I just got my T on the road and it drives alright but ,seems to have some bump steer issues but I don't really know if bump steer is the culprit, any body got any info our recommendation of set up for the front... its a 1964 ford truck axle with a home made four link 69 mustang steering box with fore and aft steering,
The difference in length of the four bars to the drag link looks wrong. You need the pivot points to be as close to the same as you can get them. If the length of the arms, four bar versus drag link, are different as yours are you will have bump steer. Do a drawing of a side view of your bars and drag link then use a compass to draw a semi circle from your rear pivot of your four bar and rear pivot of drag link. The semi circle or arcs will cause one to pull or move at a different rate equals bump steer.
ok... that makes sense to me, any way to slow the effects, without completely redoing the suspension?
10 degrees castor seems like a lot...... 6 degrees positive is the usual recommendation for non power steering straight axel setups. Do what "designs" suggested. 4TTRUK
Castor should be in the 6 degree range as 40 said. The bump steer is not controlled by caster. The more caster the harder it is to steer but it the car will try to go straighter, less caster easier to steer but can become dartier. The reason vega steering boxes became popular, cross steer, is it reduces the bump steer when installed properly. You are going to have to make some major changes to LESSON the bump steer. Lengthen the four bars , move steering box forward to line up with four bars or go to cross steering. You will also need to check if your four bars form a rectangle, which is wrong, or a parallala gram which is correct.
unkl ian, it drives straight but when you turn say at 50mph to make a simple adjustment the car darts left and then you have to correct to the right and back to get her straight again real darty I guess.
so upon reviewing the car I found that, the caster is way off at over 15 degrees and that my for bars are a parallelogram, but.....the four bars are each 24'' center to center but the drag link is 36 center to center
I think the angle is more of an issue than length. The drag link should be parallel to the 4 link arms. Raise the box, or lower the steering arm.
That much caster can create issues as well. I hope we're looking at mock up pics - there seems to be an awful lot of rod end poking out each end of the drag link & no jam nuts. The drag link is a foot longer than the four bars = classic recipe for bump steer.
I screwed the tie rod ends in more on the drag link but I don't have jam nuts just yet wotkin on that. no this ain't mock up and my box has a lot of play too, ill make the four bar longer after I get paid no money for DOM right now .
Caster is wrong, steering box loose, jam nuts missing, who knows what other half assed bullshit is hiding in there. QUIT FUCKING AROUND, BEFORE SOMEONE GETS HURT. The ass you save, may be your own.
I adjusted caster and shortened the drag link to 36 inches_// Now then, it turns way easier so thats all great and dandy but bump steer is way worse so..... the easiest things I can do are..... I can make the four bars 29 inches pretty easily (just need more tubing) Now then with 29 inch bars and a 36 inch drag link would that be close enough to lessen the effects of bumpo steer? I'm guessing the closer they are the better now when I do this i'll also raise the box about an inch and drop the steering arm some to kind of split the difference there to get it even I can do that tomorrow thanks designs, unkl, craig, relic stew really appreciate the input
If you would look at the old Pete & Jake's drawings everyone has used for all these years you would see their Mustang/Falcon steering box is mounted right up there under the 4bar bracket. The box is really easy to adjust correctly on the bench so get it up there and follow the factory adjustment procedure. Steering and stopping are all cars need to do correctly to keep you and those around you on the road ALIVE. Make it so.
I'm not gonna get into the "bumpsteer" issue...you're getting good advise and I'd only be rehashing it. The reason I'm replying at all is to say you can't just routinely alter the length of the draglink! You set your wheels straight ahead and set the box rotations to dead center...then you measure the distance between spindle and pitman arm tierod hole centers to get the proper length of your adjusted link. By changing the length to any other measurement your steering box (with the wheels straight ahead) will be off the center "tight spot" thats designed into the box and more likely to have issues like wondering, darting or even death wobble.
Add a panhard bar too. It will keep the axle centered, and eliminate that issue, as a possible cause.
Please, what is your problem?... I'm trying to figure out how to make it right cars been driven all of about 5 times to try to get a handle on whats wrong with it. I'm using the input of more experienced individuals to get a handle on the issue and attack in the most efficient way. Tell ya what, I wasnt born a world class suspension and chassis builder, all the stuff seems to be ok lookin at it in the garage, the steering box seemed ok in the darn garage, yeah I ain't got jam nuts on the drag link son of gun! (and thats a screw up) But how in the heck am I suppose to know exactly what caster exactly what length four bar, without driving it, if you have a magic formula of perfection please share it, cause right now, only way I know is trial and error. and I ain't exactly doing 100mph runs in front of a pre school, mostly been under 30 on a country road with pasture on both sides, I can pretty much tell it won't work in a 300ft stretch... I guess everything you ever built drove perfect the first time...?
ok sorry for the rant trying to be careful trying to do It right got a bit frustrated... yes I understand safety
Number one take a deep breath and relax. Number two try and ask for photos of known 4-bar set-ups that have worked and are proven. P & J's is a good example. Study the pictures and see how yours differs. It's all about geometery and a pictures is sometimes worth a thousand words. As far Unkl , I think he just doesn't want to see you or anybody else get hurt. If you know the set-up ain't right don't drive it. Find somebody around that knows a little more and go from there.
yeah no hard feelings I can see the concern but, its not like im out here being a fool, any how I built it using pictures and things but its my first time, just didn't take that piece of geometry into account. I'm going to have it revised by next week or so.... Plan of action 1. steering box has no adjustment and adjuster is rounded off, I bought this thing "rebuilt" and didn't feel slop til I drove it... 2. adjust drag link to parallel (by splitting difference on box mount and steering arm) 3.add a panhard bar what is the desired design of this? length angle etc... 4. lengthen the four bars to 30" inches 5. add jam nuts (got them laying round somewhere) and re-adjust drag link
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