Shortening strut tubes? A visual explanation

[saturnv7890]

One thing I’ve noticed here is that there are a lot of people looking to install coilovers to go and slam their cars, but don’t have the right information about why they would need to cut their housings. I think it has a lot to do with the lack of visual explanations, so I threw together a masterpiece which will hopefully aid everyone’s learning curve.

To clear up the picture, it is 3 different setups at the same ride height.
Parts:
-Spring hat (at the top, attached to the car)
-Strut tube (black casing here)
-Strut (yellow case, with the grey rod going through)

The lower a car goes, the closer the strut tube and spring hat get, for obvious reasons. Take a look at your front struts the next time you jack up your car if you don’t believe me.



So Frame 1 shows a stock tube and stock length shock, but still sitting very low (because of some nice short spring’d coilovers). You can see the shock is very close to bottoming out (grey piston getting close to the bottom of the yellow tube). Additionally, the top of the strut tube is close to hitting the bottom of the spring hat. This is what NOT to do, as you can see you can bottom out easily. This is what all those guys were taking about.

Frame 2 shows shorter a shorter strut installed in a stock length tube. The shorter strut could be an iX strut or corrado strut? So you can see that because it’s a shorter strut, the piston rod is shorter, this means at the same height, the strut is extended more, thus farther from bottoming out. You can see that, right? Now that’s all good, but the strut tube is still very close to the spring hat.

Enter Frame 3, the ideal setup. The strut tube here is cut and welded shorter, like you’ve read about people doing. It is cut and welded shorter to give more travel, very plain to see there.


NOTE: I do not claim to know everything about this stuff, I am just stating what intuitively makes sense to me. I don’t take any responsibility in anything that goes awry in your car because you took what was in this thread for fact. I definitely invite others to chime in and let me know what I’ve missed/gotten wrong.

[drulle]

Nice work, should be very helpfull info for people who like their cars low...

[DRTSRFR]

I commend you for your effort.

...but #2 is not correct. Travel is not dictated by the position of the piston.

There is no more travel in #2 than there is in #1.

[acolella76]

[saturnv7890]

I commend you for your effort.

...but #2 is not correct. Travel is not dictated by the position of the piston.

There is no more travel in #2 than there is in #1.

then why do people claim that you ride on the internal bumpstops when you lower a car too much on stock length struts?

[acolella76]

then why do people claim that you ride on the internal bumpstops when you lower a car too much on stock length struts?

Travel is the distance that the shaft moves, not the distance of the piston from the bottom of the shock. If you look at frames 1 and 2 they have equal amount of shaft sticking out.

[F34R]

It is witchcraft.

[nando]

then why do people claim that you ride on the internal bumpstops when you lower a car too much on stock length struts?

because they are talking about bilsteins, which internally are quite short, but they have huge bump stops.

[einstein57]

I like it this way. But then again i do have a surplus of Bilsteins to scavenge parts from.

[saturnv7890]

Travel is the distance that the shaft moves, not the distance of the piston from the bottom of the shock. If you look at frames 1 and 2 they have equal amount of shaft sticking out.

Yes but you can see there is actually more piston rod sticking out the top of 2 and 3, this is based on what I understood.


Apparently according to nando the only shock that limits the travel by its internal bumpstops is bilsteins, so if people slam on koni's they only need to worry about the top of the strut tube hitting the strut bearing?

[nando]

travel isn't just the length of the rod though, that's his point. in your examples, #1 and #2 both have the same amount of travel.

if you slam it on a stock length koni you will run into the same issue, where the gland nut bottoms out on the strut bearing. that is what you are depicting in #2.

there is basically zero point in running a shorter insert in a stock length strut housing, which is what you are showing in #2 I think.

[saturnv7890]

Yes I completely realize that, but I was illustrating that it's not only the strut tube that is limiting but also the travel of the shock itself, based on what I've read about people riding on their internal bumpstops.

But yes I realize #2 is a completely pointless setup, it was there just to illustrate what changing the shocks did, before illustrating what shortening the tube did. If you change both things at once it's hard to illustrate the difference.

I left out the label I was going to put in #2 to show that travel was still limited up at the top. I left it out because it looked too cluttered, and I figured people would see the difference in #3