Bumpsteer questions...

Well I know that if your drag link needs to be the same distance from the front axle as your split bones. This is supposed to get rid of your bumpsteer, what is an acceptable distance fore or aft of the radius rod mount but still not have horible bumpsteer? My radius rods will mount about 2" in front of my firewall so I'm guessing my Steering box will be about 6" in front of it. Is this going to cause extremely excessive bumpsteer? Thanks for any help.
-Jesse

 

There was a fantastic article in R&C a few months ago about front suspension geometry, wish I could remember which one... it wasn't more than 6 months ago though

 

Best way I've found is to lay a large sheet of cardboard on the ground. Draw a life size radius rod and then draw where the pivot point on the steering arm will be in relation to the radius rod ( 4 inches in front of the radius rods pivot point in your case, and at what height ?).
Then get a bit of string the same length as the radius rod and fix it to the cardboard at the pivot point of the radious rod. Tie a pencil to the other end of the string, pull it taught and draw an arc where your axle centre line is (draw it about 4 inches long - this is the suspension travel).
Now do the same thing, this time fixing the string to the proposed pivot point at the end of the steeringbox's arm, and the pencil at the centre line of the axle, a bit higher up where the steering arm would be fitted to the spindle.
These two drawn arcs should ideally overlap totally . If you move the pivot point of the steering around a bit you'll see the arcs can be totally different, meaning bump steer. Get them as similar as possible - Doesn't matter so much if they split at the end of the suspensions travel. Sorry if this doesn't sound clear.

 

the two arcs can also be parallel throughout the majority of travel for low bumpsteer, not just overlapping. keep in mind your lateral location of the axle as well, its just another dimension for all things steering to go wrong in. good explanation on the method.

 

Cool thanks for the way to check it. I read the R&C article last night and it said it's the length of the draglink and at the angle it comes off the spindle that affects bumpsteer. It also said that the Mustang boxes with the pitman arm pointing up uses a rear short drag link which causes bumpsteer, a early ford box or an F-1 with it's downward pointing pitman arm uses a long drag link which doesn't have as much. Is that what I read into it or did I completely miss something?
-Jesse

 

As long as the drag link and the 'bones are parallel,
it won't be a problem.

 

I've seen several NICE rods that have very interesting looking steering. In that article it shows a nice yellow 29 on 32 rails with a mustang box, it also has some long split bones with a short draglink(according to the article thats a bad thing). How about some pics of peoples steering/radius rod setups?
-Jesse

 

BTTT

 

Someone here turned me onto this site and it is full of cool info:

http://www.nationaltbucketalliance.com/tech_info/index.asp

I'm going into the "bad bumpsteer arena" with about 24" between rear pivot of hairpins and a Mustang box (arm pointing up). I kept everything parallel. But now I'm concerned about the Ackerman angle as well. The tie rod is infront of axle, using stock spindles.

I'm thinking of fabbing up two new arms to bolt to the top bolt holes of the spindle. I can move the tierod pivot points behind the axle and restore the Ackerman angle.The one on the Driver's side will also incorporate the steering arm pivot.

 

Jesse, interesting post....do another requesting pics of steering....be good to see some variations.
I'll go take some pics now....not digital though so will be tomorrow.

 

Thanks guys. Ya I'll just start another post askin for pics, never know someone may post one.
-Jesse