HISTORY OF THE ROLLER TOPFord selected the original roller bearing top mount from the Mk2 Cortina 1600E parts bin. It's function was twofold - The tapered roller bearings can take large axial forces (ie. they are good thrust bearings). Such forces are often experienced upon ‘bump' mode of a Macpherson strut, but they also exhibit low friction under thrust, thus offering low steering effort.
Such a combination was also felt desirable on the performance RWD Escorts, especially the heavy Pinto engined vehicles. At the finish of production of the Mk2 Escort, Ford instructed it's rubber moulder to produce 5,000 more units then cease production. The 5,000 quantity lasted only a few years and in the mid 1980's Rally Design laid down new tooling to continue production to a similar specification to the OEM units using a tapered roller bearing.
This continued until the sole bearing manufacturer demanded bigger production volumes at increasingly higher costs which forced us to transfer to using a spherical type bearing. The spherical bearing had the advantage of being able to accommodate large castor/camber angle changes but could never offer the low steering effort of a taper roller bearing.
So Rally Design can now offer two styles of roller top - this latest OEM style (RD348): ideal for OEM vehicles. A faithful copy of the original taper roller bearing top mount able to accept high axial load, but also with low steering effort. The Hi-angular style (RD300) : ideal for vehicles which are subject to high degrees of either castor or camber angles, but with a higher steering effort.
Both styles are suitable for motorsport applications, selection dependent upon the degree of castor/camber angle changes experienced on the vehicle. Note, The rally friendly encapsulated rubber roller bearing mount offers a degree of shock compliance, protecting the bodyshell. Solid aluminium top mounts are really only suitable for smooth race car useage.
David Elderfield - Managing Director, Rally Design Limited
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