Lil Demon
master
Reged: Apr 02 2007
Loc: Rocklin, California
|
|
I am getting so sick of this front end that I cannot stand it. To fix my previous bump steer issues, I spent money and bought new steering arms from LRT, adjustable tie rod ends, factory spindles, and put coil overs on it.
The car aligned great for the first time since I've owned with no issues going forward or backward - woohoo - problem solved and money well spent. Not so fast...........
Today - the car goes straight as an arrow down the track, I cross the stripe and let off and hit the brake - vicious - and I mean vicious front end shake. So bad that I couldn't see - I wanted to pull the parachute handle but was afraid to let go of steering wheel - it was that bad.
I went back to Les Schwab where we aligned it last night. The caster is at +8 (as much as it can get), the camber is at -1.8, and it was neutral on the toe.
Guys with fast(I know that is relative) back half-4 link cars - what are your front settings? Others - any recommendations?
--------------------
|
MR_P_BODY
Master
Reged: Jun 13 2003
Loc: Romeo MI
|
|
I run about 10* caster, 0 camber and 0 toe in. It
sounds like you have something flexing.... were your
wheel bearings tight/snug
EDIT
Also Bill was the front alignment done with the body
up 1"... check your toe in at 1" up... it could be
going toe out and thats not good
--------------------
W-9 9.08 @ 149.6 NOW ON E-85
Mike "Raff"...(180)Watching over us
Edited by MR_P_BODY (Sat Feb 21 2009 11:27 PM)
|
dthemi
1539whp Hemi
Reged: Oct 31 2004
Loc: back in Georgia
|
|
Yeah, I'd have some toe in it. At least a 32nd, but I'd try a 1/16 to see if it helps. I've never had luck with neutral toe on anything, even tube cars.
--------------------
|
540dust
mopar
Reged: Nov 15 2005
Loc: Kokomo, IN
|
|
Got 8 caster, 0 camber, and less than .0625" toe in. Do you have an aftermarket front end ?
--------------------
'71 540 Duster
9.13 @ 146.67 // 5.72 @ 118.77 1.26 60'
http://www.cardomain.com/ride/592869
|
Al_Alguire
master
Reged: Jan 20 2003
Loc: Fairfield, CA
|
|
I agree..For me 1/16"+- has always worked well in a back half car. You might also just give the front a once over, always a good idea. Never checked that driver side bearing at the track.
--------------------
ALGUIRE MOTORSPORTS
"I am not ashamed to confess I am ignorant of what I do not know."
Marcus Tullius Cicero
Wanted Aspen or Volare Wagon
|
Sport440
super gas
Reged: Jan 20 2003
Loc: Canton, Ohio
|
|
If its running straight as a arrow down the track and going into shimmy on decell, you still have some Bump steer or some kind of flex issues or both going on.
Your numbers on the caster are fine but why the -1.5* on the camber. Id want that at 0*
Whats the rest of the front suspension steering setup. I take it that it has a R/P in it. mike
|
Chuck@Best_Machine
Engine Builder Extraordinaire
Reged: Jan 21 2003
Loc: Farmington Hills, Mich
|
|
I had the same problem, the LRT lower arms are flexing
--------------------
All Motor 65 Coronet 572 B1MC Single 4500, Cast Intake and Mufflers 8.58 @ 156.2 True 10.5 No Wheelie Bars, No Excuses !! AM/1965
www.BestMachineRacing.com
Now located @ 20780 Parker St, Farmington Hills Mich 48336 (248)987-6038
|
Chuck@Best_Machine
Engine Builder Extraordinaire
Reged: Jan 21 2003
Loc: Farmington Hills, Mich
|
|
#2
--------------------
All Motor 65 Coronet 572 B1MC Single 4500, Cast Intake and Mufflers 8.58 @ 156.2 True 10.5 No Wheelie Bars, No Excuses !! AM/1965
www.BestMachineRacing.com
Now located @ 20780 Parker St, Farmington Hills Mich 48336 (248)987-6038
|
Chuck@Best_Machine
Engine Builder Extraordinaire
Reged: Jan 21 2003
Loc: Farmington Hills, Mich
|
|
#3
--------------------
All Motor 65 Coronet 572 B1MC Single 4500, Cast Intake and Mufflers 8.58 @ 156.2 True 10.5 No Wheelie Bars, No Excuses !! AM/1965
www.BestMachineRacing.com
Now located @ 20780 Parker St, Farmington Hills Mich 48336 (248)987-6038
|
dthemi
1539whp Hemi
Reged: Oct 31 2004
Loc: back in Georgia
|
|
The flex would make it go into bump steer, some generous toe would make it better I think. I know it's a band aid, but it's always been a cure all for the brake watoosie.
--------------------
|
Edge
enthusiast
Reged: Feb 23 2006
Loc: Alberta Canada
|
|
Had the same problem with the LRT front end on the duster. Also found some cracks in the lower arm. Repaired arm and it is now acceptable.
--------------------
76 Duster
work in progress
|
Lil Demon
master
Reged: Apr 02 2007
Loc: Rocklin, California
|
|
My front end is very bastardized. Stock front clip, DARE K-Frame (on it when I bought it - I didn't know), Magnum Force tubular uppers (non-adjustable), Stock LCAs, LRT steering arms, Flaming River Pinto R/P, Aldan coil overs.
Looking at the vids - the wheels are definitely toeing out when it lifts them in the air.
So - if I set the toe at ride height +1" - do I set it at 1/16" in?
The negative caster I think may be the best it can get - not sure. I may need adjustable UCAs 
--------------------
|
dthemi
1539whp Hemi
Reged: Oct 31 2004
Loc: back in Georgia
|
|
Yeah, make it pigeon toed, I'd get my fattest buddy to sit on the front end after you set it and roll it forward about 5 feet and check it there too. I know the brake load pulls the arms back and you can't really simulate that, but it will let you know about how it travels.
--------------------
|
MR_P_BODY
Master
Reged: Jun 13 2003
Loc: Romeo MI
|
|
Quote:
My front end is very bastardized. Stock front clip, DARE K-Frame (on it when I bought it - I didn't know), Magnum Force tubular uppers (non-adjustable), Stock LCAs, LRT steering arms, Flaming River Pinto R/P, Aldan coil overs.
Looking at the vids - the wheels are definitely toeing out when it lifts them in the air.
So - if I set the toe at ride height +1" - do I set it at 1/16" in?
The negative caster I think may be the best it can get - not sure. I may need adjustable UCAs
Yes set the toe at 1/16 in at 1" up on the body. I
assume you just made a error in saying caster instead
of camber but you would be better off with adjustable
UCA's
--------------------
W-9 9.08 @ 149.6 NOW ON E-85
Mike "Raff"...(180)Watching over us
|
540dust
mopar
Reged: Nov 15 2005
Loc: Kokomo, IN
|
|
Does it kinda do this:
http://videos.streetfire.net/video/145946.htm
--------------------
'71 540 Duster
9.13 @ 146.67 // 5.72 @ 118.77 1.26 60'
http://www.cardomain.com/ride/592869
|
Lil Demon
master
Reged: Apr 02 2007
Loc: Rocklin, California
|
|
Quote:
Does it kinda do this:
http://videos.streetfire.net/video/145946.htm
That's what it feels like it is doing when I lift and hit the brake.
--------------------
|
540dust
mopar
Reged: Nov 15 2005
Loc: Kokomo, IN
|
|
Well, that wasnt mine but I did have a Dare and it would do that too. I fought it for a while and finally got rid of it. My conclusion was that it was just not strong enough and was flexing. I don't have the problem with the RMS that I have in it now. In my situation, anytime that you would load the suspension, by braking or hitting any bumps or rough spots, (my home track is kinda rough in the shutdown), it would do just this same kind of shake. I could get off the brakes and touch the throttle a little to unload it and it would go away, this would play hell with you stopping distance though, not a safe situation. You have a PM.
--------------------
'71 540 Duster
9.13 @ 146.67 // 5.72 @ 118.77 1.26 60'
http://www.cardomain.com/ride/592869
|
Lil Demon
master
Reged: Apr 02 2007
Loc: Rocklin, California
|
|
That's what I did on the last two runs - instead of hitting the brakes and lifting, I drug them a bit and slowly rolled off and would get back on it a little to bring it back up. Used all of the runout doing that. Anything shorter and I would have to pull the chute - which would just be embarrassing in a 9.30 car.
--------------------
|
Moparteacher
member
Reged: Jul 02 2008
Loc: Nevada
|
|
The length of the inner-to-outer tie rod must be equal to the length of the lower control arm (pivot to pivot). They must also rise and drop in a parallel plain. Anything different and you get a change in toe as the suspension goes through jounce and rebound, in other words "bump steer".
The outer tie rod can be shimmed toward or away from the knuckle to obtain the parallel travel, but a rack-n-pinion (inner/outer tie rod) that doesn't match the length of the lower control arms gets a little more complicated.
You can heat and bend the lower ball joint arm up and down or inward or outward to help achieve the equal length and parallel, but only so far.
The Mopar chassis book shows you how to graph changes in toe throughout jounce and rebound and how to correct it. It works for any LSA suspension, but with miss-matched parts there may be only one solution and that's to purchase parts that are engineered to work together.
When it's all said and done camber should be at or near zero regardless. Cross-camber and cross-caster should be less than .5 degree. Preferably zero for a flat track. Excessive positive caster will cause rapid wheel shimmy. You need only enough positive caster to maintain directional stability.
One last thing. Excessive positive scrub radius will put an excessive load on the suspension components and could be a cause for flexing and cracking.
Positive scrub radius occurs when the alignment of the upper and lower ball joints meets the road inside of the point at which the center of the tire meets the road.
Positive scrub radius results from using smaller diameter wheels and tires and/or using a wheel that has little or no offset (common with front runners).
Some positive scrub radius is OK; it's the excessive that causes problems.
Good luck
Edited by Moparteacher (Sun Feb 22 2009 01:28 AM)
|
Lil Demon
master
Reged: Apr 02 2007
Loc: Rocklin, California
|
|
Quote:
The length of the inner-to-outer tie rod must be equal to the length of the lower control arm (pivot to pivot). They must also rise and drop in a parallel plain. Anything different and you get a change in toe as the suspension goes through jounce and rebound, in other words "bump steer".
The outer tie rod can be shimmed toward or away from the knuckle to obtain the parallel travel, but a rack-n-pinion (inner/outer tie rod) that doesn't match the length of the lower control arms gets a little more complicated.
You can heat and bend the lower ball joint arm up and down or inward or outward to help achieve the equal length and parallel, but only so far.
The Mopar chassis book shows you how to graph changes in toe throughout jounce and rebound and how to correct it. It works for any LSA suspension, but with miss-matched parts there may be only one solution and that's to purchase parts that are engineered to work together.
When it's all said and done camber should be at or near zero regardless. Cross-camber and cross-caster should be less than .5 degree. Preferably zero for a flat track. Excessive positive caster will cause rapid wheel shimmy. You need only enough positive caster to maintain directional stability.
One last thing. Excessive positive scrub radius will put an excessive load on the suspension components and could be a cause for flexing and cracking.
Positive scrub radius occurs when the alignment of the upper and lower ball joints meets the road inside of the point at which the center of the tire meets the road.
Positive scrub radius results from using smaller diameter wheels and tires and/or using a wheel that has little or no offset (common with front runners).
Some positive scrub radius is OK; it's the excessive that causes problems.
Good luck
You know your stuff - now - how close to Rocklin, CA are you?
--------------------
|
Moparteacher
member
Reged: Jul 02 2008
Loc: Nevada
|
|
Vegas!...OK..North Las Vegas. Autotmotive Instructor for the College of Southern Nevada.
|
Lil Demon
master
Reged: Apr 02 2007
Loc: Rocklin, California
|
|
Quote:
Vegas!...OK..North Las Vegas. Autotmotive Instructor for the College of Southern Nevada.
Cool - I'll come to the MATS a day early and you can teach your students how to fix bumpsteer on the car of an idiot who has mismatched parts - LOL!!! It's a win-win.
--------------------
|
autoxcuda
I Live Here
Reged: Jan 20 2003
Loc: So Cal
|
|
Quote:
Quote:
Vegas!...OK..North Las Vegas. Autotmotive Instructor for the College of Southern Nevada.
Cool - I'll come to the MATS a day early and you can teach your students how to fix bumpsteer on the car of an idiot who has mismatched parts - LOL!!! It's a win-win.
You need a bumpsteer gauge for that too.
There is a scrub radius gauge too. I think you could find one through the circle track suppliers like Longacre. SAI measurement on an alignment rack and some calcs should get you close too.
--------------------
Spring Fling XXIV
April 17 & 18, 2010
Woodley Park, Van Nuys CA
Thrus: Track Day, Fri: Caravan & Cruise, Sat: Cruise In, Wed: Van Nuys Blvd Cruise
www.cpwclub.com ....
Flyer/Reg
|
Chester Burnett
pro stock
Reged: Sep 04 2008
Loc: ms
|
|
Quote:
Quote:
Vegas!...OK..North Las Vegas. Autotmotive Instructor for the College of Southern Nevada.
Cool - I'll come to the MATS a day early and you can teach your students how to fix bumpsteer on the car of an idiot who has mismatched parts - LOL!!! It's a win-win.
 Lil Demon will be your "visual aid" 
|
dvw
pro stock
Reged: Mar 16 2006
Loc: MI, usa
|
|
I will be at the Mats on vacation. I have a pretty good understanding of front suspension geometry. I would be glad to look at the car and go over it with you. I can show you how to measure the components so you can get it right. I don't think we could repair it at the track but I can steer you in the right direction.
Doug
|
VernMotor
Jenni's dad
Reged: Nov 28 2003
Loc: Mt.Vernon ,Ohio
|
|
+8 caster...is too much. I run +4..and 0 on camber ...Just my 2 cents
--------------------
Racing is not a Hobby,But a way of Life
2000-2001 Pacemakers Major JR Dragster Champion
2005 PRO Class Champion
2006 PRO Class Champoin
(Jenni Vernon)
|
toddd
super street
Reged: Jan 21 2003
Loc: British Columbia
|
|
My car does the same thing as the video, but it does it when i launch.
I have a vid if anyone wants to see.
I think I might have found the problem, if it's caused by flexing?.
My question is....Should i be looking for possible component flexing to cure this OR is it the way the front end is aligned?
Thanks
todd
|
340RICK
super street
Reged: Feb 16 2003
Loc: GO BUCKS !!!!!!!
|
|
Your front end alingment is not your prob 
Like stated above its the length of tie rods and postion of the tie rod that will cause bump steer.
I would bet that you also have a K frame that is flexing as well.
The force of the spindle wanting to twist when the brakes are applied is greater than you might think.
Bondo and I went all thru this last summer in Perfecting his steering arms and tie rod ends.
--------------------
Shady Dell Speed Shop 422" W9RP....9.63 @ 139.3
Ricky Bobby Racing/Copy Cat Racing
www.bobsprofab.com
www.shadydellspeedshop.com
|
hot67cuda
enthusiast
Reged: Dec 25 2005
Loc: usa
|
|
While in enginneering school my team was given a problem to solve the 560 benz front end shimmy on decellthat was causing crashes.Thay had 10 deg of positive caster on them.1/16 toe in,0 caster.What we found was on decell when the front end went down was the driver side would drop before the pas side would creating 1.5 difference in caster,<the grocerey cart effect>to corect this we had 2 adjest the upper control arm mounting points for caster gain.The second part is with 10deg of caster setting toe is very hard to do it takes several sweeps on the tables too get it right.
|
1976 Aspen
enthusiast
Reged: Sep 11 2007
Loc: Roseau, MN
|
|
It shakes only whenyou're braking??? Sounds like warped brake rotors too me  Simple fix 
|
Lil Demon
master
Reged: Apr 02 2007
Loc: Rocklin, California
|
|
Quote:
It shakes only whenyou're braking??? Sounds like warped brake rotors too me Simple fix
I'm pretty sure the rotors are not warped, but I'll add that to the list of things to check.
--------------------
|
MR_P_BODY
Master
Reged: Jun 13 2003
Loc: Romeo MI
|
|
Some of the guys here think 8*-10* is too much caster,
what do you think all of the fastest drag cars run.
I have about 10* on my car and I can let go of the
wheel anytime after the torque of the engine is done
trying to twist the car.... even on decell on top end.
Granted its a strut. You have to look at the distance
between the ball joint centerline to the center of the tire...
thats a substantial leverage arm to apply a load
to ANY weak points/parts. In production we didnt
put a dished wheel on just to clear the fender, its
put on to align the loads
--------------------
W-9 9.08 @ 149.6 NOW ON E-85
Mike "Raff"...(180)Watching over us
|
mopar_to_ya
mopar addict
Reged: Oct 27 2004
Loc: south central,Pa
|
|
Quote:
It shakes only whenyou're braking??? Sounds like warped brake rotors too me Simple fix
My LRT does the same thing about midway through the shutdown. If I lift off the brakes and re apply then it usually stops. But if you all are cracking steering arms, that scares me. I thought I was the only one out there with this problem. I guess I'll have to do some more checking.
Rob told me that the new steering arm design would fix any issues, but I never got any to find out for sure.
|
540dust
mopar
Reged: Nov 15 2005
Loc: Kokomo, IN
|
|
Your situation may be different but when I had my Dare the more bumpsteer I took out of it made no difference at all on the shake.
--------------------
'71 540 Duster
9.13 @ 146.67 // 5.72 @ 118.77 1.26 60'
http://www.cardomain.com/ride/592869
|
Lil Demon
master
Reged: Apr 02 2007
Loc: Rocklin, California
|
|
Quote:
Quote:
It shakes only whenyou're braking??? Sounds like warped brake rotors too me Simple fix
My LRT does the same thing about midway through the shutdown. If I lift off the brakes and re apply then it usually stops. But if you all are cracking steering arms, that scares me. I thought I was the only one out there with this problem. I guess I'll have to do some more checking.
Rob told me that the new steering arm design would fix any issues, but I never got any to find out for sure.
I have the new arms and never had this issue before putting them on. I'm not blaming them, just pointing out they could be a contributing factor.
--------------------
|
Lil Demon
master
Reged: Apr 02 2007
Loc: Rocklin, California
|
|
Quote:
Your situation may be different but when I had my Dare the more bumpsteer I took out of it made no difference at all on the shake.
I'ver always had bumpsteer, but never the shakes like this.
--------------------
|
go green
enthusiast
Reged: Nov 10 2007
Loc: Sherwood park, Alberta.
|
|
I had the same problem in my Coronet .
I would have to drag the brakes two times before I could lean on them .
The Wilwood brake pad compound is junk .
I changed to a drag race pad it it help out huge.
I think I got them from strange ?
--------------------
 
7.24 @ 203.7MPH on 10.5
CNC Predator heads, twin Precision turbo Pro Mod 88mm turbo's
|
MR_P_BODY
Master
Reged: Jun 13 2003
Loc: Romeo MI
|
|
Quote:
Quote:
Your situation may be different but when I had my Dare the more bumpsteer I took out of it made no difference at all on the shake.
I'ver always had bumpsteer, but never the shakes like this.
All thats really happened is that with changing some
parts trying to get lighter you have found some weak
points, weather its a control arm or what ever, as soon
as you apply load to the tire on braking its twisting
the front end at the weak point. The guys with the
big off road tires have the same issues but they
cover it up with the damper on the steering... they
just found the weak point also. We already know its
not your alignment(if things dont change or bend)
because its not doing it during your run... this is
induced when you apply the brakes
--------------------
W-9 9.08 @ 149.6 NOW ON E-85
Mike "Raff"...(180)Watching over us
|
68Fastback
super gas
Reged: Jul 13 2003
Loc: Orange County, Ca
|
|
Hey Bill first off be careful. Do you have the old arms still, maybe you can take a step back to get the car stable under braking. Just a question, could the arms be flexing during the run causing resistance and you to scrub speed. Good luck.
|
MoparDonny
super street
Reged: Nov 05 2004
Loc: Port Alberni, British Columbia
|
|
Not that I know ANYTHING about front end geometry, but could some of this be avoided if the brake bias was a little more generous to the rear brakes? Within reason and safety of course.
Just thinking out loud.
Don.
--------------------
'71 440 Challenger 3.91's and 2-1/4 pipes
BEST TIMES!!!!
12.37 @ 107.2 on the brakes... 1.78 60 ft
12.47 @ 110.2 previous run.... 1.86 60 ft
'04 Ram 1500 HEMI
'04 SX 2.0
|
Previous
Search Results
Next
Threaded
Edit
Reply
Quote
