I think
@boogielander is mainly referring to Front spacers not being the safest or ideal way to go.
Rear spacers don't create the same geometry issues with the Rear shocks that Front spacers cause with the Front struts (ball joints, coil bind, interference, etc).
correct.
Rear spacers don't cause problems because rear is a solid axle type of suspension, where the shock and springs are separated and does not bind into anything.
Spacers are OK for solid axle use on road, but I still don't recommend it because the spring rate is incorrect.
in my customers' applications, they want spacers because of sag due to constant load that create sag. Using spacers can eliminate that sag, BUT negatively affect the ride due to wrong spring rates that are not able to handle the weight (springs are now compressed, even at ride height). It is always recommended to change to the correct spring rates to get the lift height back while retaining or even improve ride quality and handling. The only time that we use spacers for the rear (for IFS + Solid Rear) applications is when the constant load is higher than the heaviest (spring rate) available springs (think: drawer system, fridge, rear bumper with swing outs, spare tire, roof tent, tools, equipments, etc for overlanding SUV builds).
That's why even though I want to gain another inch or so to match TRX's stance, I had to scratch that plan. I could crank my preload up for another inch (since I'm at Fox's factory setting of 2" and the shock package is good for 2-3" lift), but that will sacrifice my droop and actually take away suspension travel. For the rear (since I'm already pushing the 500lb constant load limit for my Carli HD springs - I probably exceeded it by 50 or so lb already just with my weekend camping gear only), I could really benefit from using heavier rated springs or add spacers to gain another inch, but I decided against it because that means I'm sacrificing rear ride quality, control, and performance for an additional inch just for aesthetic. And that... makes no sense to me at all.
