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Pontiac of the Month

4 bucket 67's 1967 GTO

2023 December
of the Month

Emblems, Aesthetics & Functional Parts, Part II

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This section will pertain to a functional assembly, the top bearing assembly for MacPherson struts. This assembly is actually one of the many weak links of this system. Why? Well first off the load pieces, (the races) are plastic! As are the lower spring perch part that carries the lower race & the upper locator part that carriers the upper race and locates the assembly on the rubber strut isolator bushing. Secondly for the multi faceted purpose they serve, the ball bearings are almost always to small! This type of bearing is a thrust bearing, but they actually carry as much lateral shear force as they do thrust! Which means they actually need to perform as both a thrust & an axial bearing So these to a lesser degree than the lower control arm of this system, but still enough, contribute to poor handling at best & at worst, torque steer, which can get you in serious trouble!

So I set out to remedy that & make my own setup. To do so I started with the perimeters that I wanted the car to perform to. Car weight, down force in g’s, lateral force in g’s & weight transfer, moment of inertia, CG & RC, stack up height, O.D. size & durability. Plus the bearing also had to be capable of handling both thrust & axial loads. This led me to an industrial thrust bearing, an NSK 51118. The NSK 51118 off of Amazon cost $87 each, you can buy a complete Monroe quick strut for $84 & the quick strut is the strut, spring and all the bearing components, JustA put it in and done.


This is the stock strut bearing, plastic races with uncaged 1/8 diameter ball bearings.


This is the NSK 51118 bearing. High grade hardened steel races, caged 5/16 diameter ball bearings.


Above is the machined aluminum housing to retain the lower bearing race, which also has the spring isolator on the bottom side.

Below is the aluminum housing by itself. This is a lathe machined part.


Below is the upper race shield that retains the upper race & shields the bearing from debris and water.


Below is the assembly, as you can see the bearing is quite well protected. Where as the OEM is a much more open assembly which allows a greater amount of water & debris in. All of these parts can be made on a lathe or you can always take your specs to a shop and have them made!


Edited by Last Indian
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