Hi Erich:
It's my understanding that wide tires combined with full-lock low speed
turns (backing out of the driveway or making a right turn at a stop
light, for example) contribute to the lower fulcrum pins breaking. This
causes the suspension to collapse. Basically, the inherent Ackermann
angle on the Tiger causes the front tires to toe-in on a low speed turn,
rather than toeing OUT. The toe-in means the tires are literally
scrubbing, or dragging their way through the turn, rather than rolling
through the turn as they would if the tires toed out. Add in wide tires
with lots of friction and the loading on the fulcrum pins, over time,
can cause them to break.
I'm unsure of whether 'crack-free' now means crack-free in a couple of
years.
Here's a four-part recipe to resolve the issue:
1. You might want to consider Dale A's steering rack kit--Larry Paulick
tried it and measured several degrees of Ackermann correction. This'll
help resolve the initial high-loading stress that can lead to the
fulcrum pin failure. No cutting or welding, and you get quicker
steering with the MG Midget rack.
2. You might want to add John Logan's Fulcrum pin fix. I understand
this also reduces the initial load introduced to the pins and, in the
event of a pin failure, keeps the suspension from collapsing.
3. Dave Johnson strongly suggests that if you go with the polyurethane,
use bushings of similar hardness to the original rubber. Rick at
Sunbeam Specialties has two levels of Poyurethane--one is the hard poly,
and I believe that's the one to stay away from, since it has little
'give' under stress. On the other hand, with the above two fixes, using
the hard poly might not matter from a 'loading' standpoint, and, while
it would give a harsher daily ride, could contribute to a better elapsed
time when you zip through the orange cones. Dave, I respect your
opinion. Do you have any thoughts on this?
4. The fulcrum pins for Tiger and Alpine are the same. Smitty has some
lower pins that came from Alpines that I'm sure he'd sell you. Since
they came from Alpines, they never had the stresses on them that come
from our Ackermann problem. I'd have a pair of THOSE magnafluxed and
install them along with the above fixes.
There's other ways to resolve this out there, though if I were doing it
again, the above recipe is likely the one I would choose.
Best Regards
David Sosna
Kathy and Erich Coiner wrote:
>The A arm pivot bushings are looking pretty sad on my car. The boots on the
>ball joints don't look too hot either.
>While I am in there, what else should I be on the look out for? What
>upgrades might I do?
>The car will be used for "spirited street driving" It will also see
>occasional trips around the orange cones.
>
>I am concerned about the condition of the pivot shafts. I plan to get them
>magnaflux inspected. If they are crack free am I good to go for a couple
>more years?
>If they need to be replaced, who makes them, and where do I get them?
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