stock springs and B6 is your best bet. B4 is not a 36 mm monotube gas pressure unit.
you can buy the correct springs off vendors on here using the VIN of your car

 

Thank you for the reply. My stock springs seem to be just fine, was planning on re-using them. Also, visually, my rear shocks are yellow/blue color, which makes me think those are Bilstein. So maybe someone has already replaces them? What are factory rear shocks on Aero?

 

The factory struts/shocks on my 2001 Aero are Sachs. They're black.

If yours are yellow, someone has already replaced them

 

I'm aware that fronts are Sachs, black. But what about rear?

 

Yes, I have verified that the fronts are still original Sachs, but the rear struts are Bilsten, which means someone has already replaced them. So I guess I just get a set of B6 for the front. Thanks for all help.

 

I find B6 to be stiffer than they really need to be on a "premium", larger car. And I'm running stock Linear springs front and back. Certainly the car's motions are well-controlled and I can go over speed bumps without slowing down at all. But I also feel every crack in the road, and there are plenty of those around here too.

 

So what do you recommend for stock Aero setup? B4?
I don't want to change my current springs, they are just fine...

 

How will Koni Yellow up-front match up to Bilstein in the rear? (already installed)

 

Local shop said they had one or more wagons with B6 rear shocks and stock shocks in front, and the results were said to be fine.

I can't say a whole lot more since I haven't tried the combo myself.

By the way, I'm running 16" tires, though a little more inflation pressure than specified by Saab. I gave a ride to another 9-5 owner, who was quite surprised at how stiff the ride was. So it's not just me thinking that the B6 are on the stiff side.

 

shocks damp. they don't spring. end thread

 

He's not asking which springs to use.

 

EdT you said you had B6 and so the ride was stiff. The shocks have zero to do with stiff ride. In your case, higher than OEM tire pressures you have would contribute to a harsher (stiffer) ride; the tire sidewall stiffness which is influenced by tire pressure contributes to overall wheel rate

 

Well, I doubt that 2-3 PSI over the specified 34F/32R is going to make the car ride like a lowered Integra Type R. But I will check that anyway.

 

OP here is the deal. I have lots of experience with lots of shocks. EVERY TIME I second guess myself (recently) and stray from Bilstein I regret it. Koni are an inferior twin tube shock with indifferent rebound control.

Go front Bilstein B6 and be happy.

 

Bilstein B6 shocks causing a stiff ride is a common complaint on the NG900/9-3 board, especially if the sport versions are used. Bilsteins are known to have so much gas pressure in them that they can raise the static ride height of our cars. It takes some force to compress something with that much pressure, which would have to cause the ride to suffer.

 

just lol. measure the compression pressure at static ride height. It really doesn't amount to much. Tire pressure, tire aspect ratio, tire sidewall stiffness are way more significant for ride harshness.

 

true, B6's rock on the Saab 9-5.;ol;