Suspension comfort may seem like a fairly basic variable, but in reality it encompasses more detail than one might imagine at first glance. So let’s see as many parameters as possible related to the suspension comfort of a car. With those which tend to improve it and the others which tend to degrade it.
The suspension is obviously the first criterion that we think of, so in the majority of cases it is coil springs. The more they are flexible and long, the smoother the reaction of the suspended masses to the shocks and chaos of the road. Short springs, on the other hand, are made to improve handling by limiting excessive pitch. Other systems exist like the torsion bar and leaf springs, but these deniers are less convincing on the springs.
Note that the best system remains the air suspension which aims to replace the metal torsion device with airbags. And besides, we even consider this rule in mechanics: a gas is compressed but not a liquid. In reality and in physics it is wrong, but on our scales once again this can be considered valid since compressing a liquid requires extraordinary forces). A pneumatic suspension will also be more or less stiff depending on the pressure prevailing in the tubes. By increasing the latter we therefore gain in hardness (and generally this increases the attitude / ground clearance of the vehicle). There is also a system which consists in connecting “air chambers” to the circuit, the more we close (the more we isolate them from the rest of the air circuit therefore) the more we obtain firmness (we do not change here the pressure but the volume that contains the air, the smaller it is, the less easily it can be compressed). This is how the sport mode works on this kind of suspension (although in addition there are piloted shocks. They are even the number one key to firming the suspensions).
These restrict the speed of travel of the suspension. The harder they are, the less permissive they are in vertical deflections. This therefore consists in passing a liquid from one container to another (top and bottom of the shock absorber). The larger the holes, the easier it is to transfer oil from one chamber to another, the easier the transfer, the less travel is braked and the smoother the shock absorbers’ reactions to road imperfections.
The shock absorbers can also be controlled by electronics (optional on some cars). It is therefore a matter of finding a system which will modulate the ease of the oil passing from one chamber to the other. You can also look at things to assist further with coilovers for example.
Also note that the viscosity of the oil in the shock tubes can change the way they react. Worn shocks will therefore have a more fluid oil which will make them less rigorous (however, we will gain in comfort to the detriment of safety). Ditto with regard to temperatures even if the phenomenon is a little anecdotal: when it is cold the shock absorbers are potentially “harder” than when it is hot. So don’t be surprised to find your car a little softer in summer!
Wheelbase / Seat location
The worst thing is to be sitting right above the wheels (which is often the case in the backs of small cars, where there is potentially more discomfort), then you are in the place that moves the wheels the most. masses vertically. It may seem contradictory but the rigidity of the chassis promotes comfort. Indeed, the vibrations perceived by the running gear are then much less transmitted to the rest of the car when the latter is very stiff. Otherwise, the shocks vibrate the entire body with potentially more noise from furniture. And then these vibrations go through us too, which is not very pleasant.
Rims / tires
It’s a classic, the tires obviously have a very important role to play. And it is above all here the thickness of the sidewalls that counts (and the inflation of course but that is obvious and you guessed it for yourself) even if you also have to take into account the width (the wider it is) the more air there is (the more air there is, the more there is a suspension effect by the tire because there is more air to be able to compress).
It is therefore the second number located on the dimensions of a tire. Example: 205/55 R16. It is therefore the 55 that interests us here. Unfortunately this is not an absolute value but a percentage linked to the first number. Here the sidewall height = (205 X 0.55) cm. Below 12 cm we can say that it starts to type.
Note that the tires harden while driving (except when inflating nitrogen) since the air (20% oxygen + nitrogen) expands due to the presence of oxygen. So potentially the car becomes more and more steep as you drive (you can easily go from 2.2 bars to 2.6 bars). And finally the tenderness of the rubber will also have an impact on comfort when it comes to low-profile tires (this is much less noticeable on tires with thick sidewalls). The axles are not all created equal, there are the simplistic and inexpensive versions and the evolved and more complex versions. The ideal is at the level of multi-link and double wishbones (with offset pivot or not, who cares), and this is what systematically equips premium and 4-wheel drive cars (the rear axle must then be able to accommodate engine torque, so it must be sharper).
The anti-roll bar is an essential device on multi-link axles for the car to be controllable (therefore potentially one or two on each car). Basically, it’s about making a link between the left and right wheels of the car so that they keep consistency in their kinematics. The more we tighten the latter, the more we will have dry reactions of the suspension, this is also the preferred setting on high-performance cars.