I wanted to share my experience with ride quality since installing the poly version from Welsh.

To recap, I replaced the originals at about 40K even though they were still in decent shape but just starting to dust up a bit. Those replacements were from PartsGeek and they failed/collapsed within a couple years (about 20K miles that included two 3K mile trips). Since I still had the originals I popped them back in until I could get the Welsh versions. I wanted to drive the car but not ruin my tires so I figured the originals were better then nothing. I left those in for a while and finally got around to swapping them out a few weeks ago.

So about the ride quality. I thought my car rode pretty well after I got most of the rubber bits replaced in the front. Minor vibrations existed that would come and go based on road conditions. I got used to it and convinced myself that I was expecting too much out of 19" tires.

Well after installing the Welsh mounts I found that the front end is a lot smoother than it was with the standard foam rubber mounts. And I can get to speeds about 25% higher before any noticeable vibrations. How could this be? I had to think about this for a while. Foam is soft. Poly is...well..not so soft. I needed to make some sense of this revelation. I did some reading about suspension design. Talked to a few weekend track racers.

I arrived at this theory. With the poly mounts I was actually allowing the Bilsteins to do their job properly. The foam rubber mounts are giving too much and interfere with the smooth damping capability of the shocks. And aged or deteriorating foam rubber mounts just make it that much harder for the shocks to perform optimally.

So anyway its a theory. Feel free to poke holes in it.

For sure I recommend the Welsh poly mounts. I never expected such an improvement.

Now I wish Welsh would start offering the rear donuts in the same poly material. Soon I will be replacing those.

 

It would seem to me that the upper mounts are acting more like springs (force proportional to position), and either one is in series with the actual coil spring. Changing to a harder upper mount changes the net result I suppose. I am sure there is a formula somewhere for a single spring equivalent to 2 separate springs in series with different stiffness. Or we could take the view that with the weight of the car, the foam mount is just compressed to the max for all intents and purposes.

For the shock, the force is normally proportional to speed (change of position over time). I am not sure how a rubbery mount would come into play here with the dampening.

In my view, the simpler explanation is that the new upper mounts are simply taller and changed your suspension geometry a bit. It probably restored the camber (wheel face more vertical). Could have affected the toe as well. Just my thoughts. Thanks for sharing your experience, as we probably all have these mounts in our future.

 

Whatever theory it is, you just sold me on Welsh Mounts LOL!

 

I agree the outer bushing in the mount behaves more like part of the spring. Inner portion I think is more like part of the shock.

To elaborate more on my elaborate theory:

It takes a certain amount of force to activate the damping in the shock. If the soft rubber mount takes less force to collapse then the controlled damping is not utilized while the rubber mount allows the whole assembly to move up/down with whatever damping the rubber mount does or does not provide, resulting in vibrations over surfaces that have subtle short elevation changes.

It is sort of like mounting a good shock to a small shitty shock in sequence. (try saying that fast ) Overall changes in length first occur in the shitty section until completely collapsed then the good portion will collapse.

I am not a mechanical engineer....but I play one in my garage.