Installing inserts into struts

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Callumgw
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Installing inserts into struts

Post by Callumgw » Wed May 14, 2008 6:24 pm

Installing inserts into N12 Front struts.

This article talks about the modification and installation of Koni inserts to the N12 front Struts. Despite Konis being used here the work would apply to any insert.

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The first point to note is that there are two struts on the N12s with different diameters. You need to know which you intend to modify so that you get the right parts from your supplier. This will simplify the install, if you can’t get the right one you’ll need to do more work modifying the strut, but it’s best to get the right part first off.

The outside diameters are 51mm (normally on the ET and Exa Turbo) and 49mm (normally on the NA N12s). Inside diameter of my struts (51mm outer) was 45.5mm, with a small machined section near the top of 47mm.

All the N12s run a wet leg oil strut from the factory. This means the strut is full of oil and does not contain an insert that is easily removed and replace. Instead you need to drain the oil and permanently modify the strut to put in the insert. This mod only needs a drill and hack saw and the usual spanners and spring compressors. UNLESS you got the wrong diameter inserts, then you’ll need a welder and possibly a lathe!.

Starting with the strut, remove the strut from the car and without the strut top and spring.

Then drill a small hole in the base to drain the oil from the wet leg.
Before hole:

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After hole:

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Drain the oil.

Cut gently around the strut where the indents are just below the cap. Hard to see in this image:

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Easier to see here where I’ve removed the cap:

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You only need to cut as deep as the strut wall thickness all the way round, the internals can then be pulled out. You do not need to cut all the way through everything, just the outer wall of the strut.

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Remove the internals.
At this point on the inside is a seal that still needs to be pulled out. It can be a little firm, one of mine came out with a stiff jerk, the other had to be held in the vice and slowly worked free.

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Enlarge the lower hole to suit the insert retaining bolt.

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Check the insert fits the strut leg and that the leg is short enough for the insert. If the strut leg is too long cut it down to the right length.

Install the strut, tighten the lower nut and re-install in the car.

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UNLESS the strut us too large for the insert, then you’ll need to sleeve the strut to support the insert properly.

Get an appropriate steel tube, the inside and outside diameters need to be correct. In my case I needed a 45mm outer and 41mm inner. I found a 45/42mm steel for the insert.

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I couldn’t get the correct outer diameter, but the inner was 1.8mm to large, so I sleeved the sleeve with 0.8mm strap. This gave a neat fit.

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cut the sleeve to length,

Insert the sleeve into the strut

Weld in place.
I welded in the sleeve with a nice fillet weld and clean up the outside so that I could still put on coil-over platforms if I want. I also tack welded the shim, so it did fall inside the strut when installing the insert.

and paint
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Install the insert

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Reinstall in the car.

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So what's in a strut when you open it? This is one being taken apart in stages (no needed to the insert install):

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Have Fun!

C
Last edited by Callumgw on Thu May 15, 2008 9:06 pm, edited 3 times in total.

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