ZCcivic91

Doing some suspension and brake changes on my 1996 civic. One of the changes I'm making will be moving to the EM1 front LCA, this is the same style as the EK9 CTR.

I purchased a set of the Skunk 2 Alpha LCAs for the rear (Poly bushing at Chassis, Delrin for shock, and spherical at trailing arm mount), and Id like to run a Delrin bushing on the front shock mounting point as well.

My question is, is there any reason the geometry will not allow this that I'm not seeing? As Delrin doesn't move as freely as a spherical, am I screwing with lateral movement or twisting that I shouldn't? Or is it safe to "solid mount" the front shock in this case, and leave the chassis mount on the front LCA Poly?

I realize there are different opinions on Poly, Delrin, and bearing mounts and bushings. I am only concerned with if a Delrin mount in this case will have a negative effect on the geometry of the front shock LCA mounting point.

Thanks for any help

B serious

iTrader: (1)

It won't move freely like a spherical will.

The shock mount doesn't laterally deflect on cornering...if that's what you're concerned with.

The factory bushing twists rather than spins.

justinshotta

cool

Tyson

the rear LCA is different in geometry from the front LCA because the fronts have a rigid arm that goes to the compliance bushing. forcing the front arm to be rigid with the shock movement is likely over constraining, but given the nature of the "COMPLIANCE" bushing, it probably is still acceptable.

another point to mention is that a rubber bushing on the shock acts like a spring, it helps soak up the very small movements. removing the rubber forces the shock piston to move in those high frequency oscillations, putting more wear around the seal. and overall will make it feel harsher.

second point to consider, regarding the rear LCA, if say the chassis and the trailing arm ends have freely moving spherical bearings, AND the shock mount, the only thing that is "twisting" the rear LCA is the sway bar. so when you then rigidly constrain the shock mount, you now have the shock resisting all the twisting from the swaybar. in the end, probably all negligible and arguably not more worse off than using all rubber bushings, but its the cause and effects of changing one thing that affects other things.

ZCcivic91

Thanks all for the feedback.

The car is now a dedicated autoX/track day setup, but keeping it streetable with full interior, cruise and AC for funsies. I realize it will never be a true competitor in its class with my driving skill and its setup, so the fun and learning is more important here. Ride comfort will suffer, but I'm prepared for that.

With having the Delrin bushing out back for the shock, in my head I want to match it to the front. I'm sorting out a double adjustable damper setup to end up on the car, so I want to try and "solid" mount the dampers, everything else will be going to poly.

Interesting seeing your thoughts on the Rear Swaybar / Solid mounted shock twist Tyson. I'm trying to work my head around that, but Im having a hard time seeing what you mean. In my head, the all the Delrin is doing is isolating the shock more than rubber. As the car rolls left to right, the LCS is moving up or down as allowed by the spring/damper. The twisting of the sway bar is dependent and how far up or down it moves and the relation of the end link mounted to the LCA. Any link I can visually see what your getting at?

Side note, a Delrin bushing for the front is surprisingly hard to find or have someone make, so I may end up with a spherical bearing anyway, and that will annoy me to no end.

boxedfox

There's actually a reason for that. The front lower shock mounts on our cars need to be able to twist along the axis of the control arm to accommodate the movement of the lower control arm. It's very slight (which is why Polyurethane works) but it's more than what a solid Delrin can accommodate without deforming permanently. Over time the metal sleeve inside the bushing would just hog out the Delrin until it was rattling around in there.

That said putting a spherical bearing in there does wonders for on-track behavior. I had Kingpin Machine do a spherical conversion on my lower control arms and the car behaves so much more predictably through left-right transitions and over kerbs compared to my old poly bushings. Not super cheap but completely worth it for a dedicated track car.

B serious

iTrader: (1)

^all valid points...but I was under the impression that OP didn't want to hear about why poly/delrin doesn't belong in a suspension...

OEM's all build with spherical or rubber. I checked...and even the people who designed cars like SRT-4 Neons chose to stay away from poly/delrin. It doesn't work, if we're being honest...

boxedfox

Actually Delrin and polyurethane can work very well in track car applications. It's just that Delrin specifically doesn't work well in the front end of 90's double A arm front Hondas. The individual bushings have to work in torsion across multiple axes. Polyurethane is still compliant enough that it works reasonably well and helps a lot in these cars. It's just that they tend to be a bit high-maintenance compared to rubber. Even if you keep them clean and greased, polyurethane degrades and shrinks faster than rubber does. A well-cared for rubber bushing can last decades, where polyurethane bushings will start to disintegrate well before then.

Delrin works reasonably well in cars with simpler suspension geometries (e.g. older cars and Miatas). The biggest problem with Delrin is, of all things, corrosion. Because Delrin doesn't absorb water, a lot of moisture gets trapped between the bushing and the sleeve that goes inside of it and they seize together. Then the bushing starts to rub up against the walls where it contacts the control arm and will slowly destroy itself through abrasion. It's a bit ironic because Delrin as a material is designed to be self-lubricating and to resist corrosion.

While neither of these materials are as versatile as rubber, I wouldn't go so far as to say that they don't belong in an automotive suspension system. Especially not on a track toy that will see very many maintenance hours and very few street miles compared to a daily driver.

ZCcivic91

This is exactly what I was asking.

BoxedFox you said , is there anywhere I can read up on this, and the motion the LCA shock mounts needs on line? I have been having trouble finding any kind of visual or testing on this.

ZCcivic91

Staring at the LCA, I'm realizing there would be some horizontal pivoting from the compliance bushing outward. Is this where the twisting is coming from for the front shock bushing?

boxedfox

I had a race shop show this to me firsthand. They took the spring off of one corner of an EG Civic, put a jack under the control arm, and moved the suspension through its range of motion to show how the bushings deflect.

I'm not sure if I've seen too many visuals on this online, but I recall a bunch of the Northeast Honda Challenge guys (namely Spencer Anderson) talking about failed experiments with Delrin bushings which came down to exactly this point. He may have pictures on this very forum from then (maybe circa 2010?). there conversations around this on the Grassroots Motorsports forums. Not many pictures there but there are a lot of people doing these types of tests.

This could be a good idea for a video though. Maybe I'll take a crack at filming a youtube video around this using some of the cars I have laying around here.

ZCcivic91

The closest I could find for a video of this was this one:


its not great quality, and its not close enough to the shock mounting points for me to see any small movements that may be happening. If you made a video, please post it up, Id be very interested in seeing what it looked like.

In the end, I may end up going poly all the way through (other than the already installed rear Delrin mount), and changing to spherical in both front and rear in the next year or so.

boxedfox

Yes that's what's allowing it to twist. Forces from acceleration, braking, and steering act against that compliance and allow the control arm to move fore and aft, which is where some of that twisting is coming from. That combined with the fact that the top of the shock is mounted rigidly allows that pivot point to twist around the axis of the lower control arm.

boxedfox

Are the rubber bushings cracking or otherwise disintegrating? If you're planning to go to spherical bearings within the next year you might want to consider staying on the rubber bushings. Rubber bushings harden as they age, and as long as there are no cracks or tears they can become as stiff as the lower durometer polyurethane mounts from Energy Suspension / Prothane. I learned this from some Spec Miata racers who found that the cars didn't feel any less responsive after swapping their aftermarket poly control arm bushings for the old rubber bushings that they pressed out.

I'm inclined to say that unless those bushings are torn up or cracked, just leave them in place and go straight to spherical bearings. The time and money needed to convert to poly isn't worth it if you're going to convert to sphericals in a year.

ZCcivic91

Right now the front and rear suspension I am doing this on is not in the car, its on the garage floor. The car has its factory pieces in place. I'm swapping over to a EM1 brake setup, so while everything is out of the car, Ill be swapping what I can while its convenient. Ball joints, bushings, rotors blah blah blah. Id rather do it all now, drive for a season on poly, then switch to the spherical and see the difference. Learning from first hand experience is a big part of this car for me.

I've run Poly in other cars and always liked the feeling of it, so we will see what happens on this one.

Thanks for the explanation on the compliance bushing, that didn't make sense until I was looking at it in the garage. I still wish I could find a video on it so i could see the movement of that shock bushing in real time.