Front Upper A-arm Design Change

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HydroJim
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Front Upper A-arm Design Change

Postby HydroJim » 06 Nov 2018, 14:44

Originally, it looks like the front upper A-arm used a Mazda tie-rod end as the upper ball joint. Then, the design ended up switching to a bearing cup using a pressed in spherical bearing.

What was the rational for this change? What was wrong with using the tie-rod end?

The negatives I see to the spherical bearing are the use of a straight bolt in the upper spindle attachment point instead of the tapered mating surface of the tie-rod end. How is the tolerance handled when using a straight bolt?

Midlana1
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Re: Front Upper A-arm Design Change

Postby Midlana1 » 06 Nov 2018, 17:25

What's the book say?...

A tie-rod is not designed to be used in bending, and it was being used in bending. Was it a hazard? Probably not, due to its sheer size, but I chose to go with a spherical bearing and not have to worry about it.

Regarding the bolt tolerance, again, the book discusses this; since the hole is reamed, the tolerance is ~0.001".

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rennkafer
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Re: Front Upper A-arm Design Change

Postby rennkafer » 07 Nov 2018, 07:52

Midlana1 wrote:What's the book say?...

A tie-rod is not designed to be used in bending, and it was being used in bending. Was it a hazard? Probably not, due to its sheer size, but I chose to go with a spherical bearing and not have to worry about it.

Regarding the bolt tolerance, again, the book discusses this; since the hole is reamed, the tolerance is ~0.001".


If you use proper AN bolts (and you should be on something this critical), your fit is quite good. A spherical bearing with a bolt through to the upright is pretty much standard procedure on race cars.
Bill J


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