I have upgraded the suspension with new multi leaf rear springs,larger police car torsion bars,kyb's on all 4 corners,and front and rear sway bars.1" front 3/4" rear. The rear of the car oversteers badly.It may be too stiff in the rear but I would like to know if anyone can suggest some specs for a performance alignment.Something for better handling w/o uneven tire wear.
Joined: Fri Mar 13 2009, 11:21AM
Location: San Marcos, CA
Posts: 713
IMHO, go up to a 1 1/8" or 1 1/4" front sway bar I don't think that an alignment will hardly make any difference in the ballance of the car oops, sorry about the double post! <span class='smallblacktext'>[ Edited Sun Aug 16 2009, 05:56PM ]</span>
I may need to loosen up the rear some.The turn in is quick(upgraded steering box also)and the front stays flat.The rear comes around and you have to correct.With the front being so quick(steering)I end up over correcting it seems.
Hi 496, You're right about there being too much rear roll stiffness. The rear tires are being asked to do too much with the mass in relation to the rest of the setup. Here is a short list of things to decrease oversteer; Stiffer front bar or softer rear bar Stifffer front springs or softer rear springs Smaller front tires or larger rear tires Lower front tire pressure or higher rear tire pressure Weight distribution more biased to front-(I know-don't do it) Front alignment for less grip! (Don't do it) If you look at a Bugatti 35, you wonder what Ettore was thinking with the wildly positive front camber. He wasn't really unenlightened. He was combating period race vehicles propensity to oversteer by taking out front grip, and ended up with much nicer neutral handling that helped win many races. But you don't want to give away front grip, you want to balance everything so the rear does it's job. Soooo.....What dia. are those front T-bars? You could increase front roll stiffness with the Just Suspension or Firm Feel pieces. It would be easier and cheaper to increase the front bar size as mentioned in the post above. What tires do you run, and what air pressure? Is the wear nice and even across the tread? Try dropping a pound at a time from the front tires while adding a pound to the rear and see if you can find a balance while still maintaining reasonable inflation pressures. What wheels are you running also? Perhaps more rubber out back? Don't know what you've got or would be happy with. Return the leafs for a slightly less stiff set? OK, the easiest fix, and one that many would agree with is to just pull the rear bar. Many swear by them, but many just swear at them as well, and say they are unecessary. Some specs for front align without trying to fix the rear prob. with it; Dial in around 3-deg. positive caster if you can get it. Shoot for 1-deg. negative camber. 1/2-deg. to 1-1/2-deg. for a range. 3/32" toe-in is good. You can go 1/16 to 1/8" for a range. You prob. knew all this stuff, but maybe it will help. A couple of good books on handling are Fred Puhn's "How to make your car handle", and the old "Mopar Suspensions" by Mike Martin-if you can find a copy. They get heavy into roll couple, CG, instant centers and lots of stuff that may help you, but it's better to buy the book than to try and write an epic on here. Good luck and have fun!
Joined: Fri Dec 22 2006, 08:41PM
Location: Warrenton, Virginia
Posts: 1366
Glad you added your observations with the rear sway bar.
I've upgraded the suspension on my 67 300 considerably and I'm quite pleased with the results. I have NOT added a rear sway bar yet but I've gone so far as to have Firm Feel make me one of their 7/8" rear bars.
Here's my set up:
Just Suspension torsion bars 1.16" diameter Firm Feel front sway bar 1 1/8" diameter Just Suspension heavy duty strut rods, tie rods and ends. Just Suspension tubular upper A arms Firm Feel level 2 steering box
KYB shocks on all 4 corners 245/70 x 15 Yokohama Avid S/T tires all around on 15 x 7 wheels 30 to 32 psi air pressure all around
ESPO rear springs which are probably just replacement springs for a 67 300 and not heavy duty or anything.
Custom alignment: 4.5 degrees positive caster 0 degrees camber 1/8" toe in
The handling is decent and the ride is just slightly firm under most circumstances. I think the KYB's are a bit too soft....car easily bottoms on speed bumps and actually feels a bit too soft. So I'm thinking of going to the Bilsteirn shock Firm Feel offers.
Yeah, you know there's ways to make it work with it, and I threw all that other stuff out there, but the easiest way to make it more driveable at speed is to just pull the bar.
Joined: Fri Mar 13 2009, 11:21AM
Location: San Marcos, CA
Posts: 713
I set up a (sorry) '69 Roadrunner with 243"# torsion bars, 1 1/8" front sway bar and a 3/4" rear sway bar and KYB shocks, it was amazing. It handled as good or better than my friend's '70 T/A. The most important thing to balance is front to rear stiffness proportion. Too stiff in the front, it pushes too stiff in the rear it will over steer. The drifting guys run 800�# springs in the rear!
Joined: Fri May 18 2007, 04:59PM
Location: Vegas
Posts: 82
I tried a couple different sized rear sway bars on my 69 300 vert , and found that NO rear sway bar was best for handling. As a side note, I bought both rear bars used, and the sellers said that they did not like them. I should have taken there advice.
I'm not saying that better handling could not be achieved with a rear bar, but perhaps you should try removing the rear bar before you spend a bunch of money on bigger front bar, etc.
If it's worse, just hook it back up, but I'm guessing that it will be better. That's my experience anyway
Joined: Fri Dec 22 2006, 08:41PM
Location: Warrenton, Virginia
Posts: 1366
I am planning on having my Firm Feel rear sway installed eventually. Not right now though...she handles and ride pretty good. My car is a convertible, so I want to get some subframe connectors made up and installed before doing any more suspension mods...... !driving