With the advent of more advanced suspension systems coming available, many companies are offering new features to their kits which compound comparison of one kit to another. Once such feature is the Pillow Upper Mount. This article will tell you what a pillow mount is, what they are good for, and what drawbacks they can carry. This article is written for the layperson with a street sports or mild performance car.
What is a Pillow Upper Mount? A picture speaks a thousand words:
This image depicts a set of pillow upper mounts sold by Tein. There are four mounts on any given car. These mounts are designed to bolt onto the top of the damper assembly and allow installation onto the chassis. The center hole is where the shock mounts, and the studs poking up provide mounting to the chassis:
On MacPherson Strut type suspensions, such as on the WRX or RSX, we see that the pillow mount takes on a different form, occasionally allowing for camber adjustment:
Note, the Camber adjustment option will only be available on MacPherson strut cars, where the damper assembly functions as a suspension member! Double-wishbone cars such as the EG Civic or TSX will not have camber adjustable pillow mounts, as such an adjustment would not be of any effectiveness.
Why are pillow mounts good? The upper pillow mount houses a spherical bearing where the damper will fasten to. This bearing provides a more rigid mount than the standard rubber bushings on a stock vehicle. With a a more rigid mount, the shock will move more accurately and provide a more linear and direct feedback to the chassis. The effect of adding pillow mounts is very similar to adding low profile tires, or tires with very stiff sidewalls. Road feedback is very good, steering can feel much more sharp, and the ability to control the vehicle improves.
What are the drawbacks of upper pillow mounts? Upper mounts can be more noisy than stock and add to the choppiness of the ride. Rubber bushings are used by automakers because they are cheap, quiet, and soft. They provide an isolation to road irregularities. Similar to our low-profile tire reference above, pillow mounts will transmit more road noise and small bumps into the chassis. It does not make the suspension more stiff, but the suspension feels more stiff because more road irregularities are felt and heard.
Is there a compromise?
There are a few alternatives to going with a full rigid upper mount.
Some companies offer rubber upper mounts, like this one standard on the Tein CS:
The rubber bushings used here are firmer than stock, decreasing the squishiness of the mount a little.
Honda offers a metal-reinforced bushing on Type-R and S2000 vehicles that practically eliminate play in the bushing, but still provide a level of comfort not available on the full rigid mounts:
Skunk2 offers a replacement upper mount that utilizes polyurethane bushings. These are much harder than rubber mounts and only offer a fraction of comfort over rigid mounts, but these are a good choice as a very effective and less expensive option:
We hope this article clears the air a little on the topic of pillow mounts!
Marcus