SADfab Delrin Bushing Kit
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SADfab Delrin Bushing Kit
Matt set out to upgrade the suspension on his supercharged Miata to make it more competitive in the SSM autocross class. We started by moving the Xida shocks from my car to his car. Then he ordered a Delrin bushing kit from SADfab. This is how we went about installing the bushing kit.
The first step should be to read the instructions and the SADFab Bushing Mega Thread.
The second step should be to re-read the instructions and the SADFab Bushing Mega Thread.
Before removing any of the control arms we used a scribe to mark the existing alignment. I will still have the car realigned, but marking the alignment will make it easier to get things back to road worthy for the trip to Gran Turismo East.
With the front control arms removed, we laid the arms on the ground as they were on the car and marked each. This step is not required, but it is like a surgeon marking the limbs of a patient. It prevents errors.
Now that the control arms are removed and marked we could begin removing the bushings. We used extensions and sockets to span the gaps between the bushings. Pushing the flanged side of the bushing out the press made quick work of the bushings.
When we got to the lower control arms it was difficult to stabilize the arm on the press. We used a short piece of exhaust pipe to rest the collar of the arm on.
After we removed all of the old bushings I took some time with a fine file and cleaned up the edges of the bushing locations so there was no slag and so the barrels were clear of rubber and debris. Then we used a vice to press in the bushings.
At first there was a bit of confusion about the acronyms for the bushings. For instance if we should tap the grease fittings first or install the bushings first, and how far we needed to drill the holes.
Several of the bushings have a front and rear half that are different. These are marked F and R.
The acronyms for the front are as follows:
Front Upper Control Arm
Front Lower Control Arm Rear FRONT
Rear location front half
Front Lower Control Arm Rear REAR
Rear location rear half
Front Lower Control Arm Front FRONT
Front location front half
Front Lower Control Arm Front REAR
Front location rear half
The correct order of operations is as follows:
Install the new bushings
Drill and tap the holes for the grease fittings
Drill to the center of the bushing where the sleeve will be You want grease on that sleeve
Use a 7/8 bit to true the hole for the sleeves
We did this in steps testing for a snug but easy fit of the sleeve as we went
Insert the sleeves
Install the grease fittings
The Front Upper Control Arms (FUCA) have the same bushing in all locations (front and rear). We pressed each of these into place with the vice and metal plates to prevent marring of the bushing. You want to install the shoulder on the outside of the control arm on both locations.
The Front Lower Control Arms (FLCA), in the kit I ordered, use delrin in the front location and polyurethane in the rear location. Both have a different front and rear half. Make sure you have orient the control arm as it would be on the car. Then use the Front Lower Control Arm Front Front (FLCA-F-F) in the position closest to the front of the car. Use the Front Lower Control Arm Front Rear (FLCA-F-R) on the backside of that.
Repeat this step for the Front Lower Control Arm Rear Front (FLCA-R-F) and Front Lower Control Arm Rear Rear (FLCA-R-R) using the poly bushings.
Now using a 7/32" drill bit drill a hole for the grease fittings. Make sure the hole goes all the way to the center of the bushing where the sleeve goes. This will allow grease to grease the sleeve. SADFab has a very good thread on where to install the fittings, but check and double check that the fittings will not hit anything on your setup.
NOTE 1: The bushings pivot on the 7/8” sleeve.
NOTE 2: The photo is the RUCA but the idea is the same.
After we drilled the holes we used a 1/4-28 tap to tap the hole for the grease fitting. We ran the tap all the way down to make sure I had plenty of room to seat the fitting.
NOTE: Do not install the fittings yet.
Using a 7/8” bit insert the bit into the delrin bushing about 1/2” or more (this will make sure you do not harm the edges of the bushing trying to insert the drill) and start the drill. We ran the drill in and out and checked to see if the bushing could be inserted by hand with light pressure. If not we repeated the above steps working one stroke at a time until the sleeve could be inserted. Most of the holes only took 2 times reaming before they were done.
NOTE: DO NOT REAM THE POLY BUSHINGS!
SADFab Bushing Reaming Video
With all of the Delrin locations reamed use air to blow out any remaining debris from the bushing. Make sure to blow out the grease fitting holes as well. Apply grease to the bushing center and to the appropriately marked sleeves and insert them... FUCA sleeve in the FUCA locations, FLCA-F in the FLCA-F locations, etc.
The poly bushings are two piece. There are also two outer steel sleeves and an inner steel sleeve. First grease the bushings then press them in by hand. Next press the outer steel sleeves into the poly bushings with the vise. BE VERY CAREFUL. If the outer sleeves are not in line with the hole, you could cut the poly bushing. We then inserted the inner metal sleeves into the poly bushings. They slid right in.
Also there is a bag of thick washers included with the kit. One of these washers goes on either side of the FLCA-R location (the poly one). We missed this step at first. The arm will not work without them, and the poly bushing will get crushed.
Now insert the grease fittings. The instructions call for RTV on any of the short fittings. If you use RTV make sure to not block the hole on the bottom of the fitting.
You can now reinstall the control arms on the car. As you reinstall you should not tighten everything until everything is back on the car.
The rear control arms are very similar to the front. There are several acronyms similar to those used on the front of the car to denote the locations. They are as follows:
Rear Upper Control Arm INNER
Rear Upper Control Arm OUTER
Rear Lower Control Arm Inner FRONT
Rear Lower Control Arm Inner REAR
Rear Lower Control Arm OUTER
These differ slightly in the naming convention as there are more than two locations on each arm. Inner locations are the closest to the center of the car, and outer are the closest to the outside of the car.
We again marked the alignment with a scribe and marked the sides the arms came from.
Pressing the old bushings out is very similar to the front. We used large sockets and extensions to span the gaps in the locations. After we removed the bushings I cleaned each location with a fine file.
The Rear Upper Control Arm Inner (RUCA-I) bushings are the same front and rear. Simply insert two at each location.
The Rear Lower Control Arm Outer (RLCA-O) bushings had us a bit confused at first. We finally determined that we should put the flanged side on the inside in both locations.
The Rear Lower Control Arm Inner Front (RLCA-I-F) is the same front and rear. It differs from the Rear Lower Control Arm Inner Rear (RLCA-I-R) because the rear location is poly.
The Rear Upper Control Arm Outer (RUCA-O) location is part of the spindle.
We installed all of the bushings again and drilled holes for the grease fittings and tapped them. We followed that by a careful reaming of the center hole with a 7/8” bit.
Installing the sleeves is the same as above making sure to use the appropriately acronymed sleeve in the appropriate spot.
Thoughts on the SADFab kit:
I have read thread after thread that said the ride would be harsh if upgraded to Delrin; I disagree. I have run the car with stock suspension, Koni yellows and stock springs, Xidas and stock bushings, and now Xidas and delrin bushings. Stiffer shocks and springs is the only thing that ever made the ride harsher. I have helper springs on the Xidas to make the ride better, but there was no noticeable difference between the Knoi yellows and the Xidas with the Delrin in reference to harshness.
The car cornered well with the Xidas, but it is much smoother with the Delrin bushings. The Xidas account for the improved control and how flat the car stays. The difference is before I fought it around corners, and now I don’t. I have really enjoyed having the upgraded suspension on the car. I have driven it to work every mildly sunny day and autocrossed it once.
The car did very well at the autocross. I am not a national caliber driver by any stretch, but I typically hold my own locally. That said I have earned time of day once in many years of autocross. But that was with new slicks and all the other normally fast participants were on worn tires or were absent. I came very close at the recent event with the new suspension. I am still shaking down the car, and I was unable to find the course a few times, and I was driving on Nitto Neo Gens, which is not an autocross tire, I was able to stitch one run together worth having. I ended up 3rd overall. The other cars had very seasoned drivers with autocross tires. Definitely not blaming the tools. A good driver could have taken TOD easily. The takeaway is previously I needed slicks and missing drivers to come this close.
I will take the car to GTE and have it aligned and possibly corner weighted. If all goes well I will change to lightweight 9” wide rims and 225 slicks or autocross rubber for competition in 2018.
Off to the races!