subframe bushing inquiry

[frosho]

Probably pretty low, unless you're in the rust belt. People have been using them for years and years.

 

[stephen newberg]

I dropped my subframe last year to look at things, and all was fine. The ASFB have been in for maybe 7 years or so now.

pax, smn

 

[SuperHO]

the ones i've got on my 95 have been fine for years as well.

 

[firebat45]

you do realize you just posted that in the V8 section, right?

I realized right after I posted, but I'm not sure why it matters. Aren't the subframe mounts the same on all Gens? Are recall kits not needed on a Gen 3? You mentioned them in the first post...

 

[Izzmo]

I realized right after I posted, but I'm not sure why it matters. Aren't the subframe mounts the same on all Gens? Are recall kits not needed on a Gen 3? You mentioned them in the first post...

recall kits.. no

There was a Notice Bulletin though, but that's for the bolt, not the access to the SFB themselves.

 

[operdot]

Look I'm not saying your subframe is gonna fall of the car tomorrow. I do not have, nor do I plan on building and FEA(finite element analysis) models of the subframe and the bodyframe, so I do not have any difinitive answer on how long a NEW(NON-RUSTED) frame would last with ALSB. However from my engineering experience there is an increased risk of parts breaking, not just the frame.

My point is there is a better alternative to aluminum bushings. Hockeypucks + washer = 20$ where are ALSB = 100$. On top of that there is a whole slew of other reasons listed above. The other big plus is the geometry is rather simple, which makes it easy to install and inspect.

Bizzy has used hockey pucks, I think SHOBill may have too...

I actually built the subframe bizzy used. Here are the pix of her frame, this is just the rear.

And on SHOBill's Car I installed his hockeypucks.

My car was done similarly to Beth's and here are the pix 2.5 years and 30,000 miles later. The car handles great, and no wear so far on the bushings or the frame.

I dropped my subframe last year to look at things, and all was fine. The ASFB have been in for maybe 7 years or so now.
pax, smn

There is no way to 100% detect whether damage has been done. The frame maybe have plastically deformed to account for the forces applied, or may have grown miniature cracks which then you have no clue what the critical crack size is.

From Linear Elastic Fracture Mechanics:
A critical crack size is a size after which a crack propagates at the speed of sound and the part breaks. Depending of the application, a critical size may be in the microns or not propagated at all.

In this application just "looking" at the frame with a ***** eye doesn't guarantee 100% that it's fine. However it does help not to see cracks visible to the ***** eye.

There are a couple things you can do to be a 100% sure. You can have the frame inspected for crack formations. OR create a FEA model which will tell you what kind of loads you are dealing with and whether the thickness of the frame is substantial enough to account for the added stress of ALSB.


BUT UH comeon on a taurus subframe ..... best to just weld on a buncha metal and call it a day

 

[stephen newberg]

Or, with apparently no effects seven years down the road, you can just keep driving the car and when ever you drop the subframe, take a look. After all, nothing in life is 100% sure anyway.

Too easy, I know. Must do that FEA yesterday...



pax, smn

 

[operdot]

Or, with apparently no effects seven years down the road, you can just keep driving the car and when ever you drop the subframe, take a look. After all, nothing in life is 100% sure anyway.

Too easy, I know. Must do that FEA yesterday...



pax, smn

My whole point is that ALSB are not the end all of subframe bushings. There are better choices out there.

 

[operdot]

But in the end of things its a matter of personal preference and choice. If the ALSB are working out for you then I'm no-one to tell you to take them off.

I'm just describing the decision processes that went into my subframe. I too used ALSB for a couple month on my car, but I was absolutely disgusted with the ride. This is when I started looking into alternatives.

 

[Izzmo]

How would hockey pucks offer that much difference? If you have metal around the circumference of the puck.. this will not allow the puck to deform to the vibrations and offer hardly any cushion at all since the metal is in fact surrounding it. It could lower the noise a little bit, but I still think the vibration and harshness will still be there, although helped only slightly by the puck.

 

[operdot]

How would hockey pucks offer that much difference?

The pre-load of the bolt on the hockeypuck allows the hockey puck to absorb a lot of force. Think of each hockeypuck as a spring that was torqued down by a bolt, when you load it the spring takes on the load instead of transfering it to the frame.

Preload of the each of the subframe bolts:
F=T/(Ki*d)
F=65ft-lb/(.21*.039ft)=7936.5 pounds

This is the minimum clam up force of each bolt.

If you have metal around the circumference of the puck.. this will not allow the puck to deform

Even thought it may not look like there is a lot of room for the hockeypuck to "deform" it does not need to deform because it has all that reserved force to deform within.

The aluminum does not take advantage of the "spring" action that rubber offers, and simply just transmits the force though.

Its like using a string telephone vs just talking. The air absorbs the waves whereas the string can transmit them.