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Sway Bars - How they work and how to choose the right size for your needs

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  • #16
    Originally posted by Dan [Sac]
    Stock bar = 12mm
    Mazda 626 bar = 16mm
    PT bar = 17.5mm (iirc)
    AWR = 19mm (iirc)
    Addco = 22mm
    Ok, here are the calcs for the different 2nd gen sway bars:


    Mazda 626 Bar: (16^4)/(12^4) = 216% stiffer

    PT Bar:
    • vs. Stock: (17.5^4)/(12^4) = 352% stiffer
    • vs. 626: (17.5^4)/(16^4) = 43% stiffer


    AWR: (note: 19mm x 5.5626mm hollow DOM tube)
    • vs. Stock: (19^4-7.8748^4)/(12^4) = 510% stiffer
    • vs. 626: (19^4-7.8748^4)/(16^4) = 93% stiffer
    • vs. PT: (19^4-7.8748^4)/(17.5^4) = 35% stiffer


    Addco:
    • vs. Stock: (22^4)/(12^4) = 1,030% stiffer
    • vs. 626: (22^4)/(16^4) = 257% stiffer
    • vs. PT: (22^4)/(17.5^4) = 150% stiffer
    • vs. AWR: (22^4)/(19^4-7.8748^4) = 85% stiffer


    Kudos to all who check my math and make sure it's good.
    Last edited by macvelli; January 13, 2005, 05:20 PM.
    95 Laser Red SE mtx
    CAI | NGK Plugs + Wires | 6AL + TFI | SPEC Stage 3 + FW | SS Clutch Line | Civic STS
    Illuminas | Tokico Springs | Ractive FSTB | Corksport RSTB | 626 RSB
    Grounding Kit | RR Poly Inserts + Stabilizer Bushing

    Comment


    • #17
      ^^ Are those calcs really right? I'd be amazing if my AWR bar is 528% stiffer than the stock one...

      Anyway, that is some good reading
      Kevin B - Former Probe-owner
      06 Legacy GT
      98 Legacy GT

      Comment


      • #18
        The Mazdaspeed bar was 16mm. Wouldn't be surprised if it was the same bar as the 626, except painted green.

        Comment


        • #19
          for the hollow swaybars youll calculate for:
          (outer diameter) - (wall thickness x 2) = "core"

          then:

          (outer diameter)^4 - "core"^4

          you are basically treating the hollow swaybar as if its a solid bar, finding its relative stiffness and then subtracting the "core" stiffness. The final value left is that of the tubing.

          Gavin

          Comment


          • #20
            Originally posted by Hans[93GT]
            The Mazdaspeed bar was 16mm. Wouldn't be surprised if it was the same bar as the 626, except painted green.
            Thanks for the correction, Hans. I replaced Mazdaspeed with AWR for the 19mm RSB.
            95 Laser Red SE mtx
            CAI | NGK Plugs + Wires | 6AL + TFI | SPEC Stage 3 + FW | SS Clutch Line | Civic STS
            Illuminas | Tokico Springs | Ractive FSTB | Corksport RSTB | 626 RSB
            Grounding Kit | RR Poly Inserts + Stabilizer Bushing

            Comment


            • #21
              Originally Posted by gavin
              The AWR 19mm rear bar is hollow FWIW
              Gavin

              Comment


              • #22
                so, armed with all of this information, how might one go about choosing which bar is going to suit their specific application best without trying different bars?

                I have not road raced my PGT yet, but I did road race my GTI and found that it had nearly perfect balance, no under or oversteer. Now it's stock, if I were to upgrade just the rear bar on a well balanced car, wouldn't that induce oversteer?

                I was thinking about buying a beefier rear bar for the PGT for a road race next month, but would it make more sense to race as is, and then estimate what would be the best upgrade? As of now I have no idea what the over/understeer qualities on my car are as I've never pushed it anywhere near that hard in turns.

                Or, if you take into account adjustable struts and variable alignment configurations, should I buy a sway bar and adjust what I can later on to improve balance?

                Mike
                96 PGT - 14.639 @ 91.54 mph N/A 2.025 60' - 2605 lbs
                CS Lip ll Megasquirt ll ZE-IM ll Hotshot Headers ll PRM CAI ll Illuminas/Intrax ll 6 puck/MX3 FW ll RR Shifter ll 19" Giovanna Kobell Black Roof ll Black Leather
                93 PGT-ZE - 14.433 @ 96.06mph N/A 2.159 60' - street tires - 2555lbs
                ZEX ll Seli Cams ll Walbro ll Fidanza/DXD ll Addco ll PS Headers ll 65mm TB ll PRM CAI ll Blues and GC's ll MX6 Black Leather

                Comment


                • #23
                  Calculations still only give you a rough estimate on the direction you want to go in. Only actual testing will tell you what you need to know.

                  I'd say race it stock and go from there. honestly, driver improvement is the biggest single variable in improving lap times anyway, so save the sway bar money and use it for a couple of additional event fees
                  90 Mazda 323 - KLZE, fender-flared, right hand drive, 2350 lb fully loaded sex machine. || Pic Thread ||- SOLD
                  93 PGT FRANKENPROBE - 10.24 @ 139.9 mph ||545 whp @ 20 psi || Timeslip || Dyno slip|| Build Thread - GONE
                  97 GTS - Rear Wheel Drive KLZE, 6-speed, 3.90 Torsen LSD, 2650 lb, daily driver! - Build Thread - GONE
                  90 Ghettocet KLiata - forever WIP

                  Comment


                  • #24
                    Originally posted by mvaughn1
                    if I were to upgrade just the rear bar on a well balanced car, wouldn't that induce oversteer?
                    Yes.

                    Originally posted by mvaughn1
                    I was thinking about buying a beefier rear bar for the PGT for a road race next month, but would it make more sense to race as is, and then estimate what would be the best upgrade? As of now I have no idea what the over/understeer qualities on my car are as I've never pushed it anywhere near that hard in turns.
                    I would recommend at least getting the 16mm 626 RSB and a set of new endlinks. I just put one on my car with mkimber/onlyp's adjustable endlinks and the difference is very noticable. I was very surprised at how small the stock 12mm RSB really is. IIRC, the 17.5mm PT RSB would balance out the over/understeer for that neutral feel.
                    95 Laser Red SE mtx
                    CAI | NGK Plugs + Wires | 6AL + TFI | SPEC Stage 3 + FW | SS Clutch Line | Civic STS
                    Illuminas | Tokico Springs | Ractive FSTB | Corksport RSTB | 626 RSB
                    Grounding Kit | RR Poly Inserts + Stabilizer Bushing

                    Comment


                    • #25


                      Great post mr sac.
                      '95 Probe SE ATX->MTX

                      Comment


                      • #26
                        Calcs for AWR bar have been updated to reflect its hollow tube design.
                        95 Laser Red SE mtx
                        CAI | NGK Plugs + Wires | 6AL + TFI | SPEC Stage 3 + FW | SS Clutch Line | Civic STS
                        Illuminas | Tokico Springs | Ractive FSTB | Corksport RSTB | 626 RSB
                        Grounding Kit | RR Poly Inserts + Stabilizer Bushing

                        Comment


                        • #27
                          ok. got a couple questions. I NEED to replace the endlinks on my probe(rear) and looking at prices I have been considering getting a new sway bar kit and just doing the whole thing.
                          the bar I was looking at is the addco, but looking at the calculations here is it overkill, and would it cause the car to handle badly?

                          I guess my question is what way to go? what bar is the best? or what kind of results would each one cause?

                          I would like to find a full kit, end links and all. its nice that we have aftermarket support, becuase I like to replace anything that needs it with a better part.

                          suggestions?
                          --------------------- I am the American Stig -----------------------
                          95 PGT. fidanza, clutchmasters stage 3, poly mounts, short throw(thanks nick), 2.5" cat back, MS6 brakes, 245/40 18's. now rockin a mx6 tranny.... lets see how long this one lasts...

                          Comment


                          • #28
                            Originally posted by kornyguy95pgt
                            what kind of results would each one cause?
                            This is the easiest question to answer:

                            626: Noticeable improvement over stock -- still biased understeer
                            PT: Most balanced sway bar -- neutral steering
                            AWR: Next best choice for balance -- neutral to slight oversteer
                            Addco: Best autox racing bar -- tunes the car for oversteer

                            Also take prices into account:

                            626: Cheapest solution at around $55
                            PT: Was available at one time via Bulk Buys -- not sure of availability now
                            AWR and Addco: $150 each, so pick your setup and go with it

                            Decide which is more important price vs. performance, and then it should be easy to determine what is "best" for you.
                            95 Laser Red SE mtx
                            CAI | NGK Plugs + Wires | 6AL + TFI | SPEC Stage 3 + FW | SS Clutch Line | Civic STS
                            Illuminas | Tokico Springs | Ractive FSTB | Corksport RSTB | 626 RSB
                            Grounding Kit | RR Poly Inserts + Stabilizer Bushing

                            Comment


                            • #29
                              Just curious if you have had all 4 bars... if not how you came ot these descriptions...
                              MazdaSPEED6

                              Comment


                              • #30
                                Originally posted by pgt95
                                Just curious if you have had all 4 bars... if not how you came ot these descriptions...
                                Out of the four I have tried (and still use) the 626 bar, so its description is from first-hand experience. General board consensus is that the PT bar is the perfect size for setting up the Probe for neutral steering and the Addco bar produces good amounts of oversteer. So I made an educated guess on the AWR bar taking into account its relative stiffness to the PT and Addco bars.
                                95 Laser Red SE mtx
                                CAI | NGK Plugs + Wires | 6AL + TFI | SPEC Stage 3 + FW | SS Clutch Line | Civic STS
                                Illuminas | Tokico Springs | Ractive FSTB | Corksport RSTB | 626 RSB
                                Grounding Kit | RR Poly Inserts + Stabilizer Bushing

                                Comment

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