Droop
Droop is a word that by definition means to hang downward. How this applies to RC Suspension tuning
is along the same lines. Droop is a measurement that determines how far your suspension arms “hang
down” at full suspension travel. Droop is measured by measuring the center to center length of the
shock. Center to center length means the center of the upper shock mount eyelet to the center of the
lower eyelet or rod end. More droop is achieved with a longer length, and less droop is achieved with a
shorter length. Droop is a tuning tool used by ALL of the top RC Racers, in every form of racing,
especially dirt oval racing. I use droop adjustment at nearly every race I attend, and sometimes I adjust it
after each run to fine tune the handling of my chassis. Droop is an advanced chassis adjustment, and is
not recommended for all racers until a firm grasp of chassis basics is obtained.
Droop – How does it work?
As one end of the car is raised, it transfers weight to the opposite end of the car. The higher you lift that
end of the chassis, the more weight is transferred to the opposite end. The more droop you have on one
end of the chassis increases the amount of weight you can transfer to the opposite end of the chassis
during acceleration, cornering, or braking. More droop allows you to transfer more weight, while less
droop limits the amount of weight you can transfer.
What Does Droop Do?
Droop controls the amount of weight transfer that the chassis can achieve by changing the amount of
travel at one end of the vehicle. Droop DOES NOT change the overall balance of your chassis setup, it
simply controls the amount of weight transfer. Droop adjustments are considered a fine tuning
adjustment, because droop should be adjusted to change characteristics entering and exiting the corner.
If your chassis is not already “close” on setup, and the balance is not right, Droop will not save your car
from ill handling characteristics.
Front Droop
Front Droop affects the amount of weight transfer to the rear end of the car during acceleration. Front
Droop has one main job: to control weight transfer front to rear and help add or take away forward
drive. Front Droop affects ON-POWER handling.
If you decide to tune with front droop, here is a basic guide to what each adjustment does:
More Front Droop – Increased weight transfer from the front to the rear wheels, resulting in more
forward drive, and a tighter car on throttle. The car will want to drive straighter up off of the corner, and
will have more rear grip while having less on throttle steering. Ideal in lower bite/loose conditions where
forward drive is hard to come by.
Less Front Droop – Reduced weight transfer from the front to the rear wheels, resulting in less forward
drive, and a looser car on throttle. The car will want to rotate more up off the corner and will have less
rear grip while increasing on throttle steering. Ideal in Higher bite/hooked up conditions where you have
plenty of forward drive.
Rear Droop
Rear Droop affects the amount of weight transfer to the front end of the car during deceleration and
braking. Rear Droop has one main job: to control weight transfer rear to front and help add or take away
off power steering on corner entry. Front Droop affects OFF-POWER handling.
If you decide to tune with rear droop, here is a basic guide to what each adjustment does:
More Rear Droop – Increased weight transfer from the rear to the front wheels, resulting in more entry
steering, and a looser car off power. The car will want to turn more aggressively into the corner, and will
have more front grip and more overall steering. Ideal in lower bite/loose conditions where steering is
hard to gain.
Less Rear Droop – Reduced weight transfer from the rear to the front wheels, resulting in less entry
steering, and a tighter car off power. The car will want to turn less aggressively into the corner and will
have less front grip and less overall steering. Ideal in Higher bite/hooked up conditions where you have
plenty of steering.
Measuring Droop
Droop is measured using a pair of calipers. Simply measure the center to center length of the shock to
determine your current droop setting. On the car, this can be measured from the center of the upper
shock mount screw to the center of the lower shock mount screw.
Adjusting Droop
Droop can be adjusted or set using the following four methods:
- Shock Tower
- Droop Screw
- Limiters
- Rod Ends
- Shock Tower
Many chassis are designed to have droop adjustments built into the shock towers. This allows racers to
quickly and easily adjust droop, with touching their shocks. Moving up on the tower takes droop away,
while moving down on the tower adds droop. If your shocks were matched for length when built, there
is no need to measure droop after adjusting, because you are changing droop equally left to right with
the shock tower hole change.
Droop Screws
Some chassis have suspensions that utilize droop screws. Droop screws limit the downward travel of the
suspension arm regardless of the shocks total length off of the car. The more you thread a droop screw
into the arm, the more you reduce the droop of the chassis. The more you unscrew the droop screw, the
more droop you allow the arm/shock to have. When using droop screws, it is imperative that you
measure the center to center length of both shocks to ensure that you have equal droop left to right. If
not, adjust droop screws as needed until matched lengths are achieved.
Limiters
Some racers like to tune droop by adding internal shock limiters. Most racers use .030” limiters, and
sometimes run up to 5 or 6 of them inside the shock to adjust droop. Simply unthread your shock rod
end and install on the shock shaft below the piston, reassemble, and you are ready to go. Be sure to
match shock lengths before installing on chassis.
Rod Ends
A simple way to fine tune your droop adjustments is to use your lower shock rod ends. You can thread
them in or out one turn at a time which typically equals .020” of droop adjustment. This is great to fine
tune your droop, as it is less of an adjustment as using the shock tower holes, and easier than adding
limiters.
No matter which method(s) you choose to utilize for droop adjustment, one key thing needs to be
focused on before you hit the track. RECHECK YOUR CHASSIS HEIGHTS!!! After EVERY chassis
adjustment, and before EVERY run, you should check your chassis heights. Be sure you have the right
settings. Most race days have limited practice time, so why waste a run by not ensuring proper
settings?! Adjusting droop will change your chassis heights, so please, do the right thing and get your
chassis acquainted with your setup board… Your setup board and Ride Height Gauge should be your
best friends as a competitive racer.
Racers Note:
All MurfDogg Chassis are designed with symmetrical suspension geometry. Both front shocks can be
built to the exact same length, and this will result in a perfectly balanced front droop setting. The same
can be said for our rear end geometry and droop settings. The MurfDogg Team suggests tuning with
droop equally to maintain balance, meaning to adjust the droop setting of BOTH front shocks equally
during each adjustment. This maintains balance and prevents weight jacking which can change the
handling of the car elsewhere beyond the desired droop adjustment. The same thing goes for rear droop
adjustments. (Some racers with advanced chassis tuning knowledge play with more RF Droop in certain
situations. This is not “wrong”, but is suggested to be left to the advanced tuners out there, because this
changes weight jacking and balance of the chassis, as well as lateral weight transfer. I suggest keeping
things simple and tuning equally front or rear.)
Chassis Tuning 101
Matt Murphy’s Dirt Oval Chassis Tuning Guide