Larry:
Let me get out my carpet duster.
Rear Springs
No idea. So far as I can tell the best way to go is get the spring
with the correct number of leaves for your application. CB cars use less
leaves than RB cars and GTs.
Then fabricate spacers to get the car to the ride height that you want.
Alternately Doug Jackson makes some nifty plastic springs. Problems with
those are the expense, and they are now only available in one ride height.
Again spacers may be necessary. The plastic springs are really of interest
to those with V8s as the torque tends to rip regular leaf springs apart.
(ask me, I know).
Re-arching leaf springs seems to be troublesome, I've seen lots of
failures. I think this may be because British manufacturing uses different
hardening techniques and metallurgy than US.
I will know more about this after playing around with different
spring rates on my Bs. My GT V6 had new GT springs. The ride height is now
pretty low, but those springs were damaged by excessive windup before I put
on the locating bars.
My racecar got lowered springs, that raised the car 1". I built
spacers, the stiffer spring kept the inside wheel on the track and reduced
wheelspin. But then I run a rear sway bar, so I'm not following the popular
concept.
Bushings
I'm using all types.
Rubber- Black, soft often of dubious manufacture and longevity. Only
useful in fully supported situations. Typically designed to seize on ID and
OD. Pivoting is accomplished by shear, not rotation. Drawback. Many
people install with lubricant which prevents the rubber from bonding. The
soft rubber then tries to pivot which it will not do well. Also these get
installed with the car on a jack. The bonding occurs with the suspension at
full travel. When the car is at regular ride height the rubber rips.
When installed correctly there is no component to pivot movement, as
the rubber bonds to the pivot, so no sqeeks.
Metalastic- ID and sometimes OD is bonded to steel bushing. The ID bushing
is typically clamped by fastener. The OD is typically an interference fit
to component. Again rubber shear is used for movement. Again a major
problem if the bush is installed in unloaded condition. Also ID bushing can
rust to fastener or inner pivot. Greasing the ID prevents this. Since the
rubber is supported these bushings hold up well. There should be no
component to pivot movement, so no squeeks.
Poly-urethane Usually red-black. Can readily be dented by fingernail.
These pivot and work on the supporting surfaces. They do require smooth
mounting surfaces. Since there is component to pivot movement there is the
likelyhood of squeeking. Some manufacturers supply special lubricant. The
softer poly bushings seem to be pretty quiet.
Many kits include a steel sleeve which is clamped by the fastener. This
gives a smooth, replacable surface for the bush to pivot on. Again, care is
needed to ensure that this sleeve does not seize to the pivot.
Nylatron- Compound of Nylon and Molybdenum Disulphide. These can be barely
dented with a finger nail. I've had these on a street car for some years,
and have been happy. There appears to be some wear to the pivot points, but
nothing too worrisome. On the B the material works well for upper front
bush (originally metalastic) and rear spring pad and shackle. These can be
difficult to install as the material does not really give. I do'nt recomend
them for inner A arm bushings, as the geometry of the assembly has to be
perfect.
Delrin/Nitrile- Very hard, cannot be dented by fingernail. Used on racing
applications where no displacement is wanted. Geometry and condition of
pivot points has to be perfect. This typically requires additional assembly
time and effort. High wear in dusty (street) conditions. TRs use this
material on the front suspension, but have steel pivot sleeves and rubber
sealing washers.
Delrin will crack when subjected to stress, the bush must be fully
supported. I am using these on my race MGB inner A arm bushings. I have
not noticed obnoxious noise or vibration transmittal in street use. (the
car is muffled and uses street tires).
Hopefully this helps out.
Currently I have experience with the following types on an MGB, e-mail if
you want specifics.
Delrin- Inner A arm bushs
- Upper F. shock bushs
- F. sway bar end bush ***A disaster, the bush sleeve ruster to
the pivot****
Nylatron- Inner A arm bushs
- Upper F. shock bushs
- R. Spring Pads
- R. Spring shackles
Poly- Inner A arm bushs
- F. sway bar bushings
Metalastic- Inner A arm bushs
Kelvin.
> -----Original Message-----
> From: Larry Hoy [mailto:larryhoy@prodigy.net]
> Sent: Wednesday, September 22, 1999 11:18 PM
> To: MG List
> Subject: MGB rear springs
>
>
> I know this has been beat to death before, what can I say? I
> used to sleep
> through some of my classes too.
>
> I'd be interested in comments from the group regarding rear
> springs. I am
> interested in these for my 1967 MGB vintage race car,
> (roadster). It is my
> understanding that the lower the better, but stiffer isn't necessarily
> better. Apparently the front suspension needs to be stiff,
> the rear a bit
> softer. Moss shows 5 different springs in the "Accessories"
> section of
> their catalog. Any suggestions?
>
> Second item. Can someone explain the difference in the
> following bushings;
> rubber, polyurethane, Nitrile, Delrin, Nyatron. Which is
> harder, are some
> brittle?
>
> Thanks.
>
> Larry Hoy
> http://pages.prodigy.net/larryhoy/
>
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