Originally Posted by faifaisalfal
Hi Infinite 12th,
Thanks for the info. So basically the front droop is mainly by feeling and eyeballing only.
I like to measure front droop two different ways.
The first way is the easiest, and it is what I do when Im at the track and fussing around with the car. First, I will pull off the front bumper and plastic brace thingy, so that I have easy access to the chassis centerline hole.... and so that I see exactly what the ride height is. I use the Hudy pan car gauge with the .2mm increments(it ranges from 2mm to 5mm or so, so it works perfectly for 12ths).
Poke down on your rollover antenna a few times and then roll the car back and forth on the setup board. Compress the suspension again once more, for good measure. Then measure the front ride height with the Hudy gauge. It is important that you are using the gauge with the .2mm increments, otherwise the following process will not work.
As I measure the front ride height, I find exactly where the car sits at static height on the gauge. Then I slowly push the gauge farther under the car, one .2mm step at a time. Lean down to board/car level, and watch as you do this. Continue pushing the gauge under the car, until you see the front tires just
start to lift from the ground. Ideally, your car will be tweaked correctly at this point, so both front tires will lift from the ground at the same time.
Take the static front chassis ride height measurement and subtract it from the measurement where the car is currently sitting on the gauge. That will tell you your front droop. Normally, I tend to run .2-.4mm of droop at our local carpet track. So, for example, I will measure the front ride height at 3.4mm with the Hudy gauge. Then I push the gauge under the car little by little, until the front tires lift. The gauge is measuring 3.8mm at this point. So, the front droop is: 3.8 - 3.4 = .4mm.....
It's a pretty simple process really.
The second way I measure droop is by measuring the actual front axle height from the ground. I only do this when I am rebuilding/tweaking the car at home, usually. As a side note, when you assemble and set up the car (and between each race weekend/meeting), you should always be checking that the front axle height matches left to right on the car. If it does not, that is a surefire way to introduce tweak to your chassis.
Just put the car on a totally flat surface, I usually also put it on droop blocks. Then measure the distance from the ground to the very inner part of the front axle... on both sides of the car. You need a set of digital calipers for this. I try to get the front axles equal to within a tenth of a millimeter. Next, jiggle the front steering block until you find the spot where the spring begins introducing resistance. This should be easy to find, but you need to make sure you aren't actually compressing the spring, otherwise your measurements will be off. Raise your calipers from the static height until you feel that initial resistance... the delta between the two measurements is your front droop value.
This way is a little more accurate, but is much more time consuming and more difficult to get correct. I like this method because you ensure that both sides of the car have the same amount of front droop. But, again, I only take these measurements when I have plenty of time to kill at home prepping the car. I generally don't get this involved at the track, unless I had a wreck where I broke some front end pieces... or I suspect I have a collapsed front spring.
Hope this helps a bit.