Guest

Alot of talk recently about weight jacks and especially The "Ground Control" units.

Figured I would give a basic helpful thread on how to set them up and prevent mild mistakes.

First of all, when you install these for the first time and you DO NOT HAVE SCALES, you really want to keep both sides equal in length and make sure you document the amount of adjustment turns put into (We call them rounds) or take out of the coilover. If you initialy loose track of each side being identical in height, you are most likely introducing unwanted X-weight into the car which can and will lead the car to be tight turning one direction and loose turning the opposite direction.

Now when you get them installed, you will frist need to jack the car to about the desired ride height and will have to do a preliminary self alignment of the wheel camber trying to make sure both sides of the car are close to slight negative as posible. If the initial install means several new modifications to the front suspension were added then the front camber readings could acidently yeild one side positive camber and one side negative. What havoc can this cause? it will change the leverage footprint of the contact patch and thus the effect on the springs in motion ratio. Make sure both tires are resting more on the inside tread with hipefully a visual of about .5* negative camber.

Now if you have scales, then sit in the car first and roll the car ontot he scales wiuth you in the drivers seat (Do not get intot he car after sitting it on scales- yes this will take a few people...OR...place weights on the drivers seat to represent your body weight +/- 10 lbs.) Reason for having the weight in first then rolling onto the scales is the suspension will be loaded properly without scrub laterally in suspension bind by adding weight after the car is centered on scales- this will yeild a flase reading since the suspension will not be in natural rolled state.

Without scales? Really the best you can do is to jack rear axle off the ground slightly by just one jack under the diff.

(IMPORTANT NOTE: The car must be on flat concrete. Best to find a laser leveled section of shop or garage floor that is marked and trustworthy for ALL FUTURE CHANGES. Sometimes, permenantly marking square boxes on the floor for future reference of tire position is completely necessary to get the car in the exact spot for future alterations to always bring the car to the same baseline setup.)

With the car in that leveled spot that is marked and diff jacked, measure the front fender lips. This is NOT SCIENTIFIC because of cars potentially being in accidents of metal fatigie twisting body panels etc, but if you do not have scales then it may be all you have to work with. Worst comes to worst, you just leave the car with both sides of the weight jackers in the equal rounds match side to side. Assuming the car is fairly stright and fender lips are trust worthy- then proceed to dial the weight jackers to sit the car at the desired equal fender lips on each side to match, regardless fo weight jack heights being equal. Make sure both rear tires are off the ground enough not to touch, but yet not too high either to rake the rear weight of the car ontot he front coils. If you make adjustments to the front and one rear wheel strats to touch down, then slightly jack the rear more off the ground leaving about 1/2" ground clearance.

Now repeat this exact process in reaverse for the rears via jacing the front wheels off the ground slightly under the k-member center (smallest jack prong lift area is best... and centered best so as the car can teeter side to side if the fenders are leaned on.

Now when finished, sid ethe car down and check all four ride heights at fender lips. They will most likey never be perfectly equal, but both fronts and both rears sould relatively match in height. If both lefts are 1/4" higher than rights? this can be corrected, and visa versa. However, if the LF and RR are higher then their opposing sides, this is bodsy distortion that can not be corrected and the amount of tolerance play just needs to be aprox equalized with very small adjustments to once side or the other based on raising or lowering to get that desired overall stance. I will give an example. Lets say both fronts are 25", but one LR is 26, and RR is 26 1/4. We can slightly bring RR own to 26 1/8 which in turn will vring the diagonal LF up about a 1/16th to an 1/8th making the fronts within 1/8" and the rears within 1/8" on lateral tolerance in diagonal chassis tweak when pertaining to ride heights.

Now that this is set and all 4 tire positions are recorded permanantly on the garage floor, we can now take the car for a more perfect machine alignment.


Now we are 3 months down the road and we want to change the front coil springs from 700 lbs to 800 lb rates. We need an alignment again when finished right?....Wrong. We simply put the new springs in, load the seat with the same weights or driver and AGAIN,, we roll the car into those 4 spots on the garage floor after the weight is applied. We do not jack the car up and sit it back down to take any measurements without rolling the car back 10 or more feet to settle the suspension bind and re roll it back ontot he 4 tire positions. ALWAYS ROLL THE CAR BACK AND FORTH SEVERAL FET TO SETTLE THE SUSPENSION AFTER ANY JACKING OR ADDED DRIVERS WEIGHT!

You now check the fender heights and the fronts are at 25 5/8" with the 800 lb springs? you simply take out a round or two in the front weight jacks and then roll the car back and forth to settle then recheck fender heights. Once the car is back into the same positon and same fender lip heights as prior with the 700lb springs, the alignment will be prefect now with the 800 lb springs since the car is at the smae exact ride height.

Anyone please feel free to please add any tips or suggestions.

Some people choose to set the fronts in reference to how the rear tires are hanging. I do not like this method only because you are relying on tires hanfing unloaded, eather thn lloking at the loaded fender lips of the tires you are setting. To each their own, I just thought I would give merely my opinion on how I would probably try to set weight jackers without scales. Fortunately, I have access to scales, but most people do not.

Dean

Guest

My appologise. Its late, I'm tired, and my typing skills suck.

Guest

Wanna check for bumpsteer while we are at it?

What is bumpsteer? It basically is unwanted changes in alignment toe settings through suspension travel. One or both tires can hit a bump in the road and as that wheel assembly travels into compression the geometry can change and the tire can add or even loose toe setting making unwanted steering imputs without moving the steering wheel.

How do we check this. There is are simple device called toe plates that can be bought or easily made or duplicated that are merely plates thicker gauge sheet metal with a groove on each side cut into them to retain tape measure hooks and reading points on front and rear of tire path. They go aganist the sidewalls of each tire and with two people (One holding each toe plate on each side of the car) can read the total toe setting of the vehicle. The toe plate need to be relatively sized for the tire diameter for best accuracy.

Lets say you adjust your toe seetings so the front tape reads 3/32 less then the rear tape... 3/32" toe in.

Now, have a heavy friend sit on the front bumper (Or two lighter friends) while you still read those same toe gauges. If the toe increases or decreases in the suspension compression then you are experiencing bump steer. What causes this? it is a misalignment of the tierod arch when compared to the A-arm arch. How dso wwe correct this? It is accoplished by using a "bumpsteer kit" which generally consists of an after market outer tierod ends that have provisions to shim the mount height.

Which way to adjust adjustable tie rod shims? If when you increase in toe when the nose of the car is compressed, the A-arm geometry is shortening while the tierod is lengthening, the inner tie rod end needs to be lowered. If the suspension looses toe (goes higher in negative reading lest say from -3/32 to - 3/8" in compression of suspension, the tierod is shortening as the A-arm is lengthening, or the tioe rod is shortening in geometry articulation faster or steeper angle than the A-arm articulation is shortening in geometry. This case the outer tie rod needs to be shimmed lower to match the A-arm articulation swing. When the car is properly "bumped" (Checked for bump steer) there will be absolutley no gain or loss in toe reading in susoension travel.

A side note: sumtimes change is good. I will give an example. More toe out setting will make a car turn into the corner easier. and track through a corner due to a tighter radius on the inside tire path than the outside tire path (Ackerman angles) Based on the car and the steering geometry, sometimes help is needed promoting better corner Ackerman as opposed to not draging while going down a straight path. In circle track racing, one of the Vehicles I work on needs help in Ackerman to help the corner Ackerman so I leave the tierod geometry where as it increases toe by 1/8" in 2" of suspension travel. I run 1/8" out down the straight and in the bottom of the corner in the flatter section of bank (Local track here being Toyota Speedway has a banking dfegree of 6*.8* and 12* as you increase height in the corner bank. If you run the lower line, you are laying the car through the corner more flat with body roll and less compression bank than the car running the high line not turning the wheel as much because it is more banked. To get the car to rotate better on the flatter lower 6* bank, I induce toe out increase to 1/4". and on the higher bank it only increases to 3/16" on the 12* portion of the track. How do I do this? By using compression bank geometry to my favor. When the car stays flat road cornering, it still squat the right and lift the left side due to bodfy roll and no banked turn compression force to squat the left. On a banked corner, left side of the car squats more than it would on a flat corner. The right side of the car pretty much comprsses close to the same rcompressed travel regardless of 6* or 12* banking because on one it has compression bank of lets say 200 lbs and roll weight of 100 lbs, and the other it has compression bank of 250 and roll weight of 50.. both equalling 300 for this senerio example. Its the left side that will vary load and angle of toe srub to get the tire to bite and turn.

So... As the right compresses, we promote toe out gain, as the left compresses we promte toe out loss. At three degrees roll and about 2" travel of the right and 3/4" travel left side of car I get a toe increase of 1/16 total. On a higher compression bank I get 2 1/2* roll and a right compression of 2" and a left compression of 1 1/4". In that left side tierod I set the geometry to decrease 1/16" toe on that side in the 1/2" travel. I start that left side tierod at +1/16 and it ends at -1/16". I set the right die tierod at +1/16" and it ends at + 3/16".

You never feel any pulling of the car because the steering wheel imputs override and center the tire path as you are pulling the wheel into the corner and releasing coming off. Caster overides toe pull or push.

The reason why I do not have the toe at zero going down the straight is because you need a little aided effort of toe out (in this case + 1/8" total toe out) to get the car to initially rotate into the corner as well as in the track we run the car is never really ever going straight. It is somewhat always in an oval. The toe gain only happens in roll. Initial turn in has not developed roll to induce toe out gain so you always need to start with a little toe out for a good turn in grip.

Just a good example on how proper geometry can play a major part in tire contact patch and grip.

//<86TA>\\

iTrader: (15)

good write up Dean, im sure this will be helpful to a bunch of people here.

92-Formula

iTrader: (4)

Appreciate the bump steer write up - thats always something i was a little under-educated on.

TEDSgrad

iTrader: (4)

Just re-reading and bumping it to the top.

rawley2

I am installing them this weekend (I hope) so thanks!!!!