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Torque Arm Rear Suspension Questions?

Discussion in 'The Hokey Ass Message Board' started by Bass, Feb 5, 2007.

  1. Bass
    Joined: Jul 9, 2001
    Posts: 3,347

    Bass
    Member
    from Dallas, TX

    I know El Polacko is doing a lot of rear suspensions with torque arms and I really like the way they seem to work...and after doing a search and looking at some pics on here, I have a few questions.

    First off, does the torque arm have to have a pivot in line with the front U-joint on the driveshaft? It seems like this would be necessary, but does using the little extra link on the front of the torque arm get rid of the need to align the two pivot points?

    Secondly, from what I can tell, the torque arm need to be rigidly fixed at the differential, correct? And the lower 2 links need to pivot at both ends right? I believe the lower links should be parallel to the ground at ride height, but is there any restriction on whether you run them straight forward, or angled in toward the center of the chassis? How about lower link length versus torque arm length?

    Third, is there any adverse affect to using airbags with a torque arm rear suspension? Any suggestions on airbag placement in regards to both ride quality and lift?

    I'm doing a '49 Chevy Fleetline, and it's got a Mustang 2 front and I Z-ed the frame in the front also....I want it to lay on the ground, but I also want it to ride nicely.

    I was going to just go with a triangulated 4 bar, but now I am considering the torque arm setup as well....any help or advice is appreciated.
     
  2. FiddyFour
    Joined: Dec 31, 2004
    Posts: 9,008

    FiddyFour
    Member

    i considered the triangulated 4bar, and gave serious thought to the torque arm setup for the 54. . . but after building the willys and seeing how sweet the parallel 4bar and watts link setup is, thats the route i am going on the 54 when (if? . . . no, WHEN :D ) i get time to get to it... i know its not the info you are looking for, but food for thought is this:

    keeps things simple, and for a bagged suspension, it also keeps things SMALLER, and less likely to have floor and or frame clearance issues of you plan on a dirt dumping style bag set up.

    JM2C
     
  3. Bass
    Joined: Jul 9, 2001
    Posts: 3,347

    Bass
    Member
    from Dallas, TX

    Yeah, I understand the KISS principal (keep it simple stupid), and realistically the triangulated 4 link set-up is probably the easiest for this car. But I'm intrigued by the torque arm set-up and its advantages.

    Here's a couple pictures of the chassis I'm working with...

    [​IMG]

    And here's the nearly completed front Z....I still have to do a matching drop in the front of the frame for the bumper brackets and radiator.

    [​IMG]

    The rear is getting a step notch that will look alot like the front Z.
     
  4. FiddyFour
    Joined: Dec 31, 2004
    Posts: 9,008

    FiddyFour
    Member

    shit dude, that frame work kicks ass... nice and clean. is that a CE IFS crossmember up there? looks like thier towers. . .love those for adjustability. and did you install the IFS hats and crossmember before or after you stepped the frame?
     
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  5. rooman
    Joined: Sep 20, 2006
    Posts: 3,966

    rooman
    Member

    Bass,
    FiddyFour is correct on the floor clearance issue with the torque arm but that is probably the only reason for not using one. Of course you can build an arm that is structured to fit under the floor and keeping it close to the driveshaft will allow you to have it fit in the driveshaft tunnel. Just build the arm with a dropped upper tube and pivot it off the trans crossmember to get it low enough. If you have an open driveline there is no reason to align the front pivot of the arm with anything except in relationship to the arc that you want the rear end to swing. The torque arm does need to be rigid at the rear end if you want it to act as a torque arm. Ideally any other locating arms should be parallel to the ground with the car at ride height and if those arms are short compared to the length of the torque arm there should be some means for the torque arm to move back and forward at the forward mount to stop from putting the whole deal in a bind.
    If you angle the lower links inwards it will provide a deal of lateral location for the rear end (depending on the amount of angle) and if you use a panhard bar it should be as long as possible and as close to parallel with the ground at ride height as possible.
    When I first started playing with multi link suspensions I made stick models of the arms etc and ran them through the full travel to see what actually went on with pinion angle etc. Now I do it on the computer but the stick model deal still works.
    For ride quality the bags should be behind the rear end as that makes them travel further for the same amount of rear end movement compared with having them mounted ahead of the rear end ( assuming you use a torque arm). That will limit the amount of ride height adjustment however for the same reason. The mini truck/ hopper guys put their bags forward on the arms to get more travel but that also puts a lot of load (bending) on the arm and I have seen a few disasters related to that deal. Again the stick model deal will allow you to figure out just how much the pieces move in relationship to each other.
    O/T, I love your coupe. Saw it for the first time at the HCP and thought that it was the best thing on the grounds,

    Roo
     
  6. Bass
    Joined: Jul 9, 2001
    Posts: 3,347

    Bass
    Member
    from Dallas, TX

    Thanks Roo...that helps.

    I'm also considering a 3-link "wishbone" set-up like the mini-truck guys use. Basically you have the two parallel lower links, and a short wishbone at the top that mounts to an additional crossmember running across the frame in front of the rearend. Any thoughts on that setup?

    Fiddy, I think it is a CE M2 setup...it was in the car when it was delivered to me. The problem was that the front crossmember was going to contact the ground before the rockers got anywhere close to low enough....hence the Z.
     
  7. rooman
    Joined: Sep 20, 2006
    Posts: 3,966

    rooman
    Member

    Bass,
    the only problem with the short top arm 3 link is the fact that it usually results in extreme pinion angle changes due to the travel arc of the short arm. If there is not much suspension travel it is not a problem but again try the stick model test,

    Roo
     
  8. Mizlplix
    Joined: Jan 8, 2007
    Posts: 170

    Mizlplix
    Member
    from S/W USA

    A torque arm modeled after a 5.0 mustang aftermarket unit would be sweet on ur ride.

    It mounts solidly to the axle housing at the side of the diff, or to the diff itself like the dirt track units from Speedway Motors.

    On the 5.0 unit, it uses a sliding front mount. That is a 1" dia. round shaft mounted axially along the trans tail shaft and close to the driveshaft with a poly bushing to do the sliding fore and aft.

    The arm is build to fit "around" the driveshaft, thereby taking up almost no room at all.
     
  9. Bass....something like this ?
     

    Attached Files:

  10. I'm thinking of doing this set up also. I would really like to know everything Bass is asking. It does seem as though the torque arm would have to pivot with the u joint if it were solid, but the other link must change this i'm thinking? Could the ends that attatch to the read end be adjustable too?
     

    Attached Files:

    Krahnic likes this.
  11. 201
    Joined: Dec 17, 2002
    Posts: 344

    201
    Member

    Going to use the torqe arm settup from a '68 Galixie 9'' rear in my A coupe. The uper arm is not even half as long as the two lower arms, but it is adgustable to dial in the pinion angle. I'll post pic's when I get that far.
     
  12. jerry
    Joined: Mar 2, 2001
    Posts: 3,474

    jerry
    Member

    Baas, I've been running one of Elp's torque arm st ups on my truck for a few years.

    THe torque arm does not have to be the same length as it has a short link tht allows it to move forward and back. about 3-4 inches long with a bushing on each end.

    Yes, the lower arms need to be pivoted on both ends to prevent binding. Also need to run a panhard rod for location. '


    I've been running a transverse leaf setup. They can also be run with a set of coil overs.

    PM me with any other questions. See you at LSR!


    jerry
     
  13. FiddyFour
    Joined: Dec 31, 2004
    Posts: 9,008

    FiddyFour
    Member

    oh my... i think i need a cold shower.

    Johnny, you build that truck?
     
  14. Fiddy....nope. I copped that photo from a H.A.M.B. thread. It's almost exactly what I have designed for my modified. It's also very similar to the rear linkage found on a '58 Pontiac Bonneville.

    No bind and a panhard is not needed.
     
  15. Bass, call me

    602-278-6800
     
  16. john56h
    Joined: Jan 28, 2007
    Posts: 1,767

    john56h
    Member

    Mid-80's Camaro and Firebird used a torque-arm that hugs the driveshaft pretty tightly. Might fit under a stock floorboard.

    Most of them had the Metric 7.5" rng gear rearend, but some s-28 and TransAms had a Dana unit with disk brakes.
     
  17. OldSStroker
    Joined: Feb 1, 2007
    Posts: 2

    OldSStroker
    Member
    from upstate NY

    Rear Lower Control Arm (LCA) or "lower links" angle is important for rear roll steer, or "bump steer" as the car rolls in a corner. Slight roll understeer is desirable, but that requires the LCA to angle down at the front, not up in a typical torque arm suspension.

    If you design in "roll oversteer" the car becomes unstable as cornering gs increase. In other words, you turn left, the car rolls and the rear wheels steer you more left, which rolls the car more, which steers it more left, etc. until it spins. Avoid this design flaw like the clap!

    For a more in-depth discussion on torque arm rear suspensions, try this:

    http://web.camaross.com/forums/showthread.php?t=391537

    If you were to copy the geometry of a 3rd or 4th Generation Camaro you would be in pretty good shape.
     
  18. FLAT-TOP BOB
    Joined: Aug 19, 2002
    Posts: 1,964

    FLAT-TOP BOB
    HAMB O'dex Editor

    bass

    that is some great looking work!
     
  19. sodas38
    Joined: Sep 17, 2004
    Posts: 2,252

    sodas38
    Member

    I know this may be out of left field but what about copying the 2005 Mustang rear suspension? It's a 3-link set-up. There's alot going on here but I gotta believe the basic premise here is very useable. Also, you can tweak where you position the 3 links and even improve upon whats done here. See this site for your plug in numbers, etc. Got some interesting info there too.

    http://home.earthlink.net/~whshope


    [​IMG]
    [​IMG]
     
  20. Bass
    Joined: Jul 9, 2001
    Posts: 3,347

    Bass
    Member
    from Dallas, TX

    Sodas....that is almost exactly what I decided to do. In fact I ordered all the tubing and rod ends and stuff yesterday. After a LOT of measuring and headscratching, I decided to go with a 3 link setup with a fairly short wishbone on top of the differential housing, and 2 parallel lower links. Mainly for floorpan and exhaust clearance. The panhard shouldn't be necessary with the wishbone on top for triangulation.

    The design will allow me to run the bags in front of the axle and on top of the lower links for a better ride and more lift...and as an added bonus, I'll be able to run the exhaust over the rearend with plenty of room for the bags

    I'll post some pics of the finished suspension work at the end of next week.

    El Polacko....I'll be giving you a call in the near future....I still have another car to do that I think will be a good candidate for the torque arm. Thanks.

    -Brian
     
  21. Excellent work, Bass. Next time I'm in the D/FW area, I'd like to stop in & check out your place.
     
  22. twofosho
    Joined: Nov 10, 2005
    Posts: 1,153

    twofosho
    Member

    Remember, if you run the Pontiac style u shaped control arm, you can lower the rear roll center appreciably by using it as the lower link(s).
     
  23. scottybaccus
    Joined: Mar 13, 2006
    Posts: 4,106

    scottybaccus
    Member

    It looks like I am fashionably late, as usual, but anyway..

    Brian, Stop with the trick construction already. You're stomping all over my ego here. (nice work..... again...)

    Take a look at this. I found it very enlightening.

    http://www.totalcontrolproducts.com/rearcoil.html
     
  24. Tony Travers
    Joined: Jan 11, 2010
    Posts: 63

    Tony Travers
    Member

    Howdy I know this is a long time ago but how did this work out and do you have any photo's
    Cheers
    Tony
     

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