OK... getting things situated on the back end of the willys, and have come to a point where i need (yet again ) wisdom from da HAMB suspension guru's basic 4 bar setup, underslung axle brackets (top bars center on axle tube, bottom bars under the tube, coilovers to be bolted to the rear of the brackets. . .) and i'm curious about bar angle from the frame bracket to the mounts on the axle... i know 15* is the "max" downward (frame to axle) angle, and that level 0* angle gives no tire loading on accelleration... so i have tenatively decided to use a happy medium of 7* angle for my front bar mount brackets... any flaws in my thinking? SHOULD i use level ( zero bar angle) pros or cons for each??? thanks yet again fellers T PS...im in the shop as i type this, so if pics are needed, lemme know what you wanna see an i'll snap some T
no one? well, looks like silence is consent. . . so i's gunna start workin w/the 7* setup... worst case it dont work, an i gotta cut a few welds later but i'll lern a few things along the way
Not quite sure why you need the 7 degrees? Mine 4 bar rear is level to the frame & level to the ground. Could be because I have 31'' tires in the rear, or the rake of the frame, which has a 8'' kickup. How bout some pics?
For compliant road use and ride quality, bars level to ground. Race track setups aren't so good off race tracks.
Only my $.02 but I have a book on basic suspension and chassis design, that I've used to build a home made front and rear suspension for a scratch built car. It says the rear 4 bar lower link should usually be at level with the ground. It explains that this is a good compromise between antisquat and something else that I can't recall right now. I hope this helps. The book has been dead, on as far as everything else working out for me.
Here is a link for a 4 bar calculator that gives your roll axis and antisquat numbers. It was designed for the off road guys, but will work for any 4 bar. HTML version; http://mysite.verizon.net/triaged/4linkcalcv15html/index.html Excel download; http://mysite.verizon.net/triaged/files/4BarLinkV3.0.zip Here is the Excel for a 3 link with panhard; http://mysite.verizon.net/triaged/files/3LinkV1.0bBETA.zip Roll axis angle should be near flat. When the body rolls over going around the corner, the axles steer like a skateboard. The greater the angle of the axis, the more it will steer. When the axis points down toward the center of the vehicle it gives roll understeer. Roll understeer is safe, as the car leans over, the axle trys to steer it wider, so the driver instinctively gives more wheel input to maintain the line. Roll oversteer makes it turn tighter as it rolls over. The tighter turn makes the body roll more, so it becomes a "self energizing" input. The driver has to back off the wheel to maintain the line. Oversteer feels "twitchy" with the driver sawing back and forth on the wheel around hard corners. Antisquat is the tendency of the suspension to stiffen under acceleration. More than 100% will actually make the rear rise under acceleration. This puts extra force on the tires increasing traction. Too much antisqat can shock and distort the tires, reducing traction. Ladder bars are a good example of a suspension with high antisquat. On a front suspension this will be anti-dive under braking. The suspension will stiffen and reduce dive under braking. A parallel 4 bar is difficult to build with antisqat, a neutral roll axis and free travel. A better 4 link solution is to angle a pair of bars from the top view, like most late model rear drive cars ('79 up Mustang as one example).
Relic Stew! you da man... excellent links and just the kinda information imma lookin for! MUCHAS GRACIAS!
Pics for those who wanted to see how i am destroying this suspension NO... i do NOT plan on using those wheels and tires... blech. but its all i had on hand 5 on 4 1/2 for mockup
i was just playing with the same suspension from speedway right ? but mine is going in a model a even though it should fit my a has a kick up in the rear, 10 " wide tires tucked in fairly close and that changes everything. So i went over to a buddies shop to check out some factory 4 bar suspensions. I checked a mustang lower arms are 5 deg. up and the uppers are kinda hard to get to but looked close to 2 deg. down. Then checked a GTO lower arms were 2 deg. up but i think the car was lowered a little and the upper arms looked to be pointing down a couple deg. Do you think the tringulated four bar is set up any different than a straight 4 bar?
FiddyFour, Just a couple of things to think about. First is the pinion angle. In one of your pics I see a clamp temporarily positioning the link that will be welded on the rearend housing. Prior to welding you'll want to roll the rearhousing to a position that gives you some amount of neg. pinion angle. The nose of the pig will be rotated downward. 0 pinion angle would be horizontal to the ground. If you think about looking at you car from a side view, drawing a vertical line through the centerline of the rear tire and wheel, as you increase the neg pinion angle, you increase forward bite of the tire. It actually moves the contact patch forward of that centerline or rearward if you raise the nose of the pig. 5* is fine, 2 is prolly not enough. Our race cars use 11* or so, never at 0. Second is the mounting point of the 4 bars to the frame once the brackets are welded to the frame. That I will differ to the Engineers on the Forum.
I was told that the pinion angle should be set to the trans angle . so if the transmission is at 2 deg. then you would set the pinion at 2 deg.down on the rear is that correct sorry fiddy four im not trying to override your post just trying to understand what the right way is to set up a 4 bar Bill
the pinion angle is at or about 5* now, nose up... i havent set that perfectly as of yet, figured that would be easier to tack the front brackets then mess with pinion angle later once i have the engine/trans mounts made and tack'd in place to match the driveline that way...
FiddyFour, I was just trying to suggest positioning the rear axle first so that you have adjustment leeway after the installation is complete. I couldn't see the end of the radius rod that attaches to the axle housing (covered with blue tape) but on the end that I could see (frame end) you don't have a lot of adjustment. The axle needs to be in the ballpark before welding relative to the pinion angle. Any adjustment needing to made after that would be to square the rearend to the chassis. Maybe I should go back and read your original post, but how are you measuring to get the 5*? Maybe you trying to say you have +5* with the nose up. Want you want is a -5* with the nose down. By positioning the nose of the pig down, you're trying to counter act what happens to the rearend housing under acceration. It'll want to rotate up. Make sense?
kahuner, i'm not saying you're wrong, but thats something new to me, at least in that amount. what i've always done is to match the trans. angle, as mentioned. if you're trans. is down 3*, then set your pinion UP 3*, to keep the u-joints at equal angles on each end, too much deviation from equal angles will give you a vibration. depending on the amount of "give" on your mounting of the links, (heim joints, bushings etc.) you can set your pinion down another degree or so, so that under acceleration the give of the bushings will let the pinion come up to the correct angle. this has always worked for me...
A to Z; Caught this link on another post. Once on the site click on the Pinion Angle tab. http://www.quickperformance.com/tech.htm Hope that helps. Kahuner
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