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GKTech roll center correction kit

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  • #76
    I didn't want to fill your email with annoying questions.

    I take it the sales@gk address?

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    • #77
      I didn't make a user account prior to ordering so I do not have any info. Although I did make one on my second purchase

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      • #78
        Originally posted by sr23det View Post
        I didn't make a user account prior to ordering so I do not have any info. Although I did make one on my second purchase
        Yes, email to sales@gktech.com.au please

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        • #79
          This thread is from the way back, but I have thought about these and would like to have my thoughts vetted here so that they're connected to the appropriate thread for future discussion. I'm looking at these because none of the various "drop knuckles" I've looked at have provisions for ABS sensors, and I want to retain ABS. This is for an S14 that will be used for autocross and track days. It may get tagged/insured but it won't be daily driven.

          This "camber correction kit" increases the vertical distance from the ball-joint to spindle by 40mm, but it also moves the knuckle outboard 25mm on each side.

          I know that this will raise the roll center, but it will also increase the track width, static camber, and scrub. It shouldn't change the SAI because the lower ball joint is still in the same lateral location, with respect to the strut top mount.

          The scrub can be compensated by running wheels with more backspace. I've modified the ears on my struts and run high offset "Subaru fitment" wheels before, to keep the tires under the fenders. This kit might require S2k/Mustang type offsets and attention to strut clearance. I'm not too worried about having the tire hit the inner frame rails, as I don't need 70 degrees of steering angle, and I can modify the steering stops if needed, to keep from rubbing the tires on the frame rails. In my mind, tire-to-strut clearance vs. scrub adjustment is the biggest challenge.

          Static camber can be adjusted with camber plates, or at the strut ears if you have adjustment there.

          Beyond the adjustments for scrub, What about shortening the LCA's to move the tires under the fenders? I know that would change the camber gain/loss curve incrementally, because of the shorter arm, but the amount falls into the "any suspension will work if you don't let it move" zone (I've seen it done on C-prepared cars). It would also reduce SAI, but you can compensate with camber plates, or by adding more caster instead. My understanding is that between the two, caster has a better trade-off ratio than SAI, with respect to handling at speed.

          The kit also changes Ackerman somewhat, but for a non-street car that you're not parallel parking, that may not be a big deal, and there are ways around that as well.

          The kit will also move the lower strut attachment point up 25mm, but I have struts with separately adjustable height vs. spring pre-load, so that's not an issue for me.

          It will move the brake caliper out as well, so you may need to make your own brake hoses. The fancy hoses that I've bought for various cars tend to be the absolute minimum length that will work.

          Please school me on what I'm missing...,
          Don Johnson (really!)
          Just so you know.

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          • #80
            Here's an install vid of the GKTECH RCC kit:

            http://youtu.be/8TLKmYaohjo
            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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            • #81
              bump for experiences about GK knuckles for grip....

              Was going to open up the wallet and purchase their grip knuckle, but like anything else, after further research I get more hesitant.

              Their current "grip knuckle" uses OEM ackerman, which I believe is a compromise to "appeal to a wider customer base." Ackerman tuning is very tire specific, but I think it's somewhat safe to say that the tires we all use have very similar tire load sensitivities and could probably benefit from less Ackerman. Plus, I'm rarely steering more than a 1/4 turn to begin with out on track.

              Like Def mentioned earlier in the thread, a less loaded tire (inside tire) requires less slip angle to achieve peak lateral force. In conjunction to running static toe out usually on the front (which most of us do), lots of Ackerman can drag the inside tire more at corner apex, heating it up more, wearing it more and decreasing grip potential.

              The counter argument is that increased drag on the inside tire relative to the outside from pro-ackerman causes a torque on front axle in the direction of the turn, which seems like it can be beneficial.

              The general consensus in the end is that for highly transitional events like Auto-X, pro-ackerman is desirable. Car running on tracks with larger radius turns and sweepers, less ackerman should be beneficial. F1 does actually use reverse Ackerman for many tracks apparently as well.

              Since my car is track only, I'm very curious to the less ackerman approach.

              As per GK, their current V3 knuckle is near zero Ackerman with very quick steering. They actually have two V4 revisions in the works; a standard and a pro-drift. The pro-drift is similar to V3 with steering but also has extra mechanical trail. The standard V4 will be same Ackerman to their V2 but with some extra brake caliper clearance.

              Anyway, what has been everyone's experience with less Ackerman geometry at the track and GK knuckles as a whole?
              Core4 Motorsports
              CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
              S14 VQ AER Endurance Racing Team

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              • #82
                F1 cars ALWAYS use anti-ackerman from what I've seen on on-board shots. In Monaco at the hairpin it's very easy to visually see the anti-ackerman.

                Me personally, consumables are too expensive to burn up for just a theoretical tiny improvement of creating a turning torque on the front axle. And I'd argue that WHENEVER a tire slips to a large degree, it provides less grip than a tire at a small/optimal slip angle. The high inner tire wear on track with stock ackerman of many cars gives evidence that the inner tire is slipping a lot. Therefore, the whole, "it'll provide more turning torque" is debunked thoroughly with just that simple observation.


                So for me, less ackerman gave better tire wear, and it seemed like better front grip (although lots of things changed when changing the knuckles, so it's hard to narrow it down to just that).
                '18 Chevrolet Volt - Electric fun hatch for DD duty!


                DefSport Koni Sleeve and Spring Perch Buy!!!
                http://www.nissanroadracing.com/showthread.php?t=5902

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                • #83
                  What version GK knuckle did you have again?

                  I'm in the same line of thought, which is why I was surprised that they market the GK knuckle with stock ackerman as the grip knuckle. But, I also understand they want to cover a broad base. One thing their grip knuckle has is a provision for ABS sensors, where their others do not.

                  However, most of us do run some toe-out combined with -3.5+ degrees of camber, so rolling down the straights isn't doing the inside of the tires any favors either.

                  Anyone ever map out OEM Ackerman over a steering angle range? I guess I'll do this when I check bump steer as well, but I have modified OEM knuckles that I didn't modify so who knows where it's at.

                  Anyone have experience with these: https://www.driftworks.com/driftwork...ter3-hubs.html

                  Settings for drift and grip, but it doesn't say what ackerman relative to stock.
                  Core4 Motorsports
                  CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
                  S14 VQ AER Endurance Racing Team

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                  • #84
                    Aluminum modular knuckles with extreme arms.

                    The wear was always on the VERY inner edge of the "inside" wheel for the track direction that had the most wear. It wasn't from braking or going down straights, definitely a narrow strip that exactly matches what it looked like for a contact patch when cornering. My E36 M3 did the exact same thing. Going to the knuckles eliminated the wear completely. My roll center height was similar between the two knuckles (stock with FLCA and balljoints spaced down vs. GKTech and stock ball joints).
                    '18 Chevrolet Volt - Electric fun hatch for DD duty!


                    DefSport Koni Sleeve and Spring Perch Buy!!!
                    http://www.nissanroadracing.com/showthread.php?t=5902

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                    • #85
                      Were there two versions of aluminum knuckles?

                      I'll have to take a closer look at my tires next time then. Tire temp spread for the track direction inside front (RF) at my home track has inside tire temps that are 20 degrees hotter than the center. The outside tire is a 10-20 degree spread from inside to outside (-4* camber). I don't want to pull camber out of the RF either because the most important turn on the track is a left hander that starts the longest WOT section of the track.

                      So is that Driftworks/Geomaster 3 knuckle something to run far, far away from? Looks interesting nonetheless.
                      Core4 Motorsports
                      CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
                      S14 VQ AER Endurance Racing Team

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                      • #86
                        Only one version of Al upright, modular steering arms.
                        '18 Chevrolet Volt - Electric fun hatch for DD duty!


                        DefSport Koni Sleeve and Spring Perch Buy!!!
                        http://www.nissanroadracing.com/showthread.php?t=5902

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                        • #87
                          Originally posted by gills View Post

                          So is that Driftworks/Geomaster 3 knuckle something to run far, far away from? Looks interesting nonetheless.
                          It definitely has less ackerman than stock, you can see that easily enough.
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