Garage Star Delrin Door Bushing Review

Disclaimer: I am not benefiting financially from this review. I am not receiving any kick back or royalty from Garage Star for sales of these bushings. I never thought this review would become so popular or so controversial. I also have no idea if the below observations will apply to YOUR Miata. The below is my experience with the Garage Star Door Bushings. I posted it only in a desire to help others enjoy their Miatas.

The bots and the delrin.

The bots and the delrin.

This is something that totally came out of left field, at least for me. I had no idea that stiffer door blocks were a thing. I guess Toyota offers something for the FT-86/BRZ/FRS? Anyways, this was seriously not something I ever knew I needed. And just looking at them, I had no idea how they would help anything.

Spoiler: every Miata on the planet needs these. You can stop reading now if you want and go buy a set.

Ken at Garage Star has created something awesome.

Stock vs GS

Stock vs GS

How they work (I think): The Miata is floppy. This is not news to anyone. A major chassis point is apparently the spot where the door and frame connects. Mazda uses a combination steel and rubber piece to make this connection. The base is steel and soft rubber is bonded on top.

There’s a pretty good amount of space between the cup and that rubber stock door bushing. By “a good amount” I mean around 1mm of space. Add to that a soft rubber bushing. You don’t get much extra chassis rigidity from the factory parts.

Garage Star block measurements.

Garage Star block measurements.

Stock block measurements.

Stock block measurements.

The Garage Star bushings are machined to super-accurate tolerances – .01mm according to their website. This allows the door to make a firm connection with the chassis and move the sides of the box up slightly. It’s not like adding a cage or door bars or whatever, but… holy crap is it effective.

Did I mention all 4 of my stock door blocks (Sharka’s and Bucky’s) had slightly different measurements? No doubt they’ve been squished over years of driving and the doors bumping around.

They pressure fit in the stock door cups.

They pressure fit in the stock door cups.

Before you get confused, the above shot is not how they install. I’m just including it to show how tight the fit is.

The door cup is installed on the lower part of the door from the factory. The bushing is installed on the frame. As you close the door, the cup closes over the bushing. And check out how tight they fit! I was able to easily place the bushing in the cup and take this photo.

It isn’t a TIGHT fit by any means. The bushing is ever so slightly diagonal in the cup to get this photo. But just barely. On my cars, there’s less than .2mm of wiggle room between the cup and the bushing (.12mm according to my feeler gauge on this particular block). That’s just enough to allow the door to close without any extra effort, but also a tight enough fit to eliminate door rattles and firm up the chassis when it flexes.





That’s it. Two screws. I used my fancy JIS screwdriver. The P.3 was a perfect fit.

To install, just remove the old door blocks and put on the new ones. Get the screws a little more than finger tight and slam the door. Then open and slam 5x. Then tighten the screws and repeat. Your door should not be any harder to close than with the factory door bushings, but it will give this lovely little pop/click noise. When you’re happy with the fitment, tighten the screws all the way.

A note of caution – the screws can come loose if you only tighten them with a screwdriver. More on this below. The final tightening should be done with a ratchet and 10mm socket.

The "action shot."

The “action shot.”

The Review

After driving about 150 miles with these, I have a pretty good feel for them and think I can give some good feedback. (Sorry about the wall of text. Hard to take photos of feelings.)

Car: base 2001 NB with a rollbar and TEIN Basic suspension. There’s like no bracing on Bucky at all. No diagonals on the rollbar either. The windshield shakes CONSTANTLY. Or at least it did.

I installed the blocks and went for a quick 10 mile spin around some familiar city streets. The whole car felt immediately transformed. The windshield hardly shook and I could actually feel the front and rear suspensions being independent of each other. I only got cowl shake on one bump (an offset manhole cover) on this test drive. I was hugely impressed.

The door bushings seem most effective on low speed bumps, like bumps taken between 15 and 35 mph. Higher speed bumps don’t upset the chassis as much (at least not on Bucky), but the lower speed ones were always pretty punishing. The world would end for a second or two after the bump before returning to normal. Now? That’s all gone.

I then drove around 50 miles the next day. The car started out nice and firm, but by the end of the day, I was seeing some windshield shake and the car was feeling more like a normal Miata. I was a bit disappointed. I figured that the first day was just new-part-excitement and maybe things weren’t as magical as I was imagining. I don’t have any NVH meters after all. It’s all subjective. But it definitely felt shaky.

When I got home, I installed Sharka’s door blocks. I did this with a ratchet since no JIS screwdrivers were handy at the time. I was amazed at how much the bolts kept tightening down after I felt like I’d gotten them tight. The delrin smooshes down a pretty good amount. On a whim, I opened up Bucky’s driver door and tightened down the door blocks there. The driver door? TOTALLY LOOSE. The screws had worked their way loose and were barely finger tight. I zipped all 4 down with the ratchet (passenger side was decently tight still).

On the next Bucky drive, the feeling of strength and rigidity returned. Bucky felt like a real car again, and that feeling lasted all day. I covered about 35 miles today over a bunch of surfaces. The “Miata feel” of a wet noodle with a shaky windshield never came back.

I effectively gave myself a blind test. I had no idea that the door blocks had loosened and I could definitely feel something had changed when driving around with them loose. I’m rather amazed this happened. It was an awesome blind test to take.

Door blocks for every Miata!

Door blocks for every Miata!

Car: PEP (popular equipment package) 1995 NA with various braces, Blackbird Fabworks rollbar and 2nd gen XIDA suspension. And a hardtop, can’t forget that. That piece of fiberglass provides a top for the box and a tremendous amount of rigidity. Sharka is very stiff. The rollbar made an actual noticeable difference in NVH and the XIDAs mean every bump is magically handled. Sharka is not a fair test. I didn’t expect to notice anything.

And? To quote a song, you don’t know what you’ve got until it’s gone. Sharka is now invincible. All bumps just… go away. Railroad crossings used to give me a bit of mirror shake and some drama. Now? None. Bump-bump-DONE. Potholes are barely noticed. I’m afraid I’ll bend a wheel before I feel a big bump now. It’s just amazing.

Sharka now feels like a much more expensive car. BMW-like comes to mind when driving. Bumps barely exist, even with the hard Elise seats.

You need them. Go get them.

You need them. Go get them.

These things WORK. I imagine Ken will be extremely busy making these since 100% of all Miatas on the planet require them. It needs to be one of the early mods every novice Miata driver does: rollbar, shift knob, vent rings, door blocks. Not necessarily in that order.

Go get your set. It’s one of the biggest bang for the buck modifications you can do to a Miata.

Update! 7/24/2015

I’ve received a few questions about the door blocks and thought I’d address them on this post to help folks out.

Sorry about the wall of text below.

Q: There have been complaints about increased force required to close doors. Some guys have to slam the door pretty hard to get it to latch. Do you have any problems with this?

A: For me, the door effort oscillates between zero extra effort required and “some” extra effort required. It seems to depend on my parking situation. In my flat garage, my NB has zero extra effort required to close the doors. They latch easily. If I park somewhere with a less even terrain, there might be an extra shove required to get the door to close.

The first couple times this happened, I was a little concerned. One time while parked in a mall parking lot, I whipped out my ratchet and re-adjusted the passenger door bushing which seemed to be sticking. I got the slam effort dialed out and went home happily. When I got home and was parked in the garage, the door required some effort to close again. I re-re-adjusted the door block to work correctly on a flat surface and haven’t really thought of it since.

I’m attributing this effort to chassis flex. My NB is pretty flexible. Sharka, my NA, is a lot stiffer. I’ve not had any problems closing the doors on any parking surface with Sharka.

This is my own experience with my own cars. Will it be different on YOUR car? Probably. I can’t say for sure. I can only relay my experience with my own two Miatas.

Q: Some cars have problems with the lower door edge sticking out after installation of the GS door bushings. Do you have this issue?

No, I do not. Both of my cars have the same door alignment as before.

I asked Ken (owner of Garage Star) about this and he mentioned loosening the door mounting bolts and re-aligning the door itself. He did this for a local customer and the lower door poke issue was solved.

It seems to me that you might be able to massage the stock door cup into shape if it’s not allowing the door to close with the bushing installed. A bit of a nudge with a large pliers or channel-lock might get the clearance necessary. Or shaving a bit off the front edge (edge you see when the door is open) might allow the door to close without the lower edge poking out. But this is all just a guess since I never had a problem on my installation and did not test them in an attempt to fix.

Q: You are manipulating people into buying these so that you can get a kickback.

This one shocked me. It came from one of the various Miata forums. A moderator actually typed it. I’m not sure if I wronged him somehow or if he just doesn’t like toy robots. Anyways, here is my answer.

A: I have zero financial interest in this product. I posted about the Garage Star door bushings because I truly liked them and was astounded by how well they worked. The experience I posted is 100% true for my own small fleet of two Miatas. I am not receiving any royalty or “kickback” from the sales of these or any other non-revlimiter product that I’ve reviewed. I make and sell my own parts, but I don’t “review” them on here. I post about their existence and let others write reviews of my own products.

All reviews you read on this blog are my own personal opinions. I’ve never been bought off or asked to write a positive review. The great majority of my product reviews are positive because I research the hell out of everything before I buy. In the few circumstances I’ve found a product to be poor or disappointing, I’ve posted as such in my reviews.

I might have given in to hyperbole toward the end of this review what with the statement “100% of Miatas need these.” I enjoy writing about cars and attempting to be witty. Not every car is the same and, very likely, not every car will benefit. My NA did not benefit greatly. However, I could feel a pretty noticeable difference over large bumps and road imperfections like train tracks. If I’d only installed these on Sharka, my review would likely have been much different, but it would have still been a positive review.

I wrote about this part as an enthusiast in hopes of helping other enthusiasts. That’s it. No other reason.

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  • Chris says:

    Good write-up, Adam. I had no idea those were that significant in stiffening the chassis. To be honest, I really didn’t know they had a purpose at all. Let alone ever needing to be replaced.

    Might be worth looking into now that I know what they do.

    • GT-Alex says:

      Same here. I’m amazed. I’ll put those on my stock NA once I can drive it again. It will be fun to do a comparison run 🙂

      • revlimiter says:

        The fact that these are not only noticeable, but transform the car in such a way. Almost unbelievable. But it’s an honest review. I’m really blown away by these little door blocks.

    • revlimiter says:

      Agreed. I never gave those rubber blocks a second glance. Or even a first glance.

    • Daniel says:

      Is it actually chassis stiffening? Or just NVH improvement?

      When I back out of my drive in my NB and over the gutter, the chassis flexes and I get some creaks and groans – some of these I suspect are from door movement (well chassis bending against the door which is static relative to it due to being suspended on the hinges at the other end).

      I can’t imagine that they’re sufficiently strong to resist torsional (twisting) forces on the chassis that are strong enough to deform the chassis any significant amount. (I.e. how much force could the bushings take before they start to deform if they’re all that’s resisting it at that point?)

      They probably do have the effect of being a (stiff) spring at the point of twisting though, so will take up any slack/movement of the door relative to the chassis and will be good for suppressing/controlling the door movement and subsequent NVH.

      Still, even if it were only NVH improvement, sounds like they’re well worth it. I want some!

  • Joe says:

    Awesome I had herd about these and kind of laughed at the thought yha the door blocks are going to make a diff lol.

    Thanks for confirming it I plan to get a set if I ever get my car back together.

    • revlimiter says:

      Every street Miata would benefit. I was as surprised as anyone. The review threads were not quite as complete when I ordered mine, but they still convinced me to try them.

  • Sam says:

    “Kids come in here and buy every part he has, and they pay cash!”

  • Cosmin says:

    Awesome! My question is this: if the car is up on one jackstand or 2 (so the chassis is slightly twisted) will the doors open/close? I notice that my doors feel different right now when I try to close them if it’s up in the air. I’m wondering if these door blocks could make it impossible to open/close a door on when the car is on jackstands.

  • Jimmyjet says:

    Thanks for writing this up. I had no idea this existed, but with over 200k on my chassis I’m definitely getting a pair.

  • Brad says:

    You know… I dunno why I didn’t think of this already. Sounds like it will make our Miata doors close more like an old Toyota or Lexus, as if you’re shutting one solid chunk of quality against another one.

    Thanks for the review Adam, I’ll have to try out a set. Maybe this will make the doors close with a bit more than a simple, hollow thwack.

    Question though. You say that you used a ratchet to tighten it up? Is there a nut on the backside of the screw? If so, how would you get to it, remove the fender liner? Or have I misunderstood what you mean?

    • revlimiter says:

      The little screws are actually bolts. They just have a screw slot cast into them. If you look very carefully, you can see that they’re 6 sided bolts.

      A deep 3/8″ drive 10mm will fit inside the block and be able to grab the bolt. A 1/4″ drive 10mm will also fit. A standard 3/8 drive 10mm socket will not fit due to being too thick and not long enough to poke into the bushing opening.

      • Brad says:

        Ahh, I see what you mean. Shouldn’t be a problem, I’ve torn apart a Mk3 Supra into quite literally 99% of its parts. I imagine I’ve got the right sockets. =)

        Alright, fine, gonna actually go buy a set instead of just say, “that seems like it would be nice” like I usually do. Figure $60 is a cheap price to pay for a nicer quality car.

        Funny though, that I never really thought about the door staying put as a means of structural rigidity… although it makes sense. Some of us around here are probably old enough to remember people who had C4 Corvettes and had to take the glass targa panel off before jacking up the car, for fear of twisting the roof into a broken piece of glass.

        Fun experiment, try opening a car’s door when one corner is jacked up. If anything hangs up, you’re working with a pretty loose chassis… if it opens normally, you’re working with a well designed chassis. =)

  • Jordan says:

    Thanks for the great write up Adam! It was enough to convince me to buy a set. After my first drive with them I am truly amazed at how much of a difference a product that cheap and easy to install made. My 1990 doesn’t feel like it is going to fall apart after every bump!

    I will have to check out the ones on my Mazda3 (and possibly the wife’s CX-5 if it has them), I did not even think about that until I read one of your responses.

  • Jim says:

    Adam thanks so much for bringing attention to these.

    Just put a set on Ginya, and even with having FM rails, a Cannon brace, etc., they make a significant difference in vibration and rattle even on potholed San Francisco streets.

    I was skeptical, but with 330,000 miles in the pilot seat of the same MX-5, my “butt meter” never lies.

    Kudos to you and GarageStar!

  • […] what does it look like? or the dimension of it? Garage Star Delrin Door Bushings | Garage Star Garage Star Delrin Door Bushing Review — Originally Posted by Bazmeister There's heaps of MX5's being stripped in the parts section […]

  • Tom says:


    As usual, you were spot on – the door blocks made a tremendous difference. You could tell by the initial ‘thunk’, and confirmed on the first drive. I was also amazed how my oem blocks had twisted over time – they were +/-3/32″ out of true. I’m hanging onto them to see if they return back to their original form or if they are permanently deformed.

  • Brad says:

    Update in my case:
    -Car is a 99 Base with no extra bracing. Basically as loose as an NB can be. Used a 1/4″ drive (pretty much all I use on the Mazdas) 10mm socket in installation, all went smoothly, took all of about 5 minutes total for both sides.

    Result, after driving about 30 miles or so, over normal town roads, and a little bit of mild off road:
    -Backing out of driveway at an angle, car no longer squeaks when wheels drop off curb/sidewalk.
    -Seats don’t shake/shimmy from normal vibrations
    -Windshield doesn’t shake nearly as much as it used to.

    The off-road driving, still a bit of windshield shake, but that’s not at all surprising. I figure with some additional bracing such as the FM Butterfly setup that I’ve had my eye on for years, or a roll bar (possibly both) will likely make it a much more solid car overall.

    Still, for such a simple install… consider me impressed. I’ve seen a lot of simple mods over the years, for various cars, and I’d say maybe one in ten falls into the “genuinely useful” category. This is that one. =)

  • Stephen Burgess says:

    I was somewhat skeptical when I read the initial reviews of the delrin door bushings but after reading so many positive and consistent reviews, I went ahead and order a set for my 2001 Miata with 119K miles on it. Following some suggestions from other buyers, I did the following:
    1. Marked the outline of the OEM bushings with a fine point Sharpie before removal.
    2. Installed the delrin bushing within the Sharpie marks. Finger tightened the new longer bolts that came in the kit into the new bushings. Closed the door to ensure a good fit.
    3. Opened the door. Tightened the bolts with a wrench. Closed the door again, just to be sure.
    4. Opened the door. Removed one bolt only (wanted to keep the bushing in place with the other bolt tight).
    5. Applied Blue Loctite to the bolt threads. Tighted the bolt with a wrench.
    6. Repeated with the other bolt.
    7. Closed and opened the door to check the fit.
    8. Repeated the first 7 steps on the other door and let the car sit overnight so the Blue Loctite would cure. (Note that Blue Loctite is only medium strength and can be “broken loose”, unlike the Red Loctite which is permanent.
    Results: These bushings do everything claimed. The doors opening and closing sound like those on a new car. The car has better handling and less “rattling” sound of the frame (no chassis with a unibody) when I drive over washboards or rail tracks, quieter overall and yes, the door speakers for my Bose Stereo sound like the bass has intensified.
    I rate these bushings 5 stars out of 5 stars. Expensive, yes, but I got my money’s worth.

    • revlimiter says:

      Thanks for the list Stephen!! I probably should go back and hit mine with blue loctite. Actually, I need to make sure the bolts are still tight anyways… Thanks for the reminder!

  • Ken says:

    i installed these on my 2000 and they really seemed to help. Definitely a noticeable difference in the vehicle on the road especially over bumps. Mind you I run fm springs with Koni yellows and poly bushings in the rest of the suspension.

    Overall two thumbs up!

  • Ed says:

    Hey Brian mind me asking why you chose GS door bushings over KenAuto’s?

    • revlimiter says:

      When I ordered mine, I had no idea the KenAuto ones existed. Add to the fact that I’m buddies with Ken and the choice for the Garage Star ones was simple.

      (BTW, my name is Adam)

  • Ed says:

    LOL Sorry Adam. I have no clue why I typed Brian. Of course I know your name, Anyways thanks for the review. I went down to Ken’s shop and picked up a pair. In fact he installed it for me as I just had carpal tunnel surgery. Several door fitment problems I heard about KA’s.

    I am now a believer of this upgrade. The best $$ spent on my baby to date.

  • Spindiscs says:

    Thanks for review and all the comments – all positive so far.

    Seriously one of the weirdest upgrades but I like things when they work.
    Took you me and a lot of people by surprise.

  • Lou says:

    Hi Adam,
    I just stumbled across these and ordered them. I saw the blue loc-tote was recommended, does that seem to be holding?

    I have a very early 90, built in April 89, so the past few years have involved Chassis Viagra, I.e. FM frame rails, frog arms, chassis braces front and back, under hood bracing, cabin bracing, now this.
    I am avoiding the roll bar as long as I can.

  • Michael says:

    Long time lurker first time poster. I have a lower mile 90 miata about 129k and these little blocks changed things I didnt realize I had. Thank you for putting these in my sights never would have known otherwise. If my new job offer goes through you will be hearing from me soon for some of those sweet gauges.Love reading your post in general keep being inspiring to all us lowly starters.

  • nessus says:

    hi, i have been thinking about buying these door blocks and came across your post, and informative. My NA miata from rigidity point of view is similar to your Sharka, which has a harddog sports rollbar, a hardtop, sports coilovers, and struct tower brace in the engine bay. Do you think adding these blocks is still going to be noticeable? The car like you mentioned in your post, still twist at slower speeds over potholes, bumps, ramps, etc.

    • revlimiter says:

      I’m hesitant to recommend the door blocks on the chance that you’ll not notice anything and be unhappy.

      I’ll say this: I noticed a change. Behavior over low speed bumps (potholes and uneven surfaces) and railroad tracks is much better now. And driving without the hardtop isn’t quite as wet-noodle feeling either. It’s a good upgrade. I’m very happy with my door bushings.

  • Patrick says:

    Thanks for the recommendation! Just bought these and installed them…and it definitely makes a difference on my stock 92.

    Very nice.

  • […] They get daily use and have had no problems. Bucky also got a set of Garage Star door bushings. I did a blog post. I think everyone in the Miata world has read it. Door bushings: after about 6 months of use, […]

  • Steve says:

    A little loctite on the threads probably wouldn’t hurt as long as you’ve done the open and close test a half dozen times before tightening everything down.

  • […] 10mm socket and a philips head screwdriver. Revlimiter has done a pretty nice review on these items here Factory Mount (which still looked very very good) : Once removed, there was some gunk and […]

  • Cameron says:

    Do you think these would help my ’90 track car? The doors are pretty gutted and we have a full cage. My guess is no, but I thought I would ask.

  • Alan says:

    Thanks for the review, I put them on my 2001 BRG and I think they are a great addition! Love the way the door sounds now when i close it! Might need minor adjustments, but it closes well, drives a bit tighter and less noise on the road. Its got 50+k and all the strengtheners on a Special Edition, so it rode well anyway, and I plan to keep it that way!!!!

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