Obviously everyone needs a set of bypasses for their sway bars now. 🤣
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Ifs 101
- Thread starter patooyee
- Start date
Obviously everyone needs a set of bypasses for their sway bars now. 🤣
I would think the problem is compounded in the off road world due to the amount of suspension travel involved. Having 20" of available suspension travel could potentially give the sway bar quite a bit of undampened spring force when cranked to the extreme in opposite directions. I noticed in the picture of the Proformance truck posted earlier that the sway bar is connected very close to the inboard pivot points of the rear lower arms and isn't very big in diameter. My guess is that they did it that way to keep what you are talking about in check but to still give it more roll stability vs no bar.
Sway bar selection on an IFS/IRS SxS is a catch 22. Too stiff and you basically connect both sides of the suspension together making it act non independent, or to soft and you give up a bunch of handling and body roll so the suspension can do its thing over bumps.
Stephen Wilson
Well-known member
I did get in my caveat about road racing :rolleyes:, where it is a fact that needs to be considered, leading to "roll bar rock" ( or whatever you want to call it ) on cornering transitions.
Isdtbower
In for Tech
Definitely different spring rates between dive, roll, and one wheel articulation with a sway bar. Sway bars in IFS have been used mostly to minimize body roll because of the increase in positive (bad) camber. But, they also minimize one wheel articulation most needed for "rock crawling." The conundrum is very easy dive to ground out, and constrained articulation in roll and one wheel articulation. A great place for active shocks...but that is only milliseconds. Bypass shocks help this a ton!.
It amazes me that "shock testing" is done on the fast and straight. And probably left to a driver for the compromise to the rocks. I understand a rock crawler tune is significantly different than a go-fast tune. I believe in rebound. The rock crawler guy wants the tire to stay stuck and not rebound upsetting the chassis. The go fast wants quick rebound to get ready for the next whoop. INteresting to me was a 2wd TT with good camber gain going sideways thru whoops. Amazing.
Again.
Walker Evans racing sells sway bar link shocks for the Polaris Rzr.........
"No matter if you are running stock shocks or our Velocity Series shocks we can improve your driving experience with a set of “Walker Links”. These units replace the standard rear sway bar link and provide a smoother initial ride over rough and uneven terrain regardless of vehicle speed while still providing a confident feeling while cornering. With 1.5 inches of dampened action per side your rear shocks will be able to act independently until a point where the Walker Link has collapsed enough to now act like a rigid link under heavy loads and when cornering. You get the best of both worlds with these links, a more independent shock action at the initial stroke and a solid support under heavy loads, turning and when leaning on the sway bar. You can also tune your ride by installing one or both of these links depending on your driving style and terrain."
I'm tinkering with this concept of using the 2013 Chevy knuckles and a-arm geometry with the 14.75" wide Dutchman dif and extending the arm lengths out. Not necessarily because that's what I want to do, but just as a thought experiment to see what results. (I'm also not opposed to doing it if the results are satisfactory.) I've modeled up the idea with the intent of creating sketches of all the important design dimensions (roll center, etc) that change real-time as I cycle the suspension. Before I do that I figured I'd post up what I have so far because several assumptions have to be made since I don't have complete models of important things like the dif.
- With a MWS of about 70" and the 14.75" wide dif, the LCA's are about 22" and the UCA's are 13-7/8" long.
- The frame mounts are set up laterally exactly in relation to the CV shaft flanges as they would be on the stock Chevy 2500/3500. (Haven't messed with up / down yet.)
- I have no clue what the stock angle of the control arms at ride height are so I simply set the wheel flange parallel to the central plane to get a guess at that. It resulted in a slight angle down/out on the LCA that looked right, so I went with it.
- From ride height, I set max bump at the lower ball joint pivot point at 8" and max droop at 6". (My ORI's are 14".)
- I've got steering maxed at 40* but that's not important ATM and I realize that's overly optimistic. (What is a realistic number? I'll have rear steer, so I'm not obsessed with turning per axle.)
Treefrog
Book Wheeler
If the ORIs are 14", the motion ratio will result in you having more the 14" of travel
I know, but at this point there is so much that I don't know I just needed to start with something to keep the model itself from over-extending and creating physically impossible results that I then need to fix. This setup would use ball joints at the knuckle so I think, in reality, I'd probably have to go to a shorter shock to keep them happy. Again, another thing I don't know yet. If I knew the working angles of ball joints I could input more data. Before I go buying parts to measure I figured I'd see if this geometry results in anything obviously crazy though. If it's all whacked out then there's no point in investing real money into it.
Plus, camber starts going insanely negative much below this point of travel, so it's around the point that it would need to be limited.
It's also possible that ride height could be a little lower than I'm assuming. Camber has very little change from ride height to the max bump that you see in these pics. I suspect that the droop is further outside Chevy's design parameters than the bump. It would be somewhat remedied if I was incorrect on my ride height assumption. (Which I think I am, just no clue how much.)
I have a stock Chevy 2500 sitting in my driveway that I need to get off my ass and go measure. It's just a pain to do here at the house without a jack or good tools.
Edit: Here's a pic of assumed ride height. Again, only based on the wheel flanges being parallel to the theoretical central plane that isn't pictured. (IE, 0 camber.) I realize this is almost certainly not accurate, but I have to start somewere.
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Actually, I went back to the original GM suspension model that I have. If I assume that it is at ride height and duplicate those numbers, I was about 2.5" too high. So setting that as the new ride height makes things way more normal looking at full droop. At that ride height there's less than half a degree of camber with about 2.7* at full droop and .7* at bump.
So, based on this, is it safe to say that GM's design intent for camber with their geometry was to be basically as close to 0* throughout the entire range? I don't know what stock travel is (stock shock has only about 5" of travel.) but I know it's way less than 14" and somewhere within this model's current parameters. The only thing that differs is arm lengths.
So, based on this, is it safe to say that GM's design intent for camber with their geometry was to be basically as close to 0* throughout the entire range? I don't know what stock travel is (stock shock has only about 5" of travel.) but I know it's way less than 14" and somewhere within this model's current parameters. The only thing that differs is arm lengths.
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AgitatedPancake
Frobot
Just observing the action of what you have drawn, I would consider testing the geometry with the frame side UCA mounts lowered by some amount. It will increase the camber gained in bump, and decrease the camber gain in droop. Camber gain in compression helps with cornering as you have any amount of body roll (and tire tread roll), and camber gain in droop adds unneeded angle to the outer CV when the tire isn't loaded, which could otherwise be used for more droop or more steering
Isdtbower
In for Tech
Sometimes it is your driving style that dictates what you "like." Shannon likes to broad-slide rear steer and Jason likes to brake turn accelerate unless "styling."
Make sure you look at the wheel, not the tire.....unless you are tire and pressure testing.
Tech Tim
Your AD Here....
That's probably pretty close to correct. They are not looking for big performance, just good solid geometry.
I would guess that truck has around 7"~ish travel stock and probably only using 5" of that travel day to day.
You should be able to get 14"~ish with a bit of fiddling around. Your biggest sticking points will probably be CV travel.
vetteboy79
It's bent. #ttb
You've probably seen this, but figured it's relevant to this thread...
I haven't been following the build of it, just came across this pic today, but I really like the execution of it.
Weasel
Red Skull Member
On body roll, I'd like to mention that I don't think the roll is exactly why SxS get tippy but it's the jacking forces from the shorter arms. Like what was popular for awhile of raising RC to minimize body roll (we tried this as well on the buggies) the point that you would roll really didn't change, just the feedback the driver got from the vehicle went from alot, to some, to none. I personally don't think body roll is all that bad to a point, other then it slow the response time if dealing with consistent left to right transitions. But this is more of a train of thought and I don't have much practice in applying it.
Actually, something that wasn't really worth modeling up was their adjustable UCA frame mounts. So they did include a way to easily adjust camber within a few degrees. I guess their design intent was to maintain whatever camber is set.
That's definitely not a bad thing.
Yeah I’ve been following the build, talked to Gerald about weight today. He says 1920 pounds complete. That’s not what I want though. The best thing about my tracker is that the cabin is sealed tight and both the heat and a/c work.
Yeah. It's just not the way I think anyone fabbing something from scratch would ever do it, so I left it out of the model. Every offroader I've seen uses the adjustability of their joints to accomplish fine-tuning of the UCA length.
My post doesn't read correctly. I meant that the design of the GM IFS holding the camber throughout travel isn't a bad thing. I should have only quoted the last sentence.
I kinda figured you were going to use adjustable joints at the frame ends. Wouldn't make sense to build it with bushings and no adjustment.
Tech Tim
Your AD Here....
Those are cool, great way to make small adjustments and lock them in place.
What does the mounting hole look like? Slotted? Horizontal? Vertical? Just oversized?
wifes tahoe (06) had the bolt come loose. super stance'd so i better there is quite a bit of adjustment in there.
Isdtbower
In for Tech
I think I would prefer Canber Shims which are under compression with mounting bolts. If the pivot bolt above, goes loose, all the force on the top arm is on just that little pin
I do like the idea. Just in the right place or some other way of locking that adjustment. Good add to the thread.
I do like the idea. Just in the right place or some other way of locking that adjustment. Good add to the thread.
Sterlingfire
ignant
You could use safety wire to lock the nuts in. They're in an easy place to get to in most cars. Should be a pretty easy fix.
I do agree that using heims would be easiest to make adjustments. Even in the lca, heims would make it easier to square everything up and align them so you can be a small bit off once you weld the mounts in.
Comparing the early IFS designs in rock racing to the current ones, it seems like the orientation of heim joints in the arms have gone from the bolt going cross-wise to the bolt going up-down. Were people blowing the balls out of the joints sideways when the bolts were mounted crosswise?
The heims/uniballs out at the knuckle? With the RE’s oriented with the bolt horizontal the head of the RE would snap off when striking an obstacle with the tire, because the head is weaker side ways than radially. Darren Henke had a Trent fab car with IFS, and it would break the uniball carrier off the lower a-arm every race. The impact force fore and aft has no damping where as it is damped up and down. So spinning them 90° put the rod end or uniball housing in a stronger orientation.
Tech Tim
Your AD Here....
There is a lot of adjustment in that slot. You can't replicate that just by shortening the upper arm with the rod ends.
I would think going to a larger plate with a couple larger locking bolts would do the trick.
Terminology:
Uniballs = Basically a spherical bearing in a weldable cup
Vertical Uniballs = Bolts mounted horizontal
Horizontal Uniballs = Bolts are vertical
Important note: if mounting uniballs in vertical position, make sure to orient the cups so the snap ring is facing forward.
Uniball in cup with misalignment spacers in a vertical position.
Originally teams were running uniballs in vertical position because they thought they were stronger as that's how all the desert race trucks were running them, but it limits the steering angle.
We pushed real hard to get people to run them horizontally because you can get more steering angle out of them, once people saw how much steering angle a couple cars were getting, others started following suite.
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also called monoballs in the dezert world.
its my experience that the uppers were out faster than the lowers, because they are trying to the keep the top of the upright in place. ben napiers penhall car had both his uniballs mounted vertically and the uppers were not lasting an entire race. the theory is that under acceleration and braking the uniball gets a point load as the ball is being 'pushed" out of the cup. the lower is fine because it has more surface area as its 'holding' the car up.
https://www.race-dezert.com/forum/th...-racer.106279/
https://www.flickr.com/photos/bnmotorsports/with/7950385256/
on the lasernut car i never replaced the lowers due to wear, only uppers
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Weasel
Red Skull Member
Safety wire doesn't keep the bolts tight, just from falling off and sucked into something else.