SCCAForums.com

i've been eyeing that opening in the dash covered by the radio block off plate. more fab work required, but i'd be able to hide the wires better that way....

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Nate Whipple
NER
188/88 DSP ITR

Blog updated with Dial In - part 1  (corner weight and alignment)

--Andy

Andy, first of all I love reading these articles. Thanks for the extra work you put into them.

This installment raises a question. How would you corner weight a car that does not have adjustable swaybar endlinks? Would you:

a) just leave the swaybars connected and get the cross weights even

b) disconnect the swaybars, get the cross weights even, then reconnect the bars

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Paul
'90 Mazda Miata - 181 STS2
'99 Honda Prelude - 81 STS (retired)

I know this was posed to Andy, but it's b). You want to get the corner-balance set with the perches, and then connect the swaybar, eliminating preload. A car that is set up with the springs and a preloaded swaybar fighting each other isn't going to respond as well to dynamic conditions as well as one done right. If everything was perfectly linear, and swaybars acted just like springs, then it would all be the same: but nothing is ever how it is on paper, unfortunetally.

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-Philip Maynard

No weenies!

paulyg:

Andy, first of all I love reading these articles. Thanks for the extra work you put into them.

This installment raises a question. How would you corner weight a car that does not have adjustable swaybar endlinks? Would you:

a) just leave the swaybars connected and get the cross weights even

b) disconnect the swaybars, get the cross weights even, then reconnect the bars

In short, don't.

Its so easy to get the pre-load out of a sway bar through*some* means that its just plain silly not to do it.  Shims under the frame mounts, washers in the end links, etc.  Look at the application and think through the physics.  There's always a simple solution.

That said, if you just can't find a way to remove the pre-load, I'd corner weight the car with the bar installed (and car properly ballasted for your weight).  It makes no sense to corner weight the car w/o the bar, and then install it in a pre-loaded state.  The goal is for the car, as run, to have equal diagonals. 

--Andy

Andy,

This reminds me of a question I've always struggled with when doing cross weights.  What if I have a car that has an uneven front to rear weight bias and an uneven left to right weight bias?  For instance my CRX has a 62.3% - 37.7% F/R weight distribution and a 53% - 47% L/R weight bias with my weight in the drivers seat.  If the car weighs an even 2000 lbs the weight distribution on the corners without any corner weighting at all would be:
Which gives a LFRR cross weight of 50.7% and a RFLR-CW of 49.3%

Should I raise the perches on the RFLR and lower the perches on the LFRR corners to try and get the cross weights to match at 50/50 or are the cross weights shown above which are based on the L/R and F/R CG location ideal?

-Brian Meyer

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-Brian Meyer
'88 CRX - CSP

if you raise just the RF I think that would do ya or lower the LF.

Gearz:

Andy,

This reminds me of a question I've always struggled with when doing cross weights.  What if I have a car that has an uneven front to rear weight bias and an uneven left to right weight bias?  For instance my CRX has a 62.3% - 37.7% F/R weight distribution and a 53% - 47% L/R weight bias with my weight in the drivers seat.  If the car weighs an even 2000 lbs the weight distribution on the corners without any corner weighting at all would be:

LF    660    RF    586
LR    399    RR    355

Which gives a LFRR cross weight of 50.7% and a RFLR-CW of 49.3%

Should I raise the perches on the RFLR and lower the perches on the LFRR corners to try and get the cross weights to match at 50/50 or are the cross weights shown above which are based on the L/R and F/R CG location ideal?

-Brian Meyer

You have more weight on the LFRR diagonal.  So, you can do any, or all, of the following: raise RF, raise LR, lower LF, lower RR.  50.7% is pretty darned close, though.

What you cannot do, which is what some people think, is get weight off the nose or off the left side via corner weighting.  You are merely trying to get the F/R ratio the same on each side of the car.

--Andy

Updated with Dial In Part 2.

--Andy

 

Hey Andy,

First, yes, I'm lazy. Could you provide the link at least once on every page in this thread. Those of us on dial-up will thank you.

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I need a stupidity filter for the internet!

BigJon:

Hey Andy, First, yes, I'm lazy. Could you provide the link at least once on every page in this thread. Those of us on dial-up will thank you.

http://grassrootsmotorsports.com/news/category/project-cars/other-cool-cars-hanging-around-the-grm-office/1992-miata-sts2-project

 

Thanks. Second, you state you want a rwd car to understeer slightly so you can get on the throttle sooner exiting the corner. Generally when I try to do this, i get . . . more understeer. Esplain, please.

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I need a stupidity filter for the internet!

145lb ballast?!  I think we need to make you keep some ballast in the car when you run.

Sincerely,

Fat boy (1.5 Andy Hollis; 2.0 Ken Motonshi)

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Aaron Hull
Northwest Ohio Region
Occasional co-driver of: STS - '91 Saturn SC; FS - '95 Z28 1LE

Howdy,

Andy Hollis:

BigJon:

Hey Andy, First, yes, I'm lazy. Could you provide the link at least once on every page in this thread. Those of us on dial-up will thank you.

http://grassrootsmotorsports.com/news/category/project-cars/other-cool-cars-hanging-around-the-grm-office/1992-miata-sts2-project

 

Heck, those of us with really damn fast connections (but perhaps an increased ability for laziness) also thank you!

So Andy... Is the STS2 car gonna become the "official Hollis-mobile" any time soon?  Seems like you're driving a boring civic these days a lot at national events... :-)

Mark

BigJon:

Thanks. Second, you state you want a rwd car to understeer slightly so you can get on the throttle sooner exiting the corner. Generally when I try to do this, i get . . . more understeer. Esplain, please.

Sounds like you are adding power before unwinding the steering wheel.  That's a driving problem. 

Driven properly, however, having the rear tires with a little more tractive capacity than the fronts allows them to use that extra bit for forward acceleration without losing lateral grip.

--Andy

marka:

So Andy... Is the STS2 car gonna become the "official Hollis-mobile" any time soon?  Seems like you're driving a boring civic these days a lot at national events... :-)

Mark

The Miata isn't "done" yet like the Civic is.  Maybe once the Miata is faster than the Civic.  Plus, driving two vastly different cars is a great way keep your driving skills fresh.

--Andy

Final installment of the Dial In is up.  Enjoy.

--Andy

Dang, I haven't even gotten my car aligned yet......or corner-balanced.....and I can't adjust my shocks!  I feel like I'm being out-prepared even before I show up for a race!  It is very cool of you Andy to write up your car setup and testing proceedures, it shows guys like me what it really takes to prepare a car and take the time and effort to test the setups, not just guessing and using what "other people use".

Just went outside and checked rear toe.....0.25" in on the left, 0.66" out on the right, about 1/8" total toe out up front.  Could this be causing my mid-corner oversteer and inconsistency in a slalom?  Maybe I should have it aligned before Atwater........hmmm

-JW

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*Banned Again* Permanently

Andy,

Any theories on why the toe-out helped on the skid pad?  I always thought front toe-out helped initial turn-in at the expense of mid corner performance.

Great articles, keep up the great work.

Dennis

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Dennis
TVR Solo Chair
#84 BS RX-8

I talk to cones.

Toe-out's effect on steady-state cornering depends on way too many things for there to be a hard and fast rule. It can act like Ackerman, increasing the slip angle on the unweighted inside tire. Most tires can generate more force with more slip angle as load decreases, so this helps. I've only heard of this with bais-ply race tires, but it could certainly apply to radial ST* tires.

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-Philip Maynard

No weenies!