steering and suspension Loose Radius / Tension Rod bushing

[Villanuevas_BMW]

The Radius/Tenion rod IE poly bushings I'm installing are very loose at the subframe. Along with solving the problem, they are some other things I wanted to address regarding the radius rod to get a better understanding of what it does and how its related parts work just in case anybody tries to search this in the future. I did a search and the most relevant thread I came across was this, http://www.bmw2002faq.com/topic/132850-tension-strut-ie-bushing/.

 

My loose bushings:

The bushing is loose after torquing down the nut at the front end of the radius rod. Initially I thought I was running out of thread on the rod. It didn't look like it. Just in case, I added some washers to make sure that I was not running out of thread. This made no difference, so I eliminated the chance of not having enough thread.The largest washer, closest to the bushing has the same ID as the pipe in the bushing, therefore that largest washer is in contact with the inner pipe of the bushing. 

 

 

Here is an idea of how loose the bushing is.

You can see a gap between the bushing and the subframe,

 

And I can easily move the radius rod to make that gap disappear,

 

When I lift the radius rod and let go, it quickly swings back down,

 

 

So I'm guessing the bushing is not clamping/squeezing the subframe as it should. I then checked the possibility if the inner faces of the bushing halves are running into each other before the outer bushing shoulders can fully contact the subframe. Whichever way I measure, the bushings would have a gap between each other and the depth of the subframe was larger. So the bushings are not bottoming out on each other before clamping onto the subframe.

 

 

The only thing I can come up with is that the pipe that connects the two halves of the bushing is a bit long for me. Or maybe my subframe is tweaked.

 

I've come up with 2 options for this. Either add washers with an ID larger than the OD of the busing pipe, or remove material from the bushing pipe so the hardware clamps the bushing onto the subframe. Only problem is...how much material do I remove or how many larger ID washers do I add? I'm leaning toward adding the larger ID washers, since its easier to remove washers if I over do it rather than adding material back onto the pipe.

 

It all stems down to how tight the bushing should be...maybe I'm totally wrong and the bushing is supposed to be loose like this? I guess for me to understand how tight the bushing should be is to understand what it does. First, here is my guess (or misunderstanding) of the radius/tension rod. Please correct me if I'm wrong so I can revise the thread for future reference for anybody searching.

 

And I guess that's where the name "tension" rod comes from. That may also explain how the "clunk" comes toward the end of a braking sequence mentioned in the thread I referenced at the top.

 

 It always happens when im braking towards the end of my braking if you get what i mean. I do feel it slightly in my steering wheel. 

 

As the car begins to come to a compete stop, the tension decreases in the rod and that clunk is everything settling back into its static position. I'm also guessing that's why the bushing is beefier toward the front. So I think the main reason for the rod is to add rigidity to the control arm especially under braking and to minimize toe deflection. The bushing is also to allow rotational movement to follow the control arm during suspension movement.

 

 

With the added larger ID washers or shortened bushing pipe, I can easily tighten all of this up so there no movement...but what is the intended relative movement for this bushing? Is it supposed to be like any other bushing?

• Is the bushing supposed to rotate in the subframe?
• Is the bushing and subframe supposed to stay still as the inner pipe rotates? For that to happen, the bushing has to be tight in the subframe and the hardware bottoms out on the bushing pipe.
• Everything should be tight. The movement is limited to the deformation of the bushing.

thanks

 

 

 

 

 

[percy]

My experience with urethane brake rod bushings is not particularly good, which is why I use the regular oem rubber for this part.  The one or two times I tried them on a street vehicle, they were dimensionally different than the rubber they replaced (shorter and narrower).  This led to sloppiness and minor extraneous noise that was bothersome enough to warrant removal.  This was some time ago, but I remember asking the source about the problem and remember being given a "work-around"  that involved hose clamps.  I haven't looked recently, but the big washers in your picture look different than OE.  I vaguely recall all of mine being dished and dished for a reason, to allow bushing deflection.  Although I have not given this much thought, your additional washers idea might be a fair substitute.    

 

When you ask about fit, the idea of snug under all conditions comes to mind.  This is not very scientific, but there has to be a modicum of give to allow full suspension movement, but too much results in unacceptable changes in suspension geometry when braking.

 

 

 

[Villanuevas_BMW]

I have the concave washers also. Since the face of the poly bushings are flat I thought flat washers were to be used. Plus I saw them in pictures of poly bushing installs such as this one.

http://www.bmw2002faq.com/topic/132850-tension-strut-ie-bushing/#entry46689

 

If I snug everything up with the larger ID washers, then the bushings would be stationary in the subframe and I would hope that the large washer would rotate on the bushing face. I just worry with many cycles of the control arm articulating back and forth, it may cause the nut to back out, even with a new lock nut. I might just throw on a jam nut to be safe

[Hans]

Have you asked Mr. IE about this? Perhaps that is the intent.

Another option is to try the "turbo" bushing which also fits NK cars. Supposed to be tougher. Same size.

[TobyB]

The tube should be short enough that the washers

clamp the bushing securely into the subframe,

deforming it some,

but long enough so that the nut bottoms (hard) against the tube.

 

Anything else... isn't right.

 

I'd call IE.

 

t

[Villanuevas_BMW]

Those were my thoughts also, the tube prevents any excess deformation upon tightening and gets the hardware to the correct torque. What it seems like is the tube is at a length that does not allow much deformation to grab the subframe. I found some washers that allowed me to smash the bushing more. When I rotate the rod/nut, the washer and bushing stay still. So the wear during rotation will be between the rotating nut and stationary washer. I put a jam nut on it also because I worry about the nut backing out. I know (just like always) I'm over thinking this, but I never really thought into the intended movement of bushings.

 

I sent IE an email already, thanks for the input thus far, much appreciated.

[TobyB]

Hmm, yeah, email and Ireland, well, I've never had much luck there...  Maybe PM Andrew, here?

 

It's been a while, but I don't remember much beyond a nut, a small washer, and then the big washer

on the front of the radius rod.  The 'inboard' end got a big washer, and that was all.  Your spacer

out there looks odd to me.

 

fwiw,

t

[Villanuevas_BMW]

That spacer in front in the pictures was a test to make sure I wasn't running out of thread on the radius rod. I emailed Andrew too, I'll PM him to see what he thinks. I might just swing by Ireland tomorrow since I need to pick up rear subframe mounts to get ready for the back end.

[Lee]

In think there's something wrong with your tension rod install. You shouldn't need that thick spacer up front. It should be the large washer and the nut. Is it possible the tension rod has been fitted in reverse?

 

Check here for detailed installation.

 

http://www.bmw2002faq.com/topic/143729-urethanepoly-bush-fit-on-front-subframe/

 

 

 

Edited February 2, 2016 by Lee

[roadhog0]

On my IE radius rod bushings I had to take a little off the ends of the metal sleeve to get things to fit tight. These were on some much older IE bushings, the design has probably been revised since then.

[jgerock]

Stock setup for comparison

[jgerock]

I'm with Lee on this.  

In think there's something wrong with your tension rod install. You shouldn't need that thick spacer up front. It should be the large washer and the nut. Is it possible the tension rod has been fitted in reverse?

 

 

[Villanuevas_BMW]

That spacer in front in the pictures was a test...

 

I removed the massive spacer after I was sure I was not running out of thread on the radius rod, that overkill spacer was just temporary. The tube in the bushing was just a tad too long, a large washer with a slightly larger ID than the bushing tube OD did the trick, just as mentioned in the link Lee posted. I guess I missed that thread in my search, my mistake. However I did not notice (or bother to look to be honest) if there was a difference between either end of the radius rod but I think the main reason was the bushing tube was long. I have seen the stock setup as pictured by jgerock in the suspension rehab thread and thought it looked awkward with a huge washer in contact with the bushing tube, but thinking how the rod works, it makes sense. I'm guessing the rod goes into tension at the most during initial braking where the bushing deforms and brings that washer to the face of the bushing.

 

Thanks for the help everyone

[roadhog0]

I removed the massive spacer after I was sure I was not running out of thread on the radius rod, that overkill spacer was just temporary. The tube in the bushing was just a tad too long, a large washer with a slightly larger ID than the bushing tube OD did the trick, just as mentioned in the link Lee posted. I guess I missed that thread in my search, my mistake. However I did not notice (or bother to look to be honest) if there was a difference between either end of the radius rod but I think the main reason was the bushing tube was long. I have seen the stock setup as pictured by jgerock in the suspension rehab thread and thought it looked awkward with a huge washer in contact with the bushing tube, but thinking how the rod works, it makes sense. I'm guessing the rod goes into tension at the most during initial braking where the bushing deforms and brings that washer to the face of the bushing.

 

Thanks for the help everyone

 

Also, if I remember correctly, if things fail, that washer holds the radius rod in instead of letting it go flying off the car.