On Wed, 4 Sep 2002, Creamer, Mark wrote:
> Shawn, Bob, et al
Hi.
> Is the twitch phenomenon something that might have just become evident
> on my car since I switched from the old Michelin redlines to some nice
> new Yokohama AVSdb tires?
Well, you just switched from "rocks" to real tires. Hmmmm.
<sarcasm mode off>
I'd say "maybe".
The bottom line is that you have to "check things". That means get the car
up in the air and pry on the mounts and stuff looking for compliance.
The first time I drove my regular TR6 with race tires (I used to run it in
SCCA D Street Prepared), when I turned in to a longish "sweeper", I spun
the car out. The big change on those tires were that they run at MUCH
SMALLER slip angles, so the normal amount of steering input was WAAAAAY
TOOO MUCH. It did make for exciting runs, but I was not fast as a result.
But that leads to a question - what sort of tire pressures are you
running? I aks that because with many tire setups on TR6, there is so much
sidewall flex in the tire that you do get some additional "wiggling" in
the tail when you turn in hard.
Funny story - I went to a BMW club autocross with the street car. I had
the lowering springs (450/575 front/rear) and the Hoosiers on. The tech
guy tried wiggling the front suspension. It was rock solid. In fact he
couldn't get it to wiggle at all! He then sauntered over to the rear
suspension. Same thing - ONLY HARDER. With that he calls out the name of
the tech. chair: "Umm, hey Joe? Could you come over here and check this
out?" Joe comes over, wiggles the front, wiggles the rear and then steps
back looking intently at the car. "Oh," he says. "It's a British car.
They're supposed to be like that". Then he slapped the tech sticker on.
That was a great laugh!
Literally all the suspension movement was tire flex. Now, I was running
Hoosier DOT radials. The sidewalls on those tires are not to be believed.
Majorly stiff. I used to have folks push down on the rear bumper - the car
barely moved. I then would have them wiggle the car side to side. It would
wiggle a bit. Most folks would walk away shaking thier heads.
I drove that car to two VTR's setup that way, 4000 miles round trip to Ft.
Worth and about 3500 miles round trip to Hudson, WI. In fact it's still
setup that way, but it's getting saggy owing to the 30k+ miles since I
set it up...
> I don't remember it before, but I sure feel it
> now. I was afraid my suspension components were getting worn out -
> probably are anyway, though...
You should check them. Worn suspension components are not good. Plus it's
so easy to fix things on these cars... there's no excuse for sloppy TR6
suspensions!
> <mc>
C ya,
rml
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