Suspension: Shock Therapy (Tuning the OEM Struts)
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Author:  no_rust_vert [ Sat Jul 17, 2010 4:45 am ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

t3 ragtop wrote:
the compliance of oil only struts won't do for a vert. it will, however, change the handling from that of a shopping cart with one bad wheel to the handling of a shopping cart with 4 bad wheels. :-P

one of the first mods i made to a vert was to transplant a complete suspension from a gt. the oil only struts sucked. a change to gas over oil struts along with the gt sway bars and springs hooked things back up.

the vert needs the higher compliance and faster return of the gas charged struts to keep the tires planted, especially on the rears. i'm inclined to run gas overs on a gt now, too.

so are you saying i should use kyb replacements because they are gas charged??? does it matter if i order them for a vert or a gt? same question goes for the konis. im not worried about ride "harshness" or whateveri would prefer the konis. i want my car to handle at a premium. i dont care about a smooth ride. i understand you've done some r&d on suspension for our cars. the only logicle setup i can see for me would be konis, megan coilovers for civic or accord, and 95+ sway bars. mostly cuz its all easily accessable for me. i feel thats a reasonable setup. although my engine is just stock right now i would rather have the suspension dialed in first. any advise would be apreciated, like if i should just source out gt sway bars instead... thanks

Author:  t3 ragtop [ Sat Jul 17, 2010 7:04 am ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

when i caught the metro bug, the first things i worked on were the suspension mods to bring it up to the gt standards. starting there makes a lot of sense to me because even a box stock g10 will push past the limits of a base metro or vert. then, after you have the handling and brakes sorted, the car will accept the engine mods and gains without pushing it to the limits.

kyb, monroe, and gabriel make bolt on gas over front struts. you have to "build" the koni struts, adapting the strut cylinder to the saddle assembly which gets a little more involved.

coil overs get even a little more involved but we've seen a few guys adapt inexpensive aftermarket honda kits for use with the suzuki. the fronts seem pretty straight forward and simple enough but the rear set can be a challenge. there really isn't much room in the body cavity for rear coil overs, there's barely enough room for the oem struts. we've seen a couple of cars where the rear strut tunnels were opened up at the outside of the inner fender to accept a larger diameter shock assembly.

i am by no means the "authority" on the suspension or it's tuning. i have read on this forum for about 7 years and i've followed other guys' advice to get my cars dialed in. i know what i like and what i can afford and that has formed my personal opinions of how to get things done. i've built several suzuki cars that were on a par with some of the neatest sports cars i've ever owned. that, in part, is why i'm so keen on our cars. 5 or 6 hundred bucks spent on suspension parts, new and re-cycled from a gt, can transform your car from an econ-o-miser to a pocket rocket.

there are a lot of opinions available here, i'm not the only voice on suspension work. i have built a number of these suzuki variants, though, and i've picked through a lot of parts at junkyards. i consider my time at the yards "practice" for when i work on my own cars. :lol:

Author:  no_rust_vert [ Sat Jul 17, 2010 8:02 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

sounds like we have similar goals for our cars. the reason i own one in the first place was not by choice so much as luck. i bought it as a first car for my girlfriend whos come to really enjoy it. i find my self having to bomb it around once in a while and my standards of fun are a little diffrent. i dont care if its fast cuz she likes the fuel economy as is. i just want to be able to take it on some back roads and have it stick to the road so i dont feel so useless driving this thing around if u know what i meen. also would like the option of adjustability on the coilovers for i like the car as low as i can get it really. ive read the write up on making the coilovers and i just see it more reasonable with the konis as they are shorter stroke struts from my understanding which would suit having it really low. any thoughts?

Author:  t3 ragtop [ Sun Jul 18, 2010 7:26 am ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

no_rust_vert wrote:
any thoughts?

koni struts = $750 plus fabrication, kyb struts = $150 and they bolt on.

any questions? :lol:

Author:  no_rust_vert [ Mon Jul 19, 2010 7:18 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

had kyb adjustables on my accord. sucked ass. thats why i dont want em. but if people seem to say they are good for these cars and they have tried other options then i cant really complain. thats why i was interested in the konis but i was unaware they were THAT pricey. thats bs man. anywhere to find em cheaper?

Author:  Orffyreus [ Sun Aug 15, 2010 7:15 am ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

Three months ago I did phonis all round on my stock-standard Mk3 GTi. I have to be a cheapskate because I've got kids, a mortage and a wife who doesn't see any value in generating tyre smoke. But I knew that the king springs I was about to install would be horrible on the original shocks/struts which were almost totally faded. I bought Motul synthetic fork oil "Expert Med/Heavy 15W", $20 at my local motorcycle repair shop, and that was a bit of a gamble because the 10W (with the "right" viscosity of 38 cSt) was out of stock.

I drilled all four tubes about 40mm below their top weld, threaded the new holes with a bottoming M5 tap, and screwed in a cut-down M5 allen head bolt (a bit more than finger-tight) with a dot of loctite 222 after the re-oiling was done. The old fluid out the struts was watery-thin and gray, and I had to waste some new fluid flushing the last traces of gray crap out. The fluid out of the rear shocks still looked OK, but the passenger-side rear shock had faded the most. It was hard to judge 200ml with the syringe because it wept under pressure and the shock kept overflowing unless you re-primed them after every 50ml or so. By the last one I'd figured that if they were fully purge-primed and the rod was fully, then the correct volume was whatever was left over after they had overflowed. Turns out the last one (front-left) was the only one that I didn't over-fill, the two on the right were slightly over-filled and they wept excess oil past their M5 bungs for a week or so, and the left-rear was badly over-filled because I didn't fully compress it before sealing it and it actually bottomed hydraulically during the test drive and wept for a month before it lost its excess. My mag wheels got very misty-oily.

I reckon the Motul 15W (viscosity about 58 cSt) was a good choice for the front struts, with the king springs rebounding easily and no hint of nose-diving. Standard rear shocks are a different brand to the fronts so they behaved very differently. Rear impact damping was still non-existent but rebound damping was huge, so the ride was like being sucked onto the road by the back axles with every ripple in the road. The stiff rears translated into a huge improvement in front wheel traction though. Looking back I think the standard rears would be more liveable with Motul 10W instead of 15W, but the front struts might even tolerate a 50/50 mix of 15W+20W.

The lowered springs showed up a design weakness in the GTi rear end -- you run out of shock travel way before you run out of actual suspension travel and there's no bump rubbers -- BANG! So in three months of driving, including rear seat passengers, I've hammered my rear phonis to destruction. Fortunately I scored some new rear gas shocks off ebay for $70 instead of $400 retail for rear KYB's, so I cut some shims out of a nylon kitchen chopping board to bring the rear spring height back to near standard before fitting them. A good thrash on my bumpiest local road proved they won't bottom so I'm happy. If the gas shocks were stiffer the shims could be a bit thinner I think.

Shocks today are far more sophisticated then the OEM stuff from 1990. The ride quality with these rear gas shocks is incredibly good compared to the parcel-tray-shaking harshness of the rear phonis, and only a small amount of handling has been sacrificed in the name of comfort. These gas shocks are BOSS brand - made in china, softer than kyb's, but on the rear it's not so critical to have the hardest shocks. The phonis on the front work pretty well on balance, but really by today's standards they're unsophisticated and still prone to a bit of axle tramp in first gear. Geez I'm a cheapskate...

Jacking up the rear to stop the rear shocks bottoming has dulled the front suspension geometry a bit, but I reckon that camber bolts and a castor kit for the front arms will pay that back. A 19mm rear swaybar is looking like a must-have item too. I think I'll tell my wife that they'll double the front tyre life, but I won't mention that I'll drive it harder and use up the difference...

Author:  gamefoo21 [ Sun Aug 15, 2010 1:34 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

From all the reading I've done the best setup is:

Front: Koni adjustables

Back: KYB GR2

Author:  martinq [ Sun Aug 15, 2010 3:58 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

Orffyreus wrote:
The phonis on the front work pretty well on balance, but really by today's standards they're unsophisticated and still prone to a bit of axle tramp in first gear.

'axle tramp' is most likely due to torn or aged control-arm or strut-top bushings, not because of the strut (unless it has side-side play). Also, sloppy engine / tranny mounts don't help any either. Get some PL Premium and tighten it up!

Author:  ponzy [ Tue Feb 08, 2011 9:32 am ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

any pictures please? on where to drill the holes?...... anyone?


Author:  redgreen [ Tue Feb 08, 2011 11:46 am ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

hey can drill the hole anywhere.
. BUT just drill thou the wall farther..1/8"
...but i drill mine on the bottom in the center...1/8 drill
then clamp a piece of 5" long rad hose over the body. put the shock upside down in a vice
then fill the hose with whatever fluid you use...and stroke the rod until all the air's gone
BEWARE...if you slam the rod all the way in. you will damage the valve in the bottom of the body...i know i did it.... ruined the i cut it .with a big pipe i know whats inside...
no matter where your hole is .stick a toothpick in it .so you will know how long of a screw
you can use...i use real short sheet metal screws with JB weld for me...

oh..on my rallycross car i wanted to lower the back end..and still have full travel
just grind off the little tab on the side of the strut body..get a smaller clamping bolt.. use a high grade bolt and nut... by doing this i lowered the backend 1.5" and still have full travel
yes i did cut the springs too...

Author:  sswiftt [ Tue May 03, 2011 12:19 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

Curious to know and so far I've been unable to find a definitive answer. I realize this mod cannot be done to functioning gas filled shocks because they are pressurized however can this mod be attempted on gas filled shocks that the gas appears to have leaked out of, or does the absence of the gas mean that the seal has been compromised and as such will leak the higher viscosity oil out anyway...?

Author:  Teeth [ Sat Mar 17, 2012 12:51 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

Oh joy.

This stickie is one of the most intriguing yet frustrating corners on Team Swift. Between praise from T3 Ragtop and the troubles described by Orffyreous I have been convinced me that KYB gas shocks are a necessity on the rear and simply bought a set.

On the front however, this trick is so classy that I have to at least try it, and I have a pair of junkyard struts to test on before I do this to the good ones on my GT.

"It really doesn't matter" is an extremely unsatisfying answer to the question of where to drill--the fact that all the pictures are broken and the process sounds a bit finicky doesn't help. Also, those who actually did describe everything as best they could didn't seem to have such good results.

Two possibilities occur to me as making the most sense:

1. Drilling the very bottom (not on the side at all), in the center sould seem to be the easiest place to drill as far as getting oil in and out, and shouldn't interfere with the piston or valving as the shock should never be completely bottomed out. The only catch being that it's not as easy to seal the hole--I plan to weld a nut to the hole rather than tap it, then seal it with a matching screw sealed with teflon tape, if that sounds reasonable to anyone reading this.

2. Alternatively, one could drill near the top, but far enough down to make sure you are drilling into the piston. The advantage being that while purging and filling the shock might be kind of a pain, this will make sure the right amount of air does get in there and it would be easy to seal off with the radiator hose and clamp method.

Am I on the right track here? Also I am going to run Mk4 springs cut (I think, still in decision-making mode) 1.25 coils. Discussion with Superf1y and RMPRob suggests that somewhere around 80 cST is what I should be looking for to match this plan.

I am just looking for a yeah or neah from those more knowlegeable before I fire up the drill.


Oh yes, I will photograph the out comes this time, whether good or bad...

Author:  Dattman [ Sat Mar 17, 2012 1:44 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

Do NOT drill in the bottom, it will most likely leak if you try to reseal using a screw, actually it doesn't really matter where you drill but if the best place is between 25 and 30mm from the very top of the strut, this is above the oil line when the shock is fully compressed, make sure the shock is clamped upright and fully extend the strut before drilling, this sucks the oil into the inner tube, try your best to keep the swarf out of the way.

This thread is a mess as it's extemely old and has been migrated onto quite a few servers now =)

Author:  Teeth [ Sat Mar 17, 2012 3:25 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

Thanks Dattman.

Even without pictures that's pretty clear.

What the hell is a swarf?

Author:  Dattman [ Sat Mar 17, 2012 3:37 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

The bits of metal that come off your drill bit :razz: your could use a vacuum cleaner to suck the bits up as they come off your drill bit, you really don't want those bits going inside the shock as you can't get them out again.

Author:  t3 ragtop [ Sun Mar 18, 2012 11:37 am ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

i have an old electric bearing heater that i use to magnetize and demagnetize tools, screwdrivers and drill bits. i also keep a solenoid coil from an industrail hydraulic valve for that, too.

magnetize a sacrificial drill bit for the job and it will help to keep "swarf" out of the strut tubes.

Author:  Teeth [ Tue Apr 17, 2012 10:12 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)


I chose to make my first attempt at Phonis out of Mk4 junkyard struts that clearly had issues. The first thing I did after installing the refilled struts was to take the car on a 3,000 mile road trip from Louisiana to Colorado and back.

The results? Better ride than stock--maybe still ever so slightly under-damped but much, much better than OEM struts with the cut springs. Maybe the valving on my OEM GT shocks (they are in good shape) would be even better?

This was all on the front only, I got new KYB's for the rear. The combination seems to be working quite well.

What I learned:

1. Use a small drill bit. Because I am not very smart I thought I would drill 1/4" holes and weld matching nuts and bolts to the outside to seal them for convenient refill, if necessary. I drilled forever before giving up and trying a smaller bit that would just clear the tip of my "flavor injector" syringe. 9/64" bit punched right through.

2. It takes lots of pumping to get all the old crap out of there--keep it up until the resistance is almost completely gone. I tried not to completely bottom out the shock, in case that was necessary.

3. It's hard to overfill. I lost count of how many syringe-fuls I had put in there on one side but I had enough trouble getting the right amount in the other one that I just tried to fill it as much as I could before the oil started running out and have had no problems. It's hard to describe, but I did have to gently move the piston up and down a little bit to get all the fork oil in.

4. The bit of inner tube and hose clamp method of sealing is also working so far for me.


Author:  Teeth [ Mon Apr 23, 2012 5:34 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

And a picture of my "phonis".


I thought I had taken a picture of where I drilled the hole, but it's pretty obvious given where the hose clamp is--which hasn't leaked and is still working just fine, incidentally.

I do think the one on the left side is getting a little softer than the right one already though--it's odd that it isn't so apparent when driving but I think I can tell a slight difference when I compress that corner of the car by pushing on it. Still working better than the OEM, mind you, but I was worried that that one wouldn't last long from the outset as it was in pretty bad shape to begin with. Below is a picture of scoring that was already visible on the shaft when I pulled it:


So, now the question is do I just replace it with a better junkyard Mk4 strut, or, now that I know how to do this and I am convinced it is going to work well for me, do I drill my GT struts, which are probably in slightly better condition than anything I would find in the yard. They don't look the same either, though, so I wonder if they have different valving that would behave differently with the same oil? Anybody else try both GT and Mk4 shocks?


Anyway, this has now been working well for thousands of miles and I am definitely going to continue the experiments--even if they don't last many tens of thousands of miles, OEM struts are easily pulled from the local yards for next to nothing.

Author:  Teeth [ Wed Aug 08, 2012 5:52 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM struts)


This worked well enough the first time that I decided to do it again.

As can be seen in the picture above, the left side shock was pretty crappy before I refilled it last time so, while it is still working fine and provides more damping than stock, it's now softer than the other side, which is clearly not the way to go.

I was kind of on the fence about finding another Mk4 shock in better condition or just refilling my matching set of GT struts, as they are known to be more or less good as the car was riding just fine before I swapped them for the first set of Phonis. First I checked the junk yard nearest my new California digs for Mk4 struts and after some hemming and hawing, hoping they'd let me go pull it myself, told them what I wanted. The dude looked at me with a straight face and said $95. :WTF: What planet do these people live on? At another self-service place in Hesperia I pulled some CRX calipers for the brackets, planning to turn the rest of the caliper in for the core charge on the new ones I had already gotten from Autozone. They wanted $10 more than Autozone wanted for new ones--and I pulled them myself!!! I didn't think I'd miss anything about Louisiana, but no admission, no hassle, no bullshit, giant real junkyards that charge reasonable prices for junk are a nice thing to have nearby.

Sorry, venting. :furious:

So given the price of Geo Metro junk around here I decided to go ahead and refill my GT struts as at 120k, they are hardly pristine and there's no point in saving them just because they are "original". This time I tried to be even more meticulous and took a few more pictures for those who might be curious.

Hole drilling location:


Note that you can see the inside of the shock--one of my concerns was that the hole might damage seals on the the piston as it moves by, but that doesn't happen as one can see by working the shock through its motion and watching the hole--nothing passes it, it's just a hole into the reservoir.

This time I actually attempted to measure the amount of fluid that came out rather than take the figure of roughly 200ml that can be found earlier in the thread.

Here's what I got:


A little more than 100 cc's of fairly nasty looking oil.

An then the other side:


A little less tan 100 ccs but it looks much better.

While I also magnetized my drill bits and put a little bit of Lucas oil on them while drilling, I figured, since I have a lot of it I don't plan to use for anything else, that I would flush them out with a couple of flavor-injector syringe loads of automatic transmission fluid first. I pumped the shock one more time before adding the ATF and another ~ 30 cc comes out (!). After doing this twice, I am now of the opinion that getting a precisely measured amount of oil out (and therefore in) is next to impossible. Just let it sit after you've pumped it and a little more will go out (or in), seemingly indefinitely. I tried to put in roughly 150 ccs, but it's hard to do as you have to move the piston in the bore a little bit to free up space, but then when you move it back the oil shoots out of the hole. This is a messy job--here's my whole kit, including "flavor injector". I found it much easier to refill the syringe from a used lunch meat container than use it to try to measure and suck it directly out of the bottle.


And the finished "Phoni".


Lessons learned this time around:

A rubber band around the shaft of the strut will keep the piston from settling ever further into the bore while you are squeezing oil into it.

I also found that, guess what, the shock that the ugly oil came out of isn't as firm as the one that had the better looking oil. Part of this was due to not being completely filled--there was a little bit of slop before it would engage one way or the other, so I put a little more oil in it. I have no idea how much is really in the strut now, of course, but I am starting to think that this is hopeless and that I shouldn't worry about it so long as they work. And that did solve the slop problem but I am still trying to decide whether I think it still might be a little softer than the other one. The new oil seems to exaggerate slight differences in compression damping due to worn seals, I think. I might just try to put which ever one I think is firmer on the car, even though it's very different looking compared to the Mk4 strut that's on there now.

FYI, this procedure is covered in this month's Grassroots Motorsports magazine. No credit given to Murr or Team Swift of course, but at least it's acknowledged as a useful low-cost alternative that improves on the function of OEM struts.

Author:  Teeth [ Sun Aug 12, 2012 9:43 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

One quick further addendum for those that are interested:

After getting the Mk4 struts back off the car to compare, I found to my surprise that the valving is definitely different vs. the GT parts. With Belray 20wt in both pairs of struts, the Mk4 struts have (based on my "let's push this in and out by hand" subjective shock dyno) a little higher rebound damping and way less compression damping than the GT struts. Both still work well with this mod and cut springs, but I like the GT struts a bit better.

Author:  suprf1y [ Mon Aug 13, 2012 9:24 am ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM struts)

Teeth wrote:

This worked well enough the first time that I decided to do it again.

Excellent job. Thanks for the tutorial.

Just as an FYI, this chart that I posted on the previous page, the viscosity you need to be concerned with will be the Centistokes at 40 degrees C. It's not likely your shocks will see 100 degrees Celcius, so there isn't much need to find an appropriate viscosity at that temp.


Author:  suprf1y [ Sun Feb 03, 2013 11:01 pm ]
Post subject:  Re: Suspension: Shock Therapy (Tuning the OEM Struts)

If the link to this pic is lost again, refer to this site

There is some really good suspension tuning info here, and I've used it to tune the suspension on my race bikes with success.
Peter is a good guy with a good handle on how this stuff works.

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