This article is part of a section of the RcTek site devoted to radio controlled model car handling. As car handling is an extremely complex subject, it will be quite some time before it is finished.
This article contains information about suspension droop, which was mentioned on the Forum a couple of times and prompted this article. We also have a further article about the equipment that can be used in assisting you to set droop.
Suspension droop is defined as the amount of downward suspension movement there is in the wheels of a model car. The base measuring point for this droop can either be the chassis or the ride height of the car.
It is responsible for keeping the wheels in contact (or not!) when the front/rear of the car rises or falls - like going into a corner, braking/accelerating or going over bumps.
More droop obviously allows for more wheel travel to keep the tyres in contact with the track surface, but this is at the cost of agility - the car will not change direction as quickly.
The general rule of thumb with droop would be to have just enough to cope with the track you are racing at and no more.
You must also consider the affect that the damping and springing on the car has with increased droop as they have to be able to react quickly enough to move the wheel in and out of any holes, etc..
The multiple nataional and international champion, Ian Oddie of Oddified, gave good advice in his answer to one of the questions about Droop;
As with any suspension setting, there is always a compromise.
Running very little droop does make the car more stable going into corners (car stays flat) but on the exit it will loose drive easier (diff out). Conversely, a large amount of droop will be less stable on the entry to a corner (especially a sweeper) but will give better drive out. More importantly though, running very little droop or even none prevents the suspension working correctly on bumps or when riding curbs and will cause it to bounce around or step out on bumps/curbs.
As you can see, the droop setting is very important, and as rule of thumb, I always set mine so the normal ride height of the car is midway between full droop and the ground. Then adjust the car to suit the specific track.
The accepted method of adjusting the droop on a model car is shown to the left and is by the means of a screw (red) which is threaded into the wishbones that contacts the chassis.
The screws normally are fittted through the top and can be almost any Head Shape, but such as the Serpent cars use a button headed screw (left) that is fitted from the bottom.
If your model car is fitted with alloy wishbones there can be problems with the screws self-adjusting themselves due to vibrations, etc.. The use of a thread locking compound such as Loctite™ is recommended, although an improvement to this is the use of a locknut on the screw as there is no waiting time for setting of the thread lock.
Either plain nuts of self locking nuts can be used, although you will have to thread the latter on backwards. This is most easily achieved by threading the nut on the correct way first and then turning the nut around so that you have some threads cut into the nylon insert.
With plastic wishbones there is not normally any problem, but either of the above methods can provide a solution to worn screw holes.
What we do not recommened in this situation is the use of cyanoacrylate adhesive as it does not have any flexibility to resist vibration and shocks, etc... At the very least you will have a very short time solution, whilst at the worst you will have a screw that you cannot remove.
Suspension Droop Setting Equipment