CV Angles with Perch Collars

[Loufish]

Please, explain to me how adding preload to a spring changes the spring rate, or how many pounds it takes to compress the spring one inch (lbs/in)....

You are correct in that the spring rate itself does not change, but the effective rate does...
Example:
A linear spring with say a rate of 100 inch lbs and 16" long has an installed height of 14" ...it will take 200 lbs to start to compress the shock, and if you preload the installed height to 13" it will now take 300 lbs to start to compressing the shock...

 

[xrocket21]

You are correct in that the spring rate itself does not change, but the effective rate does...
Example:
A linear spring with say a rate of 100 inch lbs and 16" long has an installed height of 14" ...it will take 200 lbs to start to compress the shock, and if you preload the installed height to 13" it will now take 300 lbs to start to compressing the shock...

Well, this simply isn't true. When adding a preload collar, the spring is still in its neutral state, so you simply move that example of 14" of travel, further down in the travel.

Your example is correct if the travel is maxed out and you start compressing the spring at static height by adding more preload, but that simply isn't what is going on with the raptor and a ~2.25" collar.

You basically exchange 2.25" of down travel for 2.25" of up travel, the installed length of the spring doesn't change.

 

[tregs]

I agree with Loufish, your up-travel and down-travel are not changing. You are just preloading the stock spring by adding a collar. Thus increasing the initial load required to move the spring. Like he said, no change in spring rate. So, at static truck weight, the front suspension is more extended due to the extra preload. This would in turn increase the angle at the CV; and in theory increase stress/wear of the CV while in 4wd. What I don't get, is why there aren't more complaints about poor suspension performance after adding collars. Because, your should have to increase rebound damping to keep the same rebound speed after adding spring preload.

 

[dubya_raptor]

I've been trying to wrap my head around this preload thing for a while now. Adding preload to a coil over should not place a load on the coil, right? The only thing that the preload is doing is allowing the shock shaft to extend further out of the body, thus creating a longer static shock. This longer shock is what effectively creates lift, by pushing the lower control arm down at ride height. Right? Assuming that there is still some down travel left at ride height, why is it that ride quality suffers when preload increases?

I guess the question to ask is does adding "x" amount of preload compress the coil? And if so, is it negligible relative to the sprung load placed on that coil?

 

[Halo Raptor]

For what its worth when talking to ICON they told me about 1.5 inches seems to be the sweet spot. You can call them for some more detailed explanation of that. They told me the front shocks on the Gen 2's are a little soft and adding some pre-load actually makes the truck handle a bit better.

 

[xrocket21]

I've been trying to wrap my head around this preload thing for a while now. Adding preload to a coil over should not place a load on the coil, right? The only thing that the preload is doing is allowing the shock shaft to extend further out of the body, thus creating a longer static shock. This longer shock is what effectively creates lift, by pushing the lower control arm down at ride height. Right? Assuming that there is still some down travel left at ride height, why is it that ride quality suffers when preload increases?

I guess the question to ask is does adding "x" amount of preload compress the coil? And if so, is it negligible relative to the sprung load placed on that coil?

You are correct in your understanding of what is going on.

It doesn't affect ride quality as much as people perceive it does. But what change there is, is due to the increased angle at the arm. 5 lbs of force at a 90 degree angle is different than 5 lbs of force at an 80 degree angle.

 

[Trick.Raptor]

The Gen1 didn't see any real CV joint issues until owners of 2013+ Raptor's went to the top-perch setting on the OEM 2.5 shock. Of those who did the ones who ran the most in 4WD had the most problems while those who never went off-road or used 4WD had the least... Running hard off-road in 4WD did a number to those at top-perch!

The collars being sold for the Gen2 will not cause any CV joint issues even if you run in AWD all day long.


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