Larry,
This must be the posting you are referring to:
>On the topic of Tiger steering under hard acceleration (especially with
>positraction). As everyone knows who has a posi unit and has punched their
>Tiger hard enough to break both tires loose while turning, they very quickly
>observe the down side to the Ackermann "skuff" issue. You soon find that
>there is only one tire on the ground that is firmly planted, and it soon
>turns into the pivot point about which your little "Kitty" is spinning (sort
>of like the preverbal "Latch on the Out-house Door" very similar to the
>place for filling ones pants). The first time it happened to me, I did a 360
>in the middle of an intersection and thankfully did not hit anyone or
>anything in the process. It made a believer out of me. NO punches in the
>corners.
>
>
>Cullen Bennett
>Tempe, Arizona USA
I have a clutch disk type positraction unit on my Tiger. I installed it
about twenty years ago. I've never had quite the experience Cullen had with
his, but I can believe a posi can make matters worse if you punch it in a
turn hard enough to break both rear tires loose. Without it, you're just
spinning the inside tire, which isn't doing much as far as cornering force
anyway. This is precisely the reason I put the posi unit in - so I could
get more power down through the turns. Obviously, you can get too much of a
good thing though. One of the inherent things about a Tiger with regard to
handling is its short wheel base and small polar moment. This factor makes
the car more maneuverable, but also means it spins out easier too. The fact
that the front wheels are seriously toed-in in a turn probably doesn't help
- in any regard. But it seems to me that having the tires toed in tends to
make it understeer; i.e., the front end tends to plow in a straight line
instead of turning into the corner. As a result, the Ackerman problem might
even mitigate the tendency to 360 in a turn, but I'm not really sure - just
speculating.
I'm not sure precisely what all the Dale A. "kit" has in it, but I assume a
Midget rack (set back 1/2"), and MGB steering arms. This is essentially
what I have on mine. I think you will love it. I don't know how much
experience you have driving a stock Tiger, but this is definitely a big
improvement in every regard - even perhaps in making it less prone to spin
out when you break it loose in a corner with a positraction unit, although
I think this is always a possibility if you get too carried away in a
little car with a great big motor. I think you need to remember Doug's rule
#2 in this regard. ;-)
Let us all know when you get your Tiger back on the road.
Brgds,
Bob
At 09:57 AM 8/10/99 -0400, you wrote:
>Bob, there was an email from Bob Cullen regarding the sudden break away
>of the rear end on a Tiger with posi, due to the Ackerman Angle problem
>inherent in the Tiger design.
>
>I have installed the Dale A kit on my restoration, not yet finished, and
>have a 3.54 posi, thus the question on whether there is still a problem
>with the rear end breaking away.
>
>Your experience?
>
>Larry
Robert L. Palmer
UCSD, Dept. of AMES
619-822-1037 (o)
760-599-9927 (h)
rpalmer@ucsd.edu
rpalmer@cts.com
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