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    Results 1 to 6 of 6
    1. #1
      Join Date
      Mar 2020
      Posts
      2

      Pro-touring 2nd gen TA with drift attitude

      Hello!
      I'm very thankful for the information I have acquired reading your discussions. The answer received much depends on the question asked, so I've been preparing to formulate the request for your advice for a couple of years of my Trans AM possession.
      The car now is a '79 TA with LS1 (has 293hp to the wheels) and T56 which came off a '01 Firebird. Everything else is stock at the moment. Plans for the car: 85-90% daily street driven, 15-10% drifting (street, meets, occasional track practice). Maximum hp rating for the future is 500-550hp to the wheels (not soon), in case if I change the engine or upgrade the current one.

      Question is in suspension - what can be good for drifting a solid axle? I gathered info on f-bodies that drift, and here's what I've found regarding rear suspension (though generations of cars are different).

      Kelly Slides - 4th gen TA with 4th gen torque arm
      Josh Mason - 1st gen Camaro with self fabricated torque arm
      Mikko Viitala - 2nd gen Camaro with Competition Engineering 4link
      Speedtech - drift 1st gen Camaro with a torque arm
      Hansen - 2nd gen Firebird - leaf springs

      Therefore I'm faced with deciding which rear suspension setup to go with: 3-link (torque arm / offset link), 4 link, or... yes, mad it may sound! Maybe swap Skyline's R33 IRS? (some used parts at deal-level prices seen around). Work being done by fellow mechanics.

      I plan to do the rear first, because I want to be finally able to launch the car. With current old leaves and LS1 it's no use - wheel hop is massive, can't hook up. Regarding the front setup I will need to verify, if the stock subframe will allow to accomodate larger degree of wheel turn. Any advice here? Maybe keep the subframe stock, do the true coilovers, change arms and add rack and pinion? What are the major advantages of going with an aftermarket subframe, if I'm not planning to run very fat tires up front and apart from weight saving.

      All input is highly appreciated! To sum up: the idea is a great handling 2nd gen, comfortable to drive, but with drift pedigree in it's dna. And on economically sensible budget.

    2. #2
      Join Date
      Mar 2015
      Location
      Baton Rouge, LA
      Posts
      106
      Country Flag: United States
      Seems like most Formula Drift cars are using IRS, which I guess is mostly due to the fact that most late model production cars have IRS. I think drift cars usually have toe in at the rear and a bit of negative camber, with a solid rear axle you have no ability to adjust toe or camber.
      Vaughn Gittin Jr has a Mike Maier based 3 link in his RTR X so it seems like a torque arm, 3 link, IRS, etc. all can be made to work fairly well.

      I'd think you'd really need a one off front suspension setup, as drift cars also run tons of camber (4+ degrees) and caster compared to most pro-touring cars on top of having a much greater steering angle (which requires narrowed control arms to clear the tire).

      I'd go with an AME subframe since it uses C5/C6 suspension and then swap out the control arms and knuckles with the custom pieces Matt Field is using on his Formula Drift corvette: https://store.partsshopmax.com/shop/Corvette/ss/

      That way you're using a tried and true setup and minimize the amount of custom fabrication work to get some other off the shelf subframe to work.

    3. #3
      Join Date
      Jun 2012
      Location
      Chicago burbs
      Posts
      247
      Country Flag: United States
      I'll share my experience in the hope that it may help. Assuming the front geometry is good(your's should be much better than my stock A body), the the rear roll center will be an excellent tuning aide. I first added a frame mounted watts link to my stock triangulated 4 link. The first thin I noticed was that the rear end no longer shifted side to side in turns. The roll center alos doens't move around because it's frame mounted, which helps predictability. The coolest thing though, is that when you drop the roll center to the lowest setting, the car became a street drift hoon machine. Epicly fun. as you progressed back up the settings rear grip returned entering and coming out of turns.

      With the stock 4 link though at the adjsutment extremes(near the bottom, or near the top) the system would bind after a few degrees of roll, and would be very unpleasant to drive. I never planned on running at those extremes in real life, so it wasn't much of an issue. I did however end up converting to an adjustable 3 link so I could not be limited(yup I'm contradicting myself-I'm an emotional man and I want what I want and had a ton of fun designing and building it with my bud lol). I couldn't be happier with the car now with the 3 link and the frame mounted Fays2Watt link.

      A setup like this would probably make your car do what you want since you said 90% street. I feel like I could take mine to a drift event and have a ton of fun. I wouldn't be competitive since my steering arc is limited and I can't tune toe and camber on the rear, and a bunch of other stuff that dedicated drift cars do. All depends how much you want to trade street car for drift capabilities. Anyways, I hope this helped give you some perspective.

      1969 442 6.0L LQ9 T56
      Fab9 w/ custom 3 Link conversion
      FAYS2 Watts link
      Thanks to Mark at SC&C for his honesty and passion for the sport, and Ron Sutton for the wealth of knowledge that has helped shape so many of the cars on this site.

    4. #4
      Join Date
      Mar 2020
      Posts
      2
      ICrombie and jetmech442,
      Thank you very much for your replies and info! All you've said is food for thought, and good to ponder over!
      I'll add more data to the equation. There is trans-ocean shipping involved (Europe), which makes the end price of US goods brought here 25-40% higher than initial, depending on weight...
      Fabrication and local mechanical skill is available. ICrobie, AME subframe is a great selection, I admire it's perfection and beauty, but currently this set-up is out of my budget. Matt Field's production would be a professional and ideal way to go, if I built the project the right way from the start with proper funds. Thank you for the link! - I'll save it for the future.

      For the front I see a following plan. We'll measure the maximum possible turning angle, depending on stock front subframe and wheel arch/tire clearance. The car runs 255/45/18 in the front.
      From what I've read, Mikko Viitala 2nd gen Camaro is capable of 65° of angle with 205/55-16 tires, and that's a dedicated pro build. I don't want to go with tires this narrow in the front, so we'll see what can be compromised.
      For arms I see the following solution - maybe go with SPC arms (upper providing -3°camber and +3° caster). SPC lower arms are rated at +2.50° caster. Do the lower and upper arms' figures add up for altogether +5.5° caster? Then do a true coilover conversion and (maybe if some cash left) add a power rack.

      I'm really torn regarding a decision on the rear setup. An enlighted party of automotive graduates commits to swap in a reputable drift R33 Skyline rear IRS for a month of labour. Pros - R33 stuff around here is cheap, easy to get and lot's of tuning aftermarket goods available. Whole used kit would be around $1.3k shipped. With stock brakes!
      Because I'm not an engineer and the work will be done for me, I'm spooked by cons: possible wheel hop; never done before on a 2nd gen (project time might grow uncontrollably), so no road map available. And as far as I've heard from other experienced people, who implemented a C4 rear in a 3rd gen Trans AM, custom subframe manufacturing was involved in their project - they CAD modeled and then welded the frame, with C4 suspension, and then built TransAM's body around it. The people proposing the Skyline approach don't plan such sophistication and avoiding ruining the car I love is a major concern.
      I also see AME's approach to rear IRS installation involves connection to their rear subframe cradle. Yet as far as I understood, other aftermarket IRS systems for 2nd gen, Heidts and Speedtech, connect to the stock subframe without custom frame rails. So it's the unknown territory that terrifies (install in the stock subframe/body, or add/fabricate a craddle or frame rails). Even Gregg Hamilton (Ken BLock's mechanic) Firebird with Skyline's 4wd uses C7 cradles, not Skyline ones.. probably for some reason.

      The other solution I sympathize for my build is BMR torque arm (3 link kit), in part because of Watts link. Allows to keep the stock 10 bolt. Cons - no x-pipe (or hard to route) and ground clearance because of torque arm section.

      Will also appreciate opinions on gear selection. I look at 3.90 or 4.1 gears to go with my T56, what do you think?

    5. #5
      Join Date
      Jun 2012
      Location
      Chicago burbs
      Posts
      247
      Country Flag: United States
      I totally agree that an R33 IRS would be hella cool. I've done plenty to my ride for that same reason. So if your heart wants what it wants then make it happen cap'n! That being said, its gotta be done right. In my head, " done right" involves the following points:
      1) Instant center and roll center have to be spot on. For an IRS, instant center cannot be modified once it's installed as it is based on the convergence of the rear upper/lower control arms(and the CG and so on). The IC will be directly responsible rear grip under acceleration. just right an you can mash the pedal out of a corner, or launch real hard from a stop. Too much and the rear end raises with pedal position and is unpleasant to drive unless your only drag racing. Too little and you sacrifice grip. The opposite of all this is true when braking. if you have high antisquat, launch is great, but under braking the rear end actually pulls up and can cause wheel hop. This happened to me on track and it was very violent and luckily I was able to slide the car sloppily through the turn to scrub off the rest of the speed.
      2) Rear roll center works in harmony with the front roll center to create the roll axis. Once you correct the front geometry, the front roll center will be fixed. So the rear roll center will dictate how your car drives and responds in corners from there on out. For an IRS, I'm pretty sure it moves around with the suspension(just like the front), so the static location is unadjustable(unless you can change pickup points on the control arms?). I dunno, not an expert in IRS's.

      Getting all that perfect is hard, that's what entire engineering teams do for OEMs. And is the reason I built my antisquat and rollcenter to be adjustable. If someone with a 2nd gen could tell you the heights of the IC and RC work in their car for drifting, then you could have a target for IRS. but if not, I feel like adjustability is key.

      The torque arm is nice, but the IC is fixed at the front mounting location. BMR is very reputable, and the location of their IC may just work well for you, maybe a good convo to have with them. A 3 link is more work to get integrated, but can be easily adjustable and can be homemade. and a Watts link or panhard bar can be homemade as well.

      As for gears with a T56, you'll need to know the tire you want to run with. My car runs a real tall 28.5'' tire (295/45/R18) because the '69 wheel well is so doggone large it looks weird with anything smaller. I run a 4:56 gear in order to shift before 60. I like shifting and want to drive: my original 3.23's took me to upper 70's in first. I based my rear gears on the same splits that the pontiac G8GT(holden commodore) has. If you're tire is smaller look for a rear gear that gets your splits to something close to a performance car you like(vette, mustang, G8GT...etc). If you want I can share my janky excel sheet to help you explore.

      I'm sure there are other opinions, and I hope they chime in. The above are just the issues I see that need to be worked out for an IRS to be successful, there's probly more I don't know about. again, just wanted share my thoughts.

      1969 442 6.0L LQ9 T56
      Fab9 w/ custom 3 Link conversion
      FAYS2 Watts link
      Thanks to Mark at SC&C for his honesty and passion for the sport, and Ron Sutton for the wealth of knowledge that has helped shape so many of the cars on this site.

    6. #6
      Join Date
      Nov 2018
      Posts
      642
      Country Flag: United States
      Quote Originally Posted by jetmech442 View Post
      2) Rear roll center works in harmony with the front roll center to create the roll axis. Once you correct the front geometry, the front roll center will be fixed. So the rear roll center will dictate how your car drives and responds in corners from there on out. For an IRS, I'm pretty sure it moves around with the suspension(just like the front), so the static location is unadjustable(unless you can change pickup points on the control arms?). I dunno, not an expert in IRS's.
      This brought to mind the IRS on the Lincoln LS I used to have. The suspension had a certain amount of rear steer built into it through the use of collapsible bushings in the toe links. When you went around a corner, the links would collapse a bit adding a couple of degrees of turn into the outside rear tire and the amount it varied depended upon how hard the corner was taken. I don't know exactly how it was supposed to work. Some folks liked it, I didn't. Made the car unpredictable to me, because it didn't act the same each time you went around a corner. If you went just a little harder this time than last time, the rear tires would shift angles a bit and it would take the corner way differently that you'd predict a speed change would account for. It always felt to me like there were two people with different goals trying to steer the car at the same time. I replaced the links with solid links, ie no collapsible bushings, and the car's handling improved significantly.



      If it weren't for all the stupid problems the car had due to Ford trying to make Jaguar parts work in it, I'd have kept it. It would have been a far better car if Ford had just put a Ford 4.6L in the car instead of a Jag 3.9L.






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