They made sense before I said anything, you just managed to turn your brain off for a bit.
Best riding springs
- Thread starter shumthisway
- Start date
If you rotate the rear perches to flat to easier measure the height of the spring, then it takes roughly a 12" spring to hold up the average TJ at a 4" lift height over stock. It is very easy to create a spring with a free height of 12 1/2" which only compresses 1/2" when the weight of the rig is set on it.
That spring would also affect ride quality in a very negative manner both on compression and extension. The extension would result in an accelerated and exacerbated jarring effect when it slams into the upper perch as the axle moves back up.
The reason we have continually pounded or tried to pound the "springs set ride height" and "springs don't matter" into the group think collective over the years is due to the rest of the basic criteria that it takes to design and build a spring.
It has to have a reasonable amount of free length so they don't drop out of the bucket too far.
It has to have a reasonably few number of coils so it stays out of coil bind at full compression.
It has to have a reasonable number of coils so it doesn't fatigue quickly and break.
It has to have a rate that provides the design ride height.
Once you get reasonably close to meeting the above criteria and create something that will do the job, last a reasonable amount of time without sagging or breaking due to fatigue, then the spring rates wind up within a fairly narrow range which is unable to affect ride quality in a discernible manner.
It is also the same reason I have stated many times that if folks would set up the springs on just one set of coil overs using the basic rules of doing so properly, then all the confusion over what determines ride quality just goes away. It becomes pretty obvious when there are literally 100's of spring options and 1000's of possible combinations available that we wind up using a combined rate with about a 50 lb per inch spread.
Doesn't seem like much of a spread, right?
Here is how that works. If you take a 12" travel coil over set up with our typical balanced travel on the rear of a TJ with a sprung corner weight of 500 lbs. per corner, the spring rate to hold it at design ride height is 62.5 lbs per inch.
If you take another rig that has a sprung corner weight of 1000 lbs. per corner, the spring rate to hold it at design ride height is 125 lbs. per inch.
I picked those two because the 500 lb rig and the 1000 lb rig are anomalous in that both are pretty far outside what we normally encounter and still, at the furthest ends of the weight spectrum away from each other, the spread is a few points above the 50 lb per inch rate I mentioned. Purely to illustrate that even if you want to try and use extreme examples to make a point, they still fall within a very narrow range.
For the rear of a TJ or even a TJ Unlimited we typically see 650 to 750 lbs. per corner of sprung weight. 650 is 81.25 and 750 is 93.75 lb per inch of rate to hold them at design height. 100 lb difference in sprung weight per corner nets you a 12.5 lb per inch change in rate and yet, a rig that weighs 200 lbs more over the rear axle is a considerable difference in weight and nets a near inconsequential change in spring rate.
My final comment should not be dismissed and it is this. For all of the coil over shocks I have had tuned over the years, not a single time has my tuner asked what the spring rate is because we don't care and it doesn't matter. He tunes for the rig and how it will be used and not the spring rate.
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i think you would be surprised how little tire pressure you need with 35" tires. Take a look at a load inflation table sometime. What psi are you running?
Start with tire pressure...
You may not have to go any farther.
Tire sidewalls make a difference too. I have 265/75/16 load range E KO2s and even when I air down to 15psi the side wall show very little flex. I’m very happy with my ride comfort with my OME springs and shocks. When other Wrangler owners ride with me they comment on how nice my rig rides. My other Wrangler is an 89 YJ and that rides like a buckboard.
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