Chassis Setup (corner weights)

[260DET]

In my situation, which surely is not unique, the knowledge as to the right shock valving for my particular car is simply not available. Which is one reason why double adjustable shocks are so attractive. That plus driving the car to and from the track plus any changes that may have to be made in the future to cater for things like different tyres.

 

The bump valving has got to be changed on the front Koni Sports anyway, plus the Koni double adjustable strut inserts are available in various lengths, the shortest of which will enable the car to be set up lower with less droop than before.

[johnc]

We need to make a distinction between shock valving and adjustments. Ideally, the shocks is valved for the vehicle's sprung and unsprung weights, wheel rates, and driver preferences. The adjustments are just a fine tuning tool. You shouldn't (and most likely can't) use adjustments to compensate for incorrect valving.

 

A quadruple adjustable Penske 8760 valved for a 3,200lb Corvette Z06 can never be made to work right on a 2,200lb 240Z even though there are 10,000+ different adjustment permutations on each shock.

[74_5.0L_Z]

I am resurrecting this thread because I have made some significant changes to the car, and thought some might be interested in the changes in weight and balance.

 

My original numbers were as follows(for full detail see the first post on this thread)

 

Here are the results with 16 gallons of fuel and me (190LBs) in the car:

 

LF = 648 Lb RF = 607 Lb

 

LR = 751 Lb RR = 710 Lb.

 

Total = 2716 Lb

 

These were are my percentages:

 

(LF + RF)/ Total = (648 + 607)/2716 X 100%= 46.2 percent on the front

 

53.8 % on the rear.

 

(LF + RF)/ Total = (648 + 751)/2716 X 100% = 51.5 % on left and 48.5% on right.

 

 

my diagonals were equal ie..

 

(LF + RR) = (RF + LR) -> (648 + 710) = (607 +751) = 1358.

 

Since that time I have done the following:

Redone the body (SubtleZ with customized air dam and hood).

 

Changed from a 16 gallon RCI polyethelene tank to a 12 gallon ATL cell.

The old tank was centered, and the new tank is offest to the right.

 

Replaced the old lead acid battery with an Odyssey lightweight battery.

Moved battery forward and down from behind rear passenger side wheel well to behind passenger seat.

 

After all that, the final results were:

 

LF = 669 Lb RF = 626 Lb

 

LR = 714 Lb RR = 668 Lb.

 

Total = 2677 Lb

 

These were are my percentages:

 

(LF + RF)/ Total = (669 + 626)/2677 X 100%= 48.4 percent on the front

 

51.6 % on the rear.

 

(RF + RR)/ Total = (626 + 668)/2677 X 100% = 51.7 % on left and 48.3% on right.

 

 

my diagonals were nearly equal ie..

 

(LF + RR) = (669 + 668)= 1337

(RF + LR) = (714 +626) = 1340.

[74_5.0L_Z]

I corner balanced the car again yesterday. I try to do this whenever I make significant changes. For those of you following along, I completely changed my suspension set-up. I went from 250 rear/ 200 front springs with a 1" front sway bar to 425 rear/450 front springs and an 18 mm front sway bar. The car has also been lowered 1" all around, the stock seats have been replaced with lightweight MOMO Start2007 seats, the rear struts have been sectioned, and rear camber plates installed (all since October). So I thought it was time to rebalance the car.

 

Here are the starting numbers with driver (me) and fuel:

 

LF = 683 Lb RF = 604 Lb

 

LR = 690 Lb RR = 679 Lb.

 

Total = 2656 Lb

 

These were my percentages:

 

(LF + RF)/ Total = (683 + 604)/2656 X 100%= 48.5 percent on the front

 

51.5 % on the rear.

 

(RF + RR)/ Total = (604 + 679)/2656 X 100% = 51.7 % on left and 48.3% on right.

 

 

my diagonals were a little off:

 

(LF + RR) = (683 + 679)= 1362

(RF + LR) = (604 +690) = 1294.

 

To fix this, I raised the RF spring perch 1 turn (1/8"), and the LR 1 turn. After this minor adjustment, these were the results:

 

LF = 662 Lb RF = 623 Lb

LR = 708 Lb RR = 661 Lb.

 

(LF + RR) = (662 + 661)= 1323

(RF + LR) = (708 +623) = 1331:mrgreen:

 

Here is the thread that discusses all of the suspension stuff that has been performed since October:

 

http://forums.hybridz.org/showthread.php?t=130005

 

 

Here are the final numbers with fuel but no driver:

 

LF = 603 Lb RF = 622 Lb

 

LR = 627 Lb RR = 617 Lb.

 

Total = 2469 Lb

 

These were my percentages:

 

(LF + RF)/ Total = (603 + 622)/2469 X 100%= 49.6 percent on the front

 

50.4 % on the rear.

 

(LF + LR)/ Total = (622 + 617)/2469 X 100% = 49.8 % on left and 50.2% on right.

[tube80z]

I have been using a slightly different theory for setup based on some of what Ortiz has said. It doesn't try and set the diagonals equal but instead aims to mimic the asymmetry that's already their. Dennis Grant has a calculator that implements this principle if you want to take a look.

 

It yields

 

682.94 640.06

687.06 643.94

 

I used to try and set diagonals equal but changed to this after reading Ortiz. The seems a little easier to drive but more importantly is kinder to tires.

 

Cary

[74_5.0L_Z]

I checked my numbers with DG's calculator and came up with

 

LF = 665.31 Lb RF = 621.69 Lb

 

LR = 707.69 Lb RR = 661.31 Lb.

 

These are pretty darn close to my final numbers of

 

LF = 662 Lb RF = 623 Lb

 

LR = 708 Lb RR = 661 Lb.

[74_5.0L_Z]

I've made some significant changes to the car, so it was time to rescale everything.

 

First the engine changes:

 

I Replaced stock 5.0L bottom end with a 5.4L stroker. The new bottom end has a 3.25" stroke and 5.4 inch rods as opposed to 3" stroke and 5.090" rods. Also the new bottom end has a main stud girdle and an aluminum flywheel. I replaced the Cobra intake with a Performer RPM intake. I replaced the stock rear sump pan with a custom Kevko racing front sump pan (this required modification to the crossmember to fit).

 

Second, the wheel and tire changes:

 

Last year I was using 16x8 centerline wheel and Hoosier 245/45/16 A6 autocross tires. This year I have replaced them with 15x10 spinwerkes series 82 wheels and FA slicks (23.0x9.5x15). Last year's tire/wheel combination weighed 39.5 lbs each, and the new tire/wheel combination weighs 32.0 lbs each. (I save 7.5 pounds of unsprung rotating weight at each corner .

 

I put the car on the scales Friday night and here is what I got with me (185 lbs) and about 12 gallons of fuel in the car:

 

LF = 648 Lb RF = 610 Lb

 

LR = 692 Lb RR = 653 Lb.

 

Total = 2603 Lb

 

These were my percentages:

 

(LF + RF)/ Total = (648 + 610)/2603 X 100%= 48.3 percent on the front

 

51.7 % on the rear.

 

(LF + LR)/ Total = (648 + 692)/2603 X 100% = 51.5 % on left and 48.5% on right.

 

my diagonals :

 

(LF + RR) = (648 + 653)= 1301

(RF + LR) = (610 +692) = 1302.

 

 

The car has lost 53 lbs since last it was scaled. 30 lbs of the lost weight came from the new wheels and tires. The rest came from changes to the engine (intake and flywheel mostly). The car has significantly less unsprung and rotating weight, and a measurably improved rear weight distribution.

[TheNick]

Still pretty left side heavy - any thoughts on trying to get more weight on the right rear to put power down better and deal with the chassis asymmetries that Cary spoke about above?

[74_5.0L_Z]

I have moved nearly everything that I can to the passenger side and as far back as possible (within the confines of the wheel base). The battery is behind the passenger seat, the radiator catch can is behind the right front wheel just ahead of the firewall and just off the ground, the fuel cell is 4" off center to the right. The coil, the computer, the mass air sensor and alternator are all on the right. I have lost some weight, but I fear that I can't lose much more without donating an organ.

 

I am looking into a lighter steering column, lighter pedal assembly, and anything else that anyone could suggest. If I get really motivated, I will relocate the engine and transmission toward the passenger side by an inch. In the meantime, I look for passengers to ride along. They're usually pretty easy to find:burnout:.

[TheNick]

Cool - I'm kinda surprised at how heavy the car is - do you still have a full interior and whatnot?

[74_5.0L_Z]

My car is pretty stripped. There is no carpet, undercoating, or sound deadening material. The center console, heater/AC, windshield wipers, and radio have all been removed. The stock seats have been replaced with Momo Start2007 fiberglass racing seats which are about 15 lbs lighter than stock. The battery has been replaced with an odessey PC680 which weighs a mere 15 lbs.

 

I do have a pretty extensive cage in the car and an ATL 12 gallon fuel cell with steel can. The car also still has the full dash, all the interior plastic, and all of the glass installed.

 

The car itself without me and fuel weighs 2350 lbs. To me that is pretty light. To get it very much lighter will require me to sacrifice the convenience of roll up windows (I could save 100 pounds by gutting the doors).

[AK-Z]

Hmmm. Pretty disappointing for me , for my setup, Since I'm going to running a KA-T with a tube chassis up front. I thought I would be able make sub 2200 lbs empty.

[tube80z]

Hmmm. Pretty disappointing for me , for my setup, Since I'm going to running a KA-T with a tube chassis up front. I thought I would be able make sub 2200 lbs empty.

 

A friends NA KA powered car is 1850. So no reason you can't hit your goals.

[JMortensen]

Hmmm. Pretty disappointing for me , for my setup, Since I'm going to running a KA-T with a tube chassis up front. I thought I would be able make sub 2200 lbs empty.

Start with a 240, that will help.

[74_5.0L_Z]

My car is just approaching the minimum weight that I am likely to see based on the compromises that I am willing to make and the choices that I made.

 

If I were willing to gut the doors and remove the dash, I could lose about 130 more pounds. If I had constructed the cage of 1.5 x 0.095 tubing rather than 1.625 x 0.120 tubing, I could have saved about 35 lbs. My custom front air dam and hood are heavier than simple fiberglass skins (My air dam with fan installed weighs 20 pounds). Replacing/ removing the glass is worth ~60 pounds. There are many other little gains that are beyond what I am willing to do.

 

If minimum weight is important to you then start with an early 240Z shell. The later 260Z and 280Z shells are heavier.

 

(Jon beat me to it)

[TheNick]

I have a late 70's car titled as a 71. That makes me feel better about weight - I have basically the exact same setup in terms of motor - just need to get it in and running. But with autox season in full swing I don't see it happening till the fall.

 

I made the mistake of typing in "5.0 supercharger" into Craigslist a couple weeks ago...DON'T do that You will see money disappear very very quickly from your bank account

[260DET]

Weight only becomes an issue when power, handling or braking are not up to it. My 280ZX weighs 1245kg which is not light but its not a problem for what racing I do, its well balanced and that is what counts.

[AK-Z]

Start with a 240, that will help.

 

if i could find a decent one up here, i would

[74_5.0L_Z]

Well, it's that time again.  The car has been sitting for two years and I have made some significant changes that require redoing the corner weights.

 

Here is what I have done that changes things:

 

1.  I have changed from Hoosier FA slicks to Hoosier 275/35/15 A6 tires on all four corners.  The A6 tires are a couple of pounds heavier each.

 

2.  I have upgraded my front brakes from 11.5 x 0.81 rotors to 11.5 x 1.25 rotors.  Again these are a bit heavier.

 

3.  I have completely redone my exhaust.  I got rid of my block hugger headers and built a custom set of stainless headers and exhaust.  Overall the exhaust is about 20 pounds lighter than it was.  Here a link to the exhaust build:

 

               http://forums.hybridz.org/topic/114643-my-custom-made-headers-and-exhaust-system/

 

4.  The driver has gained about ten pounds.

 

5.  I've lowered the fuel cell,  moved it further forward,  and moved it more to the right.  This involved rebuilding the fuel cell support structure and redoing the bulkhead above the cell.

 

6. I raised the front end about 3/4" and dropped the rear spring rate from 450 to 425 lb/in.

 

So, here are the new numbers (after adjusting the diagonals):

 

 

Left Front:  658     Right Front:  620

 

Left Rear:  701     Right Rear:  653

 

 

So, my new total weight is 2632 lbs with me and a 6 gallons load of fuel in the car.

 

The front / rear weight distribution is 48.6 / 51.4  and the left /right distribution is 51.6/48.4.

Edited February 4, 2014 by 74_5.0L_Z

[clarkspeed]

That's hefty. Good thing you have the power to compensate.