What is Droop? Looking for really technical explaination.
 

I understand how to measure droop from set-up sheets. But don't we really need to know the tire size on the set-up sheet also? As my foam tires wear, I change my ride height AND droop, right?

Wouldn't spring preload (or slop) be a more useful value?

What is the effect of droop? Does it effect fore-aft weight transfer or is it more of a side-to-side effect?

As the car comes close to traction rolling, shouldn't both (front rear) inside tires come off the ground at the same time?

I can't help you with a technical answer... but droop is basically how far the chassis will rise above std ride height.
I prefer to think of it as "up travel". If your std ride height is say 6mm, and your shocks will allow the chassis to rise to a ride height of 12mm, then you are allowing a lot of weight to transfer to the opposite end of the car. This affects both lateral, and fore/aft balance. Using the droop screws on your car, (or spacers inside the shocks) you can limit how much the chassis can rise. The setting should be the same for both left & right sides of the car... this is why you would place the chassis on blocks, and measure the position of the suspension arm compared to the chassis. (you don't need to measure if using spacers inside the shocks).
Also, as foam tires wear, you lose ride height, but you still have the same amount of "up travel", though the maximum height is reduced. In the above example... If your std ride height becomes 4mm, your shocks will still allow 6mm of upward travel, resulting in a 10mm maximum ride height.

Up-travel is maybe a good way to think about droop.

So can I be gauranteed the same "up-travel" when I set my car up to a specific "droop" as per some set-up sheet when I don't know the tire size?

And if I "reset" my ride height as my foams wear, I need to "reset" the "up-travel" also, correct?

Damn...is RCTech slow tonight? Or is some router down between WI and SoCal?

Uptravel will have to be adjusted as tire diameter goes down and u adjust ride height.

U cannot just set it and leave it, The only time you can do that is when u run rubber tires assuming u only use the same brand. Since there diameter does not change you can basically set your 5mm ride height and forget it as well your uptravel can be set and left.


As explained by Thistle it effects the amount of weight transfer to oposite ends of the car.

I have used ranges of 1 to 4mm of uptravel and tune to the track from there.


Best way of checking uptravel is to measure ride height and then the uptravel wich is ride height with shocks fully extended. That way u can compare to any brand of car. IT dont mater what blocks or tools they use to compare from car to car trackside all u need is a ride height guage.'

You can not be guaranteed the same up travel when you copy somebodies droop measurement, unless you know there ride height and maximum ride height. (You also need to measure from the same location). As Joel states, the best way is to measure ride height, then measure with the shocks extended.

There ya go. Roger on the ride-height max. That seems to compensate for tire diameter.

So the Associated droop gauge is essentially worthless? (and all thier set-up sheet droop settings)

This is what I do... I set my ride height to where I want it. The I lift up on the shock tower, while holding down the tire to get a maximum reading. I adjust the droop screws to get a rough setting for maximum up travel. Next I place the car on hudy droop blocks (associated would be similar) and make sure that the left and right settings are exactly the same.

OK, that sounds reasonable. The Associated droop gauge (that comes with the TC3) measures the distance from the chassis to the a-arm tip (in Z, vertical direction). It's like a basic ride height guage (stepped), but from measures from the chassis.

Definite affirmative on left to right symmetry.

Now what happens when the front to rear up-travel is significantly different? If the rear has more up-travel, does that transfer more weight to the front under braking (loose under braking)? How would that effect the steady-state lateral behavior (push, front wheel lifting?).

"Definite affirmative on left to right symmetry." This is basically the only reason i use my hudy blocks to make sure left and right are identical, from there its track side adjustments with a ride heiht gauge and a car that is loaded race ready

Yes, if the rear has more up travel, it will allow more weight to transfer to the front under braking, and result in a loose rear end.
If you notice that a wheel is lifting during a corner (and you think it's affecting handling) you can increase up travel on that end of the car.

OK, this has been very helpful so far. Thanks.

That's what the forums for... :)

In theory droop help to increase tires traction and stabilize the car against wheel lifting.

My case is unique, my car can turn nicely if I don't use rear droop (very tiny droop) but it becomes oversteer when I applied 2mm droop ( I measure the up travel movement before rear tires lift the ground )

What happen ?:confused: :confused:

asw7576: Adding more rear droop will transfer more weight to the front wheels as the car decelerates into a corner. The added weight is helping the front tires dig in, which in turn, is breaking the rear tires free.

Thanks, that's good explaination :p you get A+ ;)