Let's talk optimal build for 31" tires

Irun said:
The springs have netted 1.5" of lift front and rear. Since I have a pair of 1" spacers, I'm going to add those this weekend and take a bunch of measurements again. I'm already at a point, with the 1.25" BL and 1.5" suspension lift, where there is more exposed wheelwell space than I would like. (y)
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Maybe remove the BL? Do you need it?
 
zebra12 said:
Are there better options if you use a bar pin eliminator on top?
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Not that I've seen. I have a Teraflex bar pin eliminator that I tested out. Unfortunately, it shortens the compressed length to 12", which seems to put everything in the 6"-7" shock travel category.
 
@Irun is it out of the question to modify the shock mounting locations? With a 1.25” body lift, you have extra room above the crossmember that the bar pin mounts to. On the bottom, you could weld on some new shock brackets, so that you can change the shock mounting position and not have your shock choice so restricted by total length.

Or if you are really desperate, find someone who will make cu$tom shocks for you... but I don’t even know if there are people who do that.
 
SecondChanceTJ said:
@Irun is it out of the question to modify the shock mounting locations? With a 1.25” body lift, you have extra room above the crossmember that the bar pin mounts to. On the bottom, you could weld on some new shock brackets, so that you can change the shock mounting position and not have your shock choice so restricted by total length.

Or if you are really desperate, find someone who will make cu$tom shocks for you... but I don’t even know if there are people who do that.
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If I could take a bar pin eliminator and flip it, I'd gain 1" and open up the options. That said, I need to look at the mount closer to see what could be done there. Seems like if this was smart, it would have been done already!
 
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Okay, need some clarification here. When cycling the suspension and measuring for shocks, do you include bump stop? For example, if I measure the compressed lengths, it's 12. inches without bump stop, or 12 .5 inches with a 1 inch bump stop. Which is the correct measurement?
 
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Irun said:
Okay, need some clarification here. When cycling the suspension and measuring for shocks, do you include bump stop? For example, if I measure the compressed lengths, it's 12. inches without bump stop, or 12 .5 inches with a 1 inch bump stop. Which is the correct measurement?
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You wouldn't want the shock bottoming out before you hit the bump stop, I'd lean towards not including bump stop so that you save the shock on a hard bump. Basically you have that extra 1/2" past the bump stop to prevent any damage.
 
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jordans05tj said:
You wouldn't want the shock bottoming out before you hit the bump stop, I'd lean towards not including bump stop so that you save the shock on a hard bump. Basically you have that extra 1/2" past the bump stop to prevent any damage.
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That's what I thought, but I'm suffering from "TJ restoration exhaustion". I'm repeating the same stupid mistakes over and over, and second guessing what I know. Maybe time for a break! :sleep:
 
Irun said:
That's what I thought, but I'm suffering from "TJ restoration exhaustion". I'm repeating the same stupid mistakes over and over, and second guessing what I know. Maybe time for a break! :sleep:
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Tell you what, we can trade Jeeps. Mine is driving great so you can take that break and do what you want to it. I feel pretty good about this swap, lemme know :ROFLMAO:
 
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Okay folks, I need a sanity check here. I've studied these numbers until I'm cross eyed. Without doing a shock out-boarding, or other shock mount modifications, the best possible shock combination I can come up with, for 31" tires, using the H&R springs and a 1" spacer is the Rancho RS55239 (Front) and Rancho RS55241 (Rear). This results in the following travel:

Front (239) = 4.57" up and 4.84" down. This gives a total front shock travel of 9.41" inches
Rear (241) = 4.5" up and 3.67" down. This gives me a total rear shock travel of 8.17"

Although the front didn't hit my target of 10", I can live with those numbers. The rear on the other hand is disappointing, since my target here was to get close to 9".

FWIW, these are other numbers I'm now seeing with a 31" tire:

-14+" at the gas tank skid
-15+" at the transfer case skid
-13+" at the front of the oil pan skid
-25.75" at the rear tub (behind the rear flare)
-2.25" suspension lift
-1.25" body lift

To get there, I was able to make the Currie front and rear track bars work with the 1" H&R springs, 1" aluminum coil spacers, Savvy control arms, and Savvy UA.

That said, given those numbers, can I call this a success? I'd really like to order the shocks and driveshafts, so I can finally test drive the work so far. Thoughts?
 
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Irun said:
Okay folks, I need a sanity check here. I've studied these numbers until I'm cross eyed. Without doing a shock out-boarding, or other shock mount modifications, the best possible shock combination I can come up with, for 31" tires, using the H&R springs and a 1" spacer is the Rancho RS55239 (Front) and Rancho RS55241 (Rear). This results in the following travel:

Front (239) = 4.57" up and 4.84" down. This gives a total front shock travel of 9.41" inches
Rear (241) = 4.5" up and 3.67" down. This gives me a total rear shock travel of 8.17"

Although the front didn't hit my target of 10", I can live with those numbers. The rear on the other hand is disappointing, since my target here was to get close to 9".

FWIW, these are other numbers I'm now seeing with a 31" tire:

-14+" at the gas tank skid
-15+" at the transfer case skid
-13+" at the front of the oil pan skid
-25 3/4" at the rear tub (behind the rear flare)

To get there, I was able to make the Currie front and rear track bars work with the 1" H&R springs, 1" aluminum coil spacers, Savvy control arms, and Savvy UA.

That said, given those numbers, can I call this a success? I'd really like to order the shocks and driveshafts, so I can finally test drive the work so far. Thoughts?
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How much actual lift do you have with 1" H&R springs + 1" spacers?
 
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Using your shock ride height estimate, Skyjacker's Black Max shocks will give you 5.41" up/3.46" down. The Rancho 55241 is the only rear shock close. How much bump stop are you using in the rear?
 
bobthetj03 said:
Using your shock ride height estimate, Skyjacker's Black Max shocks will give you 5.41" up/3.46" down. The Rancho 55241 is the only rear shock close. How much bump stop are you using in the rear?
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Fully compressed the rear is 12", but I'm running 2" bump stop out back.
 
I also found that the 55241's seemed to fit the best with my 2-2.5" of lift. I wish there were more options, but they were the best fit I could find. Outboarding is something I would love to do at some point.
 
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Did you look into moving the rear shock mounts? If I lifted 2.25” and only got slightly more than stock travel due to being limited by shocks, I wouldn’t be happy. Not saying it’s a fail! But it reminds me of that saying that floats around here, “...90% of the effort is spent getting the last 10% of performance”. But by all means, if you are satisfied with what you’ve already accomplished, then run it!
 
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I'm finding that I can't get the 241 fully compressed either. I'm also running around a 2" bumpstop extension in the rear. I have a set of BPEs that I could put in that will move the eye closer to the body at full bump which will trade that extra inch of up travel for downtravel.

The other thing that mucks with the rear end is the angle at which the shock operates. You don't have a 1 for 1 ratio like you do in the front. For every inch of compression you get in the axle, you get less compression in the shock, because of the angle it operates. Its also going to change angles as it compresses...At least, I think so...I need to test the theory, but trig tells me that its so. I need to measure the angles and actually do the calcs...

And given all that....does it even matter?
 
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