Future of KOH 4400 chassis/car development?

[Isdtbower]

There are some needs for independent suspension diffs. Short CV-CV distance for longer Half shafts. And diffs that do not hang down into the ground.

The most used is the 9" case. From the CV center to the bottom is 5". From CV-CV flange to flange series 30 is about 14" with the stock casse and about 13" when you cut off one side. Inboard rotors should nt be greater than the mentioned 10" for ground clearance.

The Aussie case is huge and heavy and is about 7-8" from CV center to the bottom. I believe they can build CV to CV for long arms but the ground clearance kind of negates some of that ability. Because of the mass you could run 15" inboard rotors, and some have.

I settled on a 12" quick change. But the CV to bottom is 7". The Flange to flange CV's 935 is 7". It might be possible to run inboards, but my 13" brakes will fit inside a deep dish 17" forged wheel.

Weismann produced an Offset Pinion independent diff that could run CV to CV back to back, But was also 7" CV 935 to bottom. The real feature was the offset pinion to get a driveshaft around a front engine pan. Used mostly in Pro Four. Cool but lots of maintenance and $30k budget.

These two considerations are just the start of whether a diff is good for you. (In my case, I considered cv-cv distance critical. I designed to 24" articulation maxing the CV's to 25* IRS. Then checked ground clearance and lost 6+ inches in stuff. (Don't let chassis pictures on jacks fool you. It didn't me but I had no clue it was that much loss. IFS front=9". IRS rear=Quick Change.

FAst 4400 cars use the hell out of brakes. They run red to white hot when on the gas. A driver will usually trail brake to use the anti's to settle the car at speed. The new active shocks can help that problem, and selectable in the cab, or in the GPS. Most car maintenance seems to be hittiing stuff (stopping the drivetrain) and from braking loads.

 

[SLOWPOKE693]

There are some needs for independent suspension diffs. Short CV-CV distance for longer Half shafts. And diffs that do not hang down into the ground.

The most used is the 9" case. From the CV center to the bottom is 5". From CV-CV flange to flange series 30 is about 14" with the stock casse and about 13" when you cut off one side. Inboard rotors should nt be greater than the mentioned 10" for ground clearance.

The Aussie case is huge and heavy and is about 7-8" from CV center to the bottom. I believe they can build CV to CV for long arms but the ground clearance kind of negates some of that ability. Because of the mass you could run 15" inboard rotors, and some have.

As soon as you add a portal box into that mix the CV center to bottom measurement becomes less critical to keep the CV's happy and the 4" of ground clearance you gain from the boxes allows you that much more usable uptravel before you get to the useless uptravel mark.

 

[AgitatedPancake]

Great points as always Ben. Narrow diffs help CV angles so much I can't help but believe they're going to become more relevant. Although I honestly would have thought we would have seen more Proformance setups racing by now as Slow noted (even with those downsides).

Excellent pic of Jason's old car too. Do you happen to have any pics kicking around of what style of rotor they ran on that car? Was it a solid lightweight unit, or a thick vented unit? With that even coloration my first guess would be a solid rotor, but I'm probably wrong haha

 

[Yotota]

With this inboard brake discussion...

Are any of the other Army dudes getting flashbacks of Humvees? Driving along, stop at an intersection, and the damn truck rocks back and forth a few times due to the slop in the CV's and portals.

Which also brings us back around to CV joints. I agree that this single component is the biggest limiting factor against IFS builds. Aside from RCV, where else can one buy high angle, well sealed, STRONG CV's?

It would be amazing to find an off-the-shelf commercial truck or industrial machine part that could be adapted. But I don't know of anything with the angles we need... At least 50° at full torque and RPM, if not 60°.

Modern 3500 hd trucks have decently strong front CV's, but probably not "45° steering at full lock, 3:1 low range, 600hp full throttle, in the rocks" strong. But still, something like this could be modified to work in a lighter rig with 300-400hp with a smart driver:

DMAX HD Extended Travel Front CV Axle Assy (LB7-LMM) (Lifetime Warranty) 2001-2010

DMAX HD Extended Travel Front CV Axle Assy (LB7-LMM) (Lifetime Warranty)

norcaldieselperformance.com

 

[Isdtbower]

Great points as always Ben. Narrow diffs help CV angles so much I can't help but believe they're going to become more relevant. Although I honestly would have thought we would have seen more Proformance setups racing by now as Slow noted (even with those downsides).

Excellent pic of Jason's old car too. Do you happen to have any pics kicking around of what style of rotor they ran on that car? Was it a solid lightweight unit, or a thick vented unit? With that even coloration my first guess would be a solid rotor, but I'm probably wrong haha

I believe that was a solid rotor or vented solid.. Everything has been on that car searching for lite and works. I bet this will be the last year on 17" rims, but the Alcons were a big step up, I believe. Calipers have always been in the $1k range each. I think the Alcon took it to another level, Brak strength is all about the bridge strength between the two sides. It was reported from Baja that some tires and wheels had inside diameters of 18" and outsides at 17".. Some of the rumors from a one day trip to the lake bed was tire guys thinking about 18 or 20's next. All about brakes driving that at the expense of rim pinch flats. Baja trucks have pressure sensors in the wheels and may have ditched liners?? . Not sure about 4400.

On CV's. Loren had to stop because a rear boot got destroyed and probably wouldn't make a lap. Another BIG chink against IFS,

Because I am recreational I went with the OLd Class1 CVs and their restrictions because of heat. 935 and 25* max, The outside front (Upright) has the series 30 for turning with a 35 spline shaft. Andrew McLaughlin ran 935 inside and 30 series outside successfully for several years. he finally went back to SA just because of maintenance.

On Halfshafts. Plunge is a big thing. In IFS you HAve to minimize plunge in the design. Less than 1/4" in the travel. All the pllunge is taken in the inside CV as the outside has to pivot along the KPI line as I remember. Plunging halfshafts have never been successful in Baja.


Probably because of larger tires and everything else Class1 is dying in the DEZ. Most are moving to trucks which are stronger. No CV's nor VW tech.

 

[JBT]

Wouldn't portals with 2.5:1 or 3:1 gear ratio be beneficial as you can use smaller axle shafts and smaller inboard brakes. Gearing issues should be possible to solve with 2.5:1 ration 9" diffs and ZF8hp transmission with single speed SCS transfer case.

 

[JR4X]

SXS’s get away with both inner and outer plunging CV’s

 

[SLOWPOKE693]

I believe they get away with alot of things because of how little they weigh vs their full side counterparts. Adding more weight means having to build bigger stronger part to handle the weight. Rinse and repeat...

 

[Yotota]

I believe they get away with alot of things because of how little they weigh vs their full side counterparts. Adding more weight means having to build bigger stronger part to handle the weight. Rinse and repeat...

Absolutely, weight is the biggest factor.

I bet one of the good desert race buggy shops could knock out a chassis that has a good balance between capability and weight. A quick check says that a Jimco class 10 buggy weighs 2500lb.

It doesn't seem impossible to put together a sub-4000lb 4400 car... LFX V6 at 400hp, IFS, 40s, and keep the drivetrain to a moderate weight. But then would it be competitive against a 800hp UFO 4400 car on 42s? It would be cheaper, that's for sure.

 

[Treefrog]

Where is the weight hiding? All the big items do not seem to add up to the weights that get mentioned. Wheels, tires, engines, trans, transfer cases, even axles. They just don't seem to add up. Is it cooling, the chassis, other places?

 

[ridered3]

Where is the weight hiding? All the big items do not seem to add up to the weights that get mentioned. Wheels, tires, engines, trans, transfer cases, even axles. They just don't seem to add up. Is it cooling, the chassis, other places?

Another bigger and adjustable weight would be gas weight. If I recall correctly, one of the Gomez cars hold like 90 gallons of gas so 750ish pounds of gas there.

 

[mobil1syn]

I bet one of the good desert race buggy shops could knock out a chassis that has a good balance between capability and weight. A quick check says that a Jimco class 10 buggy weighs 2500lb.

class 10 buggy chassis are not up to the task. the fast guys are on the edge between surviving a race and self destructing. lots of crack chasing on the fast ones

 

[SLOWPOKE693]

It only has to last 200 miles and I didn't see any parts hanging off the Miller's stock(ish) chassis after the race like I did JP's car.

 

[JR4X]

Absolutely, weight is the biggest factor.

I bet one of the good desert race buggy shops could knock out a chassis that has a good balance between capability and weight. A quick check says that a Jimco class 10 buggy weighs 2500lb.

It doesn't seem impossible to put together a sub-4000lb 4400 car... LFX V6 at 400hp, IFS, 40s, and keep the drivetrain to a moderate weight. But then would it be competitive against a 800hp UFO 4400 car on 42s? It would be cheaper, that's for sure.

I don’t think building something cheaper is going to get the desired results. Lighter might end up being as expensive if not more expensive. That is, if the goal is to be a top 10 4400 competitor anyway, and have a chance of getting on the podium.

The CanAm that is getting in the top 10 on 35’s is a $150k dollar machine. I’m absolutely confident you aren’t building a vehicle intended for 4400 for less than that and having a chance of getting in the top 10 with it. A Miller car is over 1/4 mil these days. Randy’s bomber is probably the lowest dollar build in the top 10 cars and I bet he’s turnkeying them for at least a buck fifty.

 

[bdkw1]

With portal boxes being in the mix now you would be able to get away with a much smaller and easier to package rotor and caliper because of the multiplication of the brake torque through the reduction of the box.

Lower torque requirements but higher speed. Heat generated will be the same, but with a much smaller rotor to dissipate it.

 

[bdkw1]

As soon as you add a portal box into that mix the CV center to bottom measurement becomes less critical to keep the CV's happy and the 4" of ground clearance you gain from the boxes allows you that much more usable uptravel before you get to the useless uptravel mark.

That's a lot of money to spend for 4.72" of ground clearance only to give up 2" of it to run a big rotor.

 

[bdkw1]

SXS’s get away with both inner and outer plunging CV’s

But how much steering angle do those have? Steering and droop angle does not compound. 25* of steering and 25* of droop at the same time does not equal 50*. With a NP 930, you can run 28* of droop and 32* of steering on a reliable setup.

Personally, I would never run a plunging CV in a steering situation.

 

[SLOWPOKE693]

Lower torque requirements but higher speed. Heat generated will be the same, but with a much smaller rotor to dissipate it.

If you are only trying to stop 3000lbs instead of 6000lbs your argument is a moot point because the heat generation is halfed.

 

[JR4X]

But how much steering angle do those have? Steering and droop angle does not compound. 25* of steering and 25* of droop at the same time does not equal 50*. With a NP 930, you can run 28* of droop and 32* of steering on a reliable setup.

Personally, I would never run a plunging CV in a steering situation.

That I don’t know. Wish it was more but it has enough. They can go full droop full stuff and full lock at the same time without having any bind. I’ve never burned one up and never broken just a CV or shaft.

I have broken them by breaking suspension, ripping wheels completely off and pulling them apart.

 

[bdkw1]

That I don’t know. Wish it was more but it has enough. They can go full droop full stuff and full lock at the same time without having any bind. I’ve burned one up and never broken just a CV or shaft.

I have broken them by breaking suspension, ripping wheels completely off and pulling them apart.

Ford outers like the F150 ones are good for 45*. The boots on the other hand don't like it for long.

 

[bdkw1]

If you are only trying to stop 3000lbs instead of 6000lbs your argument is a moot point because the heat generation is halfed.

If your rig is 3K ready to race you're not running portals

 

[SLOWPOKE693]

If your rig is 3K ready to race you're not running portals

Do we have any idea what those UTV's in the 4400 race weighted race ready?

A single seat chassis to eliminate 200+ lbs of co-dawg and tubing, and portals sized for UTV weights, not full size boxes meant for 6000lb 700hp and 42" tired rigs adapted to fit a UTV would make that weight easy to achieve.

 

[arse_sidewards]

With this inboard brake discussion...

Are any of the other Army dudes getting flashbacks of Humvees? Driving along, stop at an intersection, and the damn truck rocks back and forth a few times due to the slop in the CV's and portals.

Yeah so?

The late model 4Runners are making you soft.

How many times you think a race car is coming to a stop?

It simply doesn't matter if it's sloppy in a racing application or a commercial/mil application where the driver doesn't get a choice.

Jaguar ran inboard brakes for half a century. It was fine.

It would be amazing to find an off-the-shelf commercial truck or industrial machine part that could be adapted. But I don't know of anything with the angles we need... At least 50° at full torque and RPM, if not 60°.

Nothing can take "full" torque at max operating angle. It's a pure tradeoff. You want to make it handle X at full lock then it will necessarily be able to handle some multiple of that near straight line.

 

[arse_sidewards]

SXS’s get away with both inner and outer plunging CV’s

Does the shaft just float wherever or does it usually stay maxed out on one of the joints most of the time?

 

[arse_sidewards]

Lower torque requirements but higher speed. Heat generated will be the same, but with a much smaller rotor to dissipate it.

Higher heat differential = easier to cool though.

The second you get off the slow pedal a 700deg rotor is gonna drop heat a lot faster than a 300deg rotor.

 

[SLOWPOKE693]

Does the shaft just float wherever or does it usually stay maxed out on one of the joints most of the time?

BRB...

:goes out to the garage to check his Honda axles:

 

[JR4X]

Does the shaft just float wherever or does it usually stay maxed out on one of the joints most of the time?

My rzr the mid shaft just floats back and forth wherever it feels like it. When it’s sitting idle you can slide it back and forth about 2 inches.

 

[AgitatedPancake]

Does the shaft just float wherever or does it usually stay maxed out on one of the joints most of the time?

I saw a contraption somewhere where there were two male splined axle shafts connected to each other with a double female coupler. Then the coupler had long springs around the OD of the axle shafts pushing from both sides equally that kept the coupler centered. I don't know if that was something unique or standard, but seemed like an interesting idea.

 

[Yotota]

Yeah so?

The late model 4Runners are making you soft.

How many times you think a race car is coming to a stop?

It simply doesn't matter if it's sloppy in a racing application or a commercial/mil application where the driver doesn't get a choice.

Jaguar ran inboard brakes for half a century. It was fine.



Nothing can take "full" torque at max operating angle. It's a pure tradeoff. You want to make it handle X at full lock then it will necessarily be able to handle some multiple of that near straight line.

I'm not complaining about the rocking thing in a racecar, just bringing up an anecdote that popped into my head from my only experience driving inboard brakes and portals. Figured it was worth a laugh.

And yes, Jag ran rear inboards but the fronts were still hub mounted.

And yes, you're correct about the X torque at Y RPM at full lock. I was throwing out a worst case scenario.


I'm here to BS about trucks, not write a damn white paper about them.

 

[SLOWPOKE693]

I'm back.....

The axle shafts on my Honda have plunging CV's at the inner joints and are fixed outers front and rear.

After reading JRX4's response, I guess it's safe to say that some UTV manufacturers do their homework when figuring out the suspension geometry and others just wing it and throw band-aids at their mistakes. This may also explain why I see so many Polaris axles being changed at the track and why mine are still the untouched factory Honda shafts from 2019.