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short strut inserts

Nils

New member
Joined
Jul 3, 2009
this is some basic info about what strutcartridges can be used when shortening your 240 struts. low cost, so Koni race inserts are left out on purpose.
it's not complete, there are more cartridges that can be used and more information will be added when available.

please note this is general info that comes from websites across the internet, so make sure to double check any measurements before spending cash.

The strut cartridge used in 240's is a T4 cartridge.
T4 cartridges all share a few measurements, basically diameters of the housing.

stock 240 cartridge

this cartridge has monroe partnumber 73950.
Housing length: 40,64 cm
piston rod length: 20,6 cm
when fully compressed the piston rod sticks out of the housing: 1,27 cm

Saab 900 ('94-'98)

monroe partnumber: 73264
housing length: 34,9 cm
piston rod length: 17,15 cm
compressed: sticks out 2,54 cm

first thing to notice is the housing is 5,7 cm shorter.
if we use this cartridge in the 240 strut tube we have 3 options:
  1. shorten the strut tube by 5,7 cm and we have a 9,15 cm shorter piston rod compared to stock and gain a theoretical 5,7 cm extra compression travel.
    In reality we gain less travel, as it cant compress fully, the actual gain in compression travel will be 5,7+1,27 - 2,54 = 4,43 cm
  2. use a 5,7 cm spacer under the cartridge and we have a 3,45 cm shorter piston rod compared to stock. we gain no extra travel. this solution is nice if you want to lower a bit more than 40 mm and your -40mm lowering springs lose contact with the springperches at full droop. the downside to this solution is we also loose 2,54-1,27= 1,27 cm of compression travel compared to stock....not good i'd say.
  3. use a 5,7 cm spacer on top of the cartridge this solves the problem of the lost compression travel in option 2. the piston rod length will be 9,15 cm shorter than stock but we only gain 1,27 cm extra compression travel.


Saab 9.3 ('99-'02)

monroe partnumber: 73453
housing length: 34,9 cm (same as above)
piston rod length: 17,78 cm
compressed: piston rod does not stick out (yay)

  1. shorten the strut tube by 5,7 cm and have a 8,52 cm shorter piston rod compared to stock and gain a theoretical 5,7 cm extra compression travel.
    As the piston rod does not stick out at full compression we dont loose any compression travel...we gain 5,7 + 1,27 = 6,97 cm extra compression travel (yay again). so although the piston rod is a bit longer we gain more from this cartridge than we would gain from the Saab 900 cartridge above.
  2. use a 5,7 cm spacer under the cartridge and we have a 2,82 cm shorter piston rod compared to stock. we also gain 1,27 cm compression travel. this solution is nice if your -40mm lowering springs lose contact with the springperches at full droop. again this is better than the Saab 900 cartridge as with lowering we need more compression travel to not bottom out.
  3. use a 5,7 cm spacer on top of the cartridge the piston rod length will be 9,15 cm shorter than stock and we gain 1,27 cm extra compression travel.


Daewoo Lanos?

monroe partnumber: 73405
housing length: 34,9 cm (same as above)
piston rod length: 15,24 cm (freakin short)
compressed: piston rod sticks out 0,64 cm (yay)

  1. shorten the strut tube by 5,7 cm and have a 11,15 cm shorter piston rod compared to stock and gain a theoretical 5,7 cm extra compression travel.
    In reality we gain more travel, the actual gain in compression travel will be 5,7+1,27 - 0,64 = 6,33 cm ...not bad at all
  2. use a 5,7 cm spacer under the cartridge and we have a 5,36 cm shorter piston rod compared to stock. we also gain 0,63 cm compression travel. this solution is very nice if your -40mm lowering springs lose contact with the springperches at full droop. again this is better than the Saab 900 and Saab 9.3 cartridge if this is the case.
  3. use a 5,7 cm spacer on top of the cartridge the piston rod length will be 11,15 cm shorter than stock and we gain 0,64 cm extra compression travel.


thats it for now... 3 cartridges we can use, and 3 ways to use them depending on what we want to achieve.
option 1 is the typical coilover use, if the car has to be really low with sufficient travel left
option 2 is the typical "a bit more than -40mm lowering springs" use if we need to keep the springs in the perches at full droop.
option 3 is the typical "option 2 didnt do the trick"

ofcourse option 2 and 3 still give you the problem of not gaining much extra compression travel, but depending on how stiff your springs are and how low you want to go this isnt always a problem. putting more pretension on your spring actually raises the spring rate so again in some cases you wont need much extra travel.

for info about how to shorten your strut tubes here's some info written by Kyote:
http://forums.turbobricks.com/showthread.php?t=85793

and here's some p.s. stuff that i need to write down somewhere here:
  • the fact that a strut is a T4 size strut does not automatically means it fits. there are many housing lengths available and most of them are too long for the 240 struttubes and therefor useless.
  • make sure to check if the strut cartridges you want to use fit into your topmounts.
  • always use a bumpstop with sufficient length on the piston rod. the bumpstops that come with the cartridges dont automatically have the right length. unless you know what you're doing dont leave the bumpstop out.
  • the measurements above are taken from Monroe cartridges and dont neccesarily apply for other brands.
  • be carefull when using gas struts with an inverted design (Bilstein, DeCarbon, Volvo-R and others). these have an internal bumpstop which means the compressed length of the piston rod is often longer than the cartridges mentioned above. so you cant compress them all the way and have less travel than you would expect. to fix this you can remove the nut at the bottom of the strut cartridge and pull the actual damper out to shorten the internal bumpstop
  • watch out for cartridges like Bilstein B8 Sprint and Koni Yellow with additional shortened rebound as these have a shortened piston rod and then the measurements given above do not apply. normal Koni red and yellow are not shortened and therefor dont have this problem.

all typing errors or grammar mistakes are made on purpose :-P
 
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Just a heads up that the stock Boge inserts for A Saab 9.3 DO NOT fit in the strut housing. Not even close. Oh well... I got 'em for cheap(ish) and wanted to experiment. Still, :-(

M.
 
The male end was too big for the female end.

That's what she said

What happened Mark?

they're just WAY too big of diameter. the base of the strut won't even clear the threads and it tapers up larger after that so they're unusable. I'm totally broke right now so I think I may just install the coilover sleeves on the struts as is for now. I popped one in sans spring and I figure with the WeezilUSA style camber plates I'll still have a little travel (like two inches)



Here's how much space is left with the stock strut mount- pretty sure the spherical bearings on the Vurbo are almost an inch higher than the stock mounts.


I borrowed one of Jason's wobblewheels to judge. Pretty dumped, really... put in some 7" springs (350 lbs ish sound okay for 7"?) and it'll be underdamped as hell but good enough for now.

I'm on the fence on shortening now after looking at how little clearance there is... I think a VERY minor shortening (like an inch) and a careful spring choice may yield 3" of travel at a slammed ride height, but if you shorten too far you're gonna have tire/adjuster clearance woes.

BTW I used the removal technique you suggested, worked a treat. They slid about three feet. :lol:


M.
 
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We specified ET3 on Rob's 17x8 Kodiak wheels to clear the spring/seat.

If you're using inserts that are 3" shorter than stock, there's no reason why you couldn't cut 1.5" off the tube and rethread, then run a 1.5" spacer in the bottom of the strut tube.
 
We specified ET3 on Rob's 17x8 Kodiak wheels to clear the spring/seat.

If you're using inserts that are 3" shorter than stock, there's no reason why you couldn't cut 1.5" off the tube and rethread, then run a 1.5" spacer in the bottom of the strut tube.

That was my thought... mock it up with your chosen wheel/tire first and figure out what the largest amount you could lop off the strut body before your perches are rubbing the tread and then choose your spring length based off that. Toss a chunk of 2x2 lumber down the strut body as a spacer and you're rocking it full tb stylez :-P

I was thinking I might eventually order the flat shock tops too- that's another 3/4" of travel before coil bind.

M.
 
you guys know you can get a pair of spring compressors for like $15, right? :-P

Actually, if you only need to remove the springs for the purpose of coilovers, it is unnecessary and incredibly slow to use spring compressors.

Not to mention the fact that it's way safer than trusting your life to a $15 spring compressor. **** that noise.

I always get a sideways look when I mention the impact gun against the wall technique, but I've done it a hundred times.

Why spend money to do something slowly and unsafely?
 
Put the impact gun on the top of the whole assembly, push the strut into the gun against the wall & hit the trigger with something? :???:
 
Saw a guy pulling struts off a 240 at the junkyard last weekend for coilovers. I told him to zip the top nut off before dropping the strut assembly out. It's captured inside the tower, so it's not going to shoot out anywhere.

To reinstall, cut ~1.5 coils off the spring, let car down on spring to compress, strut pops through the upper mount, reinstall top nut.
 
If I get to do this again I'll post a video.

It was super fast and really easy.

For safeties sake I used a ratchet strap wrapped hooked around the very last coil and through the hole for the tie rod to keep the springs attached to the strut towers. I was doing it outside so I set up a peice of smooth wood on the ground and set the strut itself on cardboard on the wood so it'd slide smoothly... last thing I'd want is for it to catch something and buck back. I'm sure it was safer than half the crap I do in the garage on a regular basis.

M.
 
Yeah, first time Nick at Allvo told me to do it I was slightly doubtful, thought the whole thing was gonna shoot off and kill a bird. Ended up being pretty un-eventful!
 
Ended up being pretty un-eventful!

That was my thought after I did the first one... like "That's it? Really?" I had safety glasses and big leather welding gloves on... all ready for the apocalypse and it turned out to be like taking apart a ball-point pen instead.

@Adrian -yeah, hold impact gun against wall, slide strut up onto socket and (being careful not to hang on to anyplace dumb) pull the trigger. The struts slide a few feet so make sure not to do it with your collection of Wedgwood teacups in the line of fire.

M.
 
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