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post #10 of (permalink) Old 04-04-2017, 12:58 PM
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Join Date: Dec 2010
Location: SF, CA
Age: 38
Posts: 2,064
I was chatting last night with my machinist buddy who has been racing in Lemons for quite a few more years/track-hours than me.
I explained exactly where I had spun out at Sears Point and what i was felt trying to catch the slide twice before doing a 180.
Since you and I have similar suspension setups now, these tidbits might help you:

He says that it's not surprising what had happened given the track conditions and he believes it's because we stiffened up the rear a hair too much.
By doing so, as our car went through the carousel, it's going down hill at a fast clip and weighs down the car (down to the bumpstops).
Then, as you transition to the "drag strip" (which is really where the drag strip surface is at Sears Point), weight on the car shifts forward and cars with a light rear end (I think my tbird is probably more 60/40 now ) frind their back end breaking free and the whole thing destabilizes. If this happens in traffic ass puckering ensues.
Example: I think I lost it maybe 50 yards after this car as I was a littler wider at the point where he lost it.

Mike's First Suggestion:
* Soften the rear dampener slightly by going to a lighter weight oil. - Not worth it since the Bilstein's aren't easily drainable/refillable.
* Next Suggestion: If I move to a fuel cell, I'll mount it in the trunk so the weight distribution will shift rearwards and the CG will go slightly higher. While raising CG is not optimal, the wonkiness of the fuel shifting should help us reign things in before things break abruptly. IIRC, that's how the car felt before when it was much more "tossable."

* BEST SUGGESTION (esp if we don't go fuel cell): raise the front end slightly -- maybe 3/8" max by putting some rubber between the spring and the perch. That much lift shouldn't be noticable but it will mean the weight will take more time to shift forward. I know with our cut springs we are probably 1/4" too low already since the LCAs are NOT horizontal (heigher on the outside than inside). I've been told that our ackerman angle is probably slightly messed up because of this.

This should also if I understand things stiffen up the front end ever so slightly. See an exxagerated ver of this engr from a bunch of Mazda engr (literally):
FrankenMiata - Handling with a Hacksaw > MotoIQ - Automotive Tech, Project Cars, Performance & Motorsports

Bottom line MaddMartigan: you might want to think about what Mike suggested and it might be worth an experiment. I'll think about materials but I'm sure this could easily be done with everything from rubber to a cutting board.

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Last edited by S4gunn; 04-04-2017 at 03:22 PM.
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