It will change the way it rides.

Another thing to consider. The coilover assemblies designed for our trucks have a specific length when fully extended. That length is determined by the optimum travel range of both the suspension linkage, and the operation range of the CV joint. Adding a spacer on TOP of the coilver may likely forces the knuckle droop to be further than what the CV can accommodate. I.e. extreme CV angle when either of the front wheels is nearly unloaded.

Consider the scenario in which you're climbing up uneven terrain. One of your front wheels completely unloads and that CV angle is now way past the normal operating range because of the top spacer you added. ATRAC kicks in, and locks the brake at that same corner, and now your drivetrain is transmitting intermittent torque through a CV who's angle is very close to, or maxed out. Bye bye CV joint.

You're much more likely to over-stress the CV by turning sharply than you are by any reasonable amount of suspension droop. The front wheels have a maximum turning angle of around 30 degrees. To get that much of a CV angle with suspension droop would require a droop of about 7-8 inches from horizontal at the wheel. A 1" spacer isn't going to get you to that point. You'd have to do a roughly 4" spacer-only lift to get those kind of angles.

It's also worth noting that preload does not change the stiffness of a spring. Stiffness is set by spring materials and construction. Consequently preload, whether done by raising the spring perch on the shock, or by inserting a spacer at the top of the shock, does not change the ride at all unless you shift the ride height so much that you are hitting the bump stops or exceeding the shock travel. As long as the preload does not exceed the vehicle weight (which case would prevent the suspension from getting off the lower stop), the spring operating point does not change, regardless of preload. It is still the same stiffness spring, and it is still supporting exactly the same amount of weight, therefore its loaded length will be exactly the same as it was before the preload change.

Preload does bias the suspension operating point away from center. Where spacers and other lift options cause trouble is when the suspension nominal operating point is biased too far from its center value, causing the suspension to frequently hit the stops on one end or the other, or causing the spring to go into coil bind before the stops are reached. As long as neither of those situations occur, the ride should be indistinguishable from the non-preloaded case.

so how are the people on this forum reaching heights of 39 inches without complaining about cv angles and also vibration from having the cv at weird angles?

Just like I stated, you run a taller spring. Stock icon spring is 13" I believe. They have an option to order with a 14" spring or you can order 14" springs from king.

I'm sitting at almost 41" ground to fender and have like 1" of thread showing.

I have a gx470 and it comes with a negative CV angle from the factory so lifting it is pretty simple. I also do not run a diff drop and have zero issues with CV joints or vibration.

I'm at 40" ground to fender with a 1.5" BL and 33's. Longer 700# King coils and 1" of thread showing. CV angles are awesome with the diff drop but front skid plate needed lowered a bit.

People should stop measuring from the ground and start doing it from the center of the hub or something that way tire sizes and wear won't factor in.

@GX4SEVEND has 35's which screws up the comparison.

Running taller springs will have the same effect on the CV as a tall spacer. The CV only cares about the relative height of the differential compared to the center of the wheel. That's why people with large lifts do diff drops.

CV vibration may well occur at smaller angles than 30 deg, but my post was originally about breakage, not vibration. Not many people crank their steering wheels to full lock while going fast enough for vibration to be a factor, at least and live to tell about it.

Just went out and did some measurements on my stock '06 Sport, to put some science into this. The CV joints are 12 inches apart, and the CV offset is a negative 1.5 inches. That gives a CV angle of 7 degrees. Fender height is 34 inches. If I lifted to 40 inches without moving the diff, the CV offset would go to a positive 4.5 inches. That would be a CV angle of 20 degrees, still a lot less than the maximum steering angle. Dropping the diff 1.5 inches would make the CV angle a mild 14 degrees. That's assuming the entire lift was a suspension lift. If part of it was a body lift, which doesn't raise the diff, the angles would be even better.

Thanks for replies. I'd rather not put too much angle on the CV's so I'll ditch the spacers and I will try giving the collars a few more turns. If thats not enough I will begin looking for 700# springs if they don't cost too much.

Ill call icon one of these days and see what they say.

By that reasoning, wouldn't a 3" coilover lift with a 1" spacer on top of it get you damn close to it?

What about an over max suspension droop PLUS turning the wheels?