[Vwdiesel] a2 Jetta rear suspension

[mikel]

On Mon, 2008-11-10 at 07:11 -0800, vwdiesel-request at vwfans.com wrote:
> Date: Mon, 10 Nov 2008 08:40:54 -0500
> From: "Stephen Kraus" <ub3ratl4sf00 at gmail.com>
> Subject: Re: [Vwdiesel] a2 Jetta rear suspension
> To: mikel <mikel at buncombe.main.nc.us>, vwdiesel at vwfans.com
> Message-ID:
>         <f61562b0811100540v3f72f099vdece9bd6aa8e126f at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> I actually looked at pulling the springs off a small truck for my
> Jetta,
> never went through with it as I sold the car. But that would help
> raised the
> load limit on it.
> 
I was thinking about doing that too, but would have had to take a spring
off to get measurements, and then put it all back  together (it's my
daily driver) and wait for the 'right' springs to show up at the scrap
yard.  May still do it, eventually, but first I think I'll try the pipe
idea.

Date: Mon, 10 Nov 2008 16:13:01 -0600
From: James Hansen <jhsg at sasktel.net>
Subject: Re: [Vwdiesel] a2 Jetta rear suspension
To: brian at gochnauer.net
Cc: vwdiesel at vwfans.com
Message-ID: <4918B1ED.2020705 at sasktel.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

>Taking part of a compression spring out of action increases the rate,
>rate being pounds supported per inch of compression.  ie- 500 pound 
>spring needs 500 pounds to comress the first inch, 1000# to get to the 
>second inch of compression, 1500# for the third inch etc..

Seems that that would decrease the amount of travel available going this
route, so I guess you'd need to know how much travel you could afford to
give up - do these things raise the car any when installed?

>Factors you can change to increase spring rate are decreasing the
>number 
>of coils, making them bigger, or using thicker wire in the coils.
>Since 
>the spring wire can't be changed, taking a coil out of action
>increases 
>the rate, or load the spring supports per inch of travel.  When you 
>change to a "heavier" spring, that's what you're doing, selecting a 
>spring that has heavier wire, or less coils over the same distance.
>(or 
>different steel, but that's not as big a factor in passenger car stuff)
>Passenger cars also have variable rate springs, where one end has the 
>coils closer together, so part of the spring is more easily
>compressed, 
>part is stiffer, giving a better ride over small bumps.  It's pretty 
>common to lose a chunk of two off the softer end, because they fatigue 
>from doing more of the work.
>In the racecar, we just change springs to effect a rate change, and
>save 
>the spring rubbers for small adjustments at the track during race 
>conditions.

>If the car is bottoming out, you need springs of a higher rate, or to 
>load lighter.  ANYTHING you do to increase rate will improve on that. 
>For instance, if my stock car has too much travel on the right front, 
>adding half a rubber to the 1175 pound per inch spring that is in
>there 
>now will add about 60# to the rate and decrease travel by approx 3/4 
>inch in the turn.

>When you say fully bottomed out, the springs still shouldn't be in
>coil 
>bind Brian, the bump stops on the shock should prevent that.  Putting
>a 
>spring repeatedly into coil bind kills it dead, and is usually why a 
>spring gets broken- the shock dies and the oil leak kills off the bump 
>stop, which kills off the spring, increasing the $ to fix eventually.

What about the shocks, do they suffer from increased load, or does that
make their job easier when the spring rate is increased?  I can kinda
rationalize it working either way.

>Some math just for giggles:

>spring rate= modulus of spring steel X Wire diameter4 / 8 X number of 
>active coils X mean coil diameter3

>where modulus of spring steel = 11,250,000 pounds/inch2

>With this, if you want to raid the junkyard and make informed choices
>so 
>you can choose, and modify existing springs from other applications to 
>suit what you have.

>Sorry this turned into an essay....

No, that was great, thanks for the lesson.

>-james

brian gochnauer wrote:
> I agree it might work, but will it still work if the car is 'bottom'ed
out
> with the springs "fully" compressed or maybe just the shock fully
> compressed?
> 
> If you try this idea out Mike, let us know .  :)

Will do.

Mike in NC