What's new
By:
Filters

Ifs 101

On the same topic, I think a grand cherokee WK (05-10) would be a beast of a platform if exploring 4600 IFS. Only marginally larger than the WJ that has proven itself, could run a wheelbase around 110", and have the hemi as your engine platform so you can go past 400HP na pretty easily. You'd want to strip it down pretty light though. I did a back of the napkin cost analysis to build something like that with the best of the best, and got up past 50k pretty quickly.

I think that UFO configuration with pumpkin on the control arm is pretty special, that kind of innovation really gets the gears turning.
 
On the subject of bushings vs heim joints/rod ends. Both are generally used.

Before it gets too deep consider the strengths of a heim joint. Heims for IFS range from 7/8" to 1.25". In the normal direction, inline with the fine thread shaft, it is the strongest. From 50k to 100k lbs breaking strength which is usually the hoop containing the onmiball. In the cross axial direction it is very easy to push that omniball out of the hoop. A general spec is about 10% of the ultimate strength. So it only takes 5-10k lbs to push a omniball out sideways.

That is generally why a heim is NOT used on the inside bottom arm "hinge." They are used to some extent on the upright end as they are protected by the wheel and tire. On Ultra4 rigs the bushings are generally a bronze composite, but more importantly the thrust washers on both ends of the bushing is a very hard bronze composite. That is because it has to absorb all the front to back rock hits. Nylatron thrust washers break out fast and require a lot of maintenance in an area that usually has lots of damage an corresponding misalignment to replace the bushing bolts. A bushing arrangement is also smaller in diameter and easier to cover for skidding.

The top arms are usually all heim and omniballs. That is to adjust the alignment, and change geometry for the track and tire combination.

The further the bushings or heims are apart, the stronger and longer lasting.

The top arm is generally placed further ahead of the bottom for shock packaging to the bottom arm bu also allow for a steep front skid. I think a minimum angle is 45* so the car will skid over an obstacle instead of dead heading into it. Hitting that skid can hurt, but generally the hit is felt in the seat belts. If the hit continues under that is when it is felt in your back. Either way a god hit to a SA Diff or a skid is something to be considered if speed is in the cards.

We are seeing more Aluminum CNC arms because they can be machined to close tolerances. I would bet that racers would have a bottom second pair. Several have broke ending their race.

The traditional arm is CroMo fabricated and possibly heat treated. Racers will have bottom sets of these for a season of racing.

Arms have to clear the tires while turning but also the CV boots.
 
So I spent last night thinking about the UFO pumpkin in LCA thing. The reason it works for them is because the line about which the knuckle pivots is always going through the CV at the low end (if not you need two joints, one at the pumpkin, one at the knuckle). They are using the knuckle pivot for the camber change from the difference in length between the LCA and UCA. In order to add steering you need to add a second pivot for the steering angle. In order to have both steering angle and camber change without going out of alignment at the CV joint you either need a cage that allows the pivot lines to intersect at the CV. This is definitly doable. One could get some 1"x2" flat stock, make a perimeter around your knuckle of choice, drill taper holes for the ball joints in the top and bottom and then affix your camber pivot points to the sides (basically creating a knuckle that pivots vertically around a normal steering knuckle) and then go to town with the gussets. But this introduces a lot of complexity and comes with its own packaging nightmares in the brake/wheel area. Maybe someone who is runing a really tall and deep knuckle (think of something styled after the Magna-Steyr axle that comes in some Ram 5500s) that leaves a lot of room around the CV would be able to package the camber pivot contraption inside the knuckle but if you're running such a big knuckle in the first place you're doing it for strength and making the camber pivot small enough to fit inside would likely create a weak link. It would likely also greatly limit steering angle because you wouldn't be able to get too far before the knuckle wanted to contact the pivot (hence why I said you'd need a deep knuckle).

The other option as I see it would be that you need two joints and some slip (be it from a slip shaft or plunging CV) between the pumpkin and the knuckle to account for the changes in geometry from the fact that the knuckle's camber change is pivoting about the upper and lower ball joint (which are affixed to different length arms. You could also do parallel (equal length) upper and lower arms or you could delete the upper arm and do a swing axle. But with the handling that those options come with I kind of consider them non-starters.

It definitely still seems like a kick ass suspension for the rear but I definitely see why people aren't using it up front. You either wind up with a lot of complexity and resulting tradeoffs at the pivot mechanism or you wind up trying to cram a bunch of CVs in not much space. Making the diff share the same space as the engine seems like the lesser of the evils in light of that.
 
Last edited:
arse_sidewards said:
So I spent last night thinking about the UFO pumpkin in LCA thing. ....SNIP....
It definitely still seems like a kick ass suspension for the rear but I definitely see why people aren't using it up front. You either wind up with a lot of complexity and resulting tradeoffs at the pivot mechanism or you wind up trying to cram a bunch of CVs in not much space. Making the diff share the same space as the engine seems like the lesser of the evils in light of that.
Click to expand...


What benefit would it be in the front?
 
Tech Tim said:
What benefit would it be in the front?
Click to expand...

Better packaging allowing you to spend that space for better "whatever else you want" (clearance under skid, angles on arms, angles on joints, arm lengths, etc). Imagine how much easier everything would be if you didn't need to find a foot of space for a diff.
 
No problem at all finding the space for the diff, it's right between the A-arm pivots... :flipoff2:

I can see why Joe built that trailing arm rear. Makes sense as the rear is trailing (cool that Joe is trying to push the envelope).

Doesn't make sense at all for the front. The wheel control benefits of a double A-arm IFS is superior to any sort of trailing arm suspension out there. Not needed as much in the rear, definitely needed in the front.
 
SLOWPOKE693 said:
Here is my IFS question........

Why do most builders mount their front upper and lower arms level in relation the the chassis, like my above picture, vs rc cars where the front suspensions are generally tipped up in front with the arms angle back when viewed from the side?


Im sure there is a technical term for this but I R dumb. :laughing:
Click to expand...

Just coming into this thread, this may have been discussed I need to read it all, but after looking at the IFS on my 05 suburban, and my 91 rodeo, which handles great off road, I see that the tilts of the arms and the angle front to the mounts its opposite from one to the other, if I remember correctly the bottoms are parallel front to back but spread out in front on the rodeo, where on the burb the arms slope downward front to back and are inboard front and wider rear, then the uppers are tilted back on one and tilted up on the other????????????????? both handle amazingly well.
 
YotaAtieToo said:
Sxs's will get through trails on 32s that challenge rigs on 37s, but it's a totally different experience.
Click to expand...

Well if we are being a bit more realistic, if everyone was forced to wheel to rocks in the trails rather then blow up the sides we'd see some different thought. Not it direct response to just SXSs but also the other styles of big rigs.
 
Tech Tim said:
No problem at all finding the space for the diff, it's right between the A-arm pivots... :flipoff2:

I can see why Joe built that trailing arm rear. Makes sense as the rear is trailing (cool that Joe is trying to push the envelope).

Doesn't make sense at all for the front. The wheel control benefits of a double A-arm IFS is superior to any sort of trailing arm suspension out there. Not needed as much in the rear, definitely needed in the front.
Click to expand...

Wasn't Joe the guy on the old board (joefab) that built the solid axle trailing arm front suspension 4400 car?
 
Weasel said:
Well if we are being a bit more realistic, if everyone was forced to wheel to rocks in the trails rather then blow up the sides we'd see some different thought. Not it direct response to just SXSs but also the other styles of big rigs.
Click to expand...

I don't know about that anymore. The BustedKnuckle guys crawl some pretty decent lines with that 4 seet razor on 37's(?) they post in some of their videos. With the right driver and a properly set up machine a SxS is a weapon of sorts on rocks, unlike something similarly sized that.has solid axles and the same size tires would be.

Would you be faster driving a stock Can-Am X3 RC across a 1000' rock garden or a Samurai with the exact same size tires?
 
arse_sidewards said:
Better packaging allowing you to spend that space for better "whatever else you want" (clearance under skid, angles on arms, angles on joints, arm lengths, etc). Imagine how much easier everything would be if you didn't need to find a foot of space for a diff.
Click to expand...

you’re overlooking the fact that it is a static “foot of space” vs a moving “foot of space” that needs to fit around everything else. It was done in a rear engine car, but it’s not apples to apples.
 
Weasel said:
Well if we are being a bit more realistic, if everyone was forced to wheel to rocks in the trails rather then blow up the sides we'd see some different thought. Not it direct response to just SXSs but also the other styles of big rigs.
Click to expand...

Fair point, I remember watching a race and getting excited when I heard they were running up wrecking ball. Only to watch them drive around all the good stuff on dirt trails. :homer:
 
SLOWPOKE693 said:
I don't know about that anymore. The BustedKnuckle guys crawl some pretty decent lines with that 4 seet razor on 37's(?) they post in some of their videos. With the right driver and a properly set up machine a SxS is a weapon of sorts on rocks, unlike something similarly sized that.has solid axles and the same size tires would be.

Would you be faster driving a stock Can-Am X3 RC across a 1000' rock garden or a Samurai with the exact same size tires?
Click to expand...

I think he was referring to a lot of the trails in koh that have had dirt roads blown in around the big obstacles.

The BK rzr is on portals and 35 stickies. It does OK, but they also will spend hours stacking rocks to be "first rzr to run xxx trail"

I do agree with what you're getting at, but we aren't talking about long travel ifs vs leaf sprung solid axle. Give the samurai the same amount of wheel travel and caliber of shocks and there may be a technical spot where it could get ahead. But yes, most Boulder fields the independent will usually shine.
 
YotaAtieToo said:
I think he was referring to a lot of the trails in koh that have had dirt roads blown in around the big obstacles.
Click to expand...

That seems to be a lot of trails around here these days.


YotaAtieToo said:
I do agree with what you're getting at, but we aren't talking about long travel ifs vs leaf sprung solid axle. Give the samurai the same amount of wheel travel and caliber of shocks and there may be a technical spot where it could get ahead. But yes, most Boulder fields the independent will usually shine.
Click to expand...

This is where IFS really shines, the nuisance stuff on the trail is just soaked up.

When I had my Long Travel 4Runner, we would have to stop and wait for everyone to catch up through the nuisance stuff.

Bigger obstacles, we'd all take the same time crawling through, though often on slightly different lines.
 
YotaAtieToo said:
I think he was referring to a lot of the trails in koh that have had dirt roads blown in around the big obstacles.

The BK rzr is on portals and 35 stickies. It does OK, but they also will spend hours stacking rocks to be "first rzr to run xxx trail"
Click to expand...

Correct, sorry for the derail. Back to the IFS tech stuff.
 
I started thinking about those trying to use OEM parts. The most complex parts and one that really does not affect geometry is the center diff and the upright. The arms and steering location are the magic and generally needs to be fabricated anyhow. Both the arm design and the mounting points.

I made a couple IRS with Corvette centers. They are about 17" flange to flange. Wide, but if you are not looking for big articulation numbers they work. Look at the Corvette build in the build section of Irate. That would be a good start.

Several are making uprights now. I just saw that Hollander is making some for his Bronco builds. They are looking for a group mfg to cut some costs. Might be good to look into. I expect some of those related parts to be OEM also . These are for prerunners so probably pretty stout and would relate to some CV's to do the job.

Report back...

Hollandermotorsports on Instagram
 
Isdtbower said:
I started thinking about those trying to use OEM parts. The most complex parts and one that really does not affect geometry is the center diff and the upright. The arms and steering location are the magic and generally needs to be fabricated anyhow. Both the arm design and the mounting points.

I made a couple IRS with Corvette centers. They are about 17" flange to flange. Wide, but if you are not looking for big articulation numbers they work. Look at the Corvette build in the build section of Irate. That would be a good start.

Several are making uprights now. I just saw that Hollander is making some for his Bronco builds. They are looking for a group mfg to cut some costs. Might be good to look into. I expect some of those related parts to be OEM also . These are for prerunners so probably pretty stout and would relate to some CV's to do the job.

Report back...

Hollandermotorsports on Instagram
Click to expand...

I don't have IG. I see Holland Motorsports both on FB and Google, but not Hollander?

I've been appreciating all the high-end tech-talk. I've been hesitant to try and ask a few budget-oriented questions both for fear of derailing the higher-end discussion and centering the convo on my own wants / needs as that wasn't my original intent. Looking at costs of components though, one could almost spend an infinite amount of money on IFS. So there has to be a limit set somewhere. I'm not sure where my limit is but here go some more budget-minded questions:
  1. Why don't I see anyone narrowing their own stock Ford 9" housings? Seems like it would be fairly simple to run a bar through the carrier, machine some fairly simple bearing blocks, buy some shafts, and end up with something very similar to what name-brand manufacturers are selling for thousands of dollars?
  2. How bad are ball joints? Why does virtually no one run them?
  3. Are tripod joints inferior to "regular" CV joints somehow?
 
patooyee said:
[*]How bad are ball joints? Why does virtually no one run them?
[/LIST]
Click to expand...

It's an angle thing as opposed to a durability thing. Look at how much angle is on the arms when these cars are at full droop. A ball joint doesn't have the angular travel to support 15" of wheel travel whereas a heim with misalignment spacers can be oriented so the bolt is horizontal and there will be enough misalignment travel to steer.
 
patooyee said:
So there has to be a limit set somewhere. I'm not sure where my limit is but here go some more budget-minded questions:
  1. Why don't I see anyone narrowing their own stock Ford 9" housings? Seems like it would be fairly simple to run a bar through the carrier, machine some fairly simple bearing blocks, buy some shafts, and end up with something very similar to what name-brand manufacturers are selling for thousands of dollars
Click to expand...


  1. I have an IFS/IRS project I’m dying to do. But I’m looking at $13,800 just for two differentials. That’s spidertrax or Currie IFS 9’s with low pinion strange aluminum thirds ARB front, spool rear complete with 30 series diff shafts.

    thats diffs only my retail cost. Still need CV shafts, a-arms, trailing arms, knuckles, spindles, brakes, steering. All I want is to build a full size UTV minus the CVT and cost prohibitive would be the only name I could come up with for the build. I have access to to good machinists but don’t want to end up with nearly the same amount of money tied up into 1 off parts as just buying stuff that’s ready made.
 
Anyone ever see what happened with the guy machining 14b centers for ifs/irs? Obviously you take a weight penalty, but seems like a good way to save a ton of money, but still have a bulletproof big boy center.

Edit: another thought, what about toyota Sequoia rear 3rd? It's basically a Tundra suv, which uses the big 10.5" 3rd, so odds are they put a decent sized 3rd in the Sequoia.
 
Last edited:
YotaAtieToo said:
Anyone ever see what happened with the guy machining 14b centers for ifs/irs? Obviously you take a weight penalty, but seems like a good way to save a ton of money, but still have a bulletproof big boy center.

Edit: another thought, what about toyota Sequoia rear 3rd? It's basically a Tundra suv, which uses the big 10.5" 3rd, so odds are they put a decent sized 3rd in the Sequoia.
Click to expand...

I need at least 6.50:1 gears in the diffs. Being limited to 5.38’s in giant cast iron chunks is a no go regardless of cost.
 
I can find the rear diff assembly, but no specs. Anyone have any ideas on where to find our ring gear size?

May be a waste of time anyway, as it seems there is no aftermarket support for it anyway.
 
patooyee said:
I don't have IG. I see Holland Motorsports both on FB and Google, but not Hollander?

I've been appreciating all the high-end tech-talk. I've been hesitant to try and ask a few budget-oriented questions both for fear of derailing the higher-end discussion and centering the convo on my own wants / needs as that wasn't my original intent. Looking at costs of components though, one could almost spend an infinite amount of money on IFS. So there has to be a limit set somewhere. I'm not sure where my limit is but here go some more budget-minded questions:
  1. Why don't I see anyone narrowing their own stock Ford 9" housings? Seems like it would be fairly simple to run a bar through the carrier, machine some fairly simple bearing blocks, buy some shafts, and end up with something very similar to what name-brand manufacturers are selling for thousands of dollars?
  2. How bad are ball joints? Why does virtually no one run them?
  3. Are tripod joints inferior to "regular" CV joints somehow?
Click to expand...

Hey JJ, What is the build you're planning?

Maybe I missed it earlier?
 
JR4X said:
I need at least 6.50:1 gears in the diffs. Being limited to 5.38’s in giant cast iron chunks is a no go regardless of cost.
Click to expand...

I wasn't necessarily responding to you, just popped into my head. I think he had a thread on the old site.

Are you talking about using zuk drivetrain? I'm guessing that's the reason why you need deep r&p.

D60/D70 has 6.17s and 7.17s and could probably be machined in a similar way.
 
Paging ScottRS . He made his own 9" IFS center section long long ago. He should pipe up. :)

It was in this truck. Competed in Top Truck Challenge in.....2001 maybe?

white1.jpg
 
arse_sidewards said:
?????

Can you explain? Stupid high input RPMs or something?
Click to expand...

Not exactly, but exactly. I’ve been into racing for quite a while. Have had the opportunity to co-drive in some of the big name U4 cars including getting to co drive the finals in Bailey Campbell’s IFS car. Even with no overdrive 40’s and 6.20’s will go 107 mph at 7000 rpm. Most will never touch those kinds of speeds in an off road car. Jesse Haines JHF portal axles are running in the neighborhood of 7:38:1 if not lower, final axle ratio and taking the comp scene by storm.

I’ve come to find that 5:38’s and 40’s is a sad compromise in light of say 6.20’s or 6.50’s. I’ve found absolutely zero reason to not run the lower diff gears now. My favorite crawler combination so far is a 700R4 trans, 4.3 atlas and 5.38’s in the axles. That’s 71:1 low range, can still do 55 in low with 40’s at 6000 ish rpm.

If for some reason you’re limited in horse power or for some reason drivetrain length. Most common 3 speed auto’s are 2.50:1 ish first gear vs 3.07:1 that the 700 has. By running 6.50’s with a regular 3 speed auto, 4.3 t-case you end up with 69:1 crawl ratio. Close enough to the crawl ratio I find works best. Yet still low enough that high range is useable for big heavy tires.
 
Last edited:
You must log in or register to reply here.
Top Back Refresh