Figuring out my current suspension

[freedom_in_4low]

Please bear with me, I've got a lot of thoughts here as I try to plan out my next build phase which is shocks and possibly springs. This is my first rodeo with this stuff so I'd like to bounce some of it off of you that are more experienced with this.

To start, I have an unidentified lift that came on my TJ when I purchased it used in 2017. With no top on, I'm measuring 15.125" between the perches indicating 3.125" of lift, and 10.25" in the rear, indicating 2.25" of lift (measured mid-perch, since the front and back are so far off after being SYE-ized). Both axles have Rancho RS5000 shocks, without the "x", which suck and are my primary motivation for reworking my suspension.

So, onto the conundrum - I've got Rancho 239 and 241 part numbers that Rancho lists for a 2.5" lift. My front is at 20" at ride height which would be 60% uptravel/40% down, though I'm losing 1/2" of uptravel because I'm bumped to keep the diff cover out of the track bar so my ride height ends up more like 57/43 of real available travel.

My rear however, is 19.25" at ride height which means I'm at about 70% up, 30% down, and like the front I have half an inch of shock that I can't use because I'm bumped to keep the track bar bracket out of the floor. The front makes sense, but the rear seems to conflict with what I've read here about Rancho's running long considering I'm measuring even less lift than Rancho advertises these shocks for. I set up my rear suspension using the 8 control arm write-up from that other forum, so wheelbase is set for bumps centered at full stuff (including extensions, which if anything should move the axle slightly closer to the upper shock mount for a given ride height). I only mention that because moving the axle back would effectively lengthen the shock. Anyway...wondering if maybe the 256 and another inch of bump stop is a better choice for the rear and either stay with the 239 up front for current lift height or 255 if I go for the Currie 4" springs.

 

[Goatman]

It sounds like you have a 1" spring spacer up front to level out the TJ. They came with a pretty noticeable angle from the factory to help with drag and mpg's. Some like the stock slant, some don't so they add a shim up front to level it out. If you have 70% up travel in the rear I would not thing going to a longer shock advisable. You would then bottom out the shock even earlier. Or have I misunderstood the question? If you are currently happy with how the Jeep drives now I would go with a 1 1/4" body lift instead of all the cash and time for new springs (from any manufacturer).

 

[freedom_in_4low]

It sounds like you have a 1" spring spacer up front to level out the TJ.

no spacer, unless this isn't the spring isolator that came from the factory. It's only about 1/2".

If you have 70% up travel in the rear I would not thing going to a longer shock advisable. You would then bottom out the shock even earlier. Or have I misunderstood the question?

I may not be using the terminology correctly. By uptravel I was referring to the axle traveling up toward the frame, or said another way, 70% of my shock shaft is exposed at ride height and only 30% of it is available for droop, so yes, I'm thinking I want to bottom out "earlier" so I can also top out "later".

Here are my numbers for the rear:
Shock length at full stuff - 14.25"
shock length at ride height 19.25"
Shock length at full droop - 24"

Length of (currently equipped) Rancho *241 shock - 13.51-21.67"
effective available travel 14.25 - 21.67 or 7.42"
Ride height is at 70% of shock shaft exposed, 67% of effective available travel

Length of Rancho *256 shock - 15.01-24.67"
effective available travel 15.01 - 24 or 8.99"
Current ride height would be at 43% of shaft exposed, 47% of effective available travel

The longer shock seems to overlap better with the rest of my suspension, and by using most of the 2.5" more inches of droop my suspension has in it after my current shocks top out nets an 1.5" more travel.

In the front:
Shock length at full stuff - 15.125"
Shock length at ride height - 20"
Shock length at full droop - (need to recheck as I lost my measurement but I know it's longer than my current max shock length)

Length of (currently equipped) Rancho *239 shock - 14.43-23.84"
Effective available travel 15.125 - 23.84 or 8.715"
Current ride height is at 59% of shaft exposed

Length of Rancho *255 shock - 15.8-26.563 or 10.73"
current ride height would have 39% of shaft exposed, an exact 4" lift would be at 47%.

In the front my ride height is at 20" on a shock that goes from 14.43 to 23.84, again meaning that 60% of the shaft is exposed and 40% of the extension remains. The next longer shock would put me the other way at 41/59 if I kept my current ride height, perfect 50/50 with a 4" spring, and 10.2" of travel if I can fully droop out the shock.

Another question I have is am I too hung up on % and should I instead be looking at inches of shaft exposed and just making sure I have at least some minimum distance equal to or greater than what a stock Jeep would have had?

If you are currently happy with how the Jeep drives now I would go with a 1 1/4" body lift instead of all the cash and time for new springs (from any manufacturer).

well, I hate the RS5000 shocks and want to go to the RS5000x. So even if I keep the current springs I still need to nail down the right shock length.

 

[freedom_in_4low]

paging @jjvw 'cause I'm sure he's been through all this before

 

[jjvw]

The front at 57/43% sounds fine. If you were to go slightly longer, those numbers would just about flip flop, which would also be fine. 50/50 is a good goal, but hard to achieve on stock mounts. There is an argument that favoring a bit heavy on up travel is desirable if you are stuck between two options.

The rear needs a longer shock which will require more bump stop. More bump is fine if it gets you closer to 50/50.

It's far easier to just look at the actual measurement than the percentages. And then be ok with close enough being good enough. There is only so much you can do with off the shelf shocks on factory mounts.

Then I find it easier to focus on fitting the collapsed shock length and measuring the up travel from ride height. If you can get half of the shock's overall travel in there, then the down travel will sort itself out. All you need to do is make sure the drive shaft will freely spin at full droop.

You can preplan this by disconnecting the driveshaft at the axle, hanging the axle without shocks and raising the axle back up until you can bolt up the driveshaft again. Then measure the distance between shock mounts. That is your maximum extended length without a center limit strap.

 

[freedom_in_4low]

The front at 57/43% sounds fine. If you were to go slightly longer, those numbers would just about flip flop, which would also be fine. 50/50 is a good goal, but hard to achieve on stock mounts. There is an argument that favoring a bit heavy on up travel is desirable if you are stuck between two options.

The rear needs a longer shock which will require more bump stop. More bump is fine if it gets you closer to 50/50.

It's far easier to just look at the actual measurement than the percentages. And then be ok with close enough being good enough. There is only so much you can do with off the shelf shocks on factory mounts.

Then I find it easier to focus on fitting the collapsed shock length and measuring the up travel from ride height. If you can get half of the shock's overall travel in there, then the down travel will sort itself out. All you need to do is make sure the drive shaft will freely spin at full droop.

You can preplan this by disconnecting the driveshaft at the axle, hanging the axle without shocks and raising the axle back up until you can bolt up the driveshaft again. Then measure the distance between shock mounts. That is your maximum extended length without a center limit strap.

Perfect, that's exactly the sort of feedback I was looking for. Thanks!

That settles me on shocks, now I just gotta decide whether to get my next inch with springs or a body lift. I realize the body lift will be cheaper and provide for other opportunities like tucks and gas tank lifts but if I break one bolt off inside a torque box I'll be wishing I'd gone with springs.

 

[jjvw]

... now I just gotta decide whether to get my next inch with springs or a body lift. I realize the body lift will be cheaper and provide for other opportunities like tucks and gas tank lifts but if I break one bolt off inside a torque box I'll be wishing I'd gone with springs.

You can see how well the bolts loosen up before committing to a body lift.

 

[Quigley]

Spray,Spray, Spray the body mounts bolts! Take his advice and double check them so see if they will spin freely. I broke three off trying to put on a BL and I had sprayed Kroil on all the mounts for several weeks. No visible rust on the outside bolts where turning and then snap... Fragile fudge flicker!!!!! It sucked replacing three broken body mounts bolts with one requiring a new channel.

 

[jjvw]

Spray,Spray, Spray the body mounts bolts! Take his advice and double check them so see if they will spin freely. I broke three off trying to put on a BL and I had sprayed Kroil on all the mounts for several weeks. No visible rust on the outside bolts where turning and then snap... Fragile fudge flicker!!!!! It sucked replacing three broken body mounts bolts with one requiring a new channel.

Spraying were the body threads are is easier said than done.

 

[Quigley]

yes, if I had to do it over I would have drilled pilot holes everywhere to make sure I was hitting the bolt. unfortunately, my jeep lived it's first 12 years in Pennsylvania before I moved to the PNW.

 

[freedom_in_4low]

You can see how well the bolts loosen up before committing to a body lift.

if you weren't building for eventual 35's and planned on staying with 33's forever, would you have done 3" suspension plus 1.25" body for tummy tuck opportunities and a lower CoG, or straight 4" suspension to get into a shock with 1.3" more travel? Or do what you did (both) and just had more clearance than you might need for 33s?

 

[jjvw]

if you weren't building for eventual 35's and planned on staying with 33's forever, would you have done 3" suspension plus 1.25" body for tummy tuck opportunities and a lower CoG, or straight 4" suspension to get into a shock with 1.3" more travel? Or do what you did (both) and just had more clearance than you might need for 33s?

I would likely keep it as is for 33s. There really is no draw back with the extra inch of lift. The only thing I would have different is to stay with short arms for 33s.

 

[freedom_in_4low]

The front at 57/43% sounds fine. If you were to go slightly longer, those numbers would just about flip flop, which would also be fine. 50/50 is a good goal, but hard to achieve on stock mounts. There is an argument that favoring a bit heavy on up travel is desirable if you are stuck between two options.

The rear needs a longer shock which will require more bump stop. More bump is fine if it gets you closer to 50/50.

It's far easier to just look at the actual measurement than the percentages. And then be ok with close enough being good enough. There is only so much you can do with off the shelf shocks on factory mounts.

Then I find it easier to focus on fitting the collapsed shock length and measuring the up travel from ride height. If you can get half of the shock's overall travel in there, then the down travel will sort itself out. All you need to do is make sure the drive shaft will freely spin at full droop.

You can preplan this by disconnecting the driveshaft at the axle, hanging the axle without shocks and raising the axle back up until you can bolt up the driveshaft again. Then measure the distance between shock mounts. That is your maximum extended length without a center limit strap.

After I got my SYE installed and took it around the block 6 weeks ago, the left rear shock was actually bubbling fluid out of the shaft seal, so it's time, and now that I'm moved into the new house and quarantined I have time to do it.

I think I'm actually going with the longer shocks all the way around. This puts me at 47% uptravel in the rear and 41% uptravel in the front, which works out to 4.2" at both ends. The front won't be as balanced up/down from a percentage standpoint, but 4.2" doesn't seem awful and if I find it bottoming too much, I'll throw in some 3/4" spring spacers all the way around as a cheap workaround until I decide to jump for 4" springs.