Swapping to rack and pinion steering
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Many cars suffer from poor turning radius after an R&P install. There are 2 basic reasons. Either the rack was placed too far left and interferes with the wheel, or no adjustment was made to the steering arms. On a typical RB type steering box the pitman arm has a “throw” of 7 inches, side to side. It is usually connected to steering arms effectively measuring 7 inches long. (The 7 inches is measured from the center of the steering arm mount, where the king pin or ball joint pivots the spindle, to the center of the outer tie rod where the steering pivots.) Typical racks (Cavalier) have 6 inches of throw and originally connected to the upper strut in a manner that represents about 5 ½ inches from center of the strut to the center of the tie rod. Connecting the rack to the original arms causes a loss of nearly 20% of steering angle. It is strongly recommended that this be dealt with before installing the rack. | Many cars suffer from poor turning radius after an R&P install. There are 2 basic reasons. Either the rack was placed too far left and interferes with the wheel, or no adjustment was made to the steering arms. On a typical RB type steering box the pitman arm has a “throw” of 7 inches, side to side. It is usually connected to steering arms effectively measuring 7 inches long. (The 7 inches is measured from the center of the steering arm mount, where the king pin or ball joint pivots the spindle, to the center of the outer tie rod where the steering pivots.) Typical racks (Cavalier) have 6 inches of throw and originally connected to the upper strut in a manner that represents about 5 ½ inches from center of the strut to the center of the tie rod. Connecting the rack to the original arms causes a loss of nearly 20% of steering angle. It is strongly recommended that this be dealt with before installing the rack. | ||
Changes to the steering arm can affect the steering geometry and introduce bump steer. So, if you are going to address this issue, (some people don’t) do it before the rack install. | Changes to the steering arm can affect the steering geometry and introduce bump steer. So, if you are going to address this issue, (some people don’t) do it before the rack install. | ||
| − | There are two acceptable methods of dealing with this issue. The preferred method is to replace the steering arms with shorter ones. On the 41 Pontiac upgrade covered in the wiki “37 - 57 Buick Olds Pont suspension upgrade” we were able to replace the original 65-70 Chevy steering arms with a set from a | + | There are two acceptable methods of dealing with this issue. The preferred method is to replace the steering arms with shorter ones. On the 41 Pontiac upgrade covered in the wiki “37 - 57 Buick Olds Pont suspension upgrade” we were able to replace the original 65-70 Chevy steering arms with a set from a 55-57 chevy. |
| − | [[Image: | + | [[Image:55/57_arm_vs_65 chevy_arm.jpg|frame|none|Chevy 7inch/chevelle 6 inch.]] |
There is a difference in mount width between the BOP arms and Chevy arms, so they won’t work on BOP without the Chevy spindle upgrade. If you are unable to find shorter arms for your application, bending the originals is the next option. You will find mixed opinions on this issue. Some will insist that heating and bending steering arms compromises their structural integrity and should never be done. Others warn you to be sure they are forged and not cast arms. Bending forged arms is OK, bending cast is not. | There is a difference in mount width between the BOP arms and Chevy arms, so they won’t work on BOP without the Chevy spindle upgrade. If you are unable to find shorter arms for your application, bending the originals is the next option. You will find mixed opinions on this issue. Some will insist that heating and bending steering arms compromises their structural integrity and should never be done. Others warn you to be sure they are forged and not cast arms. Bending forged arms is OK, bending cast is not. | ||
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