(Delrin) Rear Subframe Bushings

TristanScott said:

Managed to remove that metal washer/cup from the rear bushings using a 3 jaw puller. It actually helps in removing the old bushing to first remove this even though it is sort of a pain to remove. It's simply pressed into the inner metal sleeve. This metal washer/cup will be reused with the delrin bushings, I made sure that the inner metal sleeve will receive it.

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I made some final changes to my design to simplify things. The subframe will technically be 0.65mm lower than stock but I really don't think this will matter at all. I measured the height of the subframe at all four corners with the stock bushings (as best as I could) and the spread between min and max distances was like 1.50mm haha.


I just sent the .step files to Sunpe (as recommended by broinkrist) for quotes. I'm getting a quote for a single set and then 10 sets.
1 set will comprise of:

• 8 identical Bushing Halves - Delrin (probably 150 or whatever common variety, I do not want "no-name" acetal.)
• 2 Front Sleeves - 304 Stainless Steel
• 2 Rear Sleeves - 304 Stainless Steel

Hoping to get these on the car ASAP for a test drive!

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Hoenig said:

Havent been under the R in a while (knock on wood) but does the rear subframe need to be dropped to install the bushings in the way that it needs to be for the fronts?

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TristanScott said:

Just got the quotes back from Sunpe and am placing the order for the one set for myself.

I wanted to try to hit the $200 per set pricepoint but after receiving the quote for the 10 sets, I think we would be looking at ~$300 per set. If there were more people buying then that would go down further I'm sure.

Curious what you guys think about that price?

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TristanScott said:

Just received the parts from the machine shop in China. I just finished verifying the measurements against my specs and everything looks really good. I'm very happy with them. Thanks again to @broinkrist for recommending the company to me.

Delrin parts were for the most part +/- 0.05mm and stainless steel parts were basically +/-0.01mm!

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I have a 3 day weekend starting tomorrow and am going to try to test fit them and hopefully get the car back on the ground for a test drive.

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TristanScott said:

The bushings are installed in the car! Looking to organize some sort of group buy. I'll keep you guys posted.

I got the bushing in and everything buttoned up last night and drove the car for the first time in months. It put a big smile on my face. Truthfully, it's not an ideal before/after comparison for a number of reasons, mainly it's first time driving it with proper Michelin PS4S (instead of flabby winter tires) after installing my rear spring seat adapters, linear rear springs, and having the car corner balanced and aligned. However, the car steers so tightly and precisely. Subjectively, it feels like the rear end no longer has a certain vagueness that it used to have. However, the last time I drove it with the Michelins, it was with the KW springs in the rear and the car wasn't corner balanced nor did it have camber bushings in the rear so the rear camber was out of control. Right now, I can toss it into a corner and it just GRIPS and does exactly what I tell it to, it's the best. It also seems like it takes much less effort to keep the car centered in my lane at highway speeds.

Only negative is that I can hear more road noise from the rear now which is to be expected. Pre-install, I thought my driver rear wheel bearing was starting to whirr under load and now I can very clearly hear it whirr when I turn right and hear it go quiet when I turn left. The increase in NVH is pretty small and similar to the NVH increase when doing the delrin front subframe bushings.

Overall the results are pretty much what you'd expect, similar to doing the fronts if you've done them. I definitely think it was worth the trouble designing and having them made. If I had the option to simply buy these (for cheaper than I paid for my one set, might I add,) I would jump on it. That's my $0.02.

I'm going to get a few quotes from the machine shop for different quantities of sets so you guys can see the price break with more or less people buying in.

I'm going to go with 4130 steel for the sleeves instead of 304 stainless. If a lot of people want stainless, we can do that, it's just probably going to be more expensive. Speak now or forever hold your peace.


Some notes on installation:

- Removing the front two bushings is very easy with a 2-1/8" hole saw. The rear two are difficult because the metal washer is sort of pressed into the sleeve. On the driver's side, I was able to use a puller to remove it. The passenger side was severely seized together. I had to basically rip the bushing apart using the puller. Once I got it all apart I cut the sleeve off of the washer on the bench since my design reuses the washers.

- Once all the bushings are installed, the rear subframe needs to be aligned. Unlike the front subframe, there are no alignment pegs on the frame. Something I noticed is that the mounting holes on the frame of the car are not perfectly on center with the subframe bushing sleeves. This could be due to manufacturing tolerances or a frame being slightly bent. I decided to 3D printed a couple of alignment sleeves that go inside the bushing's metal sleeve which basically reduce the ID down to a little larger than the subframe bolt OD. I inserted the sleeves in the front two corners of the subframe, shifted the subframe to line up the holes, and lightly tightened the front two bolts. I checked the alignment at the two rear bushings by looking up through the sleeve to see if the mounting hole was centered in the sleeve. They were a little off but I was able to shift the subframe slightly to split the difference between the two and get the subframe centered as best as I could. I had thought about tightening up the ID of the metal sleeves on my design but I now am glad that I stuck the the OE Volvo bushing sleeve ID.
After all of this, I needed to torque the bolts to spec and looked at the VIDA procedure for replacing the rear subframe and they mention using a couple of sleeves to align the subframe as well! They don't list a part number or tool number for them though which is weird. Funny that I had the same idea as them though haha. VIDA says to insert the sleeves into the rear two bushings, not the front like I did. They also say to remove the sleeves after torqueing down the front bushings. I actually ended up leaving the sleeves in the front as they're just CF-PA6 and are softer than the delrin/stainless sleeve/aluminum subframe.

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kTaLgsTo said:

Subframe bushings are a breeze with a hole saw and a power hammer/chisel. Great work man.

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TristanScott said:

Oh, just received new quotes for 10, 15, and 20 sets. There is no cost advantage to using 4130 Steel vs 304 Stainless like my prototype. Anyone have a preference?

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