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S13 subframe rear camber setting

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  • S13 subframe rear camber setting

    I've been doing a lot of thinking about some of the topics that I THOUGHT were fairly well worked out in the early days of this forum and my current internal debate is regarding the rear camber setting for a s13 rear subframe. I've been experimenting with less and less camber, currently down to 0.5*, due to a lot of the information from all the knuckle options out there today. Unfortunately I didn't have the chance to get tire temps at my last trackday as I got a little over optimistic into turn 1 and ruined my track tires. I've seen all kinds of numbers out there, from 0 to -3* that others are running, but I'm looking from actual experience from the type of person who takes tire temps from the outside, middle, and inside of the tire... HAHA! I've been away from the forums for a while so I'm not really sure what the consensus is anymore and I'd like to tinker with the alignment before my next event. Overall the balance of my car is pretty damn good, but the rear is a little "vague" at the limit and I'm thinking fine tuning the camber might help that without sacrificing much mid-corner rotation.
    function > form
    1990 240sx fastback: IN PROGRESS

  • #2
    Well, now that I've found the alignment forum, I think i'll be ok... Haven't been on much since the switch to the new format...

    Sent from my LGMS210 using Tapatalk

    function > form
    1990 240sx fastback: IN PROGRESS

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    • #3
      I have an S14, but just for a data point, I'm at -1.4-1.5 in the rear. On the heavier loaded side at my home track the temp spread was about ~15 degree from outer to inner (hotter on inner). This is with OEM upright pivot points, raised subframe and all adjustable links.

      Extending the RUCA to achieve very low camber numbers will affect your toe curve through the suspension travel. So with that said, the vagueness you feel could be a toe issue, not camber. You ever check your bump steer back there? You could be getting some steer back there that's throwing off your feel for what's going on.
      Core4 Motorsports
      CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
      S14 VQ AER Endurance Racing Team

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      • #4
        Originally posted by gills View Post
        I have an S14, but just for a data point, I'm at -1.4-1.5 in the rear. On the heavier loaded side at my home track the temp spread was about ~15 degree from outer to inner (hotter on inner). This is with OEM upright pivot points, raised subframe and all adjustable links.

        Extending the RUCA to achieve very low camber numbers will affect your toe curve through the suspension travel. So with that said, the vagueness you feel could be a toe issue, not camber. You ever check your bump steer back there? You could be getting some steer back there that's throwing off your feel for what's going on.
        I don't think bumpsteer is the issue as the car is glorious on the street/canyons. It's only at the track, on the very ragged edge, that the rear has the "vague" feeling. Part of the issue is that, since I'm running a 2-way clutch type diff, I have the rear set up fairly loose, which I like anyways. It just doesn't seem to dig in under side loading on acceleration, which is why I was thinking camber. One of my conundrums though is that everyone seems to be running s14 subframes, with risers. I'm still stock s13 subframe, no risers. I feel that with my setup I should probably run less camber in the rear than yours.
        function > form
        1990 240sx fastback: IN PROGRESS

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        • #5
          I"ll just throw some things out there for the sake of conversation as I know you know your stuff....

          Are you achieving the same amount of weight transfer/suspension travel in canyon driving as you are at the track? Toe changes the greatest further you are from static ride height.

          Vague feeling or just losing grip? If the latter, then sure, camber could be a factor.

          But, if your car is setup loose, I'd imagine this could be a culprit as well once you're at maximum lateral acceleration potential and the rear axle is teetering on the edge of grip/sliding before the front giving an uneasy feeling.

          Do you run a rear sway bar?

          Do you have solid subframe mounts?

          Again, go buy a damn tire pyrometer! I have a this one (you can find them for cheaper that MSRP): http://www.longacreracing.com/produc...ital-Pyrometer
          Core4 Motorsports
          CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
          S14 VQ AER Endurance Racing Team

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          • #6
            With the bumps and all I think the canyon/street would have more travel, and more random travel. The car doesn't seem "darty" over bumps, altogether pretty stable. Also, I do have my trac arms adjusted longer, which should help the weird toe/camber curves some. I'm really trying to walk a very fine line here, and am just looking for that little bit of stability without sacrificing turn-in or mid-corner rotation. Which is why I'm tinkering with alignment and not drastically changing the setup at all. I run 550lb front springs, 350lb rear. 27mm hollow Cusco front swaybar, 21mm hollow OEM JDM rear swaybar. Front: 2.8* camber, 8* caster, 0.1* toe out per side. Rear: 0.5* camber, 0.1* toe in per side, and lengthened trac arms. Stock bushings with collars on the subframe, funny that's the last stock bushings left on the car actually. I've got a infared thermometer. The problem was I destroyed my slicks before I even got comfortable enough with my pace to slow down a bit and do actual work. I figured taking the temps on my sweet 2014 General street tires wouldn't be very helpful... HAHA! ATM my plan is to go back to 1* camber in the rear and increase the rear toe in to 0.2*.
            function > form
            1990 240sx fastback: IN PROGRESS

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            • #7
              I'm assuming you have adjustable toe links? If you still have the inboard eccentric bolt, adjust it so it pushes the inboard pivot furthest outboard. Essentially making the toe link run as short as possible. I still need to measure it physically, but in my CAD model it definitely benefits the toe curve.

              It's interesting that your car is on the loose side with that setup. Punching those numbers into my spread sheet shows a heavily favored roll distribution % on the front axle. It's higher than mine and my car currently understeers too much at the moment. I run a 1.5 way. Maybe a combination of S13 rear subframe geometry and the rear bar.

              So yea, perhaps ragged edge cornering is allowing your subframe to tweak just enough to introduce weirdness? and I like your idea on the rear alignment.
              Core4 Motorsports
              CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
              S14 VQ AER Endurance Racing Team

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              • #8
                Thanks for the tip on the eccentric. I used to play around with those, but in the last few years kinda gave up and just installed the lockout kit. I used to set the camber arm eccentric to lengthen the arm and the toe arm eccentric to shorten the arm. I honestly think the front is a little too stiff, but I feel I need that stiffness due to the limited travel and I also spent quite a lot of brainpower setting up my bumpstops. Also, since my car is stock ka with ac and everything it's a bit more front heavy than most track cars. I've been playing around with ride heighth and taking the rake out of the chasis too, dropping the rear down, which could affect weight transfer quite a bit I would think. I stuck that rear bar on specifically to help turn-in with the 2-way diff, in past setups I ran either the stock 15mm or no bar at all. one of the things I would like to play with as well is a softer front swaybar since I think the front springs are a bit too stiff. Driving style likely has something to do with it as well, I have a tendency to turn in late and aggressively, which likely induces a bit of oversteer since the front grip and turn in is pretty solid with my current setup.
                function > form
                1990 240sx fastback: IN PROGRESS

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                • #9
                  Do you notice this behavior in both left and right turns? Having weirdness only in one direction could be telling.

                  Funny, my co-driver (who's usually a tenth or so faster than me....bastard) says I drive the same way My VQ swap is probably similar with weight distribution; 54/46.

                  My old setup which I would say wasn't necessarily loose, was more aggressive than yours in terms roll distribution. It was like a bit lively coming back on the throttle, which is why I removed the rear bar in the first place (and messed with rear link lengths, etc).

                  My old setup:
                  • 500 lbs/in front
                  • 335 lbs/in rear
                  • 28mm solid front bar (ST suspension)
                  • 24mm solid rear bar (progress)
                  • 1.5 way
                  Couple of videos for sh!ts and giggles with that setup at different types of track (Watkins = higher speed/larger radius turns on RT615K+, NJMP lightning = tighter on RA1):

                  Core4 Motorsports
                  CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
                  S14 VQ AER Endurance Racing Team

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