What is the real purpose of each of the following mentioned:

Shocks, Struts, and Springs.

Which are the most/least important.

I think I really ought to start replacing the suspension on this car, as it seems quite bumpy even on the smallest bumps...

 

I am by no means an expert on suspension and I am sure others will post the answers you are looking for. It is certainly a complicated subject. I have learned alot by searching thru the posts under the terms you have used. You probably need to state what year and model of RX-7 you have.

Struts are used in the front, shocks in the rear. Both are encircled by the springs. They all work together to control the car's handling and ride. You can buy each separately and install, or you can buy what are called 'coil-overs', where the shock and spring are one unit. If you use any combination other than stock, the car will possibly be lowered below the stock configuration. If your car is older its' possibly already low due to the age/sag of the original springs.

Generally, the more expensive the shocks/struts, the better the quality, altho the more expensive struts and shocks appear to be stiffer and give a harder ride, but also give you increased handling capabilities. If you want a street ride, no racing, however want a better ride with some increases in the handling over what stock parts give, you would probably want 'non-adjustable' struts/shocks. These are gas-assist, are an upgrade to stock, and fit/work with the standard stock springs.

After any changes/modifications to suspension you will want to perform an alignment of all wheels. Make sure your rear toe camber is checked, if improperly adjusted you will wear the rear tires unevenly, ruining them quite quickly. This I inherited with the purchase of my 86 N/A and had to buy new tires.

I cannot put up with the original and stock equipment on my N/A anymore. I have had to wrestle with my budget because all four at once can be expensive, however, I've decided to have new stock springs and gas-assist KYB's installed on my rear wheels this friday. Will have to do the fronts will be next month. Suspension is important so you need to address the ride/handling/performance as much as you do the engine/powertrain.

I have by no means exhausted this subject but maybe that will give you someplace to start.

 

How old are your tires? Because I know having bad old tires can cause a really bad ride.

 

As far as bumps/smooth ride:

Tires 60% of soft ride
Shocks - 25% of soft ride
New springs - 10% of soft ride
bushings - 5%

 

thou shall not use the lords name in vain

and where does tuna come in???