Re: [VWoT] How's my Math?

["Sandor" <sandor@xxxxxxxx>]

yup, standard fare on most mk1's I know...no front sway, big arse rear
sway and stiff inserts and springs.
Its put to very good effect when you don't slam a car, such as running the
SRS kits where the springs are close to stock height...but remember mk1's
have a suspension travel handicap from the factory, whereas mk2's and 3's
are a little better off.


sandor





> One thing I can tell you for sure about MK2 H&R race springs is that the
> spring rates are 400 lbs/in linear front, 230-260 lbs/in
> progressive rear, and this is straight from H&R by phone. Also
> according to Koni, their Mk2 Yellows are the strongest off-the-shelf
> shocks you can buy for the Mk2 (don't know how that applies to the Mk3).
>
> By removing the front sway, you have more front lean (a bit) but you
> also get more grip (oddly enough). This helps with powering out of a
> corner because for the same amount of "G"'s you retain more weight on
> the inside tire. This all happens assuming the rear bar is kept. I tried
> it on the rocco, it is a very noticeable difference, the front end has
> more grip, the rear does not, which means less understeer. You also lose
> 10-15 lbs off the car which is always a bonus.
>
> Great mod if you know how to drive, not so great for amateur winter
> drivers.
>
> SRS does have a point about excessive lowering for street cars with
> McPherson suspensions.
>
> this all is afaik, ymmv, etc ad nauseaum, feel free to correct me.
>
> D
>
>
>
> On Tue, 16 Nov 2004 23:39:45 -0500 (EST), bokchoi <bokchoi@vwot.org>
> wrote:
>> Check this out and let me know if any of these #'s make sense.
>>
>> I decide to calculate spring rates in order to figure out why i've
>> been blowing my rear shocks.  Here are my results:
>>
>> K = ((W^4)*G) / (8*N*(D^3))
>>
>> where
>> K = spring stiffness/rate (lb/in)
>> W = Diameter of the coil wire (in)
>> G = 12,000,000 (shear modulus of steel)
>> N = # of active coils (free coils + 1/2)
>> D = Diameter of the coil (in)
>>
>> OEM Mk3 Jetta 2.0L front spring
>> W = 12mm = 0.472in
>> N = 4.5
>> D = 5.0in
>>
>> Therefore K = 132 lb/in
>>
>> OEM Mk3 Jetta 2.0L rear spring
>> W = 10mm = 0.394in
>> N = 6.5
>> D = 100mm = 3.93in
>>
>> Therefore K = 92 lb/in
>>
>> H&R Race Mk2 Jetta front spring
>> W = 13mm = 0.5118in
>> N = 2.5
>> D = 128mm = 5.0in
>>
>> Therefore K = 330 lb/in
>>
>> H&R Race Mk2 Jetta rear spring
>> W = 13mm = 0.5118in
>> N = 3.5
>> D = 102mm = 4.01in
>>
>> Therefore K = 460 lb/in !!!!!!
>>
>> This could be the reason that the fronts feel so good but the rears
>> keep blowing up.
>>
>> So if i decide to play with the OEM rear springs:
>>
>> OEM Mk3 Jetta rear spring (-1 coil)
>> N = 5.5
>> K = 108 lb/in
>>
>> OEM Mk3 Jetta rear spring (-2 coils)
>> N = 4.5
>> K = 132 lb/in
>>
>> OEM Mk3 Jetta rear spring (-3 coils...that's just going too far) N =
>> 3.5
>> K = 170 lb/in
>>
>> I believe Shine Racing runs ~130-150 lb/in for the rear with their
>> kits...although they also like to remove the front sway bar and they
>> hate lowering.
>>
>> --
>> d8ve
>> 94 Golf GL - 98 Jetta GT - 01 CBR600F4i
>>
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