You should ideally buy springs and shocks as a matched set in a kit. When you get sports springs and use stock shocks, the shocks will tend to wear prematurely. They are designed to be a blend of comfortable ride and safe handling. By using shorter springs, the shocks are now overloaded. Getting a kit will mean that the shocks are matched to the length of springs.

If your car is pulling to either side, or if you feel you have to fight to keep it driving straight down the road, you probably need an alignment service.
Proper alignment extends tire life, improves fuel efficiency, and reduces wear and tear on steering component.
Experts recommend having your alignment checked every year or 12,000 km. You should also have your alignment checked after certain services, such as a strut replacement or brake replacement if it affects your suspension system. Service professionals also recommend an alignment check after the installation of new tires, to prevent premature wear and protect your investment.

Uneven or accelerated tire wear can be caused by wheel misalignment, worn suspension and steering components, and/or improper tire inflation. The most critical alignment angle with respect to tire wear is toe, Camber is also important and can be affected by caster. Misalignment is usually caused by worn, loose or bent suspension and steering parts (bad tie rod ends, idler arms, control arm bushings, ball joints, struts, etc.), but can also be due to spring sag or improper ride height. With tire inflation, underinflation is just as bad as overinflation. Both can cause uneven tire wear. Underinflation can also make a tire run dangerously hot.

Unlike some steering and suspension components, there is no significant difference in wear rates between left and right shocks or struts. If one shock or strut is shot, chances are its companion also needs to be replaced. For front versus rear, there can be differences in wear rates depending on vehicle loading and usage. Generally speaking, when front shocks or struts need replacing, so do those in the rear. Shock absorbers and struts are designed to dampen spring oscillations as the suspension goes through jounce and rebound. This prevents unwanted body gyrations and helps keep the wheels in contact with the road. The ride control elements inside perform this task by creating resistance, which in turn transforms the energy of motion into heat. The up and down strokes of the piston inside the shock or strut pumps fluid back and forth through metering orifices in the piston and valve body. After zillions of such cycles, the cylinder bore, piston and shaft seals eventually wear out. Though original equipment shocks have improved in recent years, many still may need replacing in as little as 30,000 km. With struts, the lifespan is about double that of a shock.

The most likely cause of this is the big rubber bush at the top of the front suspension mounts. If it has perished and worn out, then the top of the suspension is knocking against the inside of the suspension strut tower. Another symptom of this is if you park the car and turn the steering wheel from lock to lock, then move off slowly, there will be a "sproing" type noise as the suspension spring untensions. You should invest in new suspension bushes.

Most car companies won't tell you this, but shock absorbers and springs are pretty much end-of-life after 60,000 km of average use. You need to change them. And if you do, then change them all at once. It's dangerous to do just the front, or just the back. Few people understand that shock absorbers make a lot of difference not only to the ride of your car, but the effectiveness of the brakes. With worn shocks, the wheels bounce and skip under braking. With good shocks they don't. Guesstimates as to the difference at 100km/h can be as much as 10 metres difference in braking just because of the shock absorbers.

ABS stands for Antilock Braking System. It's a system designed to sense when the a brake is about to cause a wheel to lockup, and relieve the pressure on that brake automatically to keep the wheel turning. When the wheels are turning, not locked up, you have more control over your car.

They can, yes. As well as contributing to a heavier vehicle, adding heavier wheels adds to the unsprung weight of the vehicle. This means the engine has to work slightly harder just to turn the wheels themselves, which can rob you of power and/or fuel efficiency. They'd have to be pretty heavy wheels to see a really noticable drop in mpg though.

Timing belts have replaced timing chains on many of today's engines. Both belts and chains ensure that crankshaft, pistons and valves operate together in proper sequence. Belts are lighter, quieter and more efficient than chains. When a timing belt breaks, the engine stops. Replace belts before this occurs. Most manufacturers provide' a suggested service life and replacement schedule for this critical component.