Front Shock Tower Extension Questions

[XCRN]

I am looking at using the Poly Performance towers to extend the front shock mounting points on the front of my LJ, but I was wondering in general how much extra compressed length does such a procedure allow? I understand its a case-by-case basis, I am just trying to see if its realistic to fit Fox 2.0x11in shocks with only 1in of bump stop extension or less and no body lift. I like where everything is at now with maybe 3/4in BS extension, I just want some better tunable shocks with more overall travel. This is something I plan to do with a rear outboard with 12in shocks when I pull the tub off the frame.

 

[jjvw]

It is common to fit 11s up front with the Poly towers with the travel split 50/50. The bump stop is what it is because the shock is what determines the travel.

The purpose of the bump stop is not to stop anything. It is only there to provide a cushion to help slow shock travel speed before the shock reaches full hard compression. You build the bump stop length to do that.

 

[XCRN]

It is common to fit 11s up front with the Poly towers with the travel split 50/50. The bump stop is what it is because the shock is what determines the travel.

The purpose of the bump stop is not to stop anything. It is only there to provide a cushion to help slow shock travel speed before the shock reaches full hard compression. You build the bump stop length to do that.

My goal is trying to maintain my nearly 5.5ish" up travel and increase down travel to match with the current lift and tire size. I have the extension setup currently that is set based on tire clearance to fender, though the cheap Skyjackers now are close to the next thing limiting up-travel after that.

I just want to know what shocks I should start hunting down for this project to be able to maintain my current uptravel and keeping it at the same height.

 

[sierradmax]

What's your current limiting factor for up-travel if you pull the shocks and coils? A/C compressor, engine oil pan, or fenders?

 

[Superjay5]

I have the poly towers with 12” shocks, the point of hard contact for me was the drivers axle coil bucket. With that much uptravel the trackbar swings the axle to the passenger side causing the interference with the DS coil bucket.

The beauty of using the poly towers is you get to set the travel of the shock however you like. So if you currently have 5.5” of up travel you can maintain that and increase your down travel.

 

[XCRN]

What's your current limiting factor for up-travel if you pull the shocks and coils? A/C compressor, engine oil pan, or fenders?

Currently tires to fender is the limiting up-travel from what I have found, then shocks would likely be the next limiting factor. The planned engine swap will keep it all away from the axle, even without any bump stop extension, the only thing that could potentially interfere is front driveshaft to exhaust. The LJ in question has 32in tires with 2in spring lift, no body lift, stock fenders and some cheap stock length shocks.

My plan is to keep the LJ around 2in with 32s since this has not really limited where I want to go. Before a acquired my LJ, I installed Fox 2.0 bolt-on resi shocks on my TJ and was massively impressed how much better the ride was on and off road and the plan was to move the bolt-on Foxes to the LJ when I upgrade the TJ further with tuneable shocks. But after bringing both my Jeeps on a Silver Lake trip 2 weeks ago; this 250k mile LJ surpassed all my expectations on what it could do with less lift, less cylinders and less shock travel. I am changing plans and putting the better tuneable shocks into this when I start the frame-off process.

 

[XCRN]

I have the poly towers with 12” shocks, the point of hard contact for me was the drivers axle coil bucket. With that much uptravel the trackbar swings the axle to the passenger side causing the interference with the DS coil bucket.

The beauty of using the poly towers is you get to set the travel of the shock however you like. So if you currently have 5.5” of up travel you can maintain that and increase your down travel.

Thats what I was trying to figure out is if you can fit the towers high enough without cutting the fenders for a 17in or even 18in compressed length shock at full stuff with minimal BS extension.

 

[jjvw]

Thats what I was trying to figure out is if you can fit the towers high enough without cutting the fenders for a 17in or even 18in compressed length shock at full stuff with minimal BS extension.

I have modified 12s up front. I did it without cutting the factory inner fenders, but it did require quite a bit of hammering sheet metal and trimming the tops of the poly towers. 11s are much easier to fit.

Also, understand that this type of work is usually done with a 4" spring lift and a 1.25 body lift.

 

[XCRN]

I have modified 12s up front. I did it without cutting the factory inner fenders, but it did require quite a bit of hammering sheet metal and trimming the tops of the poly towers. 11s are much easier to fit.

Also, understand that this type of work is usually done with a 4" spring lift and a 1.25 body lift.

I figured sticking to smaller lift is a bit unconventional for this amount of work, but its just a personal preference to keep the LJ at a lower lift since this will still be seeing a lot of on-road miles to get to the off-road trails. The 4ish” lifted TJ is fun but it’s not the best for long road trips through Appalachia like it used to be when it only had 2in lift. I just REALLY liked how much improvement the bolt-on Foxes made on the TJ, so I would think the LJ with tuned (possibly also retrofitted DSC) Foxes would be significantly better.

 

[jjvw]

I figured sticking to smaller lift is a bit unconventional for this amount of work, but its just a personal preference to keep the LJ at a lower lift since this will still be seeing a lot of on-road miles to get to the off-road trails. The 4ish” lifted TJ is fun but it’s not the best for long road trips through Appalachia like it used to be when it only had 2in lift. I just REALLY liked how much improvement the bolt-on Foxes made on the TJ, so I would think the LJ with tuned (possibly also retrofitted DSC) Foxes would be significantly better.

What you will run into with less lift is finding enough room between mounts to fit the shocks without compromising the travel bias. The other issue is finding a spring with enough travel to support the shock travel.

Then, if you do build this out with an uneven travel bias, the valving becomes increasingly compromised as the up travel is decreased because the valving has less time/distance to work. The damping can be increased to account for this, but the ride quality will suffer.

 

[Superjay5]

Thats what I was trying to figure out is if you can fit the towers high enough without cutting the fenders for a 17in or even 18in compressed length shock at full stuff with minimal BS extension.

I don’t have stock fenders, but I did need to cut up my PS inner fenders…

 

[XCRN]

What you will run into with less lift is finding enough room between mounts to fit the shocks without compromising the travel bias. The other issue is finding a spring with enough travel to support the shock travel.

Thats what I was trying to find out where the towers end up from the frame or some other reference point. I cannot find any measurements on how far these can go up into the fender well compared to the stock mount. Looking only at pictures without parts on hand it looks like it could raise it 1.5-2” and the lower mount looks like it drops 1” so if those estimates are close I can get an 11” with near 50/50bias.

As far as springs, when doing the math the RockJock 2in springs would have enough travel to utilize all of the 11in travel in the front. The rear might not work out as nicely, but I am not opposed to notching the frame for a rear spring perch to use a RJ 4in spring that has disproportionally more travel than the lower lift spring options.

 

[sierradmax]

I'm not sure you'd be able to use poly's lower shock mounts in a coil sprung axle. Not sure if it was your intention.

My suggestion, is to pull the coils and shocks, measure your fully collapsed 12" (or other) travel shock is at full bump and it will give you a sense of how much more desired shock tower you can target.

 

[rasband]

I'm not sure you'd be able to use poly's lower shock mounts in a coil sprung axle. Not sure if it was your intention.

You can, it just takes some trimming.

 

[sierradmax]

You can, it just takes some trimming.

for the front? I'd like to see pictures of this.

 

[rasband]

for the front? I'd like to see pictures of this.

 

[Superjay5]

I don’t have stock fenders, but I did need to cut up my PS inner fenders…

for the front? I'd like to see pictures of this.

 

[jjvw]

Thats what I was trying to find out where the towers end up from the frame or some other reference point. I cannot find any measurements on how far these can go up into the fender well compared to the stock mount. Looking only at pictures without parts on hand it looks like it could raise it 1.5-2” and the lower mount looks like it drops 1” so if those estimates are close I can get an 11” with near 50/50bias.

...

On a normal F/R outboard with a 4"+1.25" lift, there is enough skirt left on the Poly towers to chop off a few inches of material.

A way to rough estimate the spacing of the shock mounts is to get the extended and compressed lengths of the desired shocks. With that, you know the compressed length and the half travel length between the proposed new upper and lower shock mounts. Cut those lengths out of cardboard strips and hold them up to the Jeep to see what goes where.

 

[jjvw]

I'm not sure you'd be able to use poly's lower shock mounts in a coil sprung axle. Not sure if it was your intention.

...

Both ends of mine are using the Poly lower shock mounts. It is the common way to do it.