quote:Originally posted by tyler5:
It seems no really understands my question. mabe i need to state it differently part 1 bump steer. i am up to speed. Part 2 toe out on turns, or S.A.I.(steering axis inclination). the way i understand it, this is the difference between the inside wheel circle and the outside wheel circle as it travels through the turn. the inside wheel cicle or arc is smaller therefore the wheel must turn sharper or "toe out when turning" which will vastly decrease wheel scrub.(see i avoided the eliminate word ha ha)
This is built into the geomerty, but in making the change for bump steer it also changes the rack position to the rear. which will affect S.A.I. Since panteras have a tire scrub issue I thought I would address this at the same time. Thanks for all your input hope i made my a little more clear this time. sorry for the confusion. Larry
The bump steer kit is a patch not a fix. All it does is move the bump steer arc so it's not as noticeable. Bump steer could be nearly eliminated if the steering raq was actually altered (fixed from geometry issues). They used a raq form something else and the outer rods pivot at the wrong width. I am putting in a power steering raq but I am re-welding the raq to the proper width.
If the geometry were perfect you would still get some bump steer from the SAI not being in the middle of the tire patch. Worse with larger tires.
It is true you cannot alter one thing with out changing another. Ackerman is the change in toe during a turn but it will change very little with the shims you speak of. With Ackerman the more the inside wheel turns in a turn the easier it is to turn in a parking lot. I have a 1976 Cutlass with a lot of Ackerman. It makes it easy for grandma to turn the wheel (and it is very easy) but if you jerk the wheel at speed it is actually dangerous.
When I read Pantera articles on Ackerman I knew it was misunderstood when it was improperly addressed with toe in. It was suggested the Ackerman be adjusted for the turn. Since a large track with a large radius needs less movement of the inside wheel some Ackerman was taken out or so it seemed. It was mentioned latter however the toe out in the straight aways made running a straight line squirrelly. With to much toe out in the straight away there was less toe in in the turns. This was not a properly adjusted Ackerman but a misunderstanding of how the whole thing works after reading an article in Hot Rod.
The Pantera does not have much Ackerman compared to most cars which is more suited for track to some degree. Generally going forward or rearward with the raq will alter Ackerman but I don't think the shims will change it much.