Sorry for the continued questions and lack of knowledge.
What Is the safe rake I should have? I know others have 1.5 medium rear spring with cranked TB without diff drop. Will I ruin all those parts you mentioned without a diff drop?
IronMan suspension VS. Old Man Emu?
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Sorry for the continued questions and lack of knowledge.
What Is the safe rake I should have? I know others have 1.5 medium rear spring with cranked TB without diff drop. Will I ruin all those parts you mentioned without a diff drop?
There are a lot of opinions on subject of "are dif' drops required?" I deferred to the guys at ACC. They say "no".
There is a range of rake that's acceptable. When you hear "leveling" the front end - there still has got to be a bit of rake. When my new springs and TBs were installed, the rake was initially set much too close to level. We (ACC) had a plan - "Let's get it close, drive it for a day, then let's adjust to where you want it".
That first setting - close to level... holy *$&! did it ride and drive like crap. I was sick - I thought that was just how it was going to be. By dropping the front to where I wanted it, the truck transformed - it was/is sooooo much smoother.
Rake can have an impact on caster - and overall steering geometry. But again, as long as it's in a range that's close to stock, you'll be fine.
Before and after (after shot a few months later, but adjustment was made the next day)
The CV angle is dependent upon the lift. Regardless of whether or not the torsion bars are cranked factory bars or aftermarket Old Man Emu or Iron Man, raising the front end from the stock height will increase the static CV angle, which will put more wear on the boots (and to some degree the joints themselves). Is the diff drop a "must have?" No, but you may find yourself paying to have the joints re-booted or up to your elbows in grease doing it yourself sooner than you would with the diff drop.
I will also deviate from the accepted wisdom around here and say that cranking your factory torsion bars is a perfectly acceptable way to lift the front. It does not "pre-load" the torsion bar, it just changes the starting point from which it twists. The load on the torsion bar is unchanged.
"Safe" is subjective, but with a little searching on the forum I think you'd find that most folks here are running between 1" to 1.5" of rake. It's ultimately about the caster angle, which you could have measured at an alignment shop.
Hayes, respectfully not sure I agree with you but maybe we're looking at it in different terms. What you described as "changes the starting point" is what I would understand as re-indexing the bar, ie. setting a new starting point. I was suggesting that if you simply start cranking away on the TB's from the existing position (with out reindexing), that further increases the pre-load. Backing up a second, by turning the adjustment bolt, you are twisting the torsion bar, like twisting a rubber band tighter, the result is reducing its flexibility. This creates the lift but also increases the pre-load on the bar. This loads the bar similarly to pushing down on or winding down a coil spring reducing its capacity to compress and rebound, (reducing down travel in this case). This is why its easy to get wheel lift on over cranked TB's. If Ive got it bassackwards, Im open to learning.
Manhatten- Since you have the Im TOYO13B springs, if you have time would you mind taking a measurement from your rear DS wheel hub center to the lip of the fender and letting us know how many inches?
Bucfl: Im running about 3/4" rake from rear to front, and my handling is fine. I have my front set to about 20" (+1.25 over stock) w/ IM Tb's, and the rear is just under 21" on stock springs. Took it for alignment, and it required no changes.
We may be looking at it differently, or I may indeed have it wrong, but the more I've thought about it over the years, the more I think we've all been picturing the torsion bars incorrectly. We're definitely at risk of getting off of thread topic here but...
This is how I see it:
1. The load on the torsion bars is the same, regardless of indexing and regardless of the the adjustment bolt (how cranked). That load is the static weight of the truck.
2. The bars will deflect a given amount, and only that amount, dictated by the load and the intrinsic character of the bar (spring rate).
3. Turning the adjustment bolt changes the fixed position of the frame end relative to the lower control arm end. The bar does not see any additional load (the truck weighs the same), and it deflects the same amount under that load. All you have done is change the starting angle on the lower control arm from which this load is taken up by the bar (ride height). It's akin to adding a spacer to a coil spring.
4. This is not the same as winding down a coil spring in a coil-over because the coil spring in a coil-over is between fixed perches. Winding down that coil doesn't extend the damper or move the lower control arm, it just compresses the coil. Cranking the torsion bar DOES move the lower control arm.
5. If you were crank the bar while the suspension is at full extension (where it is usually indexed to free and unloaded)--this would be preload.
I may be wrong here. But that's how I see it.
As I understand the TBs, Hayes has it right. Torsion bars are not progressive springs. Therefore, "cranking" them up a bit, doesn't increase the spring rate. So, adjusting the TB will change the height - but not the load capacity. To increase the load capacity, we've got to swap to a TB with a greater spring rate. I am absolutely certain of this... I think.
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Look to see the amount of thread left on the adjuster. On my TB's (ironman) 5 complete turns (full revolutions) is worth around an about 1" inch of lift. If you are still on stock TB's you may need to re-index. Worry about it after you get your rear springs installed and you get your new measurements.
C6H12O6
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I just did this upgrade - installed 865 springs and cranked the stock torsion bars. Saw this recommendation somewhere else and gave them both 5 turns, with more adjustment still possible with the adjuster threads. Net lift on the front was about 1", but I found this adjustment easier to measure in centimeters. One inch is equal to 2.54 cm, so it seems like each turn gets you about 1 cm of lift on the front.
I replaced the front shocks with Ironman Foam Cell Pros, so was checking droop, which was not much with the stock-length shocks. You really can't lift the torsion bars much with stock length shocks (mine were crappy KYB replacements) and still maintain the required 50-60 mm of droop. Make sure you're checking that if your shock lengths are suspected to be too short and limiting down-travel. Since all you're measuring is comparative travel, it doesn't really matter where the measurement is taken. I found lining up the measuring tape on the edge of the wheel rim was a bit easier than trying to get an exact measurement to the center of the hub. Good luck. Ride of the 865 springs was a big improvement, particularly with a load of camping gear and the boat trailer hooked up.
I replaced the front shocks with Ironman Foam Cell Pros, so was checking droop, which was not much with the stock-length shocks. You really can't lift the torsion bars much with stock length shocks (mine were crappy KYB replacements) and still maintain the required 50-60 mm of droop. Make sure you're checking that if your shock lengths are suspected to be too short and limiting down-travel. Since all you're measuring is comparative travel, it doesn't really matter where the measurement is taken. I found lining up the measuring tape on the edge of the wheel rim was a bit easier than trying to get an exact measurement to the center of the hub. Good luck. Ride of the 865 springs was a big improvement, particularly with a load of camping gear and the boat trailer hooked up.
