MattyJ540

Hi all, I installed some 3.73 gears in my 2000 z28 and it hits so hard now that i have destroyed my passanger side lower control arm bushings. So its upgrade time! I was just wondering if it would be better to use the all poly bushing control arms or if the poly/ spherical rod end are better. this car is pretty much all street driven but i do take it to the track usually once a month. Any direction or advice would be awesome thanks!

Kevin97ss

I do.

I would highly recommend replacing the bushings in your factory arms with 1LE style bushings if you daily drive on the street. They work good at the track weather it be straight or twisty, make zero noise and are very comfortable.

That said, rod/poly is better than poly/poly because it only binds in one direction if the poly is mounted body side for NVH. Also, it is adjustable if you need to bring the rear forward. I would not use either on a daily driver.

MattyJ540

Interesting. Is the reason not to use them because they are noisy and cause vibrations?

JimMueller

iTrader: (9)

Heim joints on both ends of the rear LCA's tend to fall out favor for street use because they are all metal and will potentially transmit more NVH (noise, vibration & harshness) into the cabin. They also tend to rattle when they see enough usage and you get what you pay for when it comes to heim joints.

I've probably run them for almost 10 years at this point on my daily driver. I use FK JMX 3-piece units with the Teflon liner in conjunction with Seals-It seals and I'm happy with them; but where I drive usually has decent roads. If you're sensitive to rattles or don't want to deal with it, the most cost effective solution is to do what Kevin said, use 1LE style (Moog offers them) replacement bushings in the stock arms.

With that said, when I temporarily put my stock arms with new Moog 1LE-style bushings in to isolate a noise, I could tell that the car didn't react as quickly as with the heim joints.

MattyJ540

Ok that makes sense. Appreciate the info! Looks like i need to think about it. I was almost dead set on the poly bushing with heim joint arms. I might still go with them since i plan on re-doing the the whole suspension.

Kevin97ss

The main reason I would not use poly/poly is because it will work the body side mounting points. They are made of thin sheet steel and are strong for the intended load. When the suspension articulates over bumps there are twisting and lateral loads placed upon the arms, poly is very stiff and instead of squishing it will slightly bend the metal back and forth. Over time it will cause a fracture/failure. Also, they tend to squeak over time.

Good heim joints on both ends are ideal as there is no bind but the trade off is comfort. Even when new the harshness they transmit into the body gets old quick, eventually they will start to rattle and jingle like a ring full of keys. Not an issue for LCA use on a track or limited use car. I would, however recommend using heim joints on both ends of a panhard rod even for street use.

Kevin97ss

Continued: The panhard rod does not see the same type of loading the LCA does so there is not nearly the same amount of noise, harshness or load to wear the heim but there is a significant amount of stability added which can be felt in the handling of the car. Like Jim mentioned using Seals-It here would be a good addition for daily driver use to keep them from rusting/corroding.

Poly/rod, which I currently use, was chosen because I do drive this car to and from the track so I wanted some comfort. Also, I wanted the adjustability, its not much but it was enough. Typically I leave the poly end at the body unless I go to the road course. For the road course I will swap them around so the heim is body side, keeps the poly from binding and working the thin sheet metal.

MattyJ540

Awesome advise thank you!

blackandgold

iTrader: (2)

I just had my new rear put on with heim joints all around on my LCAs. I've also put ~200 miles on them this weekend already.

1. Are they loud?
-Yes, but I have to keep my exhaust under 93db to run Auto-x in San Diego so depending on that you may not notice.
2. Are there more vibrations?
-Yes, but I also added a new Torque arm and watt's link at the same time.
3. Would I recommend them for a street car that sees a lot of miles?
-Probably not, as stated above go with good rubber bushings. Chances are you probably don't need fully adjustable LCAs anyways.

JT2000WS6

I run all poly on my rear LCA's (with relo brackets) and haven't experienced any bind problems. However this is a 99.9% street car and I'm not exactly throwing myself around curves although I do enjoy some spirited driving.

ssvert99

iTrader: (26)

Poly binds the suspension worse than any other attachment manner.

The absolute best way to have a good reacting system with NO bind is heim joints on both ends. There is a difference in heim joints, so do not let anyone convince you that they are not worthy. Will a heim joint transmit more noise than rubber... sure, but not all heim joints are created equal. If you use good joints(not cheap plastic injected or metal to metal type most manufacturers use) then the situation not near as bad as one may think.

1 FMF

iTrader: (1)

i agree. when i did the strange s60 rear and did umi adjustable LCA and PHB i noticed how thin the body mount was where the rear LCA attached to. for a straight forward force on them under stock oem power they are probably fine. when you deviate and go with more power, harder driving conditions, and change to stiffer bushings in the LCA it's just asking for problems.

i have umi's lca and phb with the poly on the body side and their roto joint on the axle side. i did have some trouble with noise but i think undoing the roto joint with their tool, cleaning them, and reassembling tight fixed everything. mine's a street only daily driver, if i had my choice i would do the roto joint on axle end and oem rubber bushing not poly on the body side. not a fan of the poly bushing, but it's acceptable.

ss1

iTrader: (32)

I put UMI rod end/poly LCA's on my car last year after previously running poly/poly boxed arms. I had to make the switch after welding on LCA relocation brackets and needed to pull the rear end forward a little bit. I didn't notice any more noise with the rod/poly combo, I'm guessing because the rod ends have the teflon liner and the poly end is attached to the body. I also have UMI subframe connectors which support the front mount that some of you mentioned being a weak point. I do know that if you use cheap rod ends they will wear out quickly and you'll hear clunking when driving around.

blackandgold

iTrader: (2)

As an aside, I discovered that my jam nuts were loosening up on me. I think that was causing the majority of noise from my heim/heim LCAs. After tightening them up it quiets down a lot. I'm going to loctite them up tonight and expect that to remedy my noise issues.

blk97z28

iTrader: (3)

I did UMI on car single adjustable poly / roto LCA's work like the best (rod end) but don't make as much noise. Single adjustable is plently

leadfoot4

iTrader: (1)

They're binding, you just don't realize it.

As the suspension rises and falls, in reaction to bumps and dips in the road, the rear axle pivots along the axis defined by the panhard bar, therefore the rear axle moves side-to-side, with respect to the car. This causes a natural bind, since the polyurethane bushings don't allow any articulation in the LCAs.

Corvett z07

iTrader: (2)

+1 I have poly/poly on my LCAs and I'm going to revert back to stock with solid bushings before too long here. I was taking a corner once and hit a break in the road and my rear end broke loose in an instant, the main factor being snap oversteer that poly/poly bushings create in the LCAs. Plus after recently reading about Hrcslam's poly incident where poly should not be used, and seeing the after effects, that just urges me toward putting factory LCA back in with a bushing that actually moves with how the geometry of the suspension is suppose to travel, or going with a rod end or of the sort. Poly IMO should only be used in the chassis side LCA, panhard bar, and torque arm. Any other suspension place wouldn't benefit from poly or it would actually be worse in some cases

blackandgold

iTrader: (2)

Hrcslam's poly problems

It's a little different scenario as poly in that location up front allows for zero movement in the bushing. Poly on the rears still alows for a good bit of movement in the required directions, so not all of the force is directed at deforming the control arm. That said, even in a straight line, the PHB will put some lateral movement on the axle which will exert lateral force on the LCAs, I'm not sure who ever though a poly/poly configuration was a good idea for our cars.