Selecting the right Anti-Roll bar

Balance of sway bar to other chassis mods
spring rates and how the total rate is shared by springs and sway bars.
When selecting a rear anti-roll bar diameter and consequently it’s stiffness the entire suspension package needs to be analyzed. Basically you are trying to keep the car from laying over with the increased cornering loads generated with grippy tires and other mods. The need roll rate is dependent on both the road springs and the bars. When the road springs are stiffer there is less need for huge bars. With soft springs, ex original base model, you can get away with the really stiff 25.5 bar. If we take the opposite limit of that and for example have a modified Viggen convertible with Koni suspension for street use it will only take a little more sway bar the 19mm will be great and was developed for this application.
This is not a case of if a little bigger is good lots bigger is better, you need to make sure you balance the total rate (spring rate + bar rate) to reach the desired effect. For a street car the 22mm bar is a good compromise and will work great with just about any setup. With the 25mm bar you can count on quite a bit of over-steer if you are not careful, on the track this can be ok but on the street with no runoff area it can get ugly.
In my attempts to make these NG900 and 9-3 autocross well I have tried as many differnt combinations of suspension to get the desired results. Some worked great others, not so well. For a while I ran a 1.5” tubular rear bar of various wall thicknesses, this was the hot setup for the base model when autocrossing. The problem came when it was installed on the rear of my new stock Viggen, It was too much rear bar when combined with the Viggens 25% stiffer rear springs and softer front bar. Also the tubular bars were too expensive to manufacture, at this point I began to experiment with solid bars larger than 22mm and found the 25.5 (1 inch) to be about the maximum limit.
For most cars with stiffer aftermarket lowering springs a 22mm bar is almost perfect. If running the 300mm rear brakes you will probably want to stop here unless you have lots of track time.
Hope this helps to eliminate some of the confusion about selecting a rear anti-roll bar for your NG900 / 9-3 ensuring it will work best for your application. Your comments are welcome.

This entry was posted on Thursday, December 28th, 2006 at 10.10 am and is filed under Chassis, HowTo. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

12 Comments 

  1. gary hughes says:
    28.12.09 at 01:19

    Hello, i have 5 door 2001 stock viggen with the steering rack brace and arm. What dia. rear roll bar should i choose? thanks

  2. Silver says:
    30.12.09 at 08:26

    Since diesel model has 28mm front bar(vs viggen 24mm), then is it better to add 25mm version to the rear? Has anybody have experience with that? Thanks

    • NickT says:
      31.12.09 at 10:43

      Viggen has 22mm bar, The SE (Aero in EU) has 24mm, the largest. 19mm on the base. NG900 Sports has 22mm front.

      You don’t count the coating on the bar. Stick with the 22mm for street use. The front weight bias of the diesel would worry me a bit. We don’t have them over here so I have not scaled one and investigated the spring-rates.

  3. Silver says:
    01.01.10 at 03:10

    Last week I stripped diesel front bar from paint(to remove rust and paint it over)
    It was definitely 28mm(without coating) as I measured with vernier caliper. The same applies to my original bar(01′ aero) – stripped the paint – got 26mm. So my plan is to put that 28mm in front of my aero and make a 25mm rear one. I have straight,solid 25mm bar waiting for bending/welding…
    NG900 owner who has 25.5 rear bar from you with stock suspension, reported he has a lot of oversteer(if not careful). So I’m guessing that 28 with 25 would be close to neutral…Will see how it turns out…

  4. Giulio says:
    25.11.10 at 21:16

    Hallo, i have a 2001 9-3 LPT SE. What’s the best anti roll bar measure for this model for a street use? Thanks

  5. PhoenixPerformance says:
    11.01.11 at 01:26

    I am ordering the Koni suspension kit (includes struts and springs) from your site. What would you recommend for this setup? I have a 2000 9-3 SE HOT 5 door.

    Thanks

    • NickT says:
      11.01.11 at 09:58

      For street use the 22. If you are going to run it on track swap to the 1″ But it will be more tail loose than you might want on the road.

  6. Naphtali says:
    13.06.11 at 23:56

    Which size diameter would I use for stock suspension on a 2000 Saab 9-3 SE?

  7. Eidinho says:
    16.09.12 at 09:27

    Hi,
    My car is 9-3 convertible (DB205 ).
    The modifies is koni sport shock & nomal spring.
    I like soft feel driving ,but i want to get straight line stability on the highway cruzing.
    Which is the best anti roll bar measure,19mm or 22mm？

    best regard,
    from Tokyo

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