I have a '97 civic sedan.
I want to lower the front of my car and lift the rear, or keep it standard.
now the body of the car is suspended a little higher than 100mm over the tyre of the car, but it seems low already.
I want the car lower, but not ridiculously low, a space should still exist between the wheels and the car, what is the higher option between a 40mm and 60mm spring? does the car get lowered 60mm, or will it be suspended 60mm over the wheel?
Checking several on line vendors specs the 40mm or 60mm refers to the amount of lowering from stock. If your stock spring leaves 100mm of tire clearance a 40mm spring would leave 60 mm of clearance. Several things must be taken into account prior to selecting your springs. Your car may already be lower than stock due to the age and condition of the springs. The 40mm drop is from a new stock spring. If you add non stock tires and wheels the clearance will change. If you haven't done so recently I would suggest getting new struts as a leading cause of spring failure is worn struts. You will also need a front end alignment after installing the springs.
There's really not enough information to accurately answer this question, but I'll try.
If you're talking about 40 mm or 60 mm as the spring diameter, the spring diameter affects the spring rate. Assuming all other attributes of the spring are equal, such as length, number of coils, etc, then a 40 mm spring will have a lower spring rate than a 60 mm spring. A lower spring rate means that it will take less force to compress the spring a certain distance.
If you're describing 40 mm vs 60 mm as the height the spring lowers the car, then the difference is a 20 mm lower ride height.
Sorry for being so vague, but you really need to add more details. If you provide links to the specific brands you're talking about, that would help.
