Modify poly LCA bushings to get more caster?

[ChargerST]

Just came to my head:
Would it be possible to get more caster if you take a poly LCA bushing and cut off some material of the tapered section? The LCA would move closer to the K-frame which should give you more caster..
Obviously you need adjustable strut rods to make this work.

Am I missing something?

 

[493 Mike]

I believe a better option would be adjustable upper control arms.
Mike

 

[ChargerST]

Maybe but lets focus on the LCA bushing for a moment, I'm well aware of the UCA option ;)

 

[RemCharger]

If you did the lca pin only, it would actually move the the balljoint backwards. Pivoting on the strut rod.
Adjustable strut rod only will give the max fwd adjustment

 

[Kern Dog]

The LCA can only move forward a small amount before the horizontal flange would make contact with the flange of the K member.

You could trim the flanges for room though. The rearmost strut rod bushing could be shaved/cut/trimmed to allow the stock strut rods to be used. Technically, you'd be increasing the wheelbase by a small amount.
I can see the appeal. You'd gain caster for almost no investment other than your time.
I'm not sure about the LCA pin and bushing. I thought the pin was either tapered slightly or had a ridge to it preventing it from being too far forward or rearward.

 

[ChargerST]

If you shave off the black part you could move the LCA half an inch or so forward..

 

[autoxcuda]

Try installing offset upper control arm bushings. K7103

DO K7103 MOOG OFFSET BUSHINGS WORK

 

[Kern Dog]

There are still issues to consider. Look at the white circled area:

That is one area that is already close. Moving the LCA forward just crowds it even more. The sway bar will now be hitting the LCA. There isn't much room to move the sway bar forward either. If you omit the sway bar, that is a backward move since it is crucial for good handling, losing it defeats any advantage from a gain in caster.

 

[Kern Dog]

Try installing offset upper control arm bushings. K7103

DO K7103 MOOG OFFSET BUSHINGS WORK
View attachment 1701965

I agree. I was able to get almost 6 degrees of caster with stock UCAs and offset bushings.

LOTS of great info here:

Alignment at home and aftermarket UCAS too.

 

[autoxcuda]

View attachment 1701957
If you shave off the black part you could move the LCA half an inch or so forward..

I would not do that.

On a poly bushing that area acts as a plain bearing. The strut rod should load the poly insert that tight against the pin. That tapered section supports that and removing it could jeopardize the LCA structure integrity

 

[ChargerST]

Thanks but this is just a theoretical discussion about the poly LCA bushing. Lets please leave the UCA options out of it (I appreciate that you all want to help me but again, I'd like to discuss my idea only).

 

[ChargerST]

There are still issues to consider. Look at the white circled area:

View attachment 1701973

That is one area that is already close. Moving the LCA forward just crowds it even more. The sway bar will now be hitting the LCA. There isn't much room to move the sway bar forward either. If you omit the sway bar, that is a backward move since it is crucial for good handling, losing it defeats any advantage from a gain in caster.

yeah, I looks quite close. Will have to put the Charger on my lift to see how cllse it really is. No point in losing the sway bar.
I would not pursue my idea any further if it involves any drastic changes but if it would mean to just trim the k-member then why not?

 

[Kern Dog]

I'm not against alternative ideas, especially those that are smart and save money.
Some ideas just suck and don't work.
A few months back I pondered over cutting and welding UCAs to gain caster. My idea involved cutting 1/4" from the rear leg of an UCA and welding it to the front, effectively moving the ball joint rearward.
Yeah, in theory it would work but then you get into the issue of weld integrity being extremely important. A failure in that could be catastrophic.
Some ideas seem good in theory but fall apart when actually tried.
I support and encourage these new ideas though. It is stuff like this that separates car guys from dorks.

 

[ChargerST]

I would not do that.

On a poly bushing that area acts as a plain bearing. The strut rod should load the poly insert that tight against the pin. That tapered section supports that and removing it could jeopardize the LCA structure integrity

yes, you are right. Maybe I wasn't clear enough but I would only remove maybe half of that section. I could also use delrin bushings which should be much stronger anyways

 

[autoxcuda]

Thanks but this is just a theoretical discussion about the poly LCA bushing. Lets please leave the UCA options out of it (I appreciate that you all want to help me but again, I'd like to discuss my idea only).

Theoretically the poly bushing material needs that volume to keep it structure. Something like delrin might be able to hold itself together better when it's thinner, but there would still need to be some sort of flange.

And moving the LCA forward brings interference issues with K-member. Which can be resolved by removing material from LCA and/or K-member, but results in weakening other structural parts.

 

[autoxcuda]

Shame, the reinforcement plate of that K-member hole for the LCA pin pushed back the LCA the thickness of that plate.

 

[Kern Dog]

Not really, Steve.

If the welded in washer isn't sticking out further than the original "lip" of the tube the factory selded into the K members. This is a 73-76 A body unit, similar to all the B and E units.

 

[ChargerST]

Shame, the reinforcement plate of that K-member hole for the LCA pin pushed back the LCA the thickness of that plate.

Just took that photo off the internet, not my LCA

 

[autoxcuda]

Not really, Steve.

View attachment 1701995

If the welded in washer isn't sticking out further than the original "lip" of the tube the factory selded into the K members. This is a 73-76 A body unit, similar to all the B and E units.

Good point. Fair enough.

 

[j-c-c-62]

Just came to my head:
Would it be possible to get more caster if you take a poly LCA bushing and cut off some material of the tapered section? .............................
Am I missing something?

Maybe. The addiction for more castor may have downsides rarely discussed.

In the October 2024 international issue of a very respected "Racecar Engineering" monthly touches on the subject. I assume the writer, Jos Claes, is more knowledgeable on the subject than myself as is everyone else contributing to the magazine. From page 5 briefly:

"The kinematic effect of any geometry, including castor angle, will result in a change in cross weights with turned steering. It helps to countersteer by holding back on some vertical load on the inner front wheel. This load would otherwise migrate to the outside of the wheels, and the effect is obviously reversed on the inner rear wheel. In other words, the limit of castor is traction capacity.

Some of us may remember the days when a weak chassis (with regards to torsional stiffness) proved faster on a wet track compared to more advanced cars that boosted far stiffer monocoques. The reason was that this weak chassis was easier to drive and, and more specifically, could drift in the rain compared to the better "dry" car. The kinematic effect of castor was much lower on torsionally weak chassis and made the four tyres operate under slower and more stable loads. Of course, such a car is significantly easier to drive, considering the endless spikes in steering wheel trace for the data of a car being driven in the wet."

In summation this is concerning the chassis lifting effects of significant castor when steering and its inherent redistribution of chassis weight when turning a castor aligned wheel. The writer uses the example of an unsuspended effectively rigid go kart to help visualize castors effects, mainly when at rest turning the wheel full lock will lift the outside tire, and why manual steering effort becomes so high.

Almost everything has a downside. Pick your poison.