Skip to main content

I  was wondering if anyone has tried machining the rear mounting face of the front upper joints and installing shims in front to increase Caster. If so, any advice? 

Also need a source for bump steer spacers? 

Just wanted to ad that The shear volume of information, resources and knowledge on this website is wild. (Information that  would be lost or could only be passed.on the old way) In the old days it would not be possible for me or others to tackle a Pantera restore/repair without hours of  costly trial and error and phone calls

Thank you all that contribute. Questions bring answers to questions that many of us don't even have to ask. I have read complete postings in some of the directories an learned a  my lot. Working way through them all  

A Greatful  Jerry Sr

Last edited by George P
Original Post

Replies sorted oldest to newest

It takes about 5mm of "machining & shimming" per 1 degree of caster.

Rounding off the OEM caster to 3 degrees, to get to 6 degrees (the pre-Ford spec) if that's your goal, would take 15mm of machining & spacers (5/8 inch). I don't think the ball joint can be "slimmed" that much.

Contact Marlin Jack about the steering rack (bump steer) spacers.

Last edited by George P

Sure have, Jerry. But there's a simpler, cheaper way- by using offset upper front a-arm poly-bushings. Max stock caster is 2.7 degrees and that can be increased to around 4 degrees with such bushings. An additional 1.5  degrees can be added by using the same offset bushings in the lower a-arms (offset the other way), and a further 1 degree can be had by shaving 0.100" from one side of the upper ball joint carrier. This last needs a 0.100" shim added. Neat thing is, it's all reversible with stock parts!

Pat Mical in Mass. at Future Auto splits the stock upper front a-arm in two, straightens the pieces and welds them back together to produce 7 degrees of caster and a custom shim-pack; this really helps stability of the wide-body cars with 10" front wheels at autobahn speeds.

Unless you add power steering, increasing caster above about 4 degrees in a Pantera- especially with wide front tires- will make low speed steering a workout unless you have exceptional upper body musculature. Contemporary 'Vettes ran 7 degrees of caster but they already had power steering as a factory option.

Bump steering shims are simple flat 5/16" strips of aluminum mounted between the rack mounts and the mounting area on the front trunk. The factory supplied these sometime in mid-'73-up. But because the area is at 45 degrees, the rack also moves fwd AND down, which reduces bump-steer but increases Ackermann toe-in. This is subtle and makes little difference to most street owners. But you should know what's happening. 

A second method is to use tapered studs in the steering arms and replace the tie-rod ends with 7/16" SAE heim-joints, which screw right onto stock Pantera steering rods. By adding washer-shims to the heim joint thus raising or lowering it, bump-steer is easily changed. Again, both are reversible. A few detailed, illustrated Tech articles in the POCA magazine have been done over the years on both subjects. Zero ill effects have been noted.

Having the control arms redone is my last choice (difficult if not I'm possible to reverse )., Buying a full set of fully adjustable aluminum control arms sends a chill up my leg but dang $$$$   The heim joint solution sounds interesting but I can't seem to  visualize it and it doesn't sound like it retains any stock appearance. (Will check out POCA

I like the use of offset bushings to get a more caster, see how it drives and alter the balljoints if more is needed. ( Marlin Jack for spacers but , source for Poly offset bushings? )  BTW my upper body musculature is very exceptional , but then again my brain still thinks my body is in it's 30's .  I would only install power steering for my wife's sake LOL

Lowering the stance to the designed heigth is high on my list ,5/16 aluminum spacers are easy enough.  The Ackerman toe shouldn't have a big effect on the handling charactaristics or my lap times, running the "Summer Ice cream parlor GTA circuit" . Lol but it will good to know why my tire scrub sounds like a screaming banshee) 

Powersteering is high on the wish list but holding off on that final decision till I get the bleeding $$$ under control. Thanks friends

Thanks .Jerry (very) Sr

I edited my first reply to make sense to more people than just myself.

I would just like to add that the control arm modification IS reversible.  It just makes it possible to adjust caster over a wider range of degrees.

Instead of one fat spacer, manufacture the spacers out of 1/8 flat stock. Caster is then variable depending upon how many spacers are stacked on either side of the ball joint.  Stack them all in front of the ball joint you'll have about 6 degrees of caster. Stack them all behind the ball joint and you're right back to the stock setting. 

Also, the reason Ford "shimmed" the steering rack in the first place was because they raised the Pantera's ride height. If you plan to lower the ride height back to the original spec, the steering rack may not require any spacers at all.

Last edited by George P

Not sure on brands. At one time, all the vendors sold offset bushings; it may mean that you will have to contact your favorite parts-seller and ask. The difference in bushings is simply the thickness of the flange machined into one end; a thick flange means no offset and a thin one means some amount of camber offset relative to 'stock'. There's normally no big price change for camber increases.

And of course there's your main problem: getting the stock rubber & their steel sleeves out of the a-arm loops without damaging the arms. To avoid the problem,. some poly bushings are/were made to fit inside the hard-to-remove steel sleeves of stock bushings.

Note that the stock a-arms are only mild steel and can safely be weld-repaired by a decent welder with oxyacetylene and a file, and anyone with a small lathe could make his/her own custom a-arm bushings, with the help of TAP Plastics. Polyurethane rod-stock is available in all kinds of firmness (durometer).

Bump-steer results from the steering rods NOT being perfectly horizontal. So you can reposition the entire steering rack, or just the tie-rod ends (with heim-joints), to level the rods. That of course means that every car will be a bit different; the stock '73-up rack spacers are an average correction but bump steer on your particular car may be correctable with more.... or less spacer thickness. Wheel & tire size may have an influence too.

Add Reply

Link copied to your clipboard.