I am trying to figure out what type of rear suspension to run in the back of a z'd and channeled to death Model A coupe that I am working on. I had a pair of Pete and Jake ladder bars. But they are too long and stick up alot higher than the floor will be. The only solution I can come up with is a very short 10" to 12" four bar set up that I would Have to make up. I do not like the look, but this thing is going to be so low you would need a mirror to even see it, and the fact that this car is all about speed maybe the four link maybe the better choice with a pair of coil overs and give up on the 40 spring and ladder bars......Any one have any pics of a super short 4 bar set up or any other ideas? The frame sits too low to go with a split wishbone to the out side of the frame.......Littleman
A little bit of trig tells us that if you have 3" of suspension travel (not much!), your rear will move just under 1/2" (a lot!) with a 10" bar... For 3" suspension travel: 10" Bar = .440" 12" Bar = .369" 24" Bar = .186" 30" Bar = .149" 36" Bar = .125" 40" Bar = .112" That's why most bars are 30" or longer - you've reached the "bend in the curve" of the logarithm. Shorter bars have greater fore/aft movements for a given arc (suspension travel) than longer bars.
same problem i had littleman, I built my own short triangulated four bar out of DOM heavy tube, but still used a transverse A spring. heres a hint-toyota landcruiser shackle bushes fit perfect inside a standard tube size,(think it was 40 nom. heavy gas pipe) and are cheap,for making the ends.set of 8 bushes is about $40 AUS. whole setup cost about 200 in bits, the aftermarket kits are about 800 here.think i posted this before, but heres the only shot i have.
I agree with Ernie. Four bars should be 18 inchs or more so you get the right amount of travel.I would suggest to use a four bar but still use the 40s spring so you kind of keep the look. I dont know if you know how to set up a 4 bar correctly but the bottom bar needs to be horizontal and the top bar needs to be angled so it is pointing directly under the front wheel this will make sure you get perfect traction. Also you will need a panard rod or you can traingulate the four bar.
jeez im a flukey bugger. just went out and checked the angles according to jungle jim,spot on! Sometimes my ability to accidently do the right thing amazes me. happened a lot with this chassis...like steering box/engine clearance,kick up height, stuff like that.just seemed to fall into place.
all i know about 4 link suspensions is related to drag racing a pro mod type chassis, however i dont know squat about street car 4 bar setups. it would seem to me that the transverse spring would act just like a panhard rod / track locater right? i like the idea of the triangulated upper bars, seems like a good idea. can all 4 bars be the same length & run parallel? also, since optimum traction is not a priority on a street car, would you not want the lower bar to run slightly uphill so when a load is applied (your fat ass) inside that it levels out? i am planning on building a slammed a or t next spring and can use this info as well.
Thanks for the math, Flat Ernie very useful info!!!! Thanks for all the pics. I've even thought of solid mounting the rearend, but that would be one harsh ride not to mention would probably shear all the bolts off eventually. Thanks again, Littleman
You have the same problem I faced when building my "T" modified. The name of the posting was "new modified ready for spring"--dated 12-25-04. I used a 3 bar + panhard bar.One bar mounted from the dr.side frame rail to the bottom of the dr. side rear axle, another bar mounted from the pass. side frame rail to the bottom of the pass. side rear axle, and the third bar goes next to the drive shaft, in the drive shaft tunnel, from the trans. mount to the top center of the rear axle mounted to the center section. I hope I made it clear.
Well....when Chevy faced the same problems with the Chevette and the 3rd gen Camaro they went with a center mounted torque arm. The arm was free to move <-> but not up and down. The two radius arms mounted to the outer ends of the axle held it in proper location front to rear. YOUR biggest issue will most likely be roll steering due to the shortness of the radius arms. You could get some info on actually putting this effect to use but maybe the best route to take would be to do away with it entirely and go for neutral handling. Stock cars...(not NASCAR)...have used a suspension that might work for you. Basicly they have a center ladder bar controlled by a "3rd coilover" to aid traction. (you don't need that part) but to give O roll steer and allow the ladder bar to act on the 3rd coilover they use a Watts link at either end of the axle housing. They actually use the housing tubes themselves as the center pivots for the Watts link but you don't NEED to do that. A simple set of tabs on the front or rear of your stock housing would do the same thing for a street car. (Your just locating the axle front to rear...the center torque arm will control rotational forces) Just be sure to allow enough room for the Watts pivot to have it's needed movement and use a rubber or urethane bushing as the Watt center pivot. You could mount the lower Watts links toward the front to keep them low and as long as possible and the uppers could go to the rear chassis section ( I know...tight on an A!, but you could do it by running the frame back to the rear body/bumper area) and be as close to the same length as the lowers as possible. Now you couldn't have unlimited suspension movement with this configuration, but it would get you 3 or 4 inches easily enough and although it seems complex...it really isn't. I'd suggest you check out stock car sites to get some idea of what I'm talking about. Oh, and a Panhard or another Watts link will be needed to control side to side movement. (Use a long, low Panhard bar...simple.) BTW...no reason the Watts links couldn't be fabbed from junkyard parts...don't need to go with Heims...just get some old OEM Panhard tubes or import rear links etc. Your not passing torque thru them...just locating the axle. The center ladder bar will be doing that part...and is free to move at the front by use of a simple bushed shackle, a Camaro torque arm mount, or a sliding tube setup. I'd go with a crossmember mounted shackle...its foolproof, strong and easy to mount to the frame itself.
[ QUOTE ] SKR8PN, who made that red chassis? Looks nice. [/ QUOTE ] Blownolds.......the main frame/suspension is an Art Morrison piece,and the rest of the brackets and mount tabs and such,are owner fabricated.
Or how about using a setup like a Land Rover 4x4? They have two lower arms...bushed to the frame and have two inline rubber bushings where the arms run UNDER and attach to the axle housing. Both bolts for the axle attachment are BELOW the housing, as are the arms themselves. The bushings allow the arms to twist independently of each other, thus allowing the axle to twist or lean in a turn etc. Could mount those low enough to clear your floor....!!?? No upper links are needed! You could make your own arms from 2" square 1/4" wall or even roundup a set of forged Land Rover arms to give a stock sorta look. A super strong split bone setup is what it actually is. With no twist binding issues. Great traction too....
Mine are pretty stumpy, but I reversed the axle plates, so the pivot point is behind the axle, allowed me a few more precious inches on the bar length. If I did it again I would make the bars a lot further apart in the vertical direction:
Another way of explaining my 3-bar set-up.The 2 lower bars parallel the frame rails [sort of like traction bars].The upper bar runs from the trans mount crossmember back [through the drive shaft tunnel]and mounts to the center of the rear axle. Up and down the bars are spaced apart the same as a 4-bar set-up. All 3 bars are about as long as the drive shaft. I used 6 heim joints. I used a model 'A' spring. Where normal ladder bars go I dropped the seat to the bottom of the frame rail on the drivers side,and on the pass side sits a 8 gal. gas tank,with seat cushion on top!
a boner, got any pics? What you've built sounds interesting. Since I built mine done I've thought of a load of different, and better, ways to do it. Can't afford the time to keep swapping and changing as I've been on it nearly three years now.
Jeeze, I keep having to post this pic. Like Hackerbill said, similar to a Firebird. I too had floor space problems.
I've run 'em as short as 18" but when you get short you really have to work with it to get a decent frame geometry. If I had to go much shorter than that I'd look for a different solution. The one's I had on the F-Truck that Scarliner now has are 30" much more forgiving. You might try setting it up like an older Chevell with your top bars jutting out from the pumkin' and longer bars on the bottom. Or maybe a 3 link setup with your top bar running up the tunnel.
Morrisman - how much up travel do you have before the bar contacts the axle tube on that setup? I would recommned a torque-link or 3-bar similar to what others have posted... Otherwise, I think you end up getting into more "exotic" stuff like watts linkages, etc.
Have you thought about 1/4 eliptical springs.....they are old school, short, ride great, easy to install, adjustable, and you can pick them up over the phone from Posies if you don't want to go to the trouble to make em'.
Going to give this a shot. '68 Galixy rear shortened for 55" flange to flange.The stock trailing arms(22" long) and the top torque arm(14"long). Top arm has an adjustment for pinion angle. The trailing arms will mount to the frame below and outside the frame rails. I'll incorperate the rear of the X- member to start off at that point to tie everything together and trianglate the forces that be.
Another pic. Going to mount coil overs to back of lower trailing arm mount.Factory mount for panhard bar was off of the top torque arm mount, don't think I'll be able to use it because of coil overs in the way. I'll go with something off the top of the rear to the side. I kind of think the stock parts get away from the new look of a 4-bar set-up.And Auto Zone's got the bushings.
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