TJ Rear Antirock Install Interference Suggestions

[mattcogdell]

Preface: This is not a TJ specific antirock. This is a universal kit.

Bar width: 45”
Arm: 18”
Link: 14”
Wheel: Moab 16”
Spacers: Spidertrax 1.25”

I’m having contact issues between the tire and the arm while cycling the suspension. This is when cycling sides separately. I’ll post a picture of the arm at ride height @mrblaine mentioned I need to get the arm higher at ride height to avoid contact on the way up. I took his advice and now have the arm as high as I can make it with 14” links. Any higher, the arm wants to go through the tub at full bump.

The arms cannot afford to have any less bend in them, on the down travel you could fit several playing cards between the upper perch and the arm. No room for less angle.

I pulled my liner and flare to get a better visualization. It’s clear to me that I either need a shorter arm with a longer link or less wheel back spacing.

A fellow jeeper is sending me a 15” TJ specific arm to experiment with. Tomorrow I’m going to stop at the hardware store and pick up a few washers to mimic 1/4” to make the wheel have 3.5” BS. Curious to see if .25” less BS helps. Spidertrax offers a 1.5” spacer so this is an option if it fixes my contact issue.

I hope these photos are clear to see what is happening. Please list any suggestions.

Driver side overall setup:

Passenger side initial contact still able to turn by hand:

Full bump, unable to turn due to tire/anti rock contact:

 

[BuildBreakRepeat]

Why not shave the spring perch and bring the arms closer in? Also you can dent the tub in if you need more room. Also how would shorter links look that tuck it below the tread?

 

[mattcogdell]

Why not shave the spring perch and bring the arms closer in? Also you can dent the tub in if you need more room. Also how would shorter links look that tuck it below the tread?

Not sure how trimming the perch would affect the spring seating in the perch. I feel hesitant towards that as I haven’t seen anyone do that before.

Denting the tub I’m fine with but I’ve maxed out the length of the link I have now without needing to. If I ran Currie 15.5” link, the tub would require more than denting.

Are you asking about running the links shorter, to tuck the arm behind the tire?

 

[mrblaine]

Not sure how trimming the perch would affect the spring seating in the perch. I feel hesitant towards that as I haven’t seen anyone do that before.

Denting the tub I’m fine with but I’ve maxed out the length of the link I have now without needing to. If I ran Currie 15.5” link, the tub would require more than denting.

Are you asking about running the links shorter, to tuck the arm behind the tire?

I've said to run the links higher to put the arm above the edge of the tire. I have not had a clear visual of the actual issue until the pictures here. You'll never fix that by making the links longer. The picture below shows what should be done. The part of the tire with the red arrow is the area that needs to be near the end of the arm to swing under the arm at full articulation. The torsion bar is too close to the tire.

 

[Fitzpatrick]

At ride height the arm should be about parallel to the frame you’ll have to cut the links down to size and get it behind the tire.

 

[mrblaine]

At ride height the arm should be about parallel to the frame you’ll have to cut the links down to size and get it behind the tire.

Doesn't matter. The problem is the location of the torsion bar. It is too close to the tire. He can do whatever he likes and unless that moves or he makes a curved arm, the tire is going to hit the arm under articulation.

 

[Fitzpatrick]

Here’s how mine was installed opposite side of yours.

 

[mrblaine]

This is roughly the distance from the apex of the tire you need the torsion bar mounted.

 

[Fitzpatrick]

Here’s how mine was installed opposite side of yours.

View attachment 162855

Nevermind looked at the pictures again no difference.

 

[Fitzpatrick]

Mine we had to cut the tub and mount back further

 

[mattcogdell]

@mrblaine the torsion bar is as far forward as possible. Butted up against the step in the tub. I’m not the greatest at interpreting photos. These photos I’m posting are TJs. Can you please help me visualize the difference between my arms and location?

 

[mrblaine]

@mrblaine the torsion bar is as far forward as possible. Butted up against the step in the tub. I’m not the greatest at interpreting photos. These photos I’m posting are TJs. Can you please help me visualize the difference between my arms and location?
View attachment 162875View attachment 162876View attachment 162877View attachment 162878View attachment 162879View attachment 162880View attachment 162881View attachment 162882View attachment 162883View attachment 162884View attachment 162885View attachment 162886

How many of them have rub marks from the tires hitting the arms under articulation after they have been in use for awhile? I can't make it work. I always put them behind the axle. I don't deal with arm angles that are that high.

 

[mrblaine]

The other thing to note is the use of wheel spacers of a lot more thickness than I would ever use unless I was dealing with a factory back spaced rim. This is not a "I saw this done so it works" thing. This is a "I saw it done and I know all the issues they solved and how they solved them" thing.

If you want to use 2" wheel spacers to wind up with 2" of effective back spacing, you can fix it most likely. If you don't want to do that, then another option will likely be used.

 

[mattcogdell]

@mrblaine can the TJ specific kit be used without modifying when running poly towers?

 

[mrblaine]

@mrblaine can the TJ specific kit be used without modifying when running poly towers?

Generally yes.

 

[mattcogdell]

The other thing to note is the use of wheel spacers of a lot more thickness than I would ever use unless I was dealing with a factory back spaced rim. This is not a "I saw this done so it works" thing. This is a "I saw it done and I know all the issues they solved and how they solved them" thing.

If you want to use 2" wheel spacers to wind up with 2" of effective back spacing, you can fix it most likely. If you don't want to do that, then another option will likely be used.

Trying to understand the “I know all the issues they solved and how they solved them” part, I went to the hardware store this morning and purchased some washers to experiment with less BS.

Rubi wheels 5” BS
Spacer 1.25”
Overall 3.75”

I started with + .25” of washers. It was noted that the scrub was lessened, overall 3.5” BS.
I then added + .25” of washers, overall 3.25” BS. At full bump I can rotate the tire, with minimal scrub, some of which is contributed to the rear arch of the fender.

It looks like at this time there’s 2 options, 1.75” spacer or mounting in another location. I’m waiting till later this week when the 15” arm arrives to experiment with.

I will note the gap between the perch and the arm on the driver side is 7/32”. Passenger side gap is 1/16”.

 

[mrblaine]

Trying to understand the “I know all the issues they solved and how they solved them” part.

You've used many pictures to counter my position that mounting in front of the axle on a TJ with standard wheelbase is not good. You also clearly show in several that the tire does get into the arm and not just a little. You also used a pic or two from what is clearly a TJ Unlimited. There is also at least one with a ridiculous arm angle because the torsion bar is too close to the tire. So sure, it is possible to mount in front of the tire if you want to make several compromises, want to run a silly spacer thickness, etc. Knowing what was done specifically to mount in front of the tire is not the same as mounting in front of the if you don't employ some of the same solutions.

 

[mattcogdell]

@mrblaine do you have any photos of a TJ with the antirock mounted behind the axle with poly towers?

 

[mrblaine]

@mrblaine do you have any photos of a TJ with the antirock mounted behind the axle with poly towers?

I don't.

 

[TJosh02]

Here’s how mine was installed opposite side of yours.

View attachment 162855

This is how mine are mounted as well. How do you do outboarding shocks with this location though? Seems like they are directly in the way, or do they have to be frenched deep inside the frame to avoid eachother?