Ifs 101

[Isdtbower]

Tim: Thanks for taking some of the heat off of me for now. I am really handicapped without the 2TB of videos, photos, and files of IFS on my desktop. As history goes.... IFS came to light when Shannon brought his car to KOH and killed the field by over an hour. (Developed by ProAM) We had all been following Shannon as he was the fastest on straight axles but all were coming to the finish with white knuckles from no control at high speeds. The best and strongest way to get articulation was with full hydro steering. At speed, there was no control as not as fully developed as today. I remember speeds of 60 mph being tops and then 80 with the first IFS. Now we are into the 120's? (And even with SA full hydro) Steering accuracy and shock work has allowed that. The key to IFS was a mechanical link to the uprights. There seemed to be general attention or just mild desert geometry to the IFS. The IFS still had to climb. Regression of the front wheels from desert designs probably didn't reason out as the 4x4IFS would not bite into a rock to climb and the torque anti's would want to lift the front end. A LOT was unknown. At That time I was taking a LOT of video for Ultra4 promotion. When you go back to edit yo may see things many times....and start to see things. IFS was clearly killing it, and "skid wheeling" from the clean skids opened the game up to quicker winching and just "hitting it." It was obvious, U4 racing had changed.

Jason Scherer and I are local to each other. He knew I was and IRS guy and building a new rig with a SA front and IRS. He put together a night of interested friends from dirt track racing, fabricators, and etc to figure out what to do. All I had to offer was what NOT to do as I had messed with it in the "70's and realized the limitations of Universal joints on turning and articulation. It lasted one day before a model 44 SA got built. IN the mean time Jason found Tim and Dallas who had been messing with Toyota IFS I believe. And they were building a project chassis to be shown at KOH that next year. Tim and Dallas went to work using the lessons from Shannons and ProAm's efforts. Through lots of trials and errors, Jason was in business and a verified contender again against Shannon. Others were also playing the game and I focused on IFS suspension. Both in how they worked on the trail and what broke. At that point, The info was flowing "in our group" I was seeing things, Jason was feeling things, the Garage and pit team were seeing things, Jason scoured for builder resources like SpiderTrax, and Dallas continued to improve on the CAD competence and movement in the designs. I am not sure where the basic geometry came from, but it is still very unique and adaptable to incorporate camber and caster gain with big articulation.

Focus on that thought. Camber and caster gain with big articulation. We knew from motorcycles, desert, and dirt track that the outside front tire, with the most weight and traction, should never go into positive camber (tuck underneath)(To the ground). Especially in a turn. Inside tires do little at speed and not critical in the rocks except for contact traction when it's got some weight.

Camber to the ground was an important concept as body roll kills camber and caster in IFS/IRS. (The best at explaining this was Bob Bolles a Circle Track tech editor. I believe he has a web site now but I am sure I will add the important Cliff Notes as we go. but some of the best understanding of tires on dirt come from his discussions and testing) From my videos and pictures from all media, a U4 rolls about 15* in the front and about 10* in the rear ( heavy sway bars). For this reason I have been encouraging designers to test their IFS geometry with 10* of body roll, and check the camber to the ground straight and maybe 20* into a turn. It is enlightening.

The picture of Jason' car is as second generation IFS which is not the best to show Camber but notice the wheel vs the tire. Tires, and air pressure make a difference and can change geometry setup considerably. I will improve on that later. Also note the "reverse Ackerman" Ackerman is for no noise on a garage floor. To me, you want that outside tire to TURN not go straight and the turning tire on the inside with no weight. Basic stuff that Bob Bolles points out. (But if you are a drifter type of driver, you may have different ideas on this as "counter steering".) For true offroading where you don't generally know the route, the fastest and safest, is to go in deeper-brake harder-turn-and come out harder. It is in the corners where you crash or destroy stuff the most...which is where all those other little items come in.

So I am being pestered to get outside and get dirty. But love the individual comments all have. This all adds into the info we all need for decisions.......... and on IFS vs SA.

I personally don't think high end IFS is necessary or advantageous until you hit that 60 mph area. Eric Miller cars with much improved hydro steering are making their mark. Not loosing much in the dez and making it back up in the rocks where 45* quick steering is making headway against 25-39* skid wheeling.

Quickly on the subject of CV's. 935 CV's have proved to live next to the center section as they rarely should be run more than 23*. The $$ series 30 is really needed at the uprights to turn 39* at stuff or droop as they will, with work, turn 45* for a short period of time. (Overheating) If turning 25* is OK for skid wheeling or recreational, OEM and 935's will offer a "slightly" less budget...maybe considerably less. And thus the question...... What are your wheeling intentions and terrain. This thread has already backed off somewhat from use of OEM parts. And it could get a LOT more technical as the Dez guys have taken it to a next level for thieir use (limited turning)

Pestered again...........................

 

[YotaAtieToo]

If you're bottoming out, and your skid plate is the bump stop, you've built it wrong, sa or ifs...
There should never be less than 6" of clearance to your skid plate from terra. Maybe my opinion, but i wouldn't go any closer than that with the bottom of my rig.

Considering portals may help with this, but your skid plate is not an effective bump stop.

You're totally missing what I'm saying.

Basically portals can equal more travel, from what I understand.

When did portals become popular? I assume you're talking about HMMWV portals since we're taking about IFS? Besides JHF where do you even find HMMWV portals these days?

Popular may have been a stretch, gaining popularity would probably be more appropriate terminology.

It's hard to find many pics online, but I believe a lot of the new awd trophy trucks are using portals for the same reason. Gear reduction is a plus as well.

 

[AgitatedPancake]

Thanks Tim. I agree, it's great seeing the minds get together for threads like this again, it's been a long time since I've looked forward to new responses on forum posts anywhere.

As far as diff height - here are the thoughts of an inexperienced overthinker:

Without portals, your range of travel is basically limited by two factors - How much diff clearance do you want at full compression? Consider tire squish when you smash through the suspension on a massive impact. So that sets your maximum uptravel wherever you chose. I've seen around 4-6" front pumpkin clearance at full compression on high performance rigs just for generic reference. Then downtravel is set by whatever maximum angle you're willing to let the CVs go to. The combination of those two factors sets your maximum travel range to either end, and you can choose to set your ride height anywhere in between.

In practice it seems that CV angle at full compression is far less than CV angle at full droop, so there's often unused up potential while all of the down potential is being maximized. This is where portals come in (besides the improved ground clearance). If you take the exact same travel range you had set above, and add portals to it, now you're using more angle in compression, and less angle in droop. So because droop is no longer CV limited, you can add more droop to configuration (or keep your droop, and run your CVs cooler because less angle).

One interesting dilemma I see people facing - what to do with camber in droop? Steering angle is usually limited on IFS cars because the outer CV has to do the work of suspension travel plus the work of steering angle, so that compound angle becomes pretty limiting. So do you sacrifice camber in droop, to allow more built in steering angle? Or do you keep a camber curve that's somewhat neutral into droop, but sacrifices max steering angle? Some 2wd trophy trucks actually begin gaining camber again towards the end of droop, but this would absolutely destroy outer CVs with any steering angle. So where's the balance?

 

[Sterlingfire]

You're totally missing what I'm saying.

Basically portals can equal more travel, from what I understand.




Popular may have been a stretch, gaining popularity would probably be more appropriate terminology.

It's hard to find many pics online, but I believe a lot of the new awd trophy trucks are using portals for the same reason. Gear reduction is a plus as well.

OK, I'm on your train of thought. You're saying with portals you can put the cv's in position to use as much of the usable load area on both bump and droop, and still have a bunch of ground clearance at full bump. Thus giving you more usable suspension travel with a more neutral cv position at ride height.
I can see why portals would become popular. Ground clearance is a big deal when you're trying to go as fast as you can through rocks and race tracks in the same day. Too bad portals aren't a little more affordable. They would be a great option for more ifs race cars. The downside would be that maybe you'd start seeing less and less straight axle rigs.

 

[patooyee]

Is there a CV 101 somewhere? I keep hearing these 934 vs 30 series labels thrown around. I don't know what they mean. And if we're talking about designing around CV working angles, I imagine there is a resource showing the working angles of them all?

 

[AgitatedPancake]

Is there a CV 101 somewhere? I keep hearing these 934 vs 30 series labels thrown around. I don't know what they mean. And if we're talking about designing around CV working angles, I imagine there is a resource showing the working angles of them all?

I'm no expert, but as I understand it, there are 3 sizes out there. 930 (small), 934/934.5/935 (medium), and series 30 (large). 930's are too small for our big/heavy uses, so they seem to get skipped over with zero consideration in this application. The 934s are the mid range and seem to work well in fun rigs, but don't give racers enough confidence to finish brutal races. Series 30 are huge, and from what I understand are the norm under the top U4 rigs. You can choose plunging or non plunging, plunging joints have much less angle available than their non plunging counterparts. The more plunge your system has, the more heat that seems to be generated (compounding on the friction from high angle usage). The price point stepping up from 934 to series 30 is massive, The 934 can be found in pretty comperably cheaper off the shelf applications, and you can ramp it up from there adding higher quality materials for durability and more meticulous polishing to reduce heat.

A number I always recall hearing from back in the day for keeping inner joints alive and happy was running them under 30* max (27* comes to mind), but it's all relative because that's not their max operating angle. Just seems to be a point people discussed past which the heat buildup became to extreme

 

[patooyee]

I'm no expert, but as I understand it, there are 3 sizes out there. 930 (small), 934/934.5/935 (medium), and series 30 (large). 930's are too small for our big/heavy uses, so they seem to get skipped over with zero consideration in this application. The 934s are the mid range and seem to work well in fun rigs, but don't give racers enough confidence to finish brutal races. Series 30 are huge, and from what I understand are the norm under the top U4 rigs. You can choose plunging or non plunging, plunging joints have much less angle available than their non plunging counterparts. The more plunge your system has, the more heat that seems to be generated (compounding on the friction from high angle usage). The price point stepping up from 934 to series 30 is massive, The 934 can be found in pretty comperably cheaper off the shelf applications, and you can ramp it up from there adding higher quality materials for durability and more meticulous polishing to reduce heat.

A number I always recall hearing from back in the day for keeping inner joints alive and happy was running them under 30* max (27* comes to mind), but it's all relative because that's not their max operating angle. Just seems to be a point people discussed past which the heat buildup became to extreme

How does 934 / 30 play into RCV's offerings? Is a 934 what they use for D60 applications? What is the big-bell rockwell CV joint that they use? And are there sources other than RCV?

 

[Tech Tim]

How does 934 / 30 play into RCV's offerings? Is a 934 what they use for D60 applications? What is the big-bell rockwell CV joint that they use? And are there sources other than RCV?

Best I can recon:
930 CV = D30/D44 RCVs
934 (aka 21 series or size 21) = D60 RCVs
30 Series = Big monster RCVs.

I ran 930 RCVs in my LT 4Runner for many years with 35s, doublers, lockers etc. Never had a single failure. Probably wouldn't run 37s with the 930s unless it was street/mild trail stuff.

30 series are the big dog stuff and cost $1200~ each. Also get the best angle out of them.

iirc Andrew McLaughlin (Let's Roll Off Road) ran the 934/935 CVs.

We designed both of Scherer's IFS to run 30 series.

 

[Toreadorranger]

Here is a visual of 934 vs 930.

 

[patooyee]

Found this pic for reference:

 

[Toreadorranger]

Here's a better comparison

Edit: patooyee beat me to it.

 

[arse_sidewards]

And these are all ball bearing type joints, correct? No "three lobes with needle roller" joints (why not?, what's the disadvantage?). And these joint series have no relation to OEM joints (unlike say 1310/30/50 and 1410/80 U joints which are fairly standarized sizes used by OEMs).

Basically what I'm getting at is that can or can't you go to a junkyard and pick up good CVs and then use them in a rig (provided you got custom length shafts as needed)?

 

[patooyee]

And these are all ball bearing type joints, correct? No "three lobes with needle roller" joints (why not?, what's the disadvantage?). And these joint series have no relation to OEM joints (unlike say 1310/30/50 and 1410/80 U joints which are fairly standarized sizes used by OEMs).

Basically what I'm getting at is that can or can't you go to a junkyard and pick up good CVs and then use them in a rig (provided you got custom length shafts as needed)?

Well, like the pic indicates, the 930 and 934 joints were used in Porsches and the smaller ones in VW's. (I think the 934 was in turbo charged porches.) I don't know what / if there was a stock application for series 30. But like u-joints, there's probably a big difference between factory joints and aftermarket with 4340 and 300m in them. Also, all the spline variations, I'm guessing, were aftermarket. (IE, I doubt there were 35 and 40-spline 934 Porches running around.)

In my mind, before I knew any of this, RCV had a totally unique product that no one else made. Now I'm starting to think that their main uniqueness was their marketing strategy.

So what is in a Chevy 3500 axleshaft? Something completely different?

 

[arse_sidewards]

Also, all the spline variations, I'm guessing, were aftermarket. (IE, I doubt there were 35 and 40-spline 934 Porches running around.)

So what is in a Chevy 3500 axleshaft? Something completely different?

That's exactly what I want to know. You don't see a lot of people popping shafts on those trucks despite the respectable power, weight and gearing they have (yes I'm fully aware that the rest of that front suspension is shit and provides a lot of other fuses to blow first).

Spline variations is why I'm thinking truck shafts. In stock applications you break the shaft long before the CV gives up. Truck applications tend to have much larger diameter shafts than car applications because the vehicles weigh so much more and are expected to be used harder.

The various axle companies will spline the end of a shaft for not that much money so getting something to deal with a custom length would be easy enough.

 

[patooyee]

Also note the "reverse Ackerman" Ackerman is for no noise on a garage floor. To me, you want that outside tire to TURN not go straight and the turning tire on the inside with no weight. Basic stuff that Bob Bolles points out.

Just making sure I understand this correctly. You're saying that, at least in this instance, "correct" Ackerman is ignored / inverted because so little weight is on the inside tire that the car is relying on the outside tire to do most of the turning? Are you implying that "correct" Ackerman is a contributor to the "plowing" that others have referred to?

 

[Weasel]

And these are all ball bearing type joints, correct? No "three lobes with needle roller" joints (why not?, what's the disadvantage?). And these joint series have no relation to OEM joints (unlike say 1310/30/50 and 1410/80 U joints which are fairly standarized sizes used by OEMs).

Basically what I'm getting at is that can or can't you go to a junkyard and pick up good CVs and then use them in a rig (provided you got custom length shafts as needed)?

I'm not aware of any OEM 3 lobe with needle rollers. Iirc they didn't tolerate large angle & plunge very well.

RCV took a product and made it work for the market. It's the same with any product really. Adapt an existing product to a new market and you have a new segment. As you mentione OEM doesn't make stuff with good materials, tight tolerances, or common spline counts.

 

[patooyee]

That's exactly what I want to know. You don't see a lot of people popping shafts on those trucks despite the respectable power, weight and gearing they have (yes I'm fully aware that the rest of that front suspension is shit and provides a lot of other fuses to blow first).

Spline variations is why I'm thinking truck shafts. In stock applications you break the shaft long before the CV gives up. Truck applications tend to have much larger diameter shafts than car applications because the vehicles weigh so much more and are expected to be used harder.

The various axle companies will spline the end of a shaft for not that much money so getting something to deal with a custom length would be easy enough.

You can find them all day long at junk yards for $30 ea.

RCV makes replacements for them, too:

https://www.rcvperformance.com/ultim...lt-flange.html

Wish they had more info about them on their site.

 

[AgitatedPancake]

On the subject of ackerman, I used to be of the thought that proper ackerman was the way to go. Then years ago Jesse Haines said something that made too much sense and flipped my thought process inside out. He was a fan of essentially zero ackerman. The reasoning: why take max available steering angle away from the outside tire, which probably has the most weight on it in most situations. For example if you have steering ujoints (or CVs in this case) capable of 40*, what that really means with proper ackerman is the inner tire can turn 40, but your outer tire where most of your weight probably is, is only turning 35* (random numbers). So why sacrifice those extra degrees of turning when it counts? Especially because we're not dealing with a static understanding of traction, and we're not exactly looking at tire slip angle or anything like that. We're frequently using the tires to straight up paddle soft materials for traction

 

[arse_sidewards]

You can find them all day long at junk yards for $30 ea.

RCV makes replacements for them, too:

https://www.rcvperformance.com/ultim...lt-flange.html

Wish they had more info about them on their site.

That's exactly why I mentioned that application.

Someone who wanted to dick around with IFS could get shafts for like $100-$200 (depending on whether you have a brigeport and can spline your own custom length shafts). Considering that you're likely to change length at least once or twice it doesn't make sense to spend the coin on RCVs initially. But once you do have the thing dialed you could upgrade from junkyard joints to nice joints.

I think it's also worth noting that OEM CVs will hold up just fine to the mildly tuned 5.whatever engines and 35-42 tires that most people are running in their buggies and crawler rigs. When aftermarket replacement shafts are $50 I'll listen to a lot of clicking before I spend $2k to make it go away.

 

[patooyee]

That's exactly why I mentioned that application.

Someone who wanted to dick around with IFS could get shafts for like $100-$200 (depending on whether you have a brigeport and can spline your own custom length shafts). Considering that you're likely to change length at least once or twice it doesn't make sense to spend the coin on RCVs initially. But once you do have the thing dialed you could upgrade from junkyard joints to nice joints.

I'm not advocating for anything here, nor disparaging RCV or any aftermarket joint maker, but I have seen so many idiots do so much dumb shit with the IFS in those trucks, it's unbelievable. People deliberately TRYING to destroy the trucks ... but those shafts always seem to survive.

 

[Wilson]

That's exactly why I mentioned that application.

Someone who wanted to dick around with IFS could get shafts for like $100-$200 (depending on whether you have a brigeport and can spline your own custom length shafts). Considering that you're likely to change length at least once or twice it doesn't make sense to spend the coin on RCVs initially. But once you do have the thing dialed you could upgrade from junkyard joints to nice joints.

I think it's also worth noting that OEM CVs will hold up just fine to the mildly tuned 5.whatever engines and 35-42 tires that most people are running in their buggies and crawler rigs. When aftermarket replacement shafts are $50 I'll listen to a lot of clicking before I spend $2k to make it go away.

would be a no-Brainer using the gm diff

 

[Weasel]

Just making sure I understand this correctly. You're saying that, at least in this instance, "correct" Ackerman is ignored / inverted because so little weight is on the inside tire that the car is relying on the outside tire to do most of the turning? Are you implying that "correct" Ackerman is a contributor to the "plowing" that others have referred to?

Yes on the tire weighting, not exactly on the plowing. Steering could effect that part but it more likely in the roll moment balances of the car.

On the subject of ackerman, I used to be of the thought that proper ackerman was the way to go. Then years ago Jesse Haines said something that made too much sense and flipped my thought process inside out. He was a fan of essentially zero ackerman. The reasoning: why take max available steering angle away from the outside tire, which probably has the most weight on it in most situations. For example if you have steering ujoints (or CVs in this case) capable of 40*, what that really means with proper ackerman is the inner tire can turn 40, but your outer tire where most of your weight probably is, is only turning 35* (random numbers). So why sacrifice those extra degrees of turning when it counts? Especially because we're not dealing with a static understanding of traction, and we're not exactly looking at tire slip angle or anything like that. We're frequently using the tires to straight up paddle soft materials for traction

Ackerman can be the way to go just depends. Like you said there is a bucket full of variables and you have to weight which your going to be in 75% of the time. For crawling Twisted guys always run reverse. You want the max steering at all times, you don't know which tire is going to have traction or weight but you want the max for cone dodging.

Now when you get into traction limited surfaces I don't think all the steering possible is going to help. There is a point and which too much steering angle is going to break traction available and the tire will just plow sideways. You reduce the angle a bit and the traction comes back and you get cornering. At speed Ackerman really doesn't have much of an effect due to loads on the tires. But if you in a low traction situation at lower speeds you could be breaking traction as the tires are fighting each other. Anyways that's my thoughts on it.

 

[Wilson]

I don’t want to necessarily quote you Weasel, but this is getting to the nuts and bolts of it. The leaf to link jump and discussion showed that links allowed you to better “dial-in” the suspension, if you paid attention, designed and built accordingly. Many shitty suspensions were built just because “links were better.” This is the next level, with the ability to tailor every parameter at each wheel.

 

[Wilson]

I do a lot of “traction limited” wheeling in the snow and there are times that there is nothing that can avoid plowing. Selectable lockers can help, but I would wager that there is nothing geometry-wise that would make the difference.

 

[Tech Tim]

That's exactly what I want to know. You don't see a lot of people popping shafts on those trucks despite the respectable power, weight and gearing they have (yes I'm fully aware that the rest of that front suspension is shit and provides a lot of other fuses to blow first).

You do see the GM IFS snap their CVs and Tripod(t) joints, especially in the pulling circles, most of the time in lifted trucks, that are already running their halfshafts at sharp angles, then the extra droop....bind....snap.

 

[Wilson]

You do see the GM IFS snap their CVs and Tripod(t) joints, especially in the pulling circles, most of the time in lifted trucks, that are already running their halfshafts at sharp angles, then the extra droop....bind....snap.

with the amount of steering failures on those trucks, it’s not surprising

 

[Provience]

On the subject of ackerman, I used to be of the thought that proper ackerman was the way to go. Then years ago Jesse Haines said something that made too much sense and flipped my thought process inside out. He was a fan of essentially zero ackerman. The reasoning: why take max available steering angle away from the outside tire, which probably has the most weight on it in most situations. For example if you have steering ujoints (or CVs in this case) capable of 40*, what that really means with proper ackerman is the inner tire can turn 40, but your outer tire where most of your weight probably is, is only turning 35* (random numbers). So why sacrifice those extra degrees of turning when it counts? Especially because we're not dealing with a static understanding of traction, and we're not exactly looking at tire slip angle or anything like that. We're frequently using the tires to straight up paddle soft materials for traction

fully agree.

ackerman, for any sort of crawler or trail rig, is not worth considering or designing for.

build for the tire that gets the weight, don't break any joints, make arms with ratios that work so that you aren't putting too much leverage into the steering system and enjoy.

 

[Isdtbower]

Just making sure I understand this correctly. You're saying that, at least in this instance, "correct" Ackerman is ignored / inverted because so little weight is on the inside tire that the car is relying on the outside tire to do most of the turning? Are you implying that "correct" Ackerman is a contributor to the "plowing" that others have referred to?

..........................................................................

I am trying to understand the word usage for plowing in 4wd. If the front outside is plowing it is not pulling around from minimal traction...or too much push from the rear. This is where you want to take video of that situation and visually see why it is plowing and not pulling the front around. Take those videos on both braking and acceleration.

Under braking the outside tire is being planted so you would want to look at loss of camber to the ground. The tire sidewall flex being so soft that the tread is folding under. Or maybe the tire tread edge design, etc. (Not how far the tire is turned...which could be too much for the speed and rear push. ) Why is it loosing traction to do it's job?

Under acceleration, now the front is being lifted. How much depends on the front and rear rear torque anti's , as well as the weight distribution generally behind the rear axle. The CG shift to the rear.

When you are under braking and turning the body goes into that roll situation where you WILL LOOSE negative Camber. The driver cannot see this but will feel it as pushing and basically a loss in wheel track width. It is really easy to flip over that outside tire (Like a tricycle crash). At this point only the pro, strong and lucky driver recovers from the roll. Many early cars and SXS had that trait. To compensate, the driver would try to slide the rear around to complete the turn. But sometimes the rear would hook a rut to delay that rotation and over they go. Many added sway bars to the front to minimize the body roll and camber loss. Added to that were tires with little sidewall strength (for lightness or ??) Tire balls helped this somewhat and now "liners" (A tire inside the outside tire.)

KOH guys run in the area of 25 psi to prevent pinch flats, but how about the recreational guy at 4 psi? I have some pictures of KOH tires with the tire edge almost to the center of the wheel in "scuff." For those types of tires you would want more camber to the ground in that situation. Tires do/should dictate geometry settings.

Someone earlier mentioned adding 3* camber to their SA set-ups. From what I have seen, I have been mentioning a similar number for both front and rear SA's. Circle track cars do this to the extent of barrel rolling the splines to account for the bind. Next level stuff but is probably being used quietly. With IFS/IRS it is just an easy adjustment.

Is this what you were thinking or ?? No stress, but definitely what is being considered if inclined that way. And Thin Air WAS onto some good stuff. We lost a valuable asset, but I can confirm that he manages at a project level higher than offroad geometry. Although it was part of a much larger project at the time. Thin Air came to us asking how to climb rocks ........... and offroad.........starting at the basics.

 

[Isdtbower]

I do a lot of “traction limited” wheeling in the snow and there are times that there is nothing that can avoid plowing. Selectable lockers can help, but I would wager that there is nothing geometry-wise that would make the difference.

Agreed, and the front is nothing but "rudders" and maybe floating The crawler buggies are fixing that with rear separate braking and open diffs. If you want to turn left with minimal front wheel contact, you "brake" the rear left wheel and the right rear spins twice as fast to push you around. (Not sure that would work in the snow but does for their crawling before resorting to rear steer and all 2wd sand buggies. Hitting the turning brake while doing a slow wheelie produces some pretty spectacular antics.

 

[Isdtbower]

How does 934 / 30 play into RCV's offerings? Is a 934 what they use for D60 applications? What is the big-bell rockwell CV joint that they use? And are there sources other than RCV?

How far a CV will turn is somewhat dictated by the shaft size used for that particular joint size. When the shaft comes over and hits the outside race. You are done. A 935 is a 934 size CV with a 35 spline shaft. A 934 has a 30/32 spline shaft...smaller. A 935 may have a max angle of 30* or so. A series 30 with a 35 spline shaft can go to 45* and why used in the turning uprights.

The magic number around 23* of max angle comes from two areas that I can see. The first being more angle means more heat generated on a consistent basis. You will also see when doing your geometry that the tire really starts to move in quickly loosing track width with very little improvement in vertical articulation. It is also hard to control camber past that angle.

Short top arms that are not parallel to the bottom arms allow the camber to be tailored at droop and stuff. Most are not so concerned about camber in the negative on droop because there is less tire weight for traction. Consider the TTB for extreme positive camber but old school popular in the dezert. I set my IRS camber with 5* of roll at 0* camber at droop and -4* at stuff. It was about -3* at "ride height." I am just going by drawings on the IFS so not checking the exact geometry but not that good with 10* roll. Newer generation designs have accounted for the body roll. The TT 4x4 designs incorporate that as they have been onto that in the 2wd trucks for some time.

with that in mind, I also agree with the Portal thoughts here. Generally moving the clearance up. But another big part of this is the use of the same diff sizes that are being destroyed every race from "too little tooth contact" The lifespan of those should be considerably more. I have also been aware of a new hyploid technology that uses more pitch angle on the pinion so that it contacts more teeth on the ring gear. Used in super cars and Mercedes to minimize diff size. I was made aware that the new JL Jeeps may have these gears in the Model 44 size axles....and much stronger that our old standard model 44. We will see. Many IFS/IRS high HP diffs hang down 7" from the CV centerline. That hurts the ground clearance on G-outs. I am living with what I have but look forward to the future now that the TT world is involved.

Apparently a 15-30k diff is irate to some here. (I get it also...but there are options in the $6-10k range where I landed. OEM just didn't have the strength for a KOH replica build. Especially alum cased.....But I digress.