GreenGSX
DSM Wiseman
- 371
- 5
- May 13, 2002
-
Rochester,
New York
Tuners Nation was kind enough to donate a set of there 1G AWD/VR-4 rear sub-frame and mustache brace bushing sets. But why would you want to install these bushings?
The job of a bushing in a passenger car is different then it is in a race car. A passenger car has to be smooth, handle well, and not do anything “twitchy†if the driver tosses it around. A race car doesn’t care if the ride is smooth, it too needs to handle well, and has to be “twitchy†to some degree to get the car to rotate in a turn.
Looking at the entire rear suspension out of the car it becomes quite clear how important the front two sub-frame bushings are to the geometry of everything that attaches to it. Take note of how the diff bolts to the sub-frame where the upper and lower control arms tie in. That makes the mustache braces job important too. Not only does it have to keep the pinion angle in control under hard launches its also the rear two attachment points for the whole rear suspension.
Just like the VR-4 rear steering and the passive toe of the 1G AWD trailing arm side to side deflection of the suspension results in a change in the rear toe. The problem is that the toe of the outside rear wheel in a turn goes “toe-in†under load which, in a simple model, tries to point the rear of the car into the apex of the corner. Think of it this way, if you are trying to turn left and the rear of the car wants to go left too or even wants to keep going in a strait line the net result is the rear is going to push the front and cause the car to understeer. To combat this we align the rear of the car with some static “toe-out†to help get the rear of the car to “rotate†to the outside of a turn. Back to were we started, rear steering, passive toe, and sub-frame deflection all result in a dynamic change in the rear toe towards “toe-inâ€. Remove the rear steering, weld the trailing arms, and install sub-frame bushings and now no matter how hard you toss the car the rear toe stays where you want it to be. Now we don’t have to use as much rear “toe-out†to get the car to turn and that helps us because too much rear “toe-out†can make the car wiggle under hard braking and less predicable over ruff track surfaces.
Inspecting the stock 200k+ mile bushings shows that they’ve lived a hard life. The sub-frame bushings were coming apart and the mustache brace bushings weren’t that far behind. Replacing them with hard urethane will hold everything in place under hard cornering and let the suspension do its job and hold the alignment to what I set it to.
Today I got to work installing them. Here is how I did it.
1. remove the parking brake cables
2. remove the rear calipers and hang them on the rear springs.
3. unbolt the lower shock bolts and separate.
4. remove the rear section of the exhaust
5. disconnect the drive shaft from the diff.
6. put a jack under the diff and remove the 6 bolts holding the rear sub-frame/mustache brace and lower everything out of the car.
The One Lap car is in pretty good shape and seeing how I've had all the rear suspension out of the car just a year ago when I built it, everything came apart easily. I think I rolled the rear suspension in about an hour.
To get the bushings out I first drilled around the center pins and then I used a sawz-all to finish cutting them out. From there is was old school, get dirty, burn the snot out of everything. I set the pins outside on a cinder block and set them on fire. Then I flipped the whole suspension with the diff pointing down so I can get at the sub-frame bushings. These have a two-piece inner sleeve that has to come out. Once again I set them on fire, waited, and then knocked them out with a hammer. There was still a bunch of rubber left in the sub-frame so I set that on fire too. Once the rubber gets hot and gooey most of it can be scraped out. To get both the pins and the bushing cavities clean up I used a wire wheel in a hand drill. I greased up the bushings and pins and used a clamp to push them in.
Taking a cue from Curtis I spent some time bracing the mustache brace by fitting and welding some angle iron onto it. This will help keep the diff where it belongs under hard launches. I got as far as rolling the suspension back under the car before I called it quits for the day
The job of a bushing in a passenger car is different then it is in a race car. A passenger car has to be smooth, handle well, and not do anything “twitchy†if the driver tosses it around. A race car doesn’t care if the ride is smooth, it too needs to handle well, and has to be “twitchy†to some degree to get the car to rotate in a turn.
Looking at the entire rear suspension out of the car it becomes quite clear how important the front two sub-frame bushings are to the geometry of everything that attaches to it. Take note of how the diff bolts to the sub-frame where the upper and lower control arms tie in. That makes the mustache braces job important too. Not only does it have to keep the pinion angle in control under hard launches its also the rear two attachment points for the whole rear suspension.
Just like the VR-4 rear steering and the passive toe of the 1G AWD trailing arm side to side deflection of the suspension results in a change in the rear toe. The problem is that the toe of the outside rear wheel in a turn goes “toe-in†under load which, in a simple model, tries to point the rear of the car into the apex of the corner. Think of it this way, if you are trying to turn left and the rear of the car wants to go left too or even wants to keep going in a strait line the net result is the rear is going to push the front and cause the car to understeer. To combat this we align the rear of the car with some static “toe-out†to help get the rear of the car to “rotate†to the outside of a turn. Back to were we started, rear steering, passive toe, and sub-frame deflection all result in a dynamic change in the rear toe towards “toe-inâ€. Remove the rear steering, weld the trailing arms, and install sub-frame bushings and now no matter how hard you toss the car the rear toe stays where you want it to be. Now we don’t have to use as much rear “toe-out†to get the car to turn and that helps us because too much rear “toe-out†can make the car wiggle under hard braking and less predicable over ruff track surfaces.
Inspecting the stock 200k+ mile bushings shows that they’ve lived a hard life. The sub-frame bushings were coming apart and the mustache brace bushings weren’t that far behind. Replacing them with hard urethane will hold everything in place under hard cornering and let the suspension do its job and hold the alignment to what I set it to.
Today I got to work installing them. Here is how I did it.
1. remove the parking brake cables
2. remove the rear calipers and hang them on the rear springs.
3. unbolt the lower shock bolts and separate.
4. remove the rear section of the exhaust
5. disconnect the drive shaft from the diff.
6. put a jack under the diff and remove the 6 bolts holding the rear sub-frame/mustache brace and lower everything out of the car.
The One Lap car is in pretty good shape and seeing how I've had all the rear suspension out of the car just a year ago when I built it, everything came apart easily. I think I rolled the rear suspension in about an hour.
To get the bushings out I first drilled around the center pins and then I used a sawz-all to finish cutting them out. From there is was old school, get dirty, burn the snot out of everything. I set the pins outside on a cinder block and set them on fire. Then I flipped the whole suspension with the diff pointing down so I can get at the sub-frame bushings. These have a two-piece inner sleeve that has to come out. Once again I set them on fire, waited, and then knocked them out with a hammer. There was still a bunch of rubber left in the sub-frame so I set that on fire too. Once the rubber gets hot and gooey most of it can be scraped out. To get both the pins and the bushing cavities clean up I used a wire wheel in a hand drill. I greased up the bushings and pins and used a clamp to push them in.
Taking a cue from Curtis I spent some time bracing the mustache brace by fitting and welding some angle iron onto it. This will help keep the diff where it belongs under hard launches. I got as far as rolling the suspension back under the car before I called it quits for the day
.
