing the springs (with my full body
>weight)
>and measuring the resulting deflection. My notes show that the fronts were
>even 10% softer than calulated.
>
>Having only a front sway bar (stock) likely is greatly responsible for the
>stock understeer, despite the stiffer rear springs.
>Once I got the set of stiffer rear springs onto the front, it greatly
>helped
>to control body roll, the stock fronts are way too soft for street
>performance.
>
> Jason K Gray
>Anchorage Alaska
>
>
>----- Original Message -----
>From: "Michael Gough" <mdg3369 at newtsplace.com>
>To: <jason510 at att.net>; <quattro at audifans.com>
>Sent: Monday, June 30, 2003 8:09 PM
>Subject: Re: where to get 4kq springs??????
>
>
> > >> One problem here, the 4KQ front spring rate is around 110#/inch and
>the
> > >>rears springs are around 160#/in. Moving the stock front springs to
>the
>rear
> > >>will dramaticly SOFTEN the rear spring rate. Combined with stiffer
>front
> > >>springs, this would make the 4KQ understeer even worse than it already
>does
> > >>with stock springs. See my 4/22/03 post (below) describing my
>dabblings
>with
> > >>stock springs.
> > >
> > >
> > > I don't want to start a war here but both my personal experience of
>actually
> > > running stock front springs in the rear of my 4kq and my knowledge of
> > > engineering say this theory of lowered spring rates is highly
>doubtful.
> > >
> > > I will stick to the "experimental results" and point out that I am not
>the
> > only
> > > one to run front springs in the rear of my car and neither I nor
>anyway
>else I
> > > have ever heard of has experienced degraded handling when doing so. To
>the
> > > contrary the handling improved with considerably less understeer and
>body lean
> > > even before I added the rear sway bar.
> >
> > Considering the fact that the majority of the weight on the 4kq is on
>the
> > front suspension, coupled with the fact that cars for the general public
>are
> > designed to understeer when pushed hard, the alleged 110/160 F/R spring
>rate
> > is VERY hard to believe....
> > How exactly did you come up with these numbers?
> > Mike
>
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