So we cornerweighted the car

[Silkworm]

Overall weight 2459, 1/4" tank of gas, all fluids, race ready setup, no driver

With driver, 2771 (Ok, yes, I'm a lard ass! ) That puts me 90lbs over minimum weight, and if my dieting works out, I should be good to go (I doubt I'm ever going to be below 220 weight wise)

First pass, eyeballed the setup, too low in the front, no driver:

LF 618 RF 659
LR 618 RR 564

LF/RR 1182, 48%
RF/LR 1277, 51.9%
F 1277 51.9%
R 1182 48.0%


With driver

LF 736 RF 669
LR 734 RR 635

LF/RR 1371 49.4%
RF/LR 1403 50.5%
F 1406 50.6%
R 1369 49.3%


2nd Pass, raised LF 3/8", RF 1/4" (3 full turns, 2 full turns)

With driver
LF 739 RF 664
LR 732 RR 637

LF/RR 1375 49.6%
RF/LR 1396 50.3%
F 1403 50.6%
R 1368 49.3%


Final Pass, raised LF 1/8" (total of 1/2" from baseline)

With driver
LF 743 RF 659
LR 726 RR 646

LF/RR 1389 50.0%
RF/LR 1385 49.9%
F 1402 50.5%
R 1371 49.4%

So there you go

PaulC

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[joeg]

Good Job, but what's the point of checking the numbers "without driver"?

That measurement is completely irrelevant. Us lard ass divers are the heaviest individual component in the vehicle!

Cheers.

[Knestis]

This is obviously not the case for you but my conclusions below are based on experience with a light, FWD chassis so the particulars don't apply but...

First, I don't buy the assumption that it is ALWAYS best to strive for a 50/50 diagonal split. Theoretically, whether we like it or not, road circuits are actually ovals connected by squiggly straights - there is ALWAYS going to be more turning in one direction than in the other. The real world will shake out differently for different tracks but right-turn gains on a clockwise track might easily offset the associated losses in left turns. Given this, an asymmetrical set-up is not out of the question.

Second, depending on the dynamic loading of the front wheels under braking (CG height, springs, shocks, F/R weight distribution, tires, surface wetness) a significant split in LF/RF weights might create lockup imbalances under braking. It is possible that this will be more of an issue with an RX7 (that works the back brakes harder than, say, a Golf).

I may be a freak, but for what it might be worth...

Kirk

[Silkworm]

joeg,

Grins and giggles mostly I wanted to see what the car looked like empty.

Kirk,

Agreed, but since this is my first race car, I haven't even raced yet (just lots of school/HPDE stuff), I have no baseline to judge whether a bit of wedge will help at certain tracks.. In the 3 NorCal tracks, we run counterclockwise at each track, but there's some significant right handers that a big different in setup might compromise speed down the resulting straight.. So maybe mid season after running these tracks for a while with the neutral setup I can make a better judgement on modifying one way or the other..

As for the braking differential, you're dead on the money, the RF brake will lock up long before the LF right now.. Unfortunately, short of adding more weight to the passenger wheel well, I don't have anything left to remove on the drivers side that would help. :/

PaulC

[C. Ludwig]

Looks alot like what I've got. My question is why is the RR so light? Even without driver. The closest I got was having the LF about 80lbs heavier than the RR (with driver) which is right where you are. The percentages all work out but the RR is still light. Seems that the body is symetrical. If we could move the battery.....

On the subject of cross weighting for different tracks, I put some "negative wedge" I'll call it, in my car for Mid-Ohio the second time there this year. Theory was that the two most important turns are right hand and the car was wanting to push off of both of them. I ended up only changing the cross by about 1% but there was a perceptible difference and improved lap times.

Chris


------------------
Chris Ludwig
08 ITS RX7 CenDiv

[This message has been edited by C. Ludwig (edited November 20, 2002).]

[Karl Bocchieri]

The right rear is always the lightest place in a 2nd gen RX-7. Just the way it is, and you can't realy do much about it.

[Eagle7]

Newby question: how/where do you weigh your car? I can't afford $1000 for the scales I see for sale.

[Silkworm]

Eagle,

Hook up with a friend who does

My friend Alan brought his over to the house, we leveled them, and did it in about 2 hours. It'll go faster next time now that I have the spots marked.

PaulC

[Quickshoe]

Originally posted by joeg:
Good Job, but what's the point of checking the numbers "without driver"?

That measurement is completely irrelevant.

I can't answer for Paul as to why he did it, but I'll tell you why I do it.

I scale the car with me in it and the fuel load that I want. Once everything is like I want it, I record the weights without me in the car. This allows me to duplicate the setup at a later date by myself.

[Greg Amy]

Originally posted by Eagle7:
Newby question: how/where do you weigh your car? I can't afford $1000 for the scales I see for sale.

You find another racer in your area that spent the coin and you toss them $100 or so to borrow them (and get good advice on using them).

Yes we did. Yes we do. Wallingford, CT.

GregA