Yes, you should replace your rear springs to match the dynamic performance of the front springs. If you don't the front end will recover quickly and the rear end will feel sloppy. Even though your only doing a 2 inch lift you should do the upper control arms to compensate for reduced caster. You will need at least 2 degrees to avoid bump steer and tracking problems. Also know that it will take at least 10,000 miles for your new springs to settle depending on how you drive. The new springs and shocks will mellow over time. As an example my rear springs and shocks were initially too high. I had an extra 1.5" that I didn't want. The rear end is now level with the front after 15K miles. In my case this makes my truck handle the way I want it to. If your towing or always carrying extra weight this is not an issue and stiffer springs are better. I have 190 lb springs. My truck is usually empty so having the a$$ way up in the air is not desirable. Don't forget to install your dif drop spacers. After 10K miles take it back in for a second alignment.

 

thanks noted on the UCA’s and The springs...would going one springs be ok to “match the dynamic performance” of the ones that Bilstein provided with the front 6112’s? Or do I have to go with an after market rear set in which case are there any rear springs that don’t lift the FJ? My aim after all was to level out the rig.

....for the dog drop spacers, need to research that one. Haven’t heard about that yet in discussions about suspension upgrades...

 

Use the B12 rear springs which are meant to match the fronts and only add 0.9" or buy another spring set like Eibach that are matched and use their shocks.

BILSTEIN Corporate - BILSTEIN

www.bilstein.com

IMO it's best to use what has been tested and balanced for your truck otherwise you can get weird behavior.

The differential drop spacers reduce the angles on your CV shafts so that they don't wear out and snap while your on the trail. As you lift the IFS differential the angles on the shafts increase and will cause premature axle failure. Kits are cheap and easy to install.

While your fitting rear springs this is a good time to look at your rear control arm bushings. Make sure they are not torn. If they are OK and the new springs are installed drive the truck around the block a few times. With the wheels on the ground torque the bushing bolts to spec. They need to be tight. Once you do get all the work done take the truck in for alignment at a real 4x4 truck shop. Don't wait on this. Alignment numbers should look like this:

 

Do I need the diff drop spacers if I’m just raising the rig by 2”?

looked at those springs...it’s confusing when they don’t list the FJ as a recommended fit:
:Bilstein B12 (Special) For 2010-2020 Toyota 4Runner 1.5" Rear Coil Springs

 

Use the B12 rear springs which are meant to match the fronts and only add 0.9" or buy another spring set like Eibach that are matched and use their shocks.

BILSTEIN Corporate - BILSTEIN

www.bilstein.com

IMO it's best to use what has been tested and balanced for your truck otherwise you can get weird behavior.

The differential drop spacers reduce the angles on your CV shafts so that they don't wear out and snap while your on the trail. As you lift the IFS differential the angles on the shafts increase and will cause premature axle failure. Kits are cheap and easy to install.

While your fitting rear springs this is a good time to look at your rear control arm bushings. Make sure they are not torn. If they are OK and the new springs are installed drive the truck around the block a few times. With the wheels on the ground torque the bushing bolts to spec. They need to be tight. Once you do get all the work done take the truck in for alignment at a real 4x4 truck shop. Don't wait on this. Alignment numbers should look like this:

View attachment 1137645

Do I need the diff drop spacers if I’m just raising the rig by 2”?

looked at those springs...it’s confusing when they don’t list the FJ as a recommended fit:
:Bilstein B12 (Special) For 2010-2020 Toyota 4Runner 1.5" Rear Coil Springs

The Dif drop kit is only $50.00 and takes 30 minutes to install. It depends on how long you want your axles to last.

Use the search engine on the Bilstein WEB site:

• 

B12 (Special) - Suspension Kit
Available From Your Local Dealer
Part Number:36-281817
Product Type:Suspension Kit
Position:Rear
MSRP:$249.00
Notes:

-Rear Lift Height: 0.9"

Product Description
Bilstein B12 (Special) suspension kits are designed to alter the vehicles ride height for optimum performance. Utilizing various different technologies to achieve the optimum ride height for a specific requirement. Bilstein B12 (Special) suspension kits provide the perfect combination of suspension dynamics, quality and aesthetics.
Buyers Guide
Toyota 4Runner 2020-2003, FJ Cruiser 2014-2007



https://cart.bilsteinus.com/details...47056532308851991&Submodel=6231015219844690056&Pos=Front&Dr=4893330155885314595

 

In theory. In reality it is 1/4 to 1/2 different depending on load. Basically looks correct to my eye and I’m extremely picky about level. Definitely not the biggest lift but a good combo of function and height. It is close enough that a 2” rear spring would give a front bias ie the dreaded California lean

 

Agree it looks level in the pic.

did you notice a performance difference without the rack? Quieter?

 

A "Technical Sales and Warranty Specialist" at Bilstein of America, replied:..."in the rear you can use the OEM springs."

 

You will be changing your rear springs soon after you do the front end and then you have to get it aligned again.

 

Thanks - I'll change up the rears at the same time I do the front. Agreed, may as well do all at the same time. I was advised that these work for the 5160's as a pair for the 6112's up front.

 

Interesting that I just got the red TRD springs delivered and they look and weigh identical to the ones that Bilstein packaged with the front 6112's (in the pic the Bilstein provided ones are gray because I've primed them ready to be painted red):

TRD springs: PTR13-35140-AA

I'll use the red ones for sure!