polyurethane bushings
12-14-2004, 02:01 PM
#61
Former Vendor
Speedracer944, the steel arm version should be out in the feb/march time frame
Like Geo says, the monoballs will not limit alignment adjustability.
The monoball is a ball and socket type arrangement. It positively positions a single "point" about which the A arm can pivot. Because it's pivoting about a "point", it can rotate freely about the X,Y, and Z axis. But that single "point" will not move. The picture below show a drawing of a spherical bearing which is the core of the monoball.
Compare this to a rubber bushing. The rubber can twist, compress and deform in any direction and can rotate about the X, Y, and Z axis. But rubber also allows the "point" to move along the X, Y, and Z axis. Note the difference between rotating about and axis and moving along that axis. This is the big negative of rubber because when the "point" moves, alignment settings wander with it.
Contrast this with a plastic bushing. It doesn't define a "point", it is a cylinder that defines an axis X. It allows rotation about that axis only, none about the Y and Z axis. Unfortunately that axis X never aligns perfectly with axis of the mount, X'. The only way the bushing can pivot about the mount axis X' is for the hard plastic to compress. But the plastic is hard and doesn't like to compress, hence it binds.
Originally Posted by sm
Thanks for the reply Chuck and I'll keep an eye out for the steel a-arm products.
Since the rubber bushings deform according to alignment changes, such as caster, and the monoballs don't allow (or is it minimize?) deforming, will the alignment adjustability be limited?
Since the rubber bushings deform according to alignment changes, such as caster, and the monoballs don't allow (or is it minimize?) deforming, will the alignment adjustability be limited?
The monoball is a ball and socket type arrangement. It positively positions a single "point" about which the A arm can pivot. Because it's pivoting about a "point", it can rotate freely about the X,Y, and Z axis. But that single "point" will not move. The picture below show a drawing of a spherical bearing which is the core of the monoball.
Compare this to a rubber bushing. The rubber can twist, compress and deform in any direction and can rotate about the X, Y, and Z axis. But rubber also allows the "point" to move along the X, Y, and Z axis. Note the difference between rotating about and axis and moving along that axis. This is the big negative of rubber because when the "point" moves, alignment settings wander with it.
Contrast this with a plastic bushing. It doesn't define a "point", it is a cylinder that defines an axis X. It allows rotation about that axis only, none about the Y and Z axis. Unfortunately that axis X never aligns perfectly with axis of the mount, X'. The only way the bushing can pivot about the mount axis X' is for the hard plastic to compress. But the plastic is hard and doesn't like to compress, hence it binds.
12-15-2004, 12:31 PM
#62
I too would be curious to see the long term life expectancy out of the sealed monoballs - the rebuildability is something extremely interesting, but I'd like to make sure I don't need to replace the cartridges yearly on a street car. Anybody with experience with the ER monoballs for primarily street use over any significant period of time that can speak to this?
12-15-2004, 01:09 PM
#63
Former Vendor
Fair question. The design life of the product is 100k miles.
The enemy of spherical bearings is dirt and water. It gets in and works like sandpaper on the bearing. Keep the contaminants out and bearing will last a long time. Note that factory ***** joints are sealed monoballs too.
We've made custom seals that are effective at keeping contaminant out. Though the product is new for the 944 series, we've been making custom weathersealed products for the 911 series for about a 18 months. The products have worked very well and that prompted the development of the 944 parts. Some customer cars are into 20k+ mileage range with every reason to think our design life expectations will be met.
The enemy of spherical bearings is dirt and water. It gets in and works like sandpaper on the bearing. Keep the contaminants out and bearing will last a long time. Note that factory ***** joints are sealed monoballs too.
We've made custom seals that are effective at keeping contaminant out. Though the product is new for the 944 series, we've been making custom weathersealed products for the 911 series for about a 18 months. The products have worked very well and that prompted the development of the 944 parts. Some customer cars are into 20k+ mileage range with every reason to think our design life expectations will be met.
12-15-2004, 09:10 PM
#65
Thanks for speaking to that question Chuck. Like I said earlier, regardless of the position I took in my posts I am actually interested in the bushings/bearings you all offer. I would like to know though, are the seals for the front monoballs oil resistant? I'm sure you realize the stock bushings most often suffer failure not only from age but from deterioration due to oil and steering fluid.
Harry,
I was kidding about originality, for the most part, when I brought that up in regards to the bushings. I was eluding to the "how dare you alter a Porsche" attitude that is so prevalent around here. That and the fact that some classes don't allow metallic bushings/bearings. Other than that I think we are mostly on the same page regarding replacement parts. It boils down to what you are trying to get out of your car.
Harry,
I was kidding about originality, for the most part, when I brought that up in regards to the bushings. I was eluding to the "how dare you alter a Porsche" attitude that is so prevalent around here. That and the fact that some classes don't allow metallic bushings/bearings. Other than that I think we are mostly on the same page regarding replacement parts. It boils down to what you are trying to get out of your car.
