i got my car lowered, and the problem is that it shakes from the back after the car reach the 40 to 50mph i havent done the aligment yet, maybe thats the problem, any help about this situation...

 

Did you use output shaft spacers?

 

That type of vibration is most often caused by out of balance wheels or worn CV joints on the half-shafts (= output shafts, or drive shafts in Honda jargon).

The easist approach is to first have the wheels balanced and then try other more expensive solutions. However, I once could not solve a vibration problem like this with balancing and had to replace the tires on my car to eliminated it.

Since you just lowered the car, my bet is on the half-shafts as the problem. I'm assuming that you are using the same tire/rim combination as before. If the car has a lot of miles, and/or was driven hard, that makes it more likely that it's the shafts.

You should try xviper's suggestion of adding shaft spacers to reproduce the same CV joint angle as before. If that doesn't work it's either something else, or the CV joints are too far gone and need replacement.

 

try an alignment first, then look at your half shafts and give the spacers a try.

 

i got the springs from a friend....didnt have any spacers in there...where can i buy this spacer and where it goes?
ps.. i got the tanabe nf210

 

A bad alignment very very rarely causes a vibration. Only if the caster settings are completely screwed can you get a vibration. I've done enough S2k alignments to find that even the cars with uneven caster don't vibrate.

Don't waste you time aligning a car to fix a vibration.

Possible causes are:

Pitted inner CV joints
Bent wheel
Out of balance tire
Flat spotted tire