Now THAT'S entertainment! (4 bar front end question.)

Sooo...
I have been working on a glass 33 ford kit. The rear of the car was converted from quarter elliptical springs to coil overs, and a poorly done panhard bar. the car was pretty undrivable. I got that sorted out today, only to discover new exciting torture!

Here's the deal.
when stopping, the front axle is rotating away from the cab of the car-which takes the steering link with it, so the wheel pulls hard to the left. (about a half a turn! Yay!)
under acceleration, it pushes the axle towards the car, making the wheel turn hard to the right. (Whee!)

under both conditions, the car behaves-meaning it isn't actually pulling either direction-unless you are actually brave enough to hold onto the spinnaker. meaning to stop, or go, you pretty much get to rely on blind faith that it's not in a rut or something making it actually turn. (Joy!)
Here's what I found. it has a 4 bar front end, and the bushings, while both new, and urethane, deflect like crazy.
should I build new ones with heim ends?
aluminum bushings? (sounds painful.)
something else? My Idea was to cut the whole mess off and go with a hairpin set up...but this poor guy has had his ass handed to him by the last several mechanics that have worked on it, and the expense of going hairpin may make him wanna just sell it and buy a corvette.
(and reguardless of how street roddy it is, we don't want that.)

suggestions?

 

The correct urethane shouldn't deflect very much. That's the way the make and sell them. If they are new, and the rest of the 4 bar setup is not, I wonder if they used a softer bushing than comes with the kit.

Sounds to me like more than that is going on, though.


PS. Aluminum bushings would rattle fillings out. Could you use the same batwing dealies and the same mounting bracket out back? That would cut the cost way down on going with hairpins. That way you could use rod ends on the back and it would look cooler. I'm sure there is a reason why this wouldn't work, but I can't think of it right now.

 

Stop by after work...We can go for a ride. I am willing to bet we won't make it around the block before you wanna get out and walk back, though.

 

Wow. Hard to imagine urethane bushings flexing that much.

Are the bolts through the rod ends moving in the frame or bending?
Is the bolt diameter smaller than the inside of the bushing (can bushings move on the bolt)?
Is the outside of the bushing too small?
Is the flex only at the bracket, or is it at the bracket and the bat-wing?

I'm assuming this is side-steer, for these symptoms to occur.

Got any pics?

 

That's usually the case when I ride with you. Why do you think I always drive!

I'm not doubting that there is an issue. I just don't think that the correct bushings would deflect so much as to let the axle move enough to turn the steering wheel that much.

 

Make some bushings from a thick piece of teflon. They're real easy to make on a lathe. They work well and last forever! I'd give that a try before scraping the whole thing.
Eddie

 

Camera broke. I took a picture of Buzzard and it hasn't been right since.

 

Why are the bushings deflecting so much? Is it a material issue, or is there THAT much force being applied to them? Kinda sounds, from the way you worded it, that the 4-bar at least looks like it was installed OK.

May be some of those Chinese-sourced bushings.

 

Is the motor/driveline twisting the suspension or is the road forces doing the twisting?

Sounds like new stiffer bushings required, why doesn't the guy want to spend the $250.00 for good quality hairpins if that is gonna fix the problem?

 

They're supposed to be from Pete and Jakes...
and they're for sure Urethane.

the kit's installation is pretty good. smoothed and fulla bondo, I'm sure, but it is in no danger of falling off the car. for a paralell 4 bar set up, Initial groping suggests it's less than paralell, but it isn't misbehaving while driving, just "stopping and going"

This shit is funky like Bootsy Collins.

 

Bump steer ?

Alignment ?

 

Not to state something you might think is obvious, but.....

Is the geometry set up properly? I would doubt that the bushings - even if they were worn out - would cause that much pain. I'm thinking that the axle twists because of the angles the arms are at. Just like a rear axle, they should be parallel, and the axle should ideally sit in a single plane.
The fact that it does this while accelerating makes me think that it's not caused by the bushings, but by the 4 link geometry when the axle travels up and down. This would still happen with aluminum bushings or rod ends.... and could be a "simple" fix with new mounts for the lower bars.

One way to check - put some extra weight on the front and measure the caster (braking) - put it back to ride height and measure (driving) - and jack the frame up a couple inches and measure. Should be the same in every point.

Just a thought....
Kamp

 

Street Beast, isn't it?

 

Initial groping suggests it's less than paralell, but it isn't misbehaving while driving, just "stopping and going"


The arms NEED to be parallel or it will do exactly what you are describing....

 

it's braking and acceleration issues doin the dirty.

primarily, the main reason I would like to fix what he has is the fact that he just spent a small fortune rebuilding the front end-along with these bushings-and he's a bit gun shy after the last two guys finished with him (understandably...he's spent 8 GRAND trying to solve this...and I spotted it by laying next to the car and watching the front end for about 30 seconds.)
Yeah...I don't see how he spent that on a straight axle (mabey they sold him a closet full?) either. but i don't want to say "Gee, mister...all we have to change is EVERYTHING."

 

I'm not a suspension engineer, but I did stay at a Holiday Inn last night...

I'd think trying another 'known-good brand' set of bushings would be cheaper than anything else a guy could do if paying for shop labor.

-bill

 

That's the other reason I'm not going over there. Make Pat ride up there and measure that shit under braking this time. I'm not all the way heeled up from last time.

 

Ah hah! A thinkin' man!

guess what!
the frame sit absolutly flat throughout all of this. no diving, no raising. (mabey...mabey 1/8 of an inch movement which is accounted for by putting the car in gear.)
looking at it, these bushings squish around ALOT.

 

Good call.
you got secrets, mains?
or am I trying to make chicken salad out of chicken shit?

 

Take it completely apart and start again

 

Pick out the gravel and take a lap, Lilly.

 

ha ha ha
As fun as that would be to watch... you can do this in your home garage.... with the car off. The "deflection" is not from the bushings or twist the brakes apply to the axle, it is caused by the weight transfer of the car during braking, causing the front end to sit closer to the ground. Under acceleration, the front end raises (changing the angle of the axle, if the arms aren't parallel). Use a cheapie angle finder and set it against the axle... it should be the same under all conditions.

Kamp

 

You're telling me that when you put the car in gear, it moves 1/8" .... but under braking or acceleration it doesn't move?

 

Is the frame twisting from the torque loads?
Is the front suspension to soft? causing excessive travel and axle shift because of the panhard?

 

That's just it...
the stuff that shouldn't be moving IS.
I can actually watch the rod ends move about 1/8th of an inch, just by shifting from reverse to drive, with the brakes applied-the chassis moves backward and forward, but not up and down.-the axle stays pretty close to where it should, but the bushings allow the whole mess to freak out.

 

no- I am sure it moves more than that under actual braking-
no load from the engine, just shifting it into reverse with the brakes engaged deflects the whole mess.

 

Rule #1 seems to be always start with the obvious.
Rule #2 is start with the cheap fix first. Make sure the bars are parallel then put some known good bushings in there. If those don't fix it, go with Unkl Ian's plan.