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New S14 bumpsteer graphs

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  • #76
    Yes.

    The FLCAs actually need to be MUCH LONGER if you don't space it very much and want to lower your car substantially, because if you don't, the angle between the FLCA's bearing cup and the knuckle's bottom will be way off, causing the tapered pin or bolt to bind up on the bearing cup as the arm moves up to get into it's finally position where it will be at static ride height.

    Lengthening the arm will help fix that binding issue.
    http://sosideways.wordpress.com/

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    • #77
      Originally posted by Full-Race Geoff View Post
      if the car is going to be lowered substantially, this requires longer lengths for the RUCA and toe arms.

      This is how the R34 nismo is all set up -- all that is, is a glorified S14 rear susp. http://www.nismo.co.jp/en/products/c...linebnr34.html


      R34 nismo trac arm length +5mm over S14
      R34 nismo RUCA length +5mm over S14

      due to this thread, i ran:
      +12.5mm over S14
      +12.5mm over S14

      so basically what the OP in this thread learned is that for a low car, arm lengths need to be lengthened
      Great info! So with Nismo adding 5mm to both arms, that's going to be roughly what the 12.25/8.50 plot looks like in my graphs on the first post. It's good to see this data come full circle.
      She's built like a Steakhouse, but she handles like a Bistro.

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      • #78
        Geoff, Are you 12.5 longer due to a longer LCA?
        When I had the ratio off with a longer traction rod, it was amazing how loose the car was. Drifters take note.

        Isn't it interesting that the STOCK ration Traction to UCA gives the best/least toe change. Nissan engineers must be fairly sharp.

        After lowering my car and looking at everything, it seems that the rear lower control arm is almost level but the upper arms are at quite an angle. Will lowering the ball joint do much for roll center/anything given that it is almost level when lowered? I believe the camber gain will still be there either way and I can't see it helping bump steer either.

        Thoughts?

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        • #79
          Originally posted by logr View Post
          Geoff, Are you 12.5 longer due to a longer LCA?
          When I had the ratio off with a longer traction rod, it was amazing how loose the car was. Drifters take note.
          Roger that.

          I'll try not to have the ratio off.
          http://sosideways.wordpress.com/

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          • #80
            Originally posted by Epstein View Post
            Great info! So with Nismo adding 5mm to both arms, that's going to be roughly what the 12.25/8.50 plot looks like in my graphs on the first post. It's good to see this data come full circle.
            YES!!! I completely agree - thank you soo much for sharing this with the community. Saved me a lot of headaches and time. Next round of susp work for me will be getting the bumpsteer measurements super precise, and then figure out a legitimate solution for the LCA roll center adjustment. I have a few ideas, but havent settled on what method im going to go with yet.

            also, going to try and use the more aggressive Nismo clutchpack kit in my OE gtr rear diff

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            • #81
              Originally posted by logr View Post
              Geoff, Are you 12.5 longer due to a longer LCA?
              When I had the ratio off with a longer traction rod, it was amazing how loose the car was. Drifters take note.

              Isn't it interesting that the STOCK ration Traction to UCA gives the best/least toe change. Nissan engineers must be fairly sharp.

              After lowering my car and looking at everything, it seems that the rear lower control arm is almost level but the upper arms are at quite an angle. Will lowering the ball joint do much for roll center/anything given that it is almost level when lowered? I believe the camber gain will still be there either way and I can't see it helping bump steer either.

              Thoughts?

              OOPS i edited my post -- i posted 12.5mm -- i meant +6.5mm !! = ~1/4" as in epsteins charts. i wrote 1/2"

              dont worry about the angles of the arm -- worry about bumpsteer for a given wheel travel range, and then keep the hub there. to keep the hub in that position while you adjust roll center, you must lengthen the LCA accordingly. but there is no need to look at the angles of the arms and come to any conclusions
              Last edited by Full-Race Geoff; 04-11-2011, 04:01 PM.

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              • #82
                Thanks for the insight Geoff

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                • #83
                  This is much delayed I'm sure, but did you try 12.00" length ruca?

                  What would be the effect?
                  1990 240sx - Aristo 2JZGTE, R154, GT37, Defsport Wilwood kit, KTS coilovers - daily driver
                  1991 civic si - B18C5 / toda / ATS / hytech - autox
                  2001 integra type R - Greddy td05-18g - garage queen

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                  • #84
                    I haven't owned a 240sx in a while now.

                    If you look at the graphs, the trend is there but it's just not clear. The three lines rotate clockwise if you look at the 12.50" vs 12.25" graphs. With a 12.00" Ruca, it would rotate even farther clockwise, where bumpsteer would be minimized with a traction arm between 8.00 and 8.25". That combination would give you a pile of camber, though.
                    She's built like a Steakhouse, but she handles like a Bistro.

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                    • #85
                      Hey Guys, so i got around to bumpsteering the rear of my S14, i have the Def/Skullworks rear sphericals on Z32 knuckles & peak perf. arms/SPL parts RUCA, stock lower cont. arms with Nismo bush. my rear center hub to edge of fender heights are about the same as Epstein,

                      The RUCA arm length is about 12.25 & trac. arm is 8.25 (this is my starting point) my initial readings from static height to 1in. bump, .155" toe in & in droop .95" toe out

                      I adjusted the Ruca to 12.25 & trac. arm to 8.50 & my readings are out of wack compared to what Epstein came up with on the graph for these length; 0-1" bump .100" toe out, droop .162" toe in, then i tried different lengths on the trac. arm & it seems like running the trac arm all the way short made the readings lower & making arm longer readings are higher,

                      the veh. has not been in any accidents. i played with camber eccentric(set full neg.) toe eccentric set in the middle, will keep trying to get readings as low as the 12.25/8.50 graph.

                      Have you guys had similar results (i know different static heights will affect readings)
                      Any suggestions????
                      Last edited by cheeky14; 08-19-2012, 10:08 PM. Reason: clarifacation

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                      • #86
                        can you share some more info, maybe post a pic of your setup? did you do the front end also

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                        • #87
                          I will take some pics tommorow, (i have veh. at my parents place; will make time to run over there & take pics)

                          thanks

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                          • #88
                            I've done lots of bumpsteer measuring on my s13 rear subframe. Running the rear trac arm way longer then the standard 240sx internet setup, or "rule of thumb" helped limit toe change. When you lengthen the upper control arm to reduce negative camber, it rolls the spindle which moves the toe arm, lengthening the trac arm rolls the spindle rearward which moves the toe arm downwards.

                            You have a lot of toe change. I've got my rear trac at 9+", and run 1.8-2.2 degrees negative camber, but don't remember my ruca numbers off the top of my head. I can get toe change down below 1mm through several inches of travel. I have a big thread with lots of info, if you are interested. It's in the alignment section somewhere...

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                            • #89
                              Originally posted by Jason M View Post
                              I've done lots of bumpsteer measuring on my s13 rear subframe. Running the rear trac arm way longer then the standard 240sx internet setup, or "rule of thumb" helped limit toe change. When you lengthen the upper control arm to reduce negative camber, it rolls the spindle which moves the toe arm, lengthening the trac arm rolls the spindle rearward which moves the toe arm downwards.

                              You have a lot of toe change. I've got my rear trac at 9+", and run 1.8-2.2 degrees negative camber, but don't remember my ruca numbers off the top of my head. I can get toe change down below 1mm through several inches of travel. I have a big thread with lots of info, if you are interested. It's in the alignment section somewhere...
                              I'd love to have/see all your settings for arm length, if possible. Is it in that thread? Have a rough estimate what page or post?

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                              • #90
                                I'am going to bumpsteer the front of the car & mod or build new spidles this fall. I also need to biuld some new rlca's for my s14 subframe so I can start devolping that aswell...
                                Here is my thread.
                                http://www.nissanroadracing.com/showthread.php?t=2674

                                EDIT: One thing I want to say about my data, is that I should of converted the Long Acre Gauge numbers to degrees, to make the numbers more relavent to the actual toe change of the tire, which changes based on tire diameter.
                                Last edited by Jason M; 08-20-2012, 10:37 AM.

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