Dropped 620 sitting on bumpstops

[69FJWagon]

the correct way I think is coilovers or convert it to ball joints and use drop spindles so you dont have to crank the torsion bars down and lose spring rate.

 

 

2eDeYe' date='04 February 2012 - 05:33 PM' timestamp='1328405591' post='626997']

How do you lose spring rate? The springs are still the same and if you re-index you still have the same leverage on the spring.

 

 

What you lose is shock travel. If you use drop spindles or lengthen the towers you get that back.

 

Torsion bars achive their spring rate by torsional twist (like a torsion bar sway bar keeps the car flat by increasing resistance or spring rate as the bar twist)so YES you would be losing spring rate because your are untwisting the bar...

 

Clayton

[jesusno2]

Torsion bars achive their spring rate by torsional twist (like a torsion bar sway bar keeps the car flat by increasing resistance or spring rate as the bar twist)so YES you would be losing spring rate because your are untwisting the bar...

 

Clayton

 

 

AMEN!

[69FJWagon]

AMEN!

 

I could be completely wrong LOL :blink:

[yello620]

But you are not changing the bar at all, you are only adjusting the position of the lever on the end of it.

 

The weight of the vehicle did not change, the diameter of the bar did not change, the lenght of the bar did not change.

 

I fail to see how the spring rate changed.

 

 

I realize how coil springs change when you cut them shorter, but this is a torsion bar that is unmodified.

 

I also realize that lowered torsion bars get blamed for a harsh ride, but this is actually due to the vehicle being closer to or on the bumpstops, or shock limited in travel. Talk to somebody that has addressed these issues and ask how the truck rides.

[Jasper]

If it comes down to doing it "right", or doing it cheap, I think any real Ratsuner will choose the cheap diy at home route. :lol:

 

Edit: I'll have to remember this thread for when I get a 620 to lower. Lots of good information.

[Guest kamakazi620]

If it comes down to doing it "right", or doing it cheap, I think any real Ratsuner will choose the cheap diy at home route. :lol:

 

Edit: I'll have to remember this thread for when I get a 620 to lower. Lots of good information.

Huh??? You make no sense,What Magical shop does it "Right"??? DIY at home is the best way you just have to KNOW WTF your doing......Yeah Redeye posted the sticky thread check it out....

[jesusno2]

Ive had lowered trucks and ive jacked up a 2wd 720 before. When the bars are cranked up all the way the suspension barley moves its super stiff! With uppers and lower bumpstops completlety gone. Every truck ive lowered it gets softer which in most cases causes alot of bottoming out your basically running no spring or very little think of it maybe like your ringing out a wet rag it gets harder the more ya twist. Theirs a reason why drop spindles are made. Thats my theory anyways a lowered truck I could see needing a huge sway bar to try and stiffen it back up.

[69FJWagon]

But you are not changing the bar at all, you are only adjusting the position of the lever on the end of it.

 

The weight of the vehicle did not change, the diameter of the bar did not change, the lenght of the bar did not change.

 

I fail to see how the spring rate changed.

 

 

I realize how coil springs change when you cut them shorter, but this is a torsion bar that is unmodified.

 

I also realize that lowered torsion bars get blamed for a harsh ride, but this is actually due to the vehicle being closer to or on the bumpstops, or shock limited in travel. Talk to somebody that has addressed these issues and ask how the truck rides.

 

The torsion bars installed with no preload on them in a fixed position most likely with the truck in the air and the suspension at full droop when you put the truck on the ground the torsion bars twist and creat resistance or spring rate, The adjusters are attached to the torsion bars and as you raise or lower the truck it either increases or decreases twist in the bar and increases or decreases spring rate...

 

thats why when ordering a torsion bar sway bar they give you options in length and wall thickness to get the proper spring rate for your application

 

again it makes sense in my head but im no engineer

 

Clayton

[Guest kamakazi620]

The torsion bars installed with no preload on them in a fixed position most likely with the truck in the air and the suspension at full droop when you put the truck on the ground the torsion bars twist and creat resistance or spring rate, The adjusters are attached to the torsion bars and as you raise or lower the truck it either increases or decreases twist in the bar and increases or decreases spring rate...

 

thats why when ordering a torsion bar sway bar they give you options in length and wall thickness to get the proper spring rate for your application

 

again it makes sense in my head but im no engineer

 

Clayton

Hence why i mentioned RE Indexing It does not change the rate only the position of the height

[]2eDeYe]

The best analogy I can think of is:

 

On a coilover you adjust the collar on the shock body to raise or lower the the car. This does nothing to the spring rate. This is almost the same as the torsion bar height adjustment as you are adjusting the position of spring.

 

 

 

That said, the control arm position does affect the spring rate slightly with both the coilover and the torsion spring setups.

 

 

The higher the angle (lifted truck position) the more the force will want to travel up the arm instead of trying to rotate the arm. With a lower angle (lowered truck) the force will rotate the arm easier and not try to travel up the arm. The more extreme the angle the more force needed to rotate the arm. This will be much more noticable in a lifted configuration.

 

 

The thing that has the most effect on your ride is the shocks. If you are at either end of your shock travel you will experience a harsher ride. With the shock fully extended it is harder to compress and only uses the compression stroke to dampen the suspension. With the shock fully compressed you get no damping and your shock is useless. Your shock should be sized appropriatly for the amount of suspension travel and located to give the optimum damping throughout the suspensions travel.

 

 

I lowered my truck and extended my shock mounts to correct the amount of travel my shock was allowed and look forward to a nice ride with my tucked tires. :)

[Siqx20]

Bag it. Nuff said....

[]2eDeYe]

Bag it. Nuff said....

 

What's the spring rate on that? :lol:

[]2eDeYe]

The adjusters are attached to the torsion bars and as you raise or lower the truck it either increases or decreases twist in the bar and increases or decreases spring rate...

 

When you adjust the adjusters you are rotating the entire spring assembly: control arm, spring and adjusters.

 

The 'twist' is only applied when the weight of the truck is on the suspension. The weight of the truck and the spring have not changed, just the angle of the control arm and the adjuster arm.

 

I will see about drawing a picture tonight to show what I mean.

 

 

Great discussion guys :)

[Siqx20]

2eDeYe' date='07 February 2012 - 01:24 PM' timestamp='1328649872' post='628843']

What's the spring rate on that? :lol:

The elite kind

[]2eDeYe]

:lol: Get out of here with your air bags :P

 

Sketch. Rotating the clock position of the control am, torsion spring and lever arm is all you are doing when 'cranking the torsion bars'. Spring rate and the load (weight of the truck) on the spring remain constant throughout the rotation.

 

 

 

 

 

Edit: One other thing possibly affecting the feel of the spring rate. Most people, when lowering or lifting via 'cranking' the torsion springs fail to loosen the upper and lower control arm mount bolts. This induces a bind in the bushings and will feel like added spring rate. This will also result in premature bushing wear.

[Siqx20]

2eDeYe' date='07 February 2012 - 05:58 PM' timestamp='1328666320' post='629032']

:lol: Get out of here with your air bags :P

I feel so unloved.... K im gonna stop shiting on what looks like a good source of info

[DaElv]

^^i wish ratsun had a best answer button^^

[jesusno2]

2eDeYe' date='07 February 2012 - 05:58 PM' timestamp='1328666320' post='629032']

:lol: Get out of here with your air bags :P

 

Sketch. Rotating the clock position of the control am, torsion spring and lever arm is all you are doing when 'cranking the torsion bars'. Spring rate and the load (weight of the truck) on the spring remain constant throughout the rotation.

 

 

 

 

 

Edit: One other thing possibly affecting the feel of the spring rate. Most people, when lowering or lifting via 'cranking' the torsion springs fail to loosen the upper and lower control arm mount bolts. This induces a bind in the bushings and will feel like added spring rate. This will also result in premature bushing wear.

 

 

Drawing makes sense. seat of the pants tells me different. I give up lol you win! I have a torsion bar im using as a sway bar on my goon and when ya get into a good tight corner you can feel the car flatten out

[yello620]

I briefly talked to my engineering professor today about this and he said we would be discussing this kind of thing in a few weeks. Has me quite curious now. Looking forward to finding the formula to calculate the spring rate.

[]2eDeYe]

Drawing makes sense. seat of the pants tells me different. I give up lol you win! I have a torsion bar im using as a sway bar on my goon and when ya get into a good tight corner you can feel the car flatten out

 

Everybody wins on ratsun :D

 

Torsion bars make excellent sway bars. They are fairly tunable as well with adjustable lever arms.

 

Edit to add pic:

 

 

I briefly talked to my engineering professor today about this and he said we would be discussing this kind of thing in a few weeks. Has me quite curious now. Looking forward to finding the formula to calculate the spring rate.

 

Sounds like a fun class. Let us know what you find out :)

 

 

I'm sure the angle of the lever and control arms in relation to the load path change the spring rate a bit, but it's definitely the damping you lose most when adjusting that angle. Shocks (dampers) work best in the middle of their travel and you might be shocked (lol) at how little they work at the ends of their travel. This is the reason for the bouncing and part of the reason for the harsh ride on a lowered or lifted vehicle.

[chebetio510]

ok,,, so havent had time to mess with the truck or bumpstops since the post... and just today my 2nd gear is now grinding.. :/ boo

lol .. will order those bumpstops... but cut first... and need someone with a welder to raise shock mount... @]2eDeYe

how does your truck feel now?

[yello620]

I relocated my shock mounts a few years ago on my 620, great improvement in ride quality, I moved my lower mounts down two inches, and that is actually a little bit too far. The shocks have plenty of compression travel now, but not quite enough extension travel. I would actually like to raise my truck up a tiny bit, but i need longer shocks to do it and maintain the ride quality. Probably going to do it anyways though.

 

Pics of mine can be seen in my build thread, as i did not modify the upper mount, but rather the lower mount, which only works on the 78 and newer lower control arms.

[]2eDeYe]

Thanks to Zeusimo for the link to those bump stops. He said he did not have to tap his but he did have to trim down the stud. His is a ball-joint truck, mine is a kingpin truck. Just another difference between the two.

 

 

The aforementioned bump stops.

 

 

Tappy, tap, tap 3/8-16

 

 

Screwed in

 

 

Locked down

 

 

Passenger side.

 

 

Amount of travel at ride height now. :cool:

 

 

 

Shocks should be in this week. Got some KYB's and I'll be checking the parts store for the rest of the bushings up front. :)

[lil89ram50]

nice! will be ordering bump stops soon!

[PDX Matt]

I noticed the Energy Suspension bump stops for the front but is there an ES option for the rear?