Length of shock Vs Lift amount

[ShastaJT6]

Hey all,

Replaced the Skyjacker M9387 front shocks and Skyjacker M9396 rear shocks that came with my lift kit recently. This was the 3.5" front / 2" rear skyjacker kit - I also have a Teraflex 1/2" coil spacer installed on each front coil. This puts me at 4" lift in the front and 2" in the rear, gives me an overall 2" lift and leveled stance. I have run this setup for.. probably 15,000 miles and multiple offroading trips and no problems.

Recently installed Fabtech Dirt Logic 2.25 FTS801402 reservoir shocks, and was really excited. They looked really nice and were really beefy. Ride quality was great - until my very first offroad trip, about 1 month after install, when both of the front shocks failed. The shocks blew out, was spraying oil all over my wheel well, had to cut my trip short and limp it home. Was really frustrated here (obviously), especially since I contacted Fabtech before purchasing these shocks and they confirmed they were a proper fit for my truck & lift. These shocks are also included in the Fabtech 3" AND 5" lift kits, so they should have worked well for me.

Just for the record, its not like I was jumping dunes in Moab - this trip was forest roads and crawling over one or two rocks. The $100 skyjacker shocks went through 10 times the abuse these $480 Fabtechs took, and the skyjackers are still working just fine. Pretty embarrassing for Fabtech.

This sent me down the rabbit hole researching different shocks and their lengths. Skyjacker doesnt list the collapsed and extended length of the M9387 front shocks on their website - I did not take the time to measure them before re-installing them to my JT, was rushing to get the truck back in driveable condition before work on monday.. but it seems like manufacturers are all over the map for recommended lengths.

Examples:

Bilstein 5100 Front shocks for Gladiator with 3-4.5" of lift
Collapsed Length: 18.52"
Extended Length: 28.76"
https://www.bilsteinlifts.com/shop/...-5-front-shocks-for-2020-2021-jeep-gladiator/

Fabtech FTS801402 Front Shocks (Included in their 3" and 5" lift kits)
Collapsed Length: 17.39"
Extended Length: 27.05"
https://fabtechmotorsports.com/product/dirt-logic-225-resi-shock-fts801402/

Rancho RS7MT Front Shocks for Gladiator with 1.5" -3" of lift
Collapsed Length: 18.39"
Extended Length: 28.58"
https://www.4wheelparts.com//p/rancho-rs7mt-monotube-front-shock-absorber-rs77067/_/R-BCKM-RS77067

Rancho RS9000XL Front Shocks for Gladiator with 2"-3.5" of lift
Collapsed Length: 18.16"
Extended Length: 25.21"
https://www.cjponyparts.com/rancho-...Yg1fjZrOtrDNL6XaqSwTlYCsxGM8ZqMcaAtvWEALw_wcB

Teraflex Falcon SP2 2.1 for Gladiator with 2"-3.5" of lift
Manufacturer website fails to list collapsed and extended lengths
https://teraflex.com/jt-falcon-sp2-2-1-monotube-shock-kit-2-3-5-lift.html#

Just among these options, weve got a pretty significant amount of variance in the collapsed and extended lengths of the shocks, and I have found that some manufacturers dont even list the specs of their shocks (Skyjacker and Teraflex for one).

The Rancho example is my favorite - their "RS7MT Front Shocks for Gladiator with 1.5" -3" of lift" are 3 inches LONGER than their "RS9000XL Front Shocks for Gladiator with 2"-3.5" of lift", which seems utterly backwards.

Also, the Bilstein 5100 Front shocks for Gladiator with 3-4.5" of lift are nearly the same specs as the Rancho RS7MT Front Shocks for Gladiator with 1.5" -3" of lift ??

So... I want to upgrade the shocks that came with my Skyjacker kit.. but Im really not sure what to get, since these values are all over the map.

To those of you with a frankenlift, how are you determining the proper shocks for your use case? I need a beer..

Edit 4/11/22:

Reached out to Radflow for the extended / collapsed length of their 2.5" - 3" front shocks and they responded that they dont have that information. If you dont even know the specs of the parts you are selling.. thats kinda scary.. so theyre not going on the list.
https://www.radflo.com/i-823-oe-rep...ght-w-remote-reservoir-radflo-suspension.html

Contacted Icon for Collapsed / Extended of their 2.5" front shocks, awaiting response
https://www.iconvehicledynamics.com...essories-18-up-jl-20-up-jt-25-front-20-vs-ir/

Edit 4/12/22:

Icon responded that they cannot share the specs, proprietary info blah blah, scratching them off the list of potential replacements.

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[hjdca]

Here is the Falcon Shock length info.

Note: You will notice a big difference in the rear shock length for a JT between the 2 to 3 inch and the 3.5 to 4.5 inch lift. It is like a 4 inch difference -- but, no difference in the front. This makes a huge difference in rear articulation, but, some manufacturers springs may unseat at that length. I have the 3.5 inch clayton lift and I am running the 3.5 to 4.5 inch Falcon lengths, and I really like the lengths so far.

 

[ShastaJT6]

Here is the Falcon Shock length info.

Note: You will notice a big difference in the rear shock length for a JT between the 2 to 3 inch and the 3.5 to 4.5 inch lift. It is like a 4 inch difference -- but, no difference in the front. This makes a huge difference in rear articulation, but, some manufacturers springs may unseat at that length. I have the 3.5 inch clayton lift and I am running the 3.5 to 4.5 inch Falcon lengths, and I really like the lengths so far.

This is really helpful, thank you. The Falcons are top of my list for a replacement set, and now I have some data to work with for those. Want to use the length of my skyjackers as a baseline since those shocks have functioned well so far. Need to measure the fronts eye-to-eye and get those values so I can pick a set from another manufacturer that is similar.

I dont want to spend another $2000 and a weekend on shocks, just to have them blow out on the first trip again...

Edit: Man, youre not kidding. the rear SP2 Monotubes for these dont match up well for me - my options are 1/2" shorter extended or 2.5" longer when extended. My belief is that the Fabtechs being shorter than the Skyjackers is what caused them to fail, but that extra 2.5" is sketchy. As you said, wouldnt want to pop a spring.

My question, ultimately, is how do we decide what length of shock is appropriate for our vehicles? Since there is so much variance in these, and the manufacturers all seem to have different recommendations, how can I make an informed decision. There must be some measurements I can take to calculate what my actual needs are..

 

[hjdca]

This is really helpful, thank you. The Falcons are top of my list for a replacement set, and now I have some data to work with for those. Want to use the length of my skyjackers as a baseline since those shocks have functioned well so far. Need to measure the fronts eye-to-eye and get those values so I can pick a set from another manufacturer that is similar.

I dont want to spend another $2000 and a weekend on shocks, just to have them blow out on the first trip again...

Edit: Man, youre not kidding. the rear SP2 Monotubes for these dont match up well for me - my options are 1/2" shorter extended or 2.5" longer when extended. My belief is that the Fabtechs being shorter than the Skyjackers is what caused them to fail, but that extra 2.5" is sketchy. As you said, wouldnt want to pop a spring.

My question, ultimately, is how do we decide what length of shock is appropriate for our vehicles? Since there is so much variance in these, and the manufacturers all seem to have different recommendations, how can I make an informed decision. There must be some measurements I can take to calculate what my actual needs are..

It is all about how long the springs will get with no load.

Since you already have the rear Springs and shocks mounted, disconnect the rear shocks axle mounting point, and use a long piece of wood and a floor jack to jack up the rear end from the rear hitch. Keep jacking it up until you feel the rear springs come a little loose. From there measure the distance from the end of the shock to the axle mounting point. This will give you your approximate max. shock length for the rear. While you are at it, you can also calculate your rear end links length. A "just right" end link length can also help keep the rear springs mounted during extreme articulation.

 

[darkhorse13]

You can always get these for the rear if you're concerned with unseating...

 

[ShastaJT6]

It is all about how long the springs will get with no load.

Since you already have the rear Springs and shocks mounted, disconnect the rear shocks axle mounting point, and use a long piece of wood and a floor jack to jack up the rear end from the rear hitch. Keep jacking it up until you feel the rear springs come a little loose. From there measure the distance from the end of the shock to the axle mounting point. This will give you your approximate max. shock length for the rear. While you are at it, you can also calculate your rear end links length. A "just right" end link length can also help keep the rear springs mounted during extreme articulation.

Perfect, I appreciate this. At this point im just using the lengths of my existing shocks as a value and looking for replacements that are close, but this sounds like a solid process to get some actual numbers to work with, thank you.

 

[ShastaJT6]

You can always get these for the rear if you're concerned with unseating...

These are cool, didnt realize these were a thing - Ive heard of limiting straps, but I like the idea of these.

 

[Wheelin98TJ]

Collapsed length is what you need to pay attention to.

1. Measure between the shock mounts at ride height.
2. Measure between the bumpstop and the point where the bumpstop contacts. Add 1" for compression of the rubber bumpstop.
3. Subtract #2 from #1.

This tells you how short you need your shock to collapse to. Without any bumpstop modifications.

Extended length is of course important too, but you will not ruin shocks over it.

 

[ShastaJT6]

Collapsed length is what you need to pay attention to.

1. Measure between the shock mounts at ride height.
2. Measure between the bumpstop and the point where the bumpstop contacts. Add 1" for compression of the rubber bumpstop.
3. Subtract #2 from #1.

This tells you how short you need your shock to collapse to. Without any bumpstop modifications.

Extended length is of course important too, but you will not ruin shocks over it.

Thanks! Ill followup on this.

 

[ShastaJT6]

Big thanks to all the folks who chimed in here and tolerated my overthinking / shenanigans.

Was doing some more looking around, and looks like Skyjacker is releasing some new reservoir shocks soon. Since I have a 3.5" front / 2" rear Skyjacker kit - and a 1/2" front spacer in addition to that - I ordered the 3.5"-4" front option. Seems like a nice upgrade from the shocks I have, but I feel confident that I dont have to worry about the lengths and whatnot being compatible.

Ive frankensteined a lot of my lift since I installed it (mixed and matched sway links from other brands, teraflex track bar, etc etc) but with all the headache ive given myself over finding compatible shocks, I think ill just slap these on when they arrive and call it a day.

https://www.quadratec.com/p/skyjack...orber-gladiator-jt/with-3.5-4-inch-lift-a2387

 

[Rzrhawg]

Big thanks to all the folks who chimed in here and tolerated my overthinking / shenanigans.

Was doing some more looking around, and looks like Skyjacker is releasing some new reservoir shocks soon. Since I have a 3.5" front / 2" rear Skyjacker kit - and a 1/2" front spacer in addition to that - I ordered the 3.5"-4" front option. Seems like a nice upgrade from the shocks I have, but I feel confident that I dont have to worry about the lengths and whatnot being compatible.

Ive frankensteined a lot of my lift since I installed it (mixed and matched sway links from other brands, teraflex track bar, etc etc) but with all the headache ive given myself over finding compatible shocks, I think ill just slap these on when they arrive and call it a day.

https://www.quadratec.com/p/skyjack...orber-gladiator-jt/with-3.5-4-inch-lift-a2387

Did you get the ADX shocks? If so, what do you think of them?

 

[ShastaJT6]

Did you get the ADX shocks? If so, what do you think of them?

Did get them, they were on backorder for a LOOOONG Time through quadratec, but I have received them. Havent had a chance to install yet, hoping to address that soon. Works been kickin my ass.

 

[IzzyO]

You can always get these for the rear if you're concerned with unseating...

I can verify that these work but are a major pain to install.

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