Re: [Spits] [TR] GT6 Bump Steer
Skip; I remember that book. I used the technique to eliminate bump steer and and another issue on my Toyota Corolla racer. I don't know what happened to the book but I'm going to see if I can find another copy of it. I also had a book (notebook) that had a lot of information on suspension design and formulas for calculating suspension layouts. Greg ** Get a sneak peek of the all-new AOL at http://discover.aol.com/memed/aolcom30tour ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
Re: [Spits] [TR] GT6 Bump Steer
Love the way this list server only puts occasional posts of mine up. Grr! Here's link to a simple picture showing bump steer. http://i44.photobucket.com/albums/f48/fox-trapper/Spitfire/bumpsteer.jpg?t=1187259934 Simply put, bump steer happens when things don't move the same. The suspension arms go around one arc, and the steering rod goes around a different arc. So the tires turn from side to side as the wheels go over a bump. Fact, you cannot eliminate bump steer. Before you jump up and down screaming "oh yes you can", read on. All the focus in this thread on bump steer has been for straight ahead driving. You can eliminate it for that condition...sometimes. But cars turn. As soon as you turn the steering wheel you move the tie rod ends out of position, and bump steer comes right back. The tighter you turn, the more bump steer you get. That's just basic geometry when it comes to cars front suspensions and steering. How bad bump steer is depends on the design of the suspension and the steering components. Something like a Spitfire with a double wishbone suspension and rack type steering gear isn't that bad when it comes to bump steer. A McPherson strut suspension is much worse. Steering box and relay rod types of steering can be remarkably bad, just watch a 4x4 truck twisting around offroad some time to see this one. Bump steer is directly related to suspension motion. The less a suspension moves, the less bump steer there is, no matter how bad the geometry. ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
Re: [Spits] [TR] GT6 Bump Steer
As the suspension travels up and down the toe changes due to the different arcs involved between the upper and lower a-arms and the steering arm. If you really know what you are doing this toe change can be sometimes useful to help steer the car, other times it works against what you are trying to do. I suspect on a street car with DOT tires you might not notice that the wheels are pointing in different directions as you travel down the street, if the bump was really severe maybe the car might be a little darty on bumpy sections. By shimming the rack, or if you are willing to put heim joints on the steering arm instead of tie-rods you can preety much make the tires travel up and down without any change in toe. ___ Christopher E. Crisenbery, P.E. Feller, Finch & Associates, Inc. 2797 Spring Arbor Rd., Suite B Jackson, MI 49203 p/n (517) 783-0710 fax (517) 783-0711 ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
