I'm running out of room for my rear links because I want a managable wheelbase. Does anyone have experience with 13" or maybe even shorter 4 link bars? I will drive this car, not trailer it, so the links will have to work not just hold the axle to the car during shows.
Its been done, but I dont recomend it, there will be extreme changes in the arc of the rear (for and aft) and pinion angle will also suffer due to the short links. No problem though,, I'm sure someone will come on and tell you that they've done it and run it several million miles like that and it was fine. I wouldnt but what do I know?
I would think it depends on how much verticle travel you are going to allow it. I just measured a link on a Volvo rear end in the garage and it's 16" and Volvo tends to be "conservative" in it's engineering and it has a lot of travel so I'd thin 13" with short travel and enough driveshaft yoke travel to handle the arc caused movement it would be ok. Pinion angle won't change as long as upper and lower link are the same length as each other, just the weelbase. Front suspension A arms work at less than that length, just in a different angle to the frame. ETA It WILL lean steer! Because on a lean one side may shorten wheelbase mor than the other, turning the (live?) axle in the chassis.
mine are 11 inches cause thats all the room there is,,its a short wheelbase high power car....most likely it will torque steer... its not finished
If my math is correct I believe my wheelbase would shorten 5/8" if it moved 4" one way. Not that I expect constant 4" compression, I just plugged in the maximum.
with a parallel 4 link the biggest problem you are going to have with links that short is bind. even with high misalignment heims it will not take much more than a couple of inches of roll before all the linkage is bound and you effective spring rate goes to infinity. The 4 link in my drag car has links that are not quite 24 inches long and I can only get one rear tire about 3 inches off the ground before the other tire is off the ground. And no, I am not running out of shock travel at that point and I am not running a rear anti roll (sway) bar. You will not run into this problem if you are using a splayed 4 link, however the drive shaft will have considerable side to side movement in an arc when body roll is induced.
I also believe that the separation of the links east to west will be a big factor in this. The closer they are the faster you approach your angle of bind. Mine will be 44" apart so I should'n get much angularity out of the tires raising. I would agree that on a drag car this would be more of a problem.
Like the little German guy said on Laugh-In, VERY interesting. Only 3" drop before a bind? That sounds like just a pot hole sized drop to me. Is the bind related to the type of rod ends? Do some rod ends allow for more twist? Or what? Not being an engineer, and wanting a 4-bar rear, I'm concerned as I'd like at least 6" of vertical travel on my diff... Gary
Certainly! Not all rodends are created equal...but for a street car I'd do my best to use rubber bushings instead of machined rod ends anyway. They last, they dampen NVH and they allow a large degree of controled misalignment and rotational flex in the arms. Theres a reason OEM uses rubber bushings and it isn't just cost either. Its durability. I don't think 13" is too short but its getting close! You'll need to pay attention to your arm angles and spring stiffness to control self-steering of the rear axle. Play with it and you'll get it...or then again, there must be a suspension angle plotter available on the web or as software that can do it for you.
My plan right now is to set it up as a triangulated 4 bar system with the bars perfectly parallel top to bottom. I won't race the car so I don't really care to invest too much time in dialing in the links for anti squat or anything like that.
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