Suspension mounts are what attaches the suspension arms of an RC car to the chassis. Typically these are attached directly to the chassis and/or the bulkhead or gearbox, and they hold a pin (aka pivot.) The suspension arm is also attached to the pin, allowing it to rotate around the pin.
In many cases, the suspension mounts hold pill inserts which in turn hold the pin, and the pill inserts can be changed in order to make fine adjustments to the angle of the pin. Read on to learn how those changes affect the suspension geometry of the car.
** Need help figuring out your suspension geometry? Try our Pill Insert Calculator
Suspension mount naming
There are several standard naming schemes used by different manufacturers.
Each set of names represents:
- Front mount of the front arms / Rear mount of the front arms / Front mount of the rear arms / Rear mount of the rear arms
Common naming schemes:
- A block or A mount / B / C / D
- Front-front (FF) / FR / RF / RR
- Front outer / front inner / rear inner / rear outer
What suspension mounts do
The front and rear suspension mounts on a car can be used to change roll center, track width, kick-up (front), anti-squat (rear), sweep, and toe.
Front suspension mounts (A/B or FF/RF):
- Move mounts out to increase track width
- Move mounts up to increase roll center
- Move front mounts up or rear mounts down to increase kick-up
- Move front mounts in or rear mounts out to increase sweep / toe-in (Toe is normally adjusted by the steering links, not via the suspension inserts. This setting will alter the wheelbase.)
Rear suspension mounts (C/D or RF/RR):
- Move mounts out to increase track width
- Move mounts up to increase roll center
- Move front mounts up or rear mounts down to increase anti-squat
- Move front mounts in or rear mounts out to increase toe (This setting will alter the wheelbase.)
Some cars also offer fairly complex upper arm suspension mount options.
Roll center
Pivot height describes the vertical position of the inner, lower suspension arm pins. It is one of the ways to adjust the car's roll center. (See our article on roll center for more details.)
Lower pivot height
- Lower roll center
- More chassis roll
Higher pivot height
- Higher roll center
- Less chassis roll
Anti-squat & Kick-up
Changing the vertical angle of the suspension arms affects anti-squat (in the rear) or kick-up (in the front.) Read their articles for more details.
Pivot width & Track width
Pivot width, or pin width, is the distance between the lower suspension arm pivots where they attach to the bulkhead.
Narrower rear pivots
- More stability under power
Wider rear pivots
- More on-power steering
- More stability in corners
Pivot width will affect track width unless the arm length is changed or the hubs are brought inward/outward to keep track width the same. See our article on track width for more details on how track width affects handling.
Toe & Sweep
Suspension mounts are usually only used to control toe in the rear of the car because in the front the steering links are used to control toe.
Toe is the angle at which the wheels point towards or away from each other when the car is viewed from above. This can be adjusted using the suspension mounts by angling the suspension pins inward or outward when viewed from above (see image below.) See our articles on toe or sweep for more details.
Sweep describes the angle at which the arms are "swept" either forwards or backwards due to the angle of the suspension mount pin, and is adjusted the same was as with toe. Sweep is not widely used for tuning, and when it is, only for the front suspension, but you do need to keep in mind that sweep and toe changes made using the suspension pins will produce changes in the car's wheelbase. For instance, on the front arms of the car, if the arms are angled rearward (swept back) when viewed from above, the front wheels will be closer to the rear wheels than normal, which will affect the car's handling.
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