Sunday, April 3, 2011

ajustments, modifications, geometry, and extra suspension info

Sorry this post took so long to come out, but i have been quite busy the past few days, not even looking at comments on my last post.

anyways, a few questions answered, as i always start with:

"[blah blah..] suspension made of aluminum?"
no it is not, if it was it would be far too flexible, and would bend, re-bend, and eventually break, and be expensive to replace. if we were to make it out of aluminum it would be of a different design so it would use the flexibility as an advantage.

"[blah blah...] how do i replace" (paraphrased a few comments into one question)
you would buy a suspension kit that is compatible with your car, or suspension type, and fit it accordingly. then you would basically remove all the original components, that you have something new to replace with, and bolt up the new is pretty straight forward, and a afternoon job.

"suspension doesnt work, [blah blah...] tires should be all rubber [blah]"
keep in mind the amount of forces that suspension goes through on just a stroll up the street. you have acceleration pushing the weight towards the back, stopping doing the opposite, and turning doing something similar. if suspension was alot softer, you would think it 'works' better, but it is impractical for more damaging impacts, like a pothole, or going too fast over a speed bump. One way around this is making more suspension travel, which would just make the car want to flip, and harder to get into, and more impractical.
the best workaround is for the suspension to be relatively stiff, and a bit low, as it is now.

as for tires, they are how they are for many reasons.
For starters, they do make tires with no air, just rubber...they are called 'run flat' tires, mainly used by special police forces, and army ect.
Secondly, the weight of a solid rubber tire is insane, it is like rolling a boulder, and it is also using alot of rubber, which is bad for the environment. Due to the weight, the rolling resistance of this is much higher, increasing acceleration times, and making stopping much harder.
tires have a optimal operating temperature, and when exceeded will take longer to cool. when too cold it will take longer to heat.

depending on the application, you might need to ajust pressure. in the snow you want a higher pressure, so you can have a smaller footprint, and for sand you want a much lower footprint to get a larger footprint. the only way to control this is air, so rubber will not let this happen.

under driving forces (seen every day, as-well) the tire takes alot of the impact of the road, such as pot-holes, small bumps, and cornering.
without the tire flexing, the suspension will seemingly work even less then you already claim.

tl;dr, just look at this clip from my favorite game, a racing is true to life, and sum's it up pretty well.  pay attention to the suspension over every bump, and the tires during corners and bumps.

anyways, now about the ACTUAL post ^^

So adjustments that effect driving, performance, tire wear, reliability ect. include simple things that make a world of difference both on the edge, and normal driving. (all can be played with in the simulator i mentioned eariler, called 'Live for speed', seen at

So to start, i will mention compression ratio, or the force it takes for the suspension to actually move at all. If you run over an ant it will not effect the suspension enough to move the suspension, but a bolder will. The amount of force required cannot be overlooked.

for street you want something soft enough for comfort, and to reduce shock on the car, and stiff enough to be able to take a beating.

on track you want something to allow the weight to transfer, but stiff to give a solid feel, without bottoming out. race cars have very stiff suspension.

relating to above, is dampening, and rebound dampening. dampening is the force holding the spring from doing repetitive motion after a bump. dampening is compression resistance, and rebound dampening is resistance of the spring unloading.

you want the suspension to do its job, then when the job is done return, nothing more, nothing less. you want these to be a bit soft for road, and for track, and bit harder.

sway bars. on the street, these tend to be soft because you may have to do street driving one day, and the next be on somewhat rough terrain. sway bars kill you off road.

on a track, you want enough sway bars to let the car stay very level during corners, but still transfer weight. too much sway bar will promote traction loss.

ride height is just basically as low as what above will allow.

now we have gone over what stays constant while driving, now what changes as you go.

camber: the angle of the wheel to the ground, for softer suspension (road) you want a positive number, to ensure the inner wheel is doing about as much work as the outer wheel. for track you want a negative number to allow the outer wheel to do as much work as possible, as that is where the weight is.

Toe, another adjustment is typically only used on the track, depending on the car. this promotes tire wear. positive toe-in would make a car more stable, and negative toe-in would make a car corner better, and feel more lively.

(not limited only to front wheels)

parallel steer, or Ackerman. this is how parallel the wheels stay while being steered, the more parallel the more the rear will want to slide out, the less parallel the more grip around the corner, and less tire wear.
the reason for this is the inside wheel takes a smaller radius turn, and should follow this path

track is the width in between the wheels, typically the more width the more stable, and therefore more grip.

caster is the angle of the wheel as you turn (camber of wheel as you turn). the reason of this is as you turn, the car might lean to one way, changing the contact patch.

(this is the best picture showing it i could find, notice the wheel changes angle due to the turn)

scrub is the amount the tire is pushing due to one of these adjustments changing the way it rolls, none is ideal, but some is going to happen.

modifications of these are just adjustments, and different types of suspension swaps, and different coil-overs, or maybe different ride heights.

motorcycles have usually just a control arm on each side of the back wheel, and the front just has forks.

each side of the forks goes to a side of the wheel, and a spring is attached to add resistance.

the back has 2 pivot points on each side of the rear of the frame which you attach each control arm, and each one goes to a side of the wheel. those 2 connect and a coil-over is attached.

adjustments of these are length of control arms, length of forks, and strength of coilover's and resistance.

like i said i am not very knowledgeable in the motorcycle field.

as always, comment, and ask any questions, they all get answered!

next time i might mention brakes a little bit, feedback please!