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  Topic Review (Newest First)
07-06-2019 04:37 AM
aaron85 i have searched for a bit but does anyone have a build thread using 99-04 f250 axles and leafs?
07-05-2019 10:22 PM
PRIMERED79 SHORT BED
Quote:
Originally Posted by BoulderBronco View Post
There are a number of factors involved here. But in general anywhere from 2-8 is where you likely want to be. Most likely you'll want to end up somewhere in the 4-6 area.
I installed a REDHEAD steering gear yesterday and today i got an alignment.
It showed my caster being + 4.9 drivers and + 4.8 pass, I have 4* c bushings installed and I'm still having issues with my steering returning to center after a turn.

Should I go ahead and install the 7* bushings to see if that helps?
Btw everything is new on the front end.
06-07-2019 10:08 AM
PRIMERED79 SHORT BED https://shop.broncograveyard.com/For...uctinfo/23209/

Does anybody know if the compressed length of these springs will be around 19.5 inches?
I want to swap out the JBG 78-79 6" springs for something softer, these springs are to stiff and its beating me to death on certain roads.
02-16-2019 04:15 PM
BoulderBronco
Quote:
Originally Posted by PRIMERED79 SHORT BED View Post
Whats the best caster angle for a 6'' lift should ppl shoot for when they sas their bko or f150's?
There are a number of factors involved here. But in general anywhere from 2-8 is where you likely want to be. Most likely you'll want to end up somewhere in the 4-6 area.
01-18-2019 10:11 PM
PRIMERED79 SHORT BED Whats the best caster angle for a 6'' lift should ppl shoot for when they sas their bko or f150's?
01-16-2019 09:51 AM
reptillikus
Quote:
Originally Posted by wolfpack91 View Post
Just a quick question. I have a 1990 Bronco with the M5od and electric Tcase, I found a complete donor 1990 F350 with a ZF5, manual T-case and solid axle. How straightforward would swapping the front and rear axles be from the 350 to the bronco being the same year? Can I reuse the F350's original mounts rewelded to the Bronco frame. I can get the donor truck for $1500 but my bronco is my DD, if it's too large of a job I wont be able to swing it but I figured I'd ask since both trucks are 1990 and should have matching or very similar frames.

Sent from my SM-N950U using Tapatalk
The F350 frame has a couple extra brackets on the frame horn to retain the shackle; its possible to cut them off and add them to the stock bronco frame horn. Ive heard of it being done, but havent seen anyone do it that way in many years.

The rear axle is a direct swap, no mods other than shortening driveshaft 1".
01-16-2019 07:57 AM
wolfpack91 Just a quick question. I have a 1990 Bronco with the M5od and electric Tcase, I found a complete donor 1990 F350 with a ZF5, manual T-case and solid axle. How straightforward would swapping the front and rear axles be from the 350 to the bronco being the same year? Can I reuse the F350's original mounts rewelded to the Bronco frame. I can get the donor truck for $1500 but my bronco is my DD, if it's too large of a job I wont be able to swing it but I figured I'd ask since both trucks are 1990 and should have matching or very similar frames.

Sent from my SM-N950U using Tapatalk
01-14-2019 10:36 PM
Shadofax
Quote:
Originally Posted by BoulderBronco View Post
I see what your saying about traction, and agree. My description of the SAS benefits was based on no locker though. With a locker, yes the traction is the same. But with open diffs, it's very important for both tires to not only make contact with the ground, but to have some force behind it to maintain contact and not just have the tire spin. Both a solid axle and IFS will droop and hang off the spring. But on an IFS there is no force pushing down after that. Where on a solid axle there is more force downward past the "hanging" point when the opposite tire is compressed up, thus creating a little extra force down to the ground which will only help with "traction" in an open diff situation. But as you said, anyone doing this kind of wheeling should put $$$ into a locker setup first and foremost.
You both are awesome in your knowledge, and both you guys have always been so respectful in your opinions on line. And you both have valid points.

Not owning a bronco any longer, this is still an absolute favorite subject of mine. Helirich, the point of coefficient of friction times weight I think is good, but then I start thinking of spiders....

I think, it would be grand if I could solid axle and force many high points of contact, this leads to STABILITY, something I could not get with even a modified IFS front, just teeter/totter on rocks. A modified 3 axle SAS or perhaps long travel IFS with LSD or locker would be super cool, if IFS was able to handle the longer travel. SAS might be simpler, and a 6x is complicated enough I'd guess as is, as I'm not thinking two axles at back but rather a push axle forward for max clearance, one far out back for departure and one near middle.

In any case, something I will never build, but point being, I think for most back yard mechanics that want a fairly serious "crawler", it's hard to get the IFS to work as well as an SAS even when locked, there just seems to be better stability in any well built SAS, 2 axle truck. The ability for one side way up, pushes other side way down, they still share contact (amount of friction of course will vary), and same with rear. But contact to ground on all fours = feeling of stability, planted.

Blast from the past:





lots of other setups do much more, this still is a very daily driver, but can keep rubber planted at all four corners.
01-14-2019 07:16 PM
BoulderBronco I see what your saying about traction, and agree. My description of the SAS benefits was based on no locker though. With a locker, yes the traction is the same. But with open diffs, it's very important for both tires to not only make contact with the ground, but to have some force behind it to maintain contact and not just have the tire spin. Both a solid axle and IFS will droop and hang off the spring. But on an IFS there is no force pushing down after that. Where on a solid axle there is more force downward past the "hanging" point when the opposite tire is compressed up, thus creating a little extra force down to the ground which will only help with "traction" in an open diff situation. But as you said, anyone doing this kind of wheeling should put $$$ into a locker setup first and foremost.
11-27-2018 10:14 PM
helirich
Quote:
Originally Posted by BoulderBronco View Post
The IFS generally does not have the flex/articulation that a solid axle does. Even if you can get the IFS to flex as much as a solid axle, the actual traction you get is limited.

When rock crawling, if one tire goes high over a rock, it actually forces the other tire down. This helps with traction over obstacles. By forcing the other side down it has a better chance of contacting the ground/rocks. If that tire floats in the air it will just spin due to how a differential works (that's another discussion). If that tire can maintain contact with the ground you will avoid the tire spinning and losing traction. An IFS axle doesn't have this force. When one side goes up on a rock, the other side droops a bit but isn't actually forced down in the same way as a solid axle suspension.
I agreed with your earlier explanations, not this one.

Obviously, if a tire is floating in air, it has no traction. This is true of solid or independent. It's been my experince that when you jack up an independent suspension by the frame or one tire, the other side drops out to the full travel of the suspension. (Not droop a bit) A solid axle will hang off the spring, but not a independent. So it can be forced down, but only till the suspension limits. Otherwise you break u-joints or brake lines.

If you look up the definition of traction, you will find that it is coefficient of friction times weight. So if you have 5000 lbs. of weight on four tires or 5000 lbs. of weight on three tires, the traction is the same. There is no "force down" except for weight. If the the solid axle forces the othe tire down with 500 lbs., that means the that tire just lost 500 lbs. of "force down".

Of course, I'm assuming you have a locker in the diffs. That should be everyone's first modification.

Now you forgot one of the big benefits of solid axle. Diff clearance.
For example, let's say you have 8" of clearance at your diff and your driving at a 4" tall rock ridge. If you driving fast enough, the independent will have both tires go up 4" and now you have 4" clearance at the diff. So if there happens to be an a 6" rock there, you hit it.

Now if you driving a solid axle under the same conditions, both tires go up 4", but the diff goes up 4" also!
So the clearance remains 8" and you sail over the 6" rock.
11-27-2018 07:08 PM
WTFBurban
Quote:
Originally Posted by BoulderBronco View Post

Sorry, that was long.
Honestly I consider myself decently educated in how stuff works in these subjects, but still found both your novels quite informative.

Thank you for the time and effort to put together such well written and informative replies.

11-27-2018 06:32 PM
BoulderBronco
Quote:
Originally Posted by White Dragon View Post
Wow,
One of the "Best" explanations on the practical differences between front Axle assemblies I have found here on FSB so far.

How would a guy account for Shock Positioning with his SAS setup?

It seems to me with 2 different travel directions being R to L (Pass to Driver) on the front Diff Track bar at droop, And F to R on the radius arms (at Droop),
There would be some competing forces on the Shock Mounts thereby adding stress ?? (breakage)

Kinda goofy i know, but I'm trying to cover my thought base through this exercise.
(I've been on the fence about switching it up for the Moab Invasion next spring. (see my sig line))

Later,
Dragon
Sorry Dragon for not responding to this. I don't get on here as much as I used to. Just swamped.
It's a good question about the shock positioning. There are a number of factors to consider. But in general it's best to have the eyelet/mounting bolt direction of the shock, both at the top and bottom, going parallel with the frame of the truck. There are two reasons this is the better way to go. First, as a solid axle (SA) flexes downward, it is also moving inward or toward toward the opposite side of the truck. With the shock mounted as I mentioned, the shock simply rotates around the mounting bolts with very little resistance. This is minimal but it is a factor.

The other more important reason is the angle at which things change is greater from side to side than it is front to back. Meaning the side to side angle of the axle when looking at the axle from the front, is typically greater than the front to back angle change, also known as caster angle. However this is not the case if you don't have a true long arm suspension.
If your radius arms are short, get new radius arms for starters. But if they are short, they can limit the travel of the axle. They will also cause the arc of the axle to be much tighter so the front to back/caster angle of the axle changes more for every 1" of droop. I think you know what caster is, but for guys who don't, it's the angle of rotation of the axle housing in relation to the ground. As the axle droops, the axle actually rotates around it's center point in a clockwise fashion as viewed from the passenger side (center point being if you draw an imaginary line from center of one hub to center of the other hub). In other words, the pinion starts rotating and pointing up.

For arguments sake and for easy math, let's say at rest the axle caster/front to back angle is 0. Let's also say your radius arms are 24" long (the reason I'm using 24" will become clear but it's because at 24" every 1" of drop equates to about a 2 degree angle change (technically it's 2.3 but...)). So with 24" radius arms, if the axle droops 6" your axle caster is changing by about 12 degrees, which is a lot. Not only is the axle rotating 12 degrees but so are the lower shock mounts. So if you have the shocks mounted as I mentioned in the beginning (parallel with the frame), and you have short radius arms, your shock mounts are going to bind as the top mount is staying at the 0 degrees, but the bottom mount is now rotated to 12 degrees. This difference is managed by the bushings at both mounting ends (mostly the lower). But this is A LOT of angle for these bushings to handle and your shocks and mounts won't like it and will likely fail at some point.

The above example is if the axle is drooping evenly, 6" on both sides. This of course is rarely the case (unless you get airborne). The suspension and axle are always moving up and down on each side. This is of course a very drastic movement when rock crawling. The math and trying to describe this gets a bit tricky here so for ease of argument and math let's use 48" as the distance from the point on the drivers tire to the point at the passenger tire where we get this 6" of droop. The actual measurement is more like 60" but using 48" is much easier and close enough for this purpose. Remember at 24", 1" of droop equates to 2 degrees of change. So from side to side at 48", 1" of droop equates to an angle change of about 1 degree. Now if your crawling over a rock on the drivers side, the suspension on that side is likely compressing and moving up, let's say 3". But there is a hole in the trail on the passenger side so the passenger side of the axle is trying to push down to make contact with the ground in that hole. So let's say that side is drooping 6". So the difference side to side is 9". Over the length of 48" that means the axle side to side angle changes 9 degrees. But the caster/front to back sees a 12 degree change. You want to mount the shocks so they rotate with the higher number. So in this scenario, you would want the mounts to be positioned parallel with the axle so the 12 degree movement rotates around the mount and not against it.

Now a properly designed radius arm suspension will have as long an arm as possible to alleviate these binding issues, among other issues. I purposefully used the and 24" numbers above for easy math on all of this. Our/Broncoairs radius arms are 48" long for exactly this reason. The longer radius arm drastically reduces stress on the bushings of both the radius arms and shocks while allowing for maximum flex. A 48" radius arm cuts those caster angle changes in half. With our arms and the axle drooping 6", the caster only changes by 6". This is WAY better than a short radius arm. Even a 36" radius arm (which many consider "long") is pretty short when you consider the changes in angles I've described. This is why you see a number of people having binding issues with their shocks and radius arms.

Let me quickly run through the same math exercise with a long radius arm suspension. With a 48" long arm setup, the caster/front to back angle change is 1 degree for every 1". So at a 6" droop, the caster angle and hence shock mount angle is only changing 6 degrees. This is well within the shocks bushing mount to compensate for. As for radius arm bind, in the scenario above where the drivers side is compressing 3" and the passenger side is drooping 6" the caster angle is wanting to to go 3 degrees positive on the drivers side and 6 degrees negative on the passenger side for a difference of 9 degrees. This is WAY better than the 18 degrees difference with the short radius arms.
Now in regard to the side to side angle change in the above scenario it is the same. The drivers side is going up 3", passenger side down 6" which gives a side to side difference of 9" which means an axle angle of 9 degrees, same as above. So you can see with the 48" radius arms the caster/front to back angle is less than the side to side angle. So with a true long arm suspension, you would want the shock mounts to be parallel with the frame so they rotate in the direction of the higher angle change.

Getting back to the caster/front to back angle changes, the other thing to understand (and this is the main argument against a radius arm style suspension), the radius arms are going to fight against each other the same way the shocks are if your flexing out your suspension. As I mentioned, when rock crawling, the axle is going up on one side and down on the other. So if your passenger side drops 6" and your drivers side rises 3", your axle is fighting the two radius arm mounts/bushings because on the passenger side the axle is wanting to twist 12 degrees where the drivers side is wanting to twist 6 degrees in the opposite direction. So the caster from one side of the axle to the other is wanting to be 18 degrees different! So each bushing is trying to allow 9 degrees of flex. This is A LOT of stress on your radius arm bushings and they likely won't allow that much flex so your suspension would bind, therefore not allowing the passenger side to reach all the way to the ground in that hole. This is what causes radius arm suspensions to bind and lose the ability to flex, not to mention pre-mature bushing failure. However this can be drastically improved with longer radius arms.

So to really determine how you should mount your shocks you would want to go through all these different calculations. But regardless of your shock mounting position, with short radius arms, your suspension will likely bind before the shock bind gets so bad that you damage your shocks or mounts. A true long arm suspension will flex much more efficiently and farther since at 6" of droop on one side and 3" rise on the other only has a difference of 9 degrees between the two. So each bushing is taking up 4.5 degrees of flex, which is well within reason of a bushing. So with a longer arm you can flex/droop twice as far than a short arm setup until you hit a critical bind point. All suspensions bind at some point. Basically it's half the stress on your suspension parts and axle, longer life and better suspension travel. The trick is designing a suspension that allows for the most droop possible before that bind occurs.

Sorry, that was long.
11-21-2018 11:04 PM
Alwaysdirty
Quote:
Originally Posted by itwasFREE!!!! View Post
Great point Dragon. On the stock side of the duff arms which seem to get in the way with larger tire and wheels, or on Top, Maybe even behind like @Alwaysdirty did. what shock towers do you go with? The stock F250/350 towers, custom hoops, or something like Ruff stuff has (which I broke last weekend doing NOTHING!). How important is the angle of the shock? The questions are endless. But I agree AWESOME description of the 2 set ups, Awesome!!!
I used adjustable shock towers from Chassis unlimited and welded the mounts to the frame, ADJUSTABLE WELD ON FRAME COIL OVER/AIR SHOCK MOUNT TOWERS - Chassis Unlimited . I narrowed them to fit. Like @White Dragon mentions, all the angles of the axle moving make shock travel movement a big variable in a solid axle setup when you want all the articulation your setup will allow. I had to cycle my suspension many times to figure out where the shock would best fit without binding or interfering with things like the frame as the axle moves towards the driver side at droop or the lower mount hitting the tires at full turn and full bump, there is a lot to consider. In the picture below you can see the shocks are at an angle in the tower to make it all work and having shocks with heim mounts helped. I do wish I went with remote reservoir shocks to have the upper mount lower. So far so good with this setup though.

11-21-2018 05:36 PM
itwasFREE!!!!
Quote:
Originally Posted by White Dragon View Post
Wow,
One of the "Best" explanations on the practical differences between front Axle assemblies I have found here on FSB so far.

How would a guy account for Shock Positioning with his SAS setup?

It seems to me with 2 different travel directions being R to L (Pass to Driver) on the front Diff Track bar at droop, And F to R on the radius arms (at Droop),
There would be some competing forces on the Shock Mounts thereby adding stress ?? (breakage)

Kinda goofy i know, but I'm trying to cover my thought base through this exercise.
(I've been on the fence about switching it up for the Moab Invasion next spring. (see my sig line))

Later,
Dragon
Great point Dragon. On the stock side of the duff arms which seem to get in the way with larger tire and wheels, or on Top, Maybe even behind like @Alwaysdirty did. what shock towers do you go with? The stock F250/350 towers, custom hoops, or something like Ruff stuff has (which I broke last weekend doing NOTHING!). How important is the angle of the shock? The questions are endless. But I agree AWESOME description of the 2 set ups, Awesome!!!
11-21-2018 02:53 PM
White Dragon
Quote:
Originally Posted by BoulderBronco View Post

I forgot to mention one important benefit of the solid axle setup.
The IFS generally does not have the flex/articulation that a solid axle does. Even if you can get the IFS to flex as much as a solid axle, the actual traction you get is limited. The reason is the same reason why the IFS rides nicer than the solid axle as I mentioned before. As I mentioned, the downside to the solid axle is it is usually a rougher ride because bumps you get on one side of the truck are not independent of the other side. So the feel of the bump transfers from one side to the other on a solid axle. This is a downside for on street driving, but it's actually a positive for offroad, especially rock crawling. It's one of the main positives of going solid axle.
When rock crawling, if one tire goes high over a rock, it actually forces the other tire down. This helps with traction over obstacles. By forcing the other side down it has a better chance of contacting the ground/rocks. If that tire floats in the air it will just spin due to how a differential works (that's another discussion). If that tire can maintain contact with the ground you will avoid the tire spinning and losing traction. An IFS axle doesn't have this force. When one side goes up on a rock, the other side droops a bit but isn't actually forced down in the same way as a solid axle suspension.

Wow,
One of the "Best" explanations on the practical differences between front Axle assemblies I have found here on FSB so far.

How would a guy account for Shock Positioning with his SAS setup?

It seems to me with 2 different travel directions being R to L (Pass to Driver) on the front Diff Track bar at droop, And F to R on the radius arms (at Droop),
There would be some competing forces on the Shock Mounts thereby adding stress ?? (breakage)

Kinda goofy i know, but I'm trying to cover my thought base through this exercise.
(I've been on the fence about switching it up for the Moab Invasion next spring. (see my sig line))

Later,
Dragon
09-19-2018 12:35 PM
BoulderBronco
Quote:
Originally Posted by cdmck View Post
@BoulderBronco That is a LOT of useful information. Thank you.

I forgot to mention one important benefit of the solid axle setup.
The IFS generally does not have the flex/articulation that a solid axle does. Even if you can get the IFS to flex as much as a solid axle, the actual traction you get is limited. The reason is the same reason why the IFS rides nicer than the solid axle as I mentioned before. As I mentioned, the downside to the solid axle is it is usually a rougher ride because bumps you get on one side of the truck are not independent of the other side. So the feel of the bump transfers from one side to the other on a solid axle. This is a downside for on street driving, but it's actually a positive for offroad, especially rock crawling. It's one of the main positives of going solid axle.
When rock crawling, if one tire goes high over a rock, it actually forces the other tire down. This helps with traction over obstacles. By forcing the other side down it has a better chance of contacting the ground/rocks. If that tire floats in the air it will just spin due to how a differential works (that's another discussion). If that tire can maintain contact with the ground you will avoid the tire spinning and losing traction. An IFS axle doesn't have this force. When one side goes up on a rock, the other side droops a bit but isn't actually forced down in the same way as a solid axle suspension.
09-19-2018 10:35 AM
cdmck @BoulderBronco That is a LOT of useful information. Thank you.
09-18-2018 06:59 PM
BoulderBronco
Quote:
Originally Posted by cdmck View Post
What's the benefit to having an SAS vs whatever other axle types are available?
So it's not so much about axle type, technically it's suspension type. The two main suspension types are Independent Front Suspensions (IFS) and mono beam/solid axle. The axle type your asking about is really a discussion about a Dana 44 axle vs. a Dana 60 axle. More on that in a minute.
Most vehicles prior to about 2000 had solid axle rear suspensions (hence a solid axle). Most front suspensions were IFS with the exception of light duty trucks (F250's and F350's). Most of those trucks had solid front axles in 4x4 versions while 2WD versions were IFS. Although after about 1985, even the F250 4x4 had an IFS.
The Bronco was solid front axle through 1979. In 1980 Ford went to the notorious IFS TTB front axle (Twin Traction Beam). It's a different design of suspension but still an IFS. The main complaints with IFS suspensions, including the Ford TTB, is they are weaker than solid axles, more complicated and prone to more failure or problems. This is mostly true but there are also benefits to the IFS. But I'll just mention the pros and cons specifically around the TTB IFS.
The TTB IFS is actually a fantastic suspension and the TTB axle itself is very strong. It is a Dana 44 axle which is a very strong axle for a 1/2 truck/Bronco. So it is just as strong as a solid dana 44 axle. The trouble/complaints with the TTB is that it is difficult to align and keep aligned. There is a lot of moving parts and a lot of geometry to keep straight. It also makes for an interesting steering setup which also has to be maintained. The strength is great, it's the maintenance that is the major complaint. The more lift and modifications you do the more difficult it is to get the truck to drive properly and keep everything in proper geometry. However it also has many benefits as it offers a nicer ride than a solid front axle since each side of the suspension is independent of the other. So one tire hits a bump, the other tire is completely isolated from the movement of that other tire/other side of the suspension. Where as on a solid axle, when one side hits a bump, the other side of the axle moves in the opposite direction (in general) an hence the bump is felt throughout the whole front suspension.
The main benefit of going to a solid front axle is to eliminate much of the geometry and trouble areas of the suspension and steering of an IFS. A solid front axle/suspenson has many less moving parts and is much easier to maintain, align and keep aligned. But the ride can be a bit rougher. The other major benefit of swapping to a solid axle is to get a stronger axle than the stock Dana 44 TTB.
So many people opt to do an SAS with a Dana 60 front axle which is considerably stronger than the Dana 44. A Dana 44 (solid or TTB) is a pretty strong axle up to about 35" tires. Add some horse power and lockers to that equation and even 35" tires can cause Dana 44's to break. So if your running 35's or larger tires and doing some moderate to serious offroading, you may want to look into the Dana 60. This is especially true if you are into rock crawling as the slow speed, high torqure with significant impacts in rock crawling can easily grenade Dana 44 u-joint or even axle shafts. A fully built Dana 44 with chromoly shafts, high end u-joints, knuckles etc. can handle more than that. But many people would just opt to go with a 60 at that point.
The Dana 60 isn't completely sheltered from damage either though. It's a super strong axle but even it has it's breaking point. In general it can handle 40" tires with locker and some HP. But it's not uncommon to break u-joints or even shafts running such a tire. Remember, our Broncos are heavy vehicles. Building a 60 with chromoly shafts, u-joints, knuckles etc can gain some great strength and is usually pretty solid with 40" tires, lockers and HP. But anything is breakable with enough weight and right foot.
09-17-2018 11:21 AM
cdmck What's the benefit to having an SAS vs whatever other axle types are available?
04-23-2018 07:51 PM
helirich
Quote:
Originally Posted by chazlowery View Post
is there any cutting or modification that needs to be made to the frame for an SAS?
While it is possible to do a SAS without cutting, there are a lot of variables like height and axle choice that make that question impossible to answer. I recommend you go through the builds and find one that is close to what you have/want.
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