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Scaling a car/Corner weight and ride height question

Posted By: Nitrofish

Scaling a car/Corner weight and ride height question - 08/11/19 07:08 PM

I scaled my 69 B-Body
496 BB - 600HP
727 4200 stall
Cal-trac mono leafs, Cal-tracs bars. 4.10
Viking double adjustable on all 4 corners
390/45/R15 M&H Racemasters. 95% Street Car.

Before, the adjustment the vehicles ride heights were even/equal on all four corners (Front Driver and Front Pass ride heights were equal). Vehicle drove and tracked true.


Starting weight: Driver in car, no cal-trac preload, front sway bar disconnected, all shocks at 0 (soft)
FL -1031 FR - 981
RL- 870 RR- 835


Next, I adjusted the drivers side torsion bar clockwise/tighter 3 turns, and loosened the passenger side torsion bar 3 turns. Driver in car the weights are:
FL- 1061 FR-951
RL -831 RR-873

While I think the weight distribution is correct, the ride height has now changed as I expected it would.
The pass side is 1/4" lower, while the drivers side is 1/4" higher from their original starting points. So now overall, the Drivers Front and Drivers Rear ride heights are now a 1/2" higher than both the Pass Front and Pass Rear. The Drivers side of the car sits a 1/2" higher than the passenger side. After a test drive the car still seems to drive well and track true under WOT and cruise speeds. However, is this normal to have this much of a difference in ride height?? Have others experienced the same?

Another option that I tested was to return the torsion bars to their previous/original loads and adjust the RR cal- trac bar by adding 1-1/2 turns (one and a half) of pre-load, this test adjustment provided near the same corner weights and ride heights as the torsion bar adjustment did. However,I felt that adjusting the torsion bars was a better route than driving around on the street with 1-1/2 turns of preload on the RR.

Open to any technical recommendations and/or comments.

Thanks!
Posted By: CMcAllister

Re: Scaling a car/Corner weight and ride height question - 08/11/19 09:02 PM

How heavy is the driver?

I always want to get the car dead level, or as close to level as possible, regardless corner weighs. 95% street car? With a driver? The first set of numbers doesn't look terrible if the car sat right.

A little bit of extra load on the LF bar and a little bit of pre-load on the RR will add weight to the RR (and the LF) if that's what is needed without making it sit goofy. Coilovers on the rear would make it easier, but preload on the bar is about all you have to work with now.

I wouldn't worry about getting the weight where it should be in a strictly drag situation if it's only going to go to the track occasionally. But if the rear weights are close to equal, it should be fine when you do go.
Posted By: Nitrofish

Re: Scaling a car/Corner weight and ride height question - 08/12/19 01:44 AM

Originally Posted by CMcAllister
How heavy is the driver?

I always want to get the car dead level, or as close to level as possible, regardless corner weighs. 95% street car? With a driver? The first set of numbers doesn't look terrible if the car sat right.

A little bit of extra load on the LF bar and a little bit of pre-load on the RR will add weight to the RR (and the LF) if that's what is needed without making it sit goofy. Coilovers on the rear would make it easier, but preload on the bar is about all you have to work with now.

I wouldn't worry about getting the weight where it should be in a strictly drag situation if it's only going to go to the track occasionally. But if the rear weights are close to equal, it should be fine when you do go.





Thanks for the reply.

Driver = 235 lbs. All weights given were with the driver in the car.

Whether I add weight to the RR with the torsion bars or with the cal-trac bar (pre-load) the ride height is offset.

I will remove some of the weight/load to the RR as you suggested. This will even out the weight in the rear and start to return ride height closer to equal. Seems that I need to find a happy medium and I likely pasted that point with the adjustments made.
Posted By: Cab_Burge

Re: Scaling a car/Corner weight and ride height question - 08/12/19 06:13 AM

Are you looking for magic, performance or looks work grin
I like performance wrench up It needs to hook and book always, no matter what it looks like sitting still or hooking boogie devil
Posted By: dvw

Re: Scaling a car/Corner weight and ride height question - 08/12/19 01:52 PM

Always start with the front equal and add load to the rear. If the front wheels come off the ground with your first method you will lose all the static weight distribution change you made. I made that mistake. Then came a long wheelie, not good. Depending on how quick the car is it may be fine with the right rear light. However as it leaves harder if the right rear is light it will steer to the right at the hit.
Doug
Posted By: polyspheric

Re: Scaling a car/Corner weight and ride height question - 08/12/19 01:55 PM

Can't help with the question, but...
1. Equal weight on rear wheels neglects how hard the weight transfer and pinion action load the right rear on launch
2. To me, the most important chassis set-up is "what makes the car go straight the whole time?", which may be quite different from best street conditions
Posted By: n20mstr

Re: Scaling a car/Corner weight and ride height question - 08/12/19 02:07 PM



My car always liked 30lbs more on the Right Rear.

Your almost 40 now. Id go even on the rear weights and see if the car goes right or left. Then add preload from there. when on the scales, see what 1/2 a turn on the T bar does, then you can make small changes at the track.

Its nice to have the tbars to adjust the weight, but yes it does make the car look weird sometimes.

LOVE my ladder bars and rear coil overs for that ….LOL
Posted By: skicker

Re: Scaling a car/Corner weight and ride height question - 08/12/19 02:32 PM

I have messed with scales a lot however everything has been for dirt car applications...

When moving cross weight (opposite corners) you need to be able to adjust in and out on all 4 corners to get the full effect.

I fully understand how this isn't always possible with leafs and torsion bars...Torsion bars will move weight just as you would like but have no adjust-ability as far as the rate...(spring rate)

If you were to use a longer shackle on the RR you would add weight there while also pushing the LF back down and leveling the ride height back out...A 1/2" lowering block on the LR may also do what your looking for as it will transfer weight onto the RR while lightening the RF.

There's a way to get nearly any number you want without sacrificing ride height but you'll have to be willing to experiment a little. twocents

Ultimately what your car likes best will determine the direction you'll need to take...
Posted By: jcc

Re: Scaling a car/Corner weight and ride height question - 08/12/19 04:21 PM

Originally Posted by polyspheric
Can't help with the question, but...
2. To me, the most important chassis set-up is "what makes the car go straight the whole time?", which may be quite different from best street conditions


That is my thinking, kinda like bowling, I don't care how you knock all the pins down. biggrin
Posted By: Nitrofish

Re: Scaling a car/Corner weight and ride height question - 08/12/19 05:50 PM

Hello All,

Thank you for your input!

I will get back at it this evening after work. Hopefully, some test and tune time very soon.
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