Sierra Upright and Maxi Bottom Ball Joint Reaming

The forum sites are full of all sorts of rubbish about reaming bottom joints.

Virtually non of it is right.

Before reading on I strongly suggest you read my previous post:

What you have read about using hand reamers should be treated as utter rubbish and potentially lethal.

Here are the problems, how you chose to solve them is your choice but this is what I did.

If you simply reamed out the bottom mount, then the hole dimensions would be too large for the Austin Maxi Ball Joint.

Tightening the clamping bolt so that it pitches up on the ball joints’ taper would cause large stresses in the upright casting. Cast materials are not known for there resistance to this kind of stress.

Reaming Sierra Upright for Maxi Ball Joint

In the above shot you can just see the sides of the standard hole (before reaming) highlighted yellow.

The upright is in Grey and the Maxi Ball Joint is in white.

The Red lines show the result of reaming out the sides of reaming the hole out to 7.15°. As you can see the ball joint can’t be pressed too much further into the hole as movement would be restricted and the rubber dust cover would also be pretty bunched up. You’d also have to put some packing washers under the lock nut.

The diameter of the hole in the standard upright is 17mm. The small diameter of the ball joint taper is 15.5mm and the largest diameter 17.4mm.

It would be simple if the ball joint was bigger wouldn’t it?!

If you simply tightened up the clamping bolt, the the casting would distort and be put under abnormal amounts of stress. Sure there are loads of cars with this modification already on the road and track but does that make it acceptable?

You could push the ball joint further into the hole so that the taper protrudes out of the top but you’d then have to insert packing spacers under the lock nut.

I wasn’t so sure, so I have now got 2 sets of uprights. (I’ve actually got loads of sets!)

Set 1 is just the standard uprights reamed out

Set 2 is the standard uprights with the hole TIG welded up, re-drilled and reamed out on a Mill so that the small diameter of the ball joints taper sits 3mm below the bolt face of the upright. That way the ball joint sits in the centre of the uprights’ casting and it isn’t pressed in as far as the above picture (3mm less).

In set 2 the ball joint sits really snug into the hole and just light friction makes it quite hard to release.

The question is, does TIG welding the upright cause huge changes to the torsional strength of the upright? Are these changes worse that simply tightening that bolt up until things grip?

The guy I got to TIG weld my uprights was a very experienced welder, which maybe why he said they welded extremely well for cast, or it could be a reflection on the quality of the uprights’ casting.

I’ll let you decide which route to take. One day I go with Set 2 then somehow Set 1 comes back out of storage.
Decisions, Decisions…..

Read that previous blog yet? DO IT NOW!
It could save your life.

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