Got tired of poly squeaking, having high stiction, needing constant regreasing...
Posted by empty_bottle_of_glue@reddit | projectcar | View on Reddit | 49 comments
I've been messing with polyurthane bushings on my NA8 Miata and SJ Forester for a while and kept running into the same issues:
OEM rubber -> too much compliance, Subaru OEM FLCA bushings tend to fail prematurely
Poly -> squeaks, binds, needs constant regreasing/upkeeping
Spherical -> too harsh / short lifespan for street
So I ended up building a quick and dirty setup from McMasterCarr:
polished 4140 sleeve
660 bronze bushings
863 thrust washers
This concept has been explored in the Miata world before (credit to Bob Bundy/SADfab). I built my own version and adapted it to other platforms like my Forester.
Been running them for a while now and the difference is actually noticeable:
tighter steering / less deflection. Basically OEM+
no squeak and zero stiction
I'll be checking on the condition on the inner sleeves and bronze bushings during my next oil change on the Forester and report back. SoCal cars so they won't see much salt/water ingress.
Honestly wasn’t planning to do anything with it, but I had a spare set sitting around and figured I’d share.
Curious what you guys think. Would you run something like this?
Deep-Hovercraft-6863@reddit
Love it. Coincidentally we have two of the same cars. I’m interested in the condition of the setup after some miles.
empty_bottle_of_glue@reddit (OP)
Appreciate it 🙏
Just curious, what bushings do you have on the Miata right now?
Deep-Hovercraft-6863@reddit
177k mile originals. The car handles like a greasy weasel.
HeirElfEsquire@reddit
Good name for a band
Deep-Hovercraft-6863@reddit
All credit to our lord and savior Clarkson.
danny_ish@reddit
Oh man, go blow a paycheck at goodwin racing and harbor freight, these things are silly easy to work on for suspension work.
fartsincognito@reddit
I also have an NA8 Miata and a Forester.
There are dozens of us. Dozens!!!
TealPotato@reddit
I also have an NA8, and my Mom has a '15 Forester XT that she bought on my recommendation.
I went to Subaru back then to look at WRXs, drove a Forester XT as I knew she was also going to buy a car soon, and as soon as I drove it I knew it was exactly what she wanted (AWD crossover with reasonable passing power and good visibility).
I've driven it a few times, I am a big fan of Subarus AWD implementation. I don't like the part time AWD systems from other brands that cut out at low speeds.
A few minor goofy things have happened, like one of the rear coil springs breaking (later recalled).
fartsincognito@reddit
Mine’s a ‘19 XT. Love it, aside from the CVT
Caustic___@reddit
Have u heard of sadfab for ur miata?
2Drogdar2Furious@reddit
I have an NA... is there a list somewhere of what I need to buy (like sizes)?
I've seen some people using 3d printed bushings and I'd like to combine this with the printed bushings. The material I have has a durometer of 98A.
Restomotive@reddit
Looks good. Nice work!)))
SensualBeefLoaf@reddit
i too have knocked off elephant racing’s polybronze bushings but for different applications. you need a grease fitting and somewhere for grease to go.
_Valet@reddit
Wrapping the steel insert in Teflon tape works for eliminating sticktion and squeaking.
FakeAssRicky@reddit
Does the poly on the edges not bind on the thrust washer once it's calmped tight to the stainless when torqued to the chassis? I understand it's outside the load bearing part of the bushing but seems like if nothing else it could cause some squeaks from the rubbing as it twists.
v8packard@reddit
Actually the perfect solution to this is a medium durometer rubber bushing. Steel/rubber silent bloc style. What you are calling compliance is actually an engineered characteristic. When combined with a proper spring rate and tires to produce the needed wheel rate the results are excellent.
How will your solution behave at max suspension travel?
kgruesch@reddit
I just used OEM grade spherical bearings, the ones used in the control arms and hubs of most BMWs. They're way beefier than the race parts most aftermarket companies use, and have full rubber seals and are designed to last several years. The ones I used were Febi/Bilstein and cost about $10 each.
I just got some sleeves machined to adapt them to the control arms. The increase in NVH really wasn't that bad, but the difference in steering feel was profound (which is saying something for the F30 chassis).
FocusedADD@reddit
What is the red material (in CAD, black on the parts)?
Could you compare it to something like a Johnny Joint?
empty_bottle_of_glue@reddit (OP)
Polyurethane. I made them red for attention lol
voxelnoose@reddit
The races around the ball are delrin or polyurethane
SprungMS@reddit
The polyurethane bushing
vehicularmcs@reddit
Where do you get the bushings? They're shelf Energy Suspension just different halves than the application uses normally?
empty_bottle_of_glue@reddit (OP)
I got these from Whiteline
vehicularmcs@reddit
How did you spec them? Is there a fitment sheet someplace?
donald7773@reddit
Why not get super pro bushings specifically sold by flying Miata for specifically this issue?
empty_bottle_of_glue@reddit (OP)
SuperPro is a solid option. I've looked into them too.
They definitely improve things on the poly side and have excellent tolerance, but I was still curious about something that articulates more freely instead of relying on the bushing's ID to act as a bearing.
I've also seen some cases where the knurls wear down over time or you still get some squeak depending on setup (i.e. cold weather), so I wanted to try a different approach.
That's kind of what led down this rabbit hole: let the poly handle misalignment/NVH and have a separate interface take care of the articulation.
donald7773@reddit
Cool! I was curious since I've pretty much decided on their bushings for my NA.
Currently torn between buying a hardtop, quick jacks, or a torsen with my tax return
empty_bottle_of_glue@reddit (OP)
hardtop before they're 6k each 😢
donald7773@reddit
Ok that's what I've been thinking. My biggest complaint about the car as it sits is it's loud and uncomfortable, hardtop should help with loud a little hopefully.
Need a dash too maybe I can find an auto with a hard top for cheap.....
DramaticOption@reddit
been running this setup for several years on a heavily modified 90 Miata. the lack of stiction is real and totally changes the ride and nvh. I literally had to stiffen my dampers after installation. I bought from sadfab and probably one of the better suspension upgrades besides xidas that you can do on a Miata. And for the guys talking about delrin, it has its place but not on my car. This is a fantastic read even if you don't have a Miata, to wrap your head around bushings
https://www.miataturbo.net/suspension-brakes-drivetrain-49/miata-bushing-megathread-heirarchy-diy-delrin-dimensions-info-discussion-87573/
empty_bottle_of_glue@reddit (OP)
That's awesome to hear and I appreciate you sharing that.
That lines up pretty closely with what I’ve been experiencing so far. Before, the suspension didn’t seem to deal with small road irregularities very well, but after switching it feels like it can actually move and do its job.
That megathread is what got me started tinkering first place!
Carbonbuildup@reddit
Lot of work when you could have just changed to Derlin which is self lubricating. Hasn’t made a squeak on my 911 in 15 years. Wears better than poly or rubber. Etc
SprungMS@reddit
Delrin is incredibly hard plastic.. NVH not an issue? Even polyurethane is too much for a lot of people
Carbonbuildup@reddit
Derlin isn’t the issue, muffler is the issue.
empty_bottle_of_glue@reddit (OP)
Yes, Delrin setups can work really well, especially when everything is aligned perfectly.
For my use I was trying to keep NVH reasonable (the Forester is a DD after all) and still allow a bit of misalignment, since most of these suspension points aren’t moving perfectly in one plane.
beakerlab@reddit
Energy Suspension has graphite injected poly bushings.
empty_bottle_of_glue@reddit (OP)
I've actually tried both the red and the black ones. In my case, I didn’t really notice a difference between them, and I still ran into stiction/binding
LethalRex75@reddit
I read the title like it’s an Eminem verse
empty_bottle_of_glue@reddit (OP)
mom's spaghetti
Friendly_Escape_1020@reddit
Delrin is popular for high performance bushings.
empty_bottle_of_glue@reddit (OP)
Correct. For what I was after (mostly street use), I found it tends to transmit more NVH and isn't very forgiving when there's any misalignment, so it wasn't the best fit for me.
ONE1-ZERO@reddit
You’re dealing with a problem since the beginning of poly. The VW guys run the poly fronts and the solid rubber r32 bushings in the rear of LCA. Just make the durometer softer.
empty_bottle_of_glue@reddit (OP)
that’s a good point. softer durometer will definitely help. In my case I didn’t always have the option to go softer depending on the parts/platform, and even around 80A (basically OEM rubber) I still ran into some binding/stiction at the inner sleeve.
That’s kind of what pushed me toward separating the two: keep some compliance on the outside, but let the inner interface move freely.
Sir_J15@reddit
Drill the sleeve that it slides into in the middle and add a grease zerk. Grease like a normal bushing after that. I do this on just about all the stuff I use poly bushings on.
empty_bottle_of_glue@reddit (OP)
yes that definitely helps. I've done the same thing before on poly setups.
My experience was it improves things short-term, but once the grease gets pushed out, you're back to the same stiction/bind.
I was trying to get away from relying on constant greasing altogether and have something that articulates smoothly on its own.
Sir_J15@reddit
I’ve never had it push out that quickly that it was any more than just normal maintenance. No increased times or frequency. The quality of the poly makes a drastic difference as well. Low quality poly such as StrongFlex and Energy Suspension are worse than something like Whiteline or SuperPro. It also helps if the poly or the inner sleeve is grooved to give the bushing a place to hold grease.
phalangepatella@reddit
This. This is the way.
amg-rx7@reddit
Pretty cool design. I gave up on poly for street cars. Not worth it to me. The nvh gets annoying. Ymmv
empty_bottle_of_glue@reddit (OP)
yeah I'm with you on that. poly can get annoying for street use.
However, I've always suspected a lot of the harshness people feel is from the bushings not articulating smoothly (stiction), so the suspension doesn't deal with small bumps as well.
That was kind of the motivation behind this setup. let it move freely without the squeak/bind.