10-06-2011, 07:04 PM
for some time now, i have been working on creating a new upper strut mount, as the OEM unit fails over time, and has limits to how much spring rate it can handle. on top of that, it is a pretty pricey part, floating around $500 each.
this part locates the strut shaft and holds it centered in the strut tower. it flexes a bit to absorb bumps, by means of a rubber molded outer encapsulating a bearing.
it's really a pretty ingenious design. it even has a tilt built into it to accommodate an angular tip of the strut (yes, the bearing inside is at an angle). this allows the springs to hold a high effective rate, while still centering the strut. you can see the angle in this shot (new one on the left. old one on the right)
i looked at a bunch of the different aftermarket units, and found that none of them use spherical bearings, which would accommodate that tilt. i'm not sure if it's because of the cost, or because of wear failure though. the problem is that if you don't have the tilt built in, you reduce effective spring rate, alter camber angles, and also create an uneven load on the strut tower. this can result in tragic failure. i've seen a few strut towers ripped out now, and it was always on a car with either a super stiff strut tower brace, a camber plate, or both. if it walks like a duck........
so, i started looking at the design to see what i could do. in doing that i also noticed that my mounts are starting to go. i replaced them a few years ago when i installed the first set of struts. however, they are already showing signs of failure. you can see this from the way the upper plate is pushing upward and inward.
you can also see how the bottom of the mount on the unit on the right in the pic below is being pushed upward due to wear. the spring is constantly pushing upward against the bearing, which takes the rubber upward with it.
stiff springs add load to the bearing, which causes the rubber to be stretched more than stock springs. this wears the unit out prematurely. were the rubber to rip, there is nothing to stop the strut shaft from punching a hole in the hood. obviously i want a stiffer suspension than stock, but i'm not looking to keep dealing with these parts, and sure don't want to see a strut shaft poking up through my hood.
the existing camber plates don't accommodate the tilt, and result in too much harsh impact being transmitted to the car. i prefer a smoother ride.
so, i am trying to figure out a mount that has a bearing that is encapsulated in rubber, so as to absorb the bumps, and also accommodates the tilt. it would also have built into it a mechanism to prevent failure.
this is definitely going to be a challenge. porsche really did a pretty danged good job of engineering this piece. it just can't handle the loads i want to subject it to. but until i come up with something, i have to keep changing these.
ah, another slippery slope. yeah. that's a big shocker.
this part locates the strut shaft and holds it centered in the strut tower. it flexes a bit to absorb bumps, by means of a rubber molded outer encapsulating a bearing.
it's really a pretty ingenious design. it even has a tilt built into it to accommodate an angular tip of the strut (yes, the bearing inside is at an angle). this allows the springs to hold a high effective rate, while still centering the strut. you can see the angle in this shot (new one on the left. old one on the right)
i looked at a bunch of the different aftermarket units, and found that none of them use spherical bearings, which would accommodate that tilt. i'm not sure if it's because of the cost, or because of wear failure though. the problem is that if you don't have the tilt built in, you reduce effective spring rate, alter camber angles, and also create an uneven load on the strut tower. this can result in tragic failure. i've seen a few strut towers ripped out now, and it was always on a car with either a super stiff strut tower brace, a camber plate, or both. if it walks like a duck........
so, i started looking at the design to see what i could do. in doing that i also noticed that my mounts are starting to go. i replaced them a few years ago when i installed the first set of struts. however, they are already showing signs of failure. you can see this from the way the upper plate is pushing upward and inward.
you can also see how the bottom of the mount on the unit on the right in the pic below is being pushed upward due to wear. the spring is constantly pushing upward against the bearing, which takes the rubber upward with it.
stiff springs add load to the bearing, which causes the rubber to be stretched more than stock springs. this wears the unit out prematurely. were the rubber to rip, there is nothing to stop the strut shaft from punching a hole in the hood. obviously i want a stiffer suspension than stock, but i'm not looking to keep dealing with these parts, and sure don't want to see a strut shaft poking up through my hood.
the existing camber plates don't accommodate the tilt, and result in too much harsh impact being transmitted to the car. i prefer a smoother ride.
so, i am trying to figure out a mount that has a bearing that is encapsulated in rubber, so as to absorb the bumps, and also accommodates the tilt. it would also have built into it a mechanism to prevent failure.
this is definitely going to be a challenge. porsche really did a pretty danged good job of engineering this piece. it just can't handle the loads i want to subject it to. but until i come up with something, i have to keep changing these.
ah, another slippery slope. yeah. that's a big shocker.
94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com
"It isn't nearly as expensive to do it right as it is to do it wrong."
(This post was last modified: 10-06-2011, 07:07 PM by flash.)
