[Fot] race alignment GT6

[Scott Janzen]

I also just monitor tire temp across the tread and wear patterns, figuring that’s a decent indicator of how the rubber is hooked up.

Sent from my iPhone

> On Jul 12, 2021, at 8:07 AM, Ponostyle <ponobill at gmail.com> wrote:
> 
> You can play with these suspension settings and try to detect the effect of the changes, assuming you have some way of obtaining an infinite amount of track time or a skid pad (limited but useful) to do the testing, or you could get a simulation program to play with. That’s how I initially dialed in Peyote and the results were good. These are dynamic systems with a lot of variables that interact. It’s not easy to optimize, but a good suspension simulation program can model everything that’s going on. The biggest problem then becomes modeling our ancient cars with their odd suspension components that no modern engineer would ever dream of using in a modern car. It can be done by approximation—even a TR3/4’s bonkers trunnion system can be approximated, it takes some work and will never be completely accurate—but it’s a lot closer than cut and try will get you. 
> 
> Bill Babcock
> Beach Bum
> bill at ponostyle.com
> https://www.Ponostyle.com
> 
>> On Jul 12, 2021, at 4:40 AM, Scott Janzen via Fot <fot at autox.team.net> wrote:
>> 
>> I can tell you what my GT6 has.  What you run I’m sure depends to some extent on tires.
>> I run Toyo R888Rs - radials.   They like negative camber.  
>> 
>> Fronts - 2.6 degrees negative camber, 1/16” toe in, castor 6 degrees.  Stock is 4, +/- 1.  I have to admit I have never tried to adjust this up or down.  With more castor, I think the camber gets a little more negative with turn-in, which is probably good as it counters body roll on the outside wheel.  However, now you’ve got me thinking, and I may dial it back to stock to see if I notice the difference.
>> 
>> Rears - 2.5 degrees  negative camber, slight toe in to counter suspension flex.
>> 
>> Hoosier bias plies (like the TD, which comes in 13” sizes) don’t like negative camber, so they are not interchangeable with these camber settings.
>> 
>> You can also adjust the castor by playing with the amount of shims front and rear on the lower a-arm, which will move the trunnion end of the A-arm front and rear.  Of course, that effects the camber, iterative process.  
>> 
>> I inherited my car with work done to reduce bump steer - mainly by bending the steering links down.  Very little bump steer within the normal operating range.
>> 
>> Be curious to hear what settings you end up with, or others use.
>> 
>> Scott Janzen,
>> ’68 GT6, but with inner and outer u-joints at the rear and spicer sliding halfshafts.
>> 
>> On Jul 2, 2021, at 5:32 AM, Enquiries Road & Track via Fot <fot at autox.team.net> wrote:
>> 
>> could anyone racing a GT6 (or even a Spitfire) please offer some comment on front alignment "settings". In particular, have you made engineering changes to increase the static caster? 
>> 
>> The most obvious option is to change to the trunnionless vertical links used on various clubman type race cars ., eg Caterham or Birkin. I have a set of Birkin alloy uprights , but i'll have to make suitable wishbones . 
>> 
>> I'm trying to recommission our Mk2 GT6 racer which we have not used for many years, and my memory was the "stock" front end was not good with "modern" slicks and particularly mid-corner indecision. 
>> 
>> Any comments gladly accepted
>> 
>> thanks
>> 
>> Terry 
>> Australia
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