Soaring

I would have to agree with the Mustang Depot guy, and with you. If poly bushings caused the strut rod to break off, then the poly bushing guys would be in deep doo doo if they continued to manufacture them. I have never heard of it, but maybe someone can chime in with a personal experience of this happening to them.

Lumbergh

I've talked to a couple of guys that have restored several mustangs including a mechanic who specializes in Mustangs, and when the discussion got around to replacing some of the suspension parts on the Mustang I recently bought, the first thing both of them said was to replace the bushings with poly bushings instead of the original style rubber bushings.

rmodel65

well all the mags ive read have stated not to ue the poly on a street car

bignatesan

I'm going to call the poly bushing manufacturer tomorrow and get their take on the issue. I'll let you know what they have to say.

I know that these things gain "urban legend" status once it happens to one guy and he tells a few friends about his strut rod breaking right after putting in a new poly bushing. No doubt poly is better on the other bushings, but like baddog said, I have read in more than one place to use rubber instead of poly on the strut rods. They even go so far as to say if you do use poly to flip the metal cap on the bushing over so it looks like an upside down mushroom.

I'll let you know what the manufacturer says, but I am willing to bet they are not going to say thier product causes stock strut rods to break.

Nate

rmodel65

what companyu in there right mind is gonna tell u its gonna make something break lol but u might get them to tell u not for street use

Scott H.

I've read some threads that had included pictures of broken and bent strut rods. Not one of them told the entire story. If you put stiff bushings on a rusted or fatigued 40 year old strut bar, or if you overtighten the nuts and squish the metal sleeves and then start driving like Parnelli Jones... Yeah, somethings gonna give, and it ain't gonna be the bushing. If you drive like an old Grandpa you could weld the strut rods to the chassis, and they probably wouldn't break.
Somewhere in the middle lies the truth. My own experience favors hard rubber, both on Ford trucks and cars. Just couldn't see the advantage on an otherwise stock front end to go Poly. You aren't going to feel the difference. And quite frankly the poly bushings do not have the give for long travel suspension.

I'd be cautious of any one person claiming they will or won't work, without first asking you what you are doing for the rest of the front end, what kind of driving are you planing on, and what kind of roads do you drive on.

bignatesan

As others have mentioned, the manufacturer said their poly bushing is not the single source of failure if a strut rod breaks. Their line is the poly bushings are fine, but they are much stronger than rubber so worn parts will wear at a higher rate if not refurbed or replaced at the same time as the poly is added. I have already ordered the reinforced rubber. If they fail in less than a year, they are easy enough to replace. However, if my 40 y/o strut rod fails, that could have a detrimental efect on the entire new front suspension I just bought.

Nate

THUMPIN455

What is the strut rods function?
What does it do?
What loads are placed on the strut rod in normal driving?
What loads are placed on the strut rod in abnormal driving?
What could cause a strut rod to break or fail?


There is no Shear on the strut rod. There is fore and aft. If there is shear then the lower controll arm is moving in a manner which it should not. That would point to the strut rod not being installed correctly. it would have gaps in the bushing so as to allow it to move fore and aft more and that would cause it to swing in an arc at the front end.

The end in question is a pivot point, a fulcrum. yes it is load bearing but only in certain directions. one thing is for sure, if the strut rod moves around the alignment is going to be EVERYWHERE. nothing would be locating the lower control arm.

Strut rods are made from hardened steel bar stock. They are under lenty of stress in compression and tension, but what would cause a 1" thick bar to break? A harder bushing? or perhaps someone using a torch to heat the bar or nut so as to losen it to remove it?

heating a piece of metal anneals it, or softens and makes it pliable. if you heat a hardened piece it is no longer hardened, it is now weaker in the location of the heat. it makes infintely more sense to me that someone heated the strut rod to losen a nut than it does that a firmer bushing caused a 1" thick bar to snap. Especially so when considering the loads and angle of said loads placed upon it.

Brandontyler65

+1

Scott H.

actually there is a bit of shear, mostly it is negligable, until you hit a curb, speed bump, or pothole. The intensity is directly related to the amount of force trying to stop the wheel from continuing in its straight forward path.
***********Edit
I forgot to mention the twisting force applied when braking. Sorry for the exclusion. That's a big factor
**********end edit
What a lot of people miss is that the lower control arm on a Mustang has a single axis in the longitudinal direction. One of the very important functions of the strut rod is to keep the lower control arm from twisting. That is where the shear force comes in, and (IMO) I agree with you, that people are either doing something seriously incorrect on installation, or are pushing the cars limits.
The strut rod does arch in deflection, under load. Eventually this arching work hardens the steel to a point of brittleness. How quickly and how brittle really depends on a whole lot of variables.

Scott