f6sk
f6sk Reader
3/26/16 10:15 a.m.

I bought some Koni inserts and want to make my own custom strut tube. What wall thickness should I look for?

Similar to this https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/2011-mazda2-not-so-srs-bzns-stf-build/100748/page1/

Trackmouse
Trackmouse HalfDork
3/26/16 10:41 a.m.

.07" on my celica's.

Knurled
Knurled GRM+ Memberand MegaDork
3/26/16 11:27 a.m.

I ended up just acquiring some strut housings from the application they were made for and went to town on them.

Interestingly, the Subaru struts I started with have the ears only welded on the bottom. I cut the bottom of the ears off and they slid right off, for an initially rust-siezed value of slid.

Dusterbd13
Dusterbd13 PowerDork
3/26/16 12:02 p.m.

This is relevant to my interest.

f6sk
f6sk Reader
3/26/16 7:18 p.m.

I don't have an application to insert them in... its an 88 Isuzu I-Mark for goodness sake. Any other thoughts on .07?

Knurled
Knurled GRM+ Memberand MegaDork
3/26/16 7:45 p.m.

What are the struts FOR? Use that application as the start of whatever you gotta do to make it fit the car.

That is easiest because the strut inserts are probably made for some weird metric size that would be hideously expensive to source.

jimbbski
jimbbski Dork
3/26/16 7:57 p.m.

The problem is not the thickness of the tube but how you plan on securing the insert inside of the tube?

I would use at least .060 wall tubing but I see no reason to go more then .090 unless you plan on cutting threads into the tube. This link below is one place to get tubing in small quantities at reasonable prices.

http://www.shapirosupply.com/index.php?main_page=index&cPath=117_584

I suggest Chromoly steel as it's available in many different OD's and wall thicknesses. Also you don't have to get a tube size that is only just bigger ID then the OD of your insert. A simple spacer can take care of any size difference. Do you know anyone with a lathe? It will help in this project.

f6sk
f6sk Reader
3/26/16 8:26 p.m.

Mine are universal Koni inserts made for custom tubes. I want to do this: I have already ordered the flange nut to hold the struts in place. I just want to know what thickness would work best. I don't want my tubes so hard (stainless) that I cant reasonably tap them, but I also don't want them too weak.

Knurled
Knurled GRM+ Memberand MegaDork
3/27/16 5:24 a.m.

You don't want stainless anyway, as it is craptacular strength wise. It's more like frozen peanut butter than steel.

I'd look for .125 wall minimum if you're going to be buttwelding ears on like that.

DeadSkunk
DeadSkunk UltraDork
3/27/16 7:54 a.m.

VW Rabbit strut housings are 48mm OD and 42mm ID, so 3mm wall thickness. So I would think a 0.125" wall DOM tube would be a decent place to start.Make the bottom closure piece considerably thicker.

Knurled
Knurled GRM+ Memberand MegaDork
3/27/16 8:41 a.m.

Oh yeah. When I put my Konis in the Subaru housings, I saw that they wanted me to put the locating bolt right in that thin lower plate. I said berk that. I grabbed some leftover sock absorber washers and used them as beef plates. One on the inside and one on the outside, which I think I even welded into place.

My style Koni insert is held in plate entirely by one 8mm bolt in the bottom. I really, really would hate for that to tear out.

DeadSkunk
DeadSkunk UltraDork
3/27/16 10:02 a.m.

"My style Koni insert is held in plate entirely by one 8mm bolt in the bottom. I really, really would hate for that to tear out."

What? No gland nut at the top of the strut?

jimbbski
jimbbski Dork
3/27/16 1:38 p.m.
DeadSkunk wrote: "My style Koni insert is held in plate entirely by one 8mm bolt in the bottom. I really, really would hate for that to tear out." What? No gland nut at the top of the strut?

Many replacement strut inserts come with a threaded hole on the bottom. to install the insert you cut the top of your OEM strut with a pipe cutter or a hack saw and remove the top of the strut and empty the contents. You then drill the strut tube bottom and install a bolt from the bottom to secure the insert in the tube. It's a whole lot easier to do in a custom install then trying to internally thread a tube to match a retaining nut. The ones that I've seen are very fine threads.

Knurled
Knurled GRM+ Memberand MegaDork
3/27/16 2:05 p.m.

Yep, mine are Koni Yellows for the rear of a WRX. I bought them at Summit for maybe 10% retail and figured it would be an easily flip. Turns out nobody wants them because you have to modify the old struts.

So I used 'em myself.

f6sk
f6sk Reader
3/28/16 8:13 p.m.

.125 wall it is. Thanks for the input

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