Gunn's Tbird Front Suspension Options including Bilstein Inserts DIY


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Sep 22, 2023
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95 T-bird with 5.0and m5r2 swap for lemons
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S4Gunn's Tbird Front Suspension Options DIY

Here are your options if you want stiffer front shocks to match the Bilstein rears you purchased based on this thread:
UPDATE March 2017: I bought the Bilstein 34-050224 (B8 SP series) for $265/shipped from summit (price matched) and after my first race found them to be almost too stiff when the track is wet (cannot apply full throttle without spinning tires out of a corner). I'm now looking at ways to soften the rear or get a little more time before the rear end breaks free (going to a thinner rear swaybar, upgrading tires from 16x7 to 17x8, raising the ride height of the front 1/4", or moving from a fuel tank to a fuel cell to shift the weight balance rearward.)

UPDATE 4/14/17:
As an alternative option for people with too much money in their pocket, these look to be the current top of the line rear setup in terms of adjustability:
Here's another option for the rear for people who insist on spending a ton of money on their tbird:

QA1 Double Adjustable Rear shocks @ ~$245/ea (yeah, that's $490/pair)

- Can be adjusted 18-ways for compression and 18-ways for rebound
- Stupid expensive

This is based on my research and experimenting in Nov-Dec 2016 for a car I use for track racing (road course - not drag). NOTE: I use the terms struts/shocks interchangably. Some nerds will state that our car uses shocks for both the front and rear but often you will see the fronts advertised as Struts and the rears advertised as shocks. Whatever.

Suggested Reading:

Basic Steps:
1) Decide which insert you want from the list below
2) Cut down two front shocks.
3) Assemble the shock assembly with the insert. You may need to modify the shock body OR (easier) the insert.
4) Fabricate/Modify the shock top mount as needed
4) Assemble the whole front shock as if it was an OEM replacement

Easiest Option - Buy Tokico Illumina 2s #EU3869 and set to firm: $150/ea as of 11/2016 or Tokico Blues #TOHU3689

* Simple installation
* Likely have a similar amount of hydraulic fluid inside compared to a stock shock so if you are doing endurance racing, you'll have more fluid to heat up before seals start breaking down.

* Stiffest direct fit but not that stiff. See these comments: "Softer than my stock SC shocks after 60K mi"
"a little stiffer than stock on FIRM setting"

* I also found comments that they blew fairly quickly (<60K mi) but this could have been a bad batch

* If you don't have ARC on your car (the electronically controlled suspension system), you will need to set them to FIRM and then add RTV/Hotglue/whatever to the top to prevent them from switching modes while you drive.

DAMPENER OPTION 1: Bilstein Inserts for Mitsubishi 3000GT - Bilstein #34-050224: ~$132 price matched
DIY Here: Proven by Saturn5/MaddMartigan:

- 36mm diameter: 1.41" (should drop in)
- Top Nut: (holds spring retainer plate): M14x1.5 nut
- Bottom Nut (to Shock Assembly): M10x1.0 lock nut
- Amount of 5/8" diameter shaft above flange to retain dust guard: 40mm (2cm threaded, 2cm unthreaded)
- Weight of tbird front very similar to 3000GT.
- Good feedback from a guy with an S14 that autocrosses and has already blown several KONI inserts up multiple times already: Nissan Road Racing Forums - View Single Post - Jason Merritt's 2014 Street Mod Build...

- Much beefier shaft and larger volume than the circle track shocks below. This was designed as an insert.
- Stiffer than the circle track shocks. I'm not a super heavy guy @ +/- 150LBs but i really have to lean into it to get it to compress.
- Monotube design. More fluid capacity and better for racecar

- Simpler installation into cut down strut assembly (bolts through hole you will drill in the bottom vs needing a horizontal bolt to be placed/drilled).

- Price is $50 more than the circle track Bilsteins but you get a significantly beefier shock and in my unscientific method (my weight on the shock vs. a shock dyno), the Bilstein inserts are a TON stiffer.
- Will likely require that you enlarge the ID of the cut down strut assembly OR press fit the insert in). The bottom-most section is only 1.717" in diameter (43.6118mm) but it flares out about 2.5" from the base. The challenge is that the ID of my cut down shock (a Monroe Sensatrac) is 1.787" or 45.39mm. This is a delta of 0.482mm or .019" you need to make up by shoving the bilstein down into the shock, putting the bilstein insert into a lathe, or reaming the shock out. All of this is discussed below.
- REQUIRES an modified spring retainer plate with an enlarged opening (5/8" hole vs 0.5" hole in stock spring retainer plate). See below for suggestions.

DAMPENER OPTION 2: Bilstein "circle track" shocks as inserts - #S7G-5555 aka F4-BE3-C239-H0: ~$80/ea or $158/pair

DIY Here:

- 36mm diameter, 17.25" extended (assuming with the eyebolt you will remove), 11.75" collapsed
- Does NOT need a modified shock top mount (shaft is narrow enough to fit in stock shock top mount
- Challenge: Need to bolt through body of strut assembly. While the spring is holding most of the weight, the bolt going through the cut strut assembly is taking all the force of the dampener) so use a Grade 8. I went with a 1/2"-13 x 2.5" long.
- Slides in (doesn't need press fitting as interior of stock strut assembly is 1.79"
- Proven by tbirdtess: Bilstein racing shocks - Front Shock Custom Design

- POST TEST UPDATE: Unlike what Paul/tbirdtess suggested, the Bilstein S6G-5555 (#F4-BE3-A213-M6) are IMO too short to use even with a lowered car. I purchased these shocks and found that in order to make them work, I would have to place the bolt ABOVE the bottom most bracket (that mounts the strut to the LCA) instead of 1/2" below the top of the bracket. This would mean that the horizontal 1/2" bolt would only be supported by the thickness of the cut-down strut body vs the thickness of the cut-down strut body AND the brackets.

- Nut Removal: After removing the top eye-bolt, I also noticed that removing the nut below the top eye-bolt will require you to hit the nut while holding the shaft with a sheet of rubber or something else non-marring. I can confirm though that the shaft diameter will fit through a stock strut assembly (once this nut is removed).

* Cheapest "race" shock. These things are impressively stiff.
* Bilsteins have great support in the US. Can be revalved/rebuilt by third parties. Bilstein themselves will do it but the cost is greater than just buying a new replacement ($95/ea - Service)
* Compared to the insert route, this will be MUCH easier to fabricate.

* The body of the shock is tiny so I'm personally concerned about overheating the fluid in my application (endurance racing). Paul races on dirt w/o any issues (bumpier so will generate much more heat) but IIRC, races are measured in minutes vs. hours.

- Double adjustable (Rebound on top, compression on bottom) 8611-1259RACE - $340/ea
- Single adjustable (rebound on top) KONI 8610-1437RACE - $240/ea

- 1.71" diameter (may need to press fit).
- UNKNOWN: not sure if insert will be needed to place insert at right height
- Rebuildable. Twin tube hydraulic (not necessarily as good as the monotube bilsteins)
- Adjustable (you will need a bigger hole on bottom vs. the Bilsteins to access the compression adjustment)
- CONCERN: The S14 autocrosser mentioned above blew out 8611-1257RACE (same as 1259RACE inserts but with a slightly shorter stroke) and this drove him to the Bilsteins.


- Buy and install
- Favorable review

- Crazy expensive.. esp considering that the shocks themselves are only $260/pair. FWIW, the premium you are paying covers the tbird specific brackets + this retailer's R&D.
- Springs NOT included with this setup but 650LB QA1 springs were ~$30 at Jegs when on sale

- This is PURE speculation but I suspect you might be able to piece this kit together yourself but you'll have to fabricate your own brackets. A stock strut might be the right donor for the bottom mount but you will need to fabricate your own top mount

Reference: Front Spring Options
Most people looking to fabricate their front dampeners probably already have aftermarket springs on their tbird. Just in case you haven't picked one out yet or are looking for something stiffer, here are the options I've found.

The classic lowering springs article on TCCOA: Thunderbird Lowering Springs

Besides the SC springs, Eibach, Suspension Techniques, Tokico, JAMEX, here are two more options to consider:
* Sprint Springs #2200: 1.5" drop but ???? spring rate. Maddmartigan uses them.
* QA1 Springs QA1-650 (10" long, 650LB-IN linear springs): stupid cheap at $28.85 on sale @ JEGS
Also available in 450LB and 550LB variants but at 2x more each
QA1 10-650: 10" Powdercoated Coil Spring Rate: 650 lbs | JEGS

MY CHOICE: Bilstein inserts
* I originally ordered the Bilstein circle track shocks but was surprised a bit at how small they were compared to the OE shock. My concern is that for endurance racing, we would cook the hydraulic oil (get it hotter than spec) which would cause the seals to fail.

* Since I also ordered the slightly shorter shock (S6G-5555) and realized that it wasn't going to be ideal for my needs and would need to be returned, I debated about what I should buy (S7G-5555, Bilstein inserts, or Tokicos).

* I ultimately decided on inserts for availability reasons and because quite a few people coming from SC shocks weren't happy with the Tokicos. At this point, no SC shock is available that ISN'T beat to hell (100K mi).

TIPS: How to cut down an existing strut assembly for insert installation
- The key here is to start with as blown a front shock as you can find. This will minimize the spewage under pressure.
- Drill a small hole (take your smallest bit) at the center of bottom of the shock assembly since you are going to need to drill an insert mount hole at that point anyway.
- Contents may be under pressure (esp if it's not completely blown). I found it was easiest to do this by using a hand drill and doing this within a dry cleaning bag (or any other large plastic bag) as this will catch any side spraying. Just in case though, keep you mouth closed and the hole aimed in a direction where it won't spray too much stuff in your garage. Do NOT do this in your living room even if you are a bachelor as the oil is kinda stinky (not gear oil stinky but still stinky).
- A rag in the plastic bag is also handy to mop up any spray.
- Once the drain hole is made, drain the shock completely. I found pumping the shaft helps as well as leaving it to dribble out into a rag in a cup overnight.
- Once completely drained, cut the top off and remove the guts. You don't need to be accurate here but I would aim for ~3/4" below the lip. Keep in mind that you will likely need to cut it down again as you don't want the shock body to be higher than the body of the bilstein insert as that could potentially limit travel).

CHALLENGE: make the Bilstein insert fit
There seems to be a ton of variance on how the OE/OEM shocks were made so your particular experience may be slightly different. See this pic of how two shock bodies have substantially different body thicknesses. The one on the left is a Monroe Sensatrac and the one on the right is an Ford OE shock from a SuperCoupe. Go figure.

- MaddMartigan used a pipe cutter and found he had to press fit his inserts. This could be due to the pressure of the pipe cutter taking the body out of round OR it could be the ID of the shock housing (more likely).
- In the 4 shocks I cut down, I used both a bandsaw and an angle grinder. Both worked equally well and if you cut just the outer body, the guts can all come out with the shaft.
- My goal was to make the bilstein servicable without cutting off the shock and having to redo this work so I set about looking for the right combination of tools to allow the Bilstein insert to drop in.
- Drill any additional holes as needed (across the bottom bracket if using the Bilstein circle track shocks, on the bottom if using inserts).
- Your sacrificial shock assemblies may be different but I found that the Monroe Sensatracs were just a hair (0.019") too small for the Bilstein inserts to drop right in.

There seems to be a good deal of variance here in how the original shocks were built so depending on what issues you encounter, you may need one/all of these techniques to get your Bilsteins to drop in:

1) Reaming the inside of the shock assembly out 0.019". I found this method to be ineffective as while it caused some rubbing, it didn't really cut much metal.

2) Use a Lathe to reduce the oD of the bilstein insert: it was a ton easier to put the bilstein insert itself on a lathe and mill it down by 0.019". You are in effect making the upper half of the Bilstein insert a similar diameter as the lower 2.5" section. This took <15 min so even if you are paying a machine shop retail pricing, it shouldn't cost too much. Finally, it should be noted that the now thinner Bilstein body is still a good deal thicker than the stock shock assembly so you aren't sacrificing strength of the body here. Since the stock bilstein insert is narrower at the bottom than the top and they probably didn't machine the tube out of billet, it's very likely that the Bilstein body started out as one thicker tube and was cut down thinner at the bottom end.

3) Press it in (this is what MaddMartigan did).

CHALLENGE: Bolting the Bilstein inserts to the donor shock assembly
On both the SC OEM shock and the (3) Monroe shocks I cut down, I found that the bottom of the shock was formed by a cap that is stuck inside the shock body and then crimped down. The result is that the ID inside is more like 0.05" smaller than the OD of the shock and prevents the bottom mounting thread from sticking through the mount hole.

- MaddMartigan encountered a similar issue and his solution was to press the bottom of the donor shock to be flat using a hydraulic press.
- My ultimate solution for the second shock was a "nut sleeve" -- basically a bolt with the threads on the inside of the shaft vs outside. Since I couldn't find any in the US (even online) in M10x1.0, I decided to make my own and it took surprisingly less time on a lathe than expected. NOTE: I did find some "union couplers" for european brake lines but i'm not 100% sure that the M10x1.0 threading is the same for flare fittings as what I'm using. There are both brass and steel variants but my machinest friend suggested to avoid the brass fittings as the threading might not be strong enough). The length is also questionable so I skipped them.
- A more detailed step-by-step instruction list on how to do this on a lathe can be found in this post:
- Unverified suggestion: for those of you without access to a lathe and are too cheap to pay someone to make one of these for you fairly quickly, you might be able to build one out of an existing M14 or M16 bolt and trying to drill through the center yourself before hand-tapping it. I would try to use one of the softer bolts (Class 8.8 or Stainless vs Class 10.9 or 12.9 - as drilling through hardened steel doesn't seem like fun. Here's a DIY that suggests how to do so with a decent drill press (basically using it as a mini-lathe):



- Dust Cover: The shiny silver dust cover seemed to act like a way to prevent gunk that might attach to the central shaft from entering the Bilstein body. The problem is that the dust cover's OD is slightly larger than the OD of the shock assembly by maybe 1/8". I went all over my local ACE HW store and couldn't find an appropriate rubber gasket. I ended up using some rubber from an semi truck inner tube (like the ones you float down the river in).
1) Cut up a 1" wide strip of rubber material the length of the circumference of the shock assembly and super glue it to the top of the cut shock.
2) After the glue dries, drop in the Bilstein insert and bolt it to the bottom of the shock assembly.
3) Drop the dust cover down and with a little force install the cover snuggly. It's not going to ride up the shaft under compression.
4) Finally, take a razor and cut off any excess rubber visible from beneath the dust cover.
5) Once you have the Spring retainer plate put together(see below), just assemble and install.



CHALLENGE: Front Spring Retainer Plate modification (Shock Top mount)
- In an earlier thread, MaddMartigan exposed me to this as his thought on what a better spring retainer plate/shock top would look lite.

- If you go the insert route, you WILL already need to modify the spring retainer plate as the hole in the stock plate isn't big enough to fit the insert's shaft. In the stock retainer plates (vs aftermarket replacements), you can remove the short metal tube that guides the dampener shaft and it's surrounding rubber. IMO though, you cannot just let the dampener shaft move freely in the larger opening - hence the interest in using a monoball for allow for articulation without letting the dampener shaft wander from the center of the spring retainer plate opening..

- If you do fabricate your own spring retainer plate out of a flat plate, you will need some amount of rubber to act as an insulator between the plate and the spring.
- You also want a little amount of articulation here to let the shock around a bit so you can't just weld a plate with a 5/8" hole up top.
- While some cars replace the shock tops with plates to allow additional camber adjustment, MadMikeyL says that the way our suspension is setup w/ adjustment in the control arms, moving the shock in/out will NOT affect camber. Therefore, there is no reason to move the shaft anywhere from it's stock position in the center of the shock top mount.

MY CHOSEN IMPLEMENTATION: Monoball method (under spring retainer plate recommended)
- Cost: $33.70 shipped for a pair of monoball kits + some washers
- Quite a few of the camber plates and fancier shock tops use Monoball bearings to allow articulation whereas the stock setup relies on some rubber surrounding the dampener shaft in the hole in the spring retainer plate to allow for some movement.
- In several discussions with maddMartigan, our concensus was that mounting the monoball housing to the underside of the spring retainer plate would allow for the most articulation with the least amount of force required to compress the spring retainer plate to the spring.
- While I originally learned about monoball housings from UB Machine, the best deal I could find for the 5/8" uniball bearing, housing, and retaining clip was from a company that specializes in hardware for serious offroad cars.
Steinjager #J0024085 $13.20/set or $33.70 shipped 2-day for a pair of two kits.
0.625 Bore Uniballs
- Gunn's Current Configuration (from top to bottom): Nut from Bilstein, 9/16" washer, spring retainer plate, monoball housing welded into pocket underneath plate, & Bilstein dust cover.
- While it does restrict articulation slightly, a washer is required above the spring retainer plate to spread the force of the bilstein nut. I also experimented with a rubber spacer between the monoball housing and the flared section of the dampener shaft but none was needed as there as no "slop" between the shaft and the monoball when the nut was tightened all the way down.
- Please note that MaddMartigan and I have looked at 3 or 4 different spring retainer plates as starting points and they all have different sized diameters for the central hole from 0.83" to 1.25" (even with the rubber+metal sleeve removed). Some are smaller than the monoball housing and others are just large enough to go around it. Exactly what spring retainer plate you start with may influence whether or not you place the monoball housing underneath or on top of the spring retainer plate.
- If you place it on top of the spring retainer plate, you maximize articulation possible but may lower the # of threads which will be exposed to the nut when the spring is in place and compressed.
- If you place it in the middle of the hole (so the spring retainer plate looks like a ring of saturn orbiting the monoball "planet" instead of a washer above/below the monoball housing), your welds become the potential point of failure here as they will be holding the resistence of the spring in check.
- If you place the monoball underneath the monoball housing, you maximize the # of threads which can be captured but trade-off the maximum amount of articulation the plate can achieve.

Q: IMO, I went with the third option (monoball below plate) because a) how much articulation do you expect to see anyway as articulation means the spring is being compressed unevenly and b) I don't trust my welds as much as I do the bilstein supplied nut and the spring retainer plate acting as a washer.

NOTE: to check how much of the threaded shaft you can grab, just stack the spring retainer plate and monoball on the dampener shaft and tighten the nut without a spring in place.




As an alternative, here is how MaddMartigan built his spring retainer plates (with the Monoballs on top)



Alternative Implementation: Washer and spacer method
- Cost: $9/pair for the washer+spacer in CA prices (cheaper if you use scrap)
- The idea here is to remove the metal spacer in the center of the shock (my old torn ones already have this piece removable) and replace it with a thicker shaft.
- A washer welded to the top will resist movement a bit BUT there will still be some give if you insert the spacer back into the rubber piece that originally surrounded the stock shock top mount's central metal tube..
- Best example here:
This is MaddMartigan's rev 1:



Please note that I took a bit of effort to make them look as subdued as possible (because cheaty racecar).
UPDATE Nov 11, 2017: I have since these this suspension in a full race and a track day (~16 hours of on track time). Setup works perfectly.


MaddMartigan's Ver 1 (with the washer and sleeve vs monoball)


Quick Tips on How to Reinstall the Shock Assembly
While a wall mount spring compressor is always an easy way to get the front shock/spring assembly put together, you do NOT need one. I also wanted to point out that you don't even need to use the mcpherson strut compressor tools that prevent the spring from fully extending (helpful for the disassembly of the shock/spring assembly).

I've done this before but seeing as how I recently did this tonight, I thought I should update my DIY with a quick summary of the steps.

1) Use the 3 bolts to mount the spring retainer plate/shock top mount to the chassis. I mount it finger tight so the assembly can move slightly but it will mostly stay in place.

2) Place the spring on top of the shock and seat it properly on the base. This means make sure the spring is in the right orientation. Follow Rayo's sticky:

3) It will be a little unwieldy but take the loose spring and shock and work them under the UCA and over the LCA.
- It helps if the UCA is disconnected from the spindle.
- It also helps to push the sprindle/LCA downwards slightly to give you a little more room to have the top of the spring clear under the UCA that's dangling from above.

4) Run the bolt through the LCA and the bottom of the shock.

5) Place a floor jack under the LCA where the shock mounts and use the jack to life the LCA up. As you do so, make sure the top of the spring is in the right orientation underneath the spring retainer plate/shock top and the central shaft of the shock is going through the right spot of the spring retainer place (through the monoball if you went the Bilstein insert route that started this thread).

6) Continue pressing the floor jack up until the spring starts compressing (the weight of the car will push down on it) and the top threads of the spring shaft peek up through the top of the spring retainer plate.

6.25) Before proceeding to step 6.5, if you've hung the brake caliper out of the way make sure it's on the right side of the spindle before bolting the spindle to the UCA.

6.5) I also found this to be a good time to maneuver the top of the spindle to the ball joint of the UCA and bolt those two together.

7) Once the spring doesn't want to compress any more and the body of the car starts lifting, take out your impact gun and hit the main nut on the shaft to make sure it's cinched down tight. Also, fully tighten the 3 nuts that hold the spring retainer plate to the chassis.

8) Remove the floor jack and admire your work.

UPDATE 1/23/2017: Drag Racing Front Suspension
Here's another interesting option I found while on SCCOA that Pro Street Rich has been working on for his dedicated drag race tbird.

To complement his tubular front subframe and suspension setup, PSR has also eliminated the heavy stock spindles by integrating it with his DIY coilover setup. I don't have any part #s (PM this guy on SCCOA to find out more but i thought I should add it here for the sale of complete-ness).

In addition to the strut assembly with the spindle on the bottom, this setup requires a tubular front subframe to replace the stock k-member and tubular UCAs and LCAs.

If I understand it correctly, the main difference with this setup is that it changes the suspension geometry of the tbird. Instead of having the strut assembly attached between the body of the car and a 3/4 down the stock LCA, the strut is mounted at the end of a tubular UCA at the top and a new spindle assembly on the bottom at the end (vs 3/4 down the LCA).

When the car is at rest, the LCA will push the UCA all the way up until it touches the chassis.

My Thoughts - Pros:
- Replaces the weight of the stock front spindle assembly (8LB/side) of semi-sprung weight with something lighter. That's apparently worth a lot to Pro Street Rich.

My Thoughts - Cons/Unknowns:
I'm not sure how good an idea this is for daily driving/road course work. PSR admits himself his car is purely a drag weapon now.
- When a stock geometry tbird suspension is under compression (think: car is at the bottom of the hill and the road flattens out or a fat guy is sitting on your hood), the front spring is compressed but the camber doesn't change. This is because as the stock front spindle wants to move in an upward arc when the spring is compressed, the UCA being attached to the top of the spindle and keeps the 'face' of the wheel in the same position (perpendicular to the surface of the road if camber = 0 degrees). This articulation is allowed for the ball joint connecting the stock spindle to the UCA and the stock spindle to the LCA.
- With Pro Street Rich's setup, the spindle is now fixed to the bottom of the spring vs attached with a ball joint. As the spring compresses and the LCA moves in an upward arc, the tire camber should go negative since the spindle face is now travelling along the arc of the LCA articulation. Exactly how much I don't know.
- It also looks like the coilover setup is set backwards slightly whereas the stock strut assembly is much more vertical. I believe is essentially setting up a bit of negative caster here (since the upper strut mount is more rearward than the lower ball joint). Negative caster is allegedly supposed to help with stability for drag applications BUT may also contribute to additional tire wear.

- I'm also not sure how the tubular LCA allows for adjustment of front caster (since there's no longer a strut rod in place to set that measurement.)

Check it out @

It's very interesting.
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