[Spits] Rear spring GT6

[Jim Muller]

On 25 Dec 2008 at 15:20, Joe Curry wrote:

> Your friend steered you wrong.  The springs are the same
> width (length).

I was hoping somebody more knowledgeable than I would jump in.  If it 
was about Spitfire springs I would have answered directly.

My uncertainty, which Joe "Fluif" Curry wouldn't necessarily share, 
is that they would have calibrated the GT6 springs differently from 
the Spitfire because of the greater weight.  They *might* have made a 
longer spring for the late GT6 to match the longer axle but length by 
itself is not enough information.  If it was longer without being 
stiffer it would be effectively softer, and a spacer between diff and 
spring would be the wrong thing to do because the car would sit even 
lower.  If they the spring stiffer they could have made it longer, 
but longer or not, they would have had a goal to match the weight for 
a given axle length.  So if they combined stiffness and length to 
match the longer '73 axle and you installed one on the shorter axles, 
it would indeed be too stiff, making the car ride higher.

The Spitbits website lists a different part number for early 
Spitfires, swing-spring Spitfires, Mk2 and early Mk3 GT6, and Mk1 and 
later Mk3 GT6.  Certainly the GT6 spring is not the same as the 
Spitfire's for any suspension setup.  But the curious thing is that 
they listed only one spring as Mk1 and Mk3 after KF20001.  Can't tell 
from the picture whether it is the swing-spring or not.  However this 
suggests that either they don't offer have both early and very late 
GT6 springs or Triumph reverted to the non-swing spring in '73.  I 
suspect the former.

> The difference is that the later spring is a swing spring which
> ... allows the rear to have more body roll.

I'm not sure what Triumph did for the GT6 but for the Spitfire the 
swing-spring also came with a stiffer swaybar.  Todd, you need to 
consider whether the PO swapped that too.  Or just update the rear to 
your preference then choose a swaybar based on how it corners.


Todd also asked:
> I don't believe there is a bushing in the ends of the spring.
> Does there have to be?

There should be something (they are only $5 from Spitbits).  It is 
not a super tight fit.  It is more critical on the Mk2 because the 
spring acts as the upper control arm.  On the swing-axle versions it 
doesn't but you should still have something to spread out the stress.

-- 
Jim Muller
jimmuller at rcn.com
'80 Spitfire, '70 GT6+