Guide: Ng900 / 9-3 Chassis Tuning

I get lots of questions about what exact parts to install etc. Truth is there is no one right answer. I have built the same cars lots of different ways. The goal with modifications is the improve the cars feel and performance ability in the drivers view. Sometimes this can be just more tire pressure, others full custom springs etc. This is a long one…

For the fist step on the NG900/9-3 chassis is upgrading the rear sway bar from stock 14mm to 22mm bar. This will have the most improvement for the least investment and easy install. Roll is reduced so that both front tires stay planted improving straight line acceleration. The second benefit is keeping the car flatter during cornering to help overloading the outer front tire. Even my shop loaner cars get the 22mm bars. There is another article in here about the other sway bar sizes. Read that before thinking of the 25mm bars.

Assuming there are decent sport tires on the car the next step is to help the steering feel. The sway bar helped some of this but the next step is to hold the steering rack more solidy. The point to do thing this is eliminating the deflection that occurs laterally in sthe steering rack when you initially correct the steering. The second part is when you have corrected but there is this stored energy in the steering rack mounts causing an overshoot back. While we eliminate this deflection from the stock rubber bushings we also brace the rack mount on the firewall to the sturdy frame. The rack appears to mount on the firewall shear plane but actually is mounted on 2″ tall flexible standoff. Rack brace is a simple bolt on part. 1 hour max with basic hand tools.

From there it gets a bit tricky balancing install difficuly and retunr on investment.
For Convertibles we install the 6-point brace to triangulate the front chassis. This helps by reducing the cowl shake/scuttle that is more apparent with the CV top lowered. The same applies to the hardtops but they are less compromised to start with so you get a decent improvement just not OMG that you get on a vert. 6-point install is still quite basic. Some people with less patience will fight the rivets. Just 6-bolts. Again under an hour to install. No compromises either No more harshness etc.

Shocks and springs help with the vehicle dynamics. This is the first place there is a hint of compromise comes in since stiffening the shocks or bushings will add some ride harshness. The reward is greatly improving the vehicle dynamics. The kit we build most of the cars with in our workshop is the Koni Sport shocks and Koni or Vogtland shocks. Nice stance and the shocks have adjustable rebound to tune it to you the driver. Fitting Konis to stock springs helps. Not the best setup for max performance but a viable option for some people. Fitting lowering springs to stock shocks is a bad idea and results in underdamped and bouncy suspension. The koni kit has matched dampers and springs so it all works great together.

While you have the front struts out it is a good time to save some labor and throw suspension bushings in. The outer bushings are replaced to help with wheel hop off the line and stability under braking. Basically the fore/aft location of the wheel. The inner bushings will help with side chatter during aggressive cornering and also helps the outer bushings do their job. Usually replaced in full sets of both bushings. Will need a press to get the old bushings out. Some people pull them then take it to a local machine shop. You may notice I don’t make/sell the rear bushing in the front arms. The stock is perfectly capable and actually stiffer than the “purple” bushings out there. No reason to replace it with aftermarket.

This is usually where most stop. There are other mods to address certain deficiencies as those bother the driver. Again back to no need to replace the parts unless it fixes what the Driver feels is the issue. Not just bolt every single part on the car because.

The Brakes The first brake upgrade is not with the brakes. Its better TIRES! Brakes cannot do anymore work once the tires slide. The stock brakes do an adequate 1 time stop. The problem comes when you ask for more before they have time to thermally recover. This can be from using the wrong pads or not enough brake diameter. Sport pads are a first step. Hawk HPS or similar. Next is to fit the 308mm “Viggen” fronts. After that or for Viggens is to add the “9-5″ 300mm vented rears. This helps with lots more cooling and also more brake torque. The extra rear brake torque helps to pull the rear down on hard high speed braking. One of the best felt upgrades on a Viggen. I had goodridge make custom lines to add the 9-5 style sliding rear calipers. The best part with this upgrade is that the spare parts aside from lines are available at ever Saab dealer.

From there we move on to power. Will add the rest of the chassis mods and expand this based on your feedback.

5 Comments  »

  1. Martin W says:

    Very nice write up. This is the exact set up I have on my 2000 Viggen, except for the rear brakes, but with Limited Slip Differential. I am using TRW pads and find them more durable on the street and on the track than the original stock pads. Haven’t tried the Hawks HPS. On the track R compound tires Toyo R888 or RA1 235/40/17 make a huge improvement. For daily driving Toyo 235/45/17 T1R do fine.
    I am debating what to do next. 1. One of your tuning software packages seems like a likely choice, but 2. more breaks would also be good. 3. Slightly wider exhaust will also be needed since I am still on my original exhaust!

  2. GerritN says:

    Hi Nick,
    You forgot to mention the sport engine and transmission mounts. I’ve put those in together with a 22mm rear sway bar and am very pleased with the result. I always had the feeling that the engine was happily moving around in its bay, kind of scary to see the shift stick move along with it. Since installing the stiffer mounts it feels like engine and chassis have become more one unit. Definitely has increased my driving fun, also hearing/feeling the engine a bit more adds to a more engaging driving experience.

    Still thinking about the steering rack brace. Without any power upgrades I don’t really need it, I think. So, as long as my wife doesn’t alow me to get an ECU upgrade I’ll probably stick with the current setup.

    • NickT says:

      Thats coming in the Powertrain tuning guide. :) Engine, Gearbox, Clutch, Mounts etc.

  3. Martin W says:

    Yes, the stiffer transmission mount adds a little vibration at idle. Not everybody’s cup of tea, I think, but I also like to feel the engine. Together with the short shifter they add to driving experience. I would emphasize gradual change to everybody. Finding a happy balance between performance and daily driveability should be tailored to individual taste.

  4. Giovanni Valentino says:

    My Car = 1999 9-3 Coupe: Great wirte up nick! i actually did things backwards, just to see what the effects would be, for example i did the bushings first then the steering brace, the 22mm sway bar, then the enigne mounts, and then the springs with KYB shocks (not to bad, but) Koni shocks after which were amazing! , and finally the 6 point sub frame. which tied everything together, followed by the rear bushings! um i know you didn’t mention it but i was wondering why… what about the engine bay top shock tower mount sturt bar? and the hatch strut bar? where do they come into play cause they are litterally the only things left i need for the complete suspension package from GS… Can’t wait to read more! please keep it coming!

    Thanks a lot

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