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New S14 bumpsteer graphs

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  • #61
    MOTON = omfg

    oops

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    • #62
      Originally posted by Epstein View Post
      Don't forget that where your ride height is set (and the subsequent 0 height) will affect your graph. The overall shape should be the same, though.

      As far as the ziptied shorter traction arm theory, I really don't think bumpsteer has anything to do with it. With a short traction arm, the spindle rolls forward a lot quicker than with a longer one. That tells me that anti-squat is being changed. I really doubt the drift guys have bumpsteer issues anyways, considering the fact that they don't have any compliance to begin with. That's one way to solve bumpsteer.... don't have any bump.
      anti-squat is determined by the location of the two inner pivots on the lower control arm. the traction arm doesn't change anti-squat.

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      • #63
        yes, and the angle of the subframe is the easiest way to change the plane that the LCAs rotate on - or you could cut the lca tabs off and relocate like many do to S13 subframes to convert to s14

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        • #64
          Excellent work! I am quite impressed. One thing though...

          Did you play with the toe arm lengths at all???

          That seems to be the only other thing to adjust without fabrication work.
          function > form
          1990 240sx fastback: IN PROGRESS

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          • #65
            look at his 8.5" / 12.25" plot, it goes real nice from toe in, to 0 to toe in. This amount of toe in gain just means that epstein needs the toe arm shortened (since its behind the hub, it would need to be lengthened if in front of the hub) to get it just right.

            ->the toe arm is longer than it needs to be, so shorten the toe arm by moving the eccentric to the furthest position

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            • #66
              I don't have anything constructive to add, other than to say this is an awesome thread and it is exactly this sort of thing that made me sign up to this forum.

              I am just beginning to experiment with alignment settings and the data in this thread has given me an entirely new insight into the whole process.

              Keep the data coming!

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              • #67
                Originally posted by Full-Race Geoff View Post
                look at his 8.5" / 12.25" plot, it goes real nice from toe in, to 0 to toe in. This amount of toe in gain just means that epstein needs the toe arm shortened (since its behind the hub, it would need to be lengthened if in front of the hub) to get it just right.

                ->the toe arm is longer than it needs to be, so shorten the toe arm by moving the eccentric to the furthest position
                Thanks for the info! when I build my subframe I am going to weld washers onto it and eliminate the cam bolts altogether. I figure now that the geometry has been kinda figured out there isn't much need for adjustment once you position the mounts to the best of current knowledge.
                function > form
                1990 240sx fastback: IN PROGRESS

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                • #68
                  Are these lengths measured from the centers of both bolt holes?

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                  • #69
                    Originally posted by GodspeedS13 View Post
                    Are these lengths measured from the centers of both bolt holes?
                    Yes. If they're in the car and the bolts face the same way, its easier to turn the heads to you get 2 parallel flat sides and measure that way. It's a hell of a lot more accurate than eyeballing bolt centers.
                    She's built like a Steakhouse, but she handles like a Bistro.

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                    • #70
                      Originally posted by Epstein View Post
                      Yes. If they're in the car and the bolts face the same way, its easier to turn the heads to you get 2 parallel flat sides and measure that way. It's a hell of a lot more accurate than eyeballing bolt centers.
                      Yea i figured it out when i went outside to adjust everything. Hopefully its set up good enough for an autocross on sunday.

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                      • #71
                        Originally posted by Full-Race Geoff View Post
                        i did what you are suggesting and it was not ideal -- what i am doing now is this:

                        8.5" traction rod
                        12.25" RUCA -- adjusting camber with eccentric
                        toe rod eccentric moved to make the toe rod as *Short* as possible, then toe is adjusted with the rod length


                        just had a quick question, to verify what you explained about adjusting rear toe arm eccentric to furthest position; you are referring to adjusting the eccentric fat side towards the outside (towards the wheel) in this way the inner pickup point for the toe arm is more inboard in the subframe making the toe arm length shorter & then adjusting the toe arm via the buckle, like you would the front suspension toe arm, correct?

                        then adjusting rear camber via the eccentric once ruca & trac arm lengths are set

                        hope to see what you came up with as far as ruca & trac arm lengths in the future

                        also wanted to verify on the procedure of bump gauging rear, when the gauge/rig is setup the vehicle has to be level to the ground or at the static ride height in other words the rear can't be jacked up only, also i have been told that camber & toe settings should be set before gauging bump, is this correct?

                        i would assume this is correct, so as to be as close to the goal camber & toe settings to begin with

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                        • #72
                          I have been experimenting with these lengths. Not sure why but my UCA's are different lengths to get the same camber on both sides. I found I was tail happy/ loose one recent weekend. I had one longer traction rod. I measured UCA lengths and put the traction to UCA ratio back to 12/8.25 and things worked much better.

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                          • #73
                            sorry it took me so long to get to this post. Ive been meaning to take some pics of a full time attack R34 GTR suspension setup we had at the shop, it really explains a lot. ill get to that in my next post

                            Originally posted by cheeky14 View Post
                            to verify what you explained about adjusting the rear toe arm eccentric to furthest position; you are referring to adjusting the eccentric fat side towards the outside (towards the wheel) in this way the inner pickup point for the toe arm is more inboard in the subframe making the toe arm length shorter & then adjusting the toe arm via the buckle, like you would the front suspension toe arm, correct? then adjusting rear camber via the eccentric once ruca & trac arm lengths are set
                            YES that is correct. You want a fixed RUCA and TRAC arm length!

                            To adjust camber, do it with the eccentric!! Do not change RUCA length, just the eccentric bolt's position. Use the same lengths on both L&R sides (assuming your crossmember, LCA and bushings are all proper and undamaged, you would be surprised how many cars have bent lcas or subframes).

                            To adjust toe, DONT do it with the eccentric! run the eccentric so that the toe arm is the shortest possible length, then adjust toe with the arm length.

                            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:
                            +6.35mm over S14 trac arm length
                            +6.35mm over S14 RUCA length

                            i hope we can get more plots with my toe settings, and +5mm, +8mm, and + 15mm over S14 for final verification.... i just dont have the time lately


                            Last - if you decide to use any sort of roll center adjuster the REAR LCA MUST BE LENGTHENED, ie moonface ball joints (OR if those hardrace ones are legit, but i think they are bunk? ) but read that again -- roll center adjusters require longer LCA's!!!

                            so basically what the OP in this thread learned is that for a low car, arm lengths need to be lengthened

                            Originally posted by cheeky14 View Post
                            also wanted to verify on the procedure of bump gauging rear, when the gauge/rig is setup the vehicle has to be level to the ground or at the static ride height in other words the rear can't be jacked up only, also i have been told that camber & toe settings should be set before gauging bump, is this correct? I would assume this is correct, so as to be as close to the goal camber & toe settings to begin with
                            a friend of mine wrote a GREAT step by step tutorial on this, ill ask him to post it up on this forum i think he would be interested

                            Originally posted by logr View Post
                            I have been experimenting with these lengths. Not sure why but my UCA's are different lengths to get the same camber on both sides. I found I was tail happy/ loose one recent weekend. I had one longer traction rod. I measured UCA lengths and put the traction to UCA ratio back to 12/8.25 and things worked much better.
                            use the same length UCA, however do not use the same camber bolt position for anything but the toe rod.

                            i hope that makes sense

                            EDIT: FIXED
                            Last edited by Full-Race Geoff; 06-08-2010, 09:35 PM.

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                            • #74
                              Originally posted by Full-Race Geoff View Post
                              Last - if you decide to use any sort of roll center adjuster the REAR LCA MUST BE LENGTHENED, ie moonface ball joints (OR if those hardrace ones are legit, but i think they are bunk? ) but read that again -- roll center adjusters require longer LCA's!!!

                              so basically what the OP in this thread learned is that for a low car, arm lengths need to be lengthened
                              Amen to that.

                              You need to do the same thing up front too.

                              My FLCAs are... well, lengthened. By a lot.

                              I haven't set it in stone as far as the length goes yet, so once I do, I will take measurements.

                              But yeah, FLCAs have to be lengthened too if you have roll center correction via longer ball joints or using longer bolts with spacers, when the car is substantially lowered.
                              http://sosideways.wordpress.com/

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                              • #75
                                Originally posted by SoSideways View Post
                                Amen to that.

                                You need to do the same thing up front too.

                                My FLCAs are... well, lengthened. By a lot.

                                I haven't set it in stone as far as the length goes yet, so once I do, I will take measurements.

                                But yeah, FLCAs have to be lengthened too if you have roll center correction via longer ball joints or using longer bolts with spacers, when the car is substantially lowered.
                                Am I correct in thinking that the FLCA/RLCA must be made longer because the longer ball joints change the angle and reduce the "effective length"?
                                Don Johnson (really!)
                                Just so you know.

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