Custom Offset Delrin LCA bushings for G-Body\S10 front suspension ?s

[ArtosDracon]

Ok, I've been working on designing this suspension for about a year now. Just the other day, with some inadvertent help from another member here, I was reading through the SCCA Street Touring rule book and noticed that offset LCA bushings are allowed. I can't believe I hadn't thought of that yet. I have a lathe and drill press and a basic end-mill(all hand made by my grandfather and great grandfather) so making them won't be an issue.

G-body LCA bushings are 1.9" diameter if I'm not mistaken, and the S10 stock uses different bolts for the bushings, 14mm for one and 12mm the other. My thoughts were to offset the brass center .5" in the delrin and convert it so both are 14mm. I was also intending on designing them with the brass long and slip fit to the delrin so the rotation will occur between the brass and delrin to help ensure no bind.

For the Delrin itself I was planning on a two piece bushing so I get equal contact on the edges where the stock LCA puts the load and can grease from the center.

UCA will be an SPC fully adjustable and it will have tall ball joints, so alignment won't be an issue. I'm still working out how to fix the bumpsteer on these, possibly with a custom center link, but that will be dealt with separately.

Any thoughts?

[dontlifttoshift]

Not an answer, but more questions. What do you gain by relocating attachment points a .5" or so? Are you trying to go in, out, up, or down?

I would make the inner sleeves out of steel and polish them. The delrin is pretty slick as is and I think brass is to soft for that kind of setup. If understood right you want the frame mounts to tighten against the brass. It seems to me that the brass would deform under proper torque in the frame mount.......although maybe that is the plan.

So you know we are on the same team, I've got a 99 extreme reg cab, 4.3, 5 speed that is my daily. I have grand plans for it but the list of projects in front of it will likely carry me to my deathbed.

[ArtosDracon]

Was planning on strictly out, but out and up would be better. Though moving the arm up in the stock mount I'm worried about it hitting under high bump.

The idea with moving it out would be mostly to aid camber gain, and pick up a little bit of track width. The G-body\S10 has such a backwards design, I'm hitting everything I can find to better geometry. Unfortunately I'm on a really tight budget too, so I'm pushing my limited fabrication ability as far as I can. Hopefully I'll have some time to measure my truck up(been using GM diagrams as a reference thus far) an dinput everything into SA2 and see how big of a difference I can make.

I've actually been toying with the idea of getting an offset upper cross shaft, flipping it the opposite of what most do, and using it with a heim jointed fully adjustable UCA with custom spacers to shorten the upper as much as I can. As well as move the UCA down about a quarter as well as level it off a bit to slow caster gain.

Too much maths.

[ArtosDracon]

Found problem numero uno, lol. With the drop spring I'm planning on using the .5" offset would be too much to keep the spring lined up in the pocket even decently, I would be forced into a coil-over.

[monteboy84]

Keep the LCA pickups in stock location, and have Savitske put together a ball joint and UCA kit for you. I really don't see much reason to be moving the mount points in the way you're discussing.

-matt

[ArtosDracon]

Keep the LCA pickups in stock location, and have Savitske put together a ball joint and UCA kit for you. I really don't see much reason to be moving the mount points in the way you're discussing.

-matt

I thought I had outlined it pretty well above. Tall ball joints and adjustable upper control arms will only get you so far, and it still won't be "ideal", you can't even get "ideal" with AFX spindles IMHO, though that is about the best you can get with the stock pick-up points. The next best option then is to move the pick-up points. Unfortunately I can't weld currently, would love to learn, but don't have it in the budget right now. The whole point of this is to better the geometry on as minimal of a budget as possible, just throwing parts at it is neither an option, nor the best way to go about fixing the geometry on these cars.

[brrymnvette]

What's the point of tall upper ball joints? Is it to make the upper arm parallel to the ground?

[monteboy84]

I get what you're saying, but offset bushings don't actually change the pick-up points, they just move the control arm. Unless you get ones with an offset shaft, which it doesn't sound like you're describing.

-matt

[monteboy84]

I'm still working out how to fix the bumpsteer on these, possibly with a custom center link, but that will be dealt with separately.

Any thoughts?

Savitske already handles that with taller LBJ's. It's not like other cars where the tie rod end needs to be dropped from the spindle, the tie rod needs to land where the steering arm is in stock config, which means taller LBJ's are needed to raise the steering arm, which helps to further fix the camber curve, and improve the roll center.

-matt

[ArtosDracon]

What's the point of tall upper ball joints? Is it to make the upper arm parallel to the ground?

The point is essentially to make the spindle taller, and hopefully get the upper arm with the outter point higher than the inner so it can pull the top of the tire in as fast as possible, to a point. Level is the bare minimum needed.

[ArtosDracon]

I get what you're saying, but offset bushings don't actually change the pick-up points, they just move the control arm. Unless you get ones with an offset shaft, which it doesn't sound like you're describing.

-matt

I stand corrected, it doesn't move the pick-up point in reference to the chassis, but it does lengthen the arm, which moves the spindle away from the same pick-up point, essentially making the lower control arm longer, and thus, with the same length upper control arm, will increase static camber, camber gain and slightly decrease caster gain, which is too high to begin with. And there is no cross shaft in lower control arm, just bolts.

[ArtosDracon]

Savitske already handles that with taller LBJ's. It's not like other cars where the tie rod end needs to be dropped from the spindle, the tie rod needs to land where the steering arm is in stock config, which means taller LBJ's are needed to raise the steering arm, which helps to further fix the camber curve, and improve the roll center.

-matt

Except that when lengthening the lower control arm, you are further altering bumpsteer by changing the relative angle of the lower control arm and the steering arm. I understand that the tie rod is 5/8" too low, however that is with the stock lower control arm. Lengthening the control arm should decrease that ammount to nearer .5", which is the height added by a tall lower ball joint.

However, bumpsteer is affected by ackerman as well, which will be altered by the longer control arm and longer tie rod, so like I said, it's still getting sorted.

[tmcmillan5]

"However, bumpsteer is affected by ackerman as well, which will be altered by the longer control arm and longer tie rod, so like I said, it's still getting sorted."
__________________

Question, Is this a good thing or bad.

Thanks , Tony

[ArtosDracon]

"However, bumpsteer is affected by ackerman as well, which will be altered by the longer control arm and longer tie rod, so like I said, it's still getting sorted."
__________________

Question, Is this a good thing or bad.

Thanks , Tony

Neither? While I might call it unfortunate, it is just how the physics work on this style suspension. It's definitely a take it or leave it situation. I will say though, that I'm very glad of two things. It's not a rear steer design, so it's going to be possible to make it better. And there is plenty of room for change, which also makes it possible to make it better. I coult :nopity:all day about the different aspects of this suspension that suck horribly, this was definitely a :2nd: design done by GM, but it's what I got myself into, and have to work my way out of. It's definitely not fighting my way out of a paper bag, and is slightly :jump:but I love the challenge.

I hope that answers your question.

If you were looking for a more technical answer, I can say that the additional length of the total tie-rod to tie-rod distance will likely bring my ackerman closer to "ideal" than I could have gotten it without the extra distance, however without changing spindle design I don't forsee a way of completely removing bumpsteer with the stock centerlink and pitman\idler arm locations. While the pitman\ilder arms being as close together as they can be overcome with a better designed centerlink, that ability I fear is likley out of my reach.

[MonzaRacer]

while your trying to think its over think. to fix the camber curve you mod the design of the upper control arm.
Tall lower ball joint will lower vehicle a tad, and bring the steering arm more parallel with lower control arm minimizing bump steer.
Now if the rule allow you can cut and widen the center link to move the inner nearer to the control arm pivot point BUT this jacks with needing steering stops inside box changed.
but honestly get tall ball joints, an spc upper arm, if you really need it the bumpsteer kits are available to move outer tie rod up or down.
G body /s10 FE isnt that bad and after helping some guys do SCCA and dirt stuff too many mads hurt more than help.
So actually what are looking to do with it and what have you done so far. SC&C sourced SPC arms are big help. Marcus can help you a lot. and actually lengthening the lower arms just doesnt help enough to factor in as cost effective, unless your racing all year every weekend and sponsored.
If its for fun and stuff stick with SC&C kits.
and Del-Alum bushings work better over straight delrin. oh and which ever , Gbody Ithink, has smaller bushings results in less deflection. also making some 11ga or 3/16" reinforcement plates can help as much or more than redesign.
also dont forget about looking into the spring cups that are adjustable and moding to use those so you can reset the front end height. as at static ride height try for level lower ball joint to lower control arm pivot bolt ride line and tierods in same line. add in a Lee performance box and good pump cooler and your golden.
Oh and proper alignment. if you pay extra after adjusting ride height, get shim packs made for race alignment and road alignment. simply swap them out between racing and driving.
you can make a simple toe gauge with 2 pieces of conduit that slide together mark it off or simply glue on some pieces of tape measure and weld on some arms with bolts to just touch the rim lips, and if your real anal make marks on wheel so you can reset on same place.
Oh nad if you are toeing in or out a proper toe wrench, good 6 pint sockets and end wrench so you can move the toe sleeves. and remember to move with all on one side(messes with lock to lock and steering wheel center) or same amount of turns on each side.
Set marks for stock drive toe, install shim packs(racheting box wrench works good and double nut the uppers) then set toe.
Set marks for race setup then swap packs and reset to race toe.
If you have SPC arms, I have actually seen them set it up for stock with shims and without at race specbut depends on design of car.
Good Luck

[monteboy84]

And there is no cross shaft in lower control arm, just bolts.

Right, I was just referring to a delrin or other custom bushing where you would potentially have a shaft as part of the bushing. If that shaft was an eccentric in relation to the bolt itself, it'd be moving the pivot point.

Anyway, sounds like you know what you're trying to achieve, between fixing the camber gain, bumpsteer, and throwing a bunch of caster at it, these things will hang with the best of 'em.

-matt

[ArtosDracon]

Del-Alum bushings work better over straight delrin.

Is that because the Del-Alum outer aluminum re-inforces the stock arm? Becasue I was thinking about that, and did find some aluminum tubing on McMaster with a 1.9" OD that I was considering, but I didn't really know if it would be worht the price.

As for over-thinking, all I've got the budget to do right now is think, so I have plenty of time to work myself in circles. :)

And cost on these will be identical regaurdless of where I drill the delrin for the brass inner race, and will be about half the price of the global west, if I do use the aluminum outter, without it's more like 1/3rd, but a lot of time and labor.