[Gwagensteve]

So I threw a comment into the mix on zuckerbook that was a bit deliberately controversial, but I do, genuinely, believe, and the more time I'm spending working with 4WD's, the more I believe it.

There is no difference between an effective on and off road suspension setup.

(I'm not talking about making a 4X4 circuit race car - just making the car not feel horrible on road)

I just think we've all brainwashed ourselves that our cars have to handle badly in order to have the best possible off road performance. I used to think that was inevitable, but I don't now.

What I do think is that cars that behave badly on road also behave badly off road, but we put up with it, or have very low expectations of off road handling because so long as it flexes it must be good, right?

Going through all of the possible suspension parameters, the only one that I can see as a conflict is roll centre. High roll centres aid stability and predictability in off camber situations, but on road they act like antiroll bars and "lock" the suspension up which reduces traction, increases oversteer (in the rear) and adds to instability.

There is one other "sort of" conflict, which is that on road we have more traction, which applies more force into the suspension at speed, which can exacerbate poor behaviour. I'm not totally buying this because when we drive our cars int he bush on high traction surfaces like really hard pack dirt or rock, you'll often see the car behaving badly (poor axle control, tramp etc) because it doesn't work properly under high grip.

I'd like to think this can spark some discussion amongst us. I' starting to see more conservatively built cars that are quite roadable performing just fine, alternatively, look at something like ultra4, where cars can crawl and work on high traction/off camber situations, but can still carry speed.

Here's some parameters. have a think about them and whether they're opposite or exclusive of off and on road use.

Roll stiffness
Roll axis
Roll centre
Centre of gravity (side/side, front/back)
Caster
Instant centre "antisquat"*
low speed shock valving
high speed shock valving
compression travel
droop travel
spring rate

[Gwagensteve]

Oh, I put an asterisk next to antisquat because I'm not convinced it's relevant on or off road. I say that because everyone seems to get obsessed about it, but when people ask for critique on their link numbers, people pipe up with massively different antisquat numbers and claim they work fine. radius arms basically have infinite antisquat, while some link suspensions get close to squat and still work.

I do know that with a leaf car, a vertical shackle creates more antisquat, but that is detrimental to general vehicle behaviour so stressing about antisquat might not be worth it.

I have heard an interesting summary of antisquat though - high antisquat basically means the axle is being pushed into the ground under torque, whereas if the car squats, the axle is being pulled towards to body. that's a good description of how high antisquat aids traction.

[alien]

Love this and I'm 100% on board.

While the UFO was a compromised setup, what isn't? It passed the lane change test and handled better than a stock sierra in every way. It kept up with heavily modified bigger 4WDs (like a twin locked patrol on 38's) running 31" tyres (also twin locked) but also was faster than most small hatches on the road, and had no trouble doing 50km/hr around a 90 degree corner (in the dry).

Testament to your statement also, see Shandy92's bucks party from many moons ago, where a stock hyundai excel drove the powerlines track out, back and made it home to be sold the next day:
https://www.youtube.com/watch?v=_Ile94sQK5s

I've driven a number of front wheel drives offroad and all went FAR further than you'd expect, with ground clearance almost always being a burden before lack of traction.

Now, where'd I put that popcorn?

[shep]

I am very happy with the way my current toy car drives both on and off road.
It was a bit of a pig on road until I got the castor and control arms right, that fixed how it behaves under brakes.

Adding the rear antirock seemed to get all the other suspension components working as a unit off road. The difference was
Quite pronounced when I fitted it.

Planning my next build now and even though the new car has electric sway bar disconnects
I think that will all get binned for a pair of antirocks.

[shep]

alien wrote:

I've driven a number of front wheel drives offroad and all went FAR further than you'd expect, with ground clearance almost always being a burden before lack of traction.

Now, where'd I put that popcorn?

Before the 60 series was made there wasn’t a family friendly 4wd so it was all 2wds.
The places we went when I was a kid in a XA wagon now are considered major expeditions. Just to drive from Darwin to Adelaide was a 1400km dirt track. Was a brilliant time to be a kid

[sideways]

I think in terms of ultimate offroad capability in large ruts you want minimal up travel, narrow bumpstop spacing, a minimum of roll stiffness no impedance on downtravel for maximum pressure applied to the drooping wheel. Just like Bills Landy. That is going to give a poor ride, it's going to get unsettled around corners and it is going to have a lot of body roll. In short, it will handle poorly.

Off road capability is highly variable too, Bills Landy would suck on sand. All of it's special suspension tricks do just about nothing there, even if it had the power it couldn't put it down and cover rough ground at speed. Flex acheives little on sand but the ability to build and keep momentum is everything. If you were building an ultimate capability sand car it would handle well, that's just a factor of the terrain.

Still somethings like Bills Landy or a rock crawler are totally 1 dimensional. A bulldozer is a fantastically capable vehicle but you wont commute to work in it. That's why ultra4 or dragweek capture our imaginations.

Gwagensteve wrote:

Going through all of the possible suspension parameters, the only one that I can see as a conflict is roll centre. High roll centres aid stability and predictability in off camber situations, but on road they act like antiroll bars and "lock" the suspension up which reduces traction, increases oversteer (in the rear) and adds to instability.

Is a high roll centre really more capable? It is only more capable because our COG is high. With high roll centre it will lean less on side hills but then under roll/articulation it will push the body and thus cog over to the wrong side. I think a high roll centre car feels better offroad, the ultimate capability answer would be low roll centre and equally low COG but that's impossible whilst providing adequate clearance. The problem with high roll centre on road is the jacking effect like a single A Arm with side loads. Ultimately it's not that extreme but it will load up on the outside edge of the tyre and try to pick up the inside.

If we're talking more mild offroading then I don't think handling/capability is exclusive at all. Although very mildly modified compared to most my Jimny is miles better than a stock one offroad and it both handles and rides better too, same with my Sierra. Can either of them do anything at Bills block? Probably just get up the driveway.

Define poor handling though? I think poor handling is a car that can't corner comfortably at reasonable road speeds or suddenly loses traction with no warning. Everyone thinks a 6" lifted GQ with no swap bars handles poorly but I've driven a fair few and they all handle just fine unless you really want to throw them around, even then it's just body roll. It's not like they're going to suddenly loop out on you or roll over with no warning. That said, are rolly 6" lifted GQ actually that capable offroad? Eh, maybe in sand or mud.

Even a series land rover or LJ handle just fine if you understand the vague steering. Even with the ultra soft suspension and bartreads I can comfortably corner at higher speeds than the speed advisory signs in the LJ and it's never bitten me. Some people who have driven the LJ think it handles terribly but it's not the handling that is bad more just the steering. It takes a bit of practice to understand the vagueness. There's actually a lot of feel and response in it, you just have to understand how to work it and drive with your finger tips.

[missmyljdaze]

sideways wrote:

A bulldozer is a fantastically capable vehicle but you wont commute to work in it.

am I evil for thinking the only thing better than a dozer for commuting - is a universal carrier

[Gwagensteve]

Good points sideways, especially about roll stiffness.

Bill's Wildfing is an interesting case. Bill road drove it for many, many years in it's current suspension configuration. (It also has reverse Ackerman, like an old tractor). I'm sure it drives fine for it's weight and power, as it can't actually body roll far - the compression side of it's springing is very stiff and it has little compression travel. In this case, all things considered, it's offroad focus probably isn't impeding its road performance much - it did start out as an SIIA landcover. .

However, as you point out, it's off road performance is so one dimensional as it sits it's not a good example. Like all cars with uncontrolled travel, it goes to pieces if it needs any momentum to clear an obstacle. Bill's block rarely requires that though. on something like cockpit creek track where wheel speed, momentum and compliance are required to maintain traction, it would be awful. If it had enough horsepower to carry speed on road I'm sure it would be terrible.

I also have no issue with body roll on road, (says the guy with a Discovery 1) and I don't think it's a handling problem, it's a perception issue

I do also think people have a strange concept of what handling is. Most often they associate it with crisp turn in and high traction, but a car with appalling handing can have both of those, like a WRX. I haven't driven an LJ any distance, but Sierras don't handle badly at all, they just have slow turn in and low grip. The biggest problem I see with a Sierra (other than slow and vague steering off centre) is they're typically harsh riding which hurts traction, and once an owner puts big, heavy tyres on them, they have too much dry grip which makes them edgy. They're much better with less tarmac grip.

Anyway, that's a bit of a diversion. I think we're broadly agreeing that off road and on road capability aren't necessarily different things and/or exclusive.

I think lots of people associate capability with flex alone and will pay no attention to suspension behaviour at all. The more attention you pay to suspension behaviour the better the car will drive on and off road. It's hard to achieve good suspension behaviour with a leaf sprung sierra because the leaves locate the axle, but making the steering looser or under-damping the rear suspension on the grounds of "more flex" win't make for a better, or more capable car.

[MrRocky]

What some people consider hardcore wheeling others would consider a chicken track.
Alot of cars seem to handle worse than they have to onroad for no real gain offroad, you also have to remember sierras are a bit different to most 4x4s as well.
Ive driven most publicly accessable tracks in wa including bobs hill in 2 minutes running 2" efs susp and skinny 32" tyres.
Correct gearing, selectable lockers and efi is probably the most beneficial offroad with the single biggest factor being seat time and learning how to actually drive a sierra.

[Gwagensteve]

MrRocky wrote:

Alot of cars seem to handle worse than they have to onroad for no real gain offroad.

I guess this is my point. (we're a bit outside of tech talk now, but I think it will get back on track)

I'm not sure if it's careless modifications, laziness, ignorance, or the "tough guy sticker" effect.

The "ignorance" thing is interesting, I think. when I started messing around with Sierras, it was pre-internet. we really only had magazines and stuff we were seeing driving around. We didn't know better and say, extended shackles, for example, just seemed like a no brainer. There isn't really an excuse now with the amount of information readily available, but people still want SPOA and whacky shackles etc because it's perceived as the easy way to mad flex and that's good right - because that's what everyone tells everyone. Hell, how many photos of my car have I posted flexed up - because I'm proud of it and that's what people like to see - but it's really hard to make a car flex well and still work effectively. That flex is a byproduct of wanting to make the car balance properly, which makes the car easier to drive and trust- that's a boring story.

I think the "tough guy sticker" effect is the same reason it's popular to drive around town with four maxtrax and a hilft on the roof of a brand new Ranger. In Suzuki culture it seems to be at it's worst in the US where it appears necessary to have a SPOA, whacky shackles and -44 rims to run 31's and drive easy trails. Maybe it reinforces the owner's credibility to have to manage an awful car to drive - it shows devotion to the cause of 4WDing.

Maybe there's another thing going on too. A car that's behaving badly - lifting wheels and pin balling all over the place, for example- is "spectacular," and I think some people (and every advertising executive) associate that with capability - it's "send it" culture. When you add the last point and this together, maybe that's an explanation for why people are willing to degrade their cars handing and suspension behaviour for no benefit.

[MrRocky]

Its all relevant to the kits people sell as well.
My gu ran 6" lift size shocks but only had 1.5" of lift
A suspension shop or facebook would tell you this wont work, but if you add some bumpstops, hyperflex arms, 35" tyres and raised shock towers you have a standard looking car with a low cog that will outperform the big lifted fancy cars offroad and handle much nicer onroad.
Admittedly i didnt run a front swaybar so handling was somewhat compramised over standard but a stiffer rear spring seemed to allieviate it to a comfortable degree onroad.

[Gwagensteve]

I had to think about this a bit.

sideways wrote:

Is a high roll centre really more capable? It is only more capable because our COG is high. With high roll centre it will lean less on side hills but then under roll/articulation it will push the body and thus cog over to the wrong side. I think a high roll centre car feels better offroad, the ultimate capability answer would be low roll centre and equally low COG but that's impossible whilst providing adequate clearance. The problem with high roll centre on road is the jacking effect like a single A Arm with side loads. Ultimately it's not that extreme but it will load up on the outside edge of the tyre and try to pick up the inside.

Having driven my car with no other change than raising the rear roll centre, I can say categorically the car is more capable with a higher rear roll centre. My car used to body roll significantly from the rear and this would make the front unload. As the front unloads, the COG at the front rises quickly and the car would start to flop over.

Thing is, by japanese 4WD standards, I already had quite a high rear roll centre



And in fact, I think I only raised it about 100mm, but I think the closer you can get roll centre and COG the more stable the car.

Here's my car at it's absolute worst once it was coiled both ends. loose coils, low rear roll stiffness and low rear roll centre, and short springs. This is very steep and off camber, but the suspension is behaving terribly here. - it's almost totally unloaded. It was OK on the road, but understeery, rolly, and would pick up front wheels like a lifted patrol. Whilst I hadn't specifically chased flex at the expense of everything else, I hand't paid enough attention to limiting flex either. It also had almost no front compression travel. If I got it out of shape enough on the tarmac, I'm sure it would have looked like this too, shortly before it killed me.



but on level ground, It was all hektik



I limit strapped the car and that helped keep it more balanced, but I was still unstable and unpredictable on side angles until I raised the rear roll centre, which, as I explained, I did with no other changes. The car was much more stable on side angles. The effect was very significant.

[vet 180]

If you have driven a polaris rzr or something similar on and off road it would indicate they are not exclusive

Sent from my SM-N960N using Tapatalk

[sideways]

Gwagensteve wrote:

Having driven my car with no other change than raising the rear roll centre, I can say categorically the car is more capable with a higher rear roll centre.

You've missed the point of what I'm saying. To be very clear, raising the roll centre closer to the COG will improve capability.

What I'm saying is high roll centre irrespective of COG has no benefit to us. There is nothing about a high roll centre that intrinsically makes the car more capable, the added capability is from moving it closer to the COG. Of course it would be of far more benefit to move the COG closer to the roll centre but that's generally impractical.

I'd be interested in driving a vehicle with the roll centre higher than the cog, that would certainly take some getting used to.

A high roll centre has well understood handling negatives but then it depends what you call poor handling, I think we've defined it as good enough to drive normally on the road.

[Zook_Fan]

I'm late to the party but love this type of discussion so lets play.

Regardless of where you are driving the limiting factor of forward momentum is traction. The key difference I can identify between on-road and off-road is the angles that we apply force to a vehicle, on-road we apply side loads to the vehicle creating body roll and off-road we drive through creeks, up hills, etc. making the car bounce around. The "failure mode" of any vehicle is a loss of traction by not enough downforce on the tyres. Either because we have exceeded the traction limit of a mobile car causing over/understeer or the tyre grip has remained high while a sideways force has rolled the COG far enough to cause the vehicle to roll.

We really want a vehicle to oversteer/understeer rather than the roll in pretty much all cases. Imagine you are travelling along the side of a hill, the car can either loose traction and slide sideways down the hill or the outside tyre grips and the car rolls over that tyre. The difference between these two scenarios is that in the first case all 4 tyres are still sharing the load of the car, you have more ability to make a change in direction and wheel speed versus the second scenario whereby the two tyres that were on the high side of the hill effectively reduce traction to 0% and the outside 100% of vehicle weight. Winding ruts/creek beds is just this scenario occurring over and over.

Looking at your dynamic variables this is my approximation of how they work to achieve the above scenario.
Roll stiffness - Stiffness is more about how the car feels than how it dynamically drives. A spring does not prevent load transfer, it is just a variation of displacement for a given load. A car with low roll stiffness will feel loose but the outside tyre experiences a similar force for a given cornering force than the same car with a higher roll stiffness. Considering feel is a big part of how we drive sway bars can make or break our driving experience. Roll stiffness can take away from travel in two cases - the spring is too stiff or it causes binding. I think stock sway bars generally bind at the extremes we want, aftermarket bars have more travel and are tunable.

Roll axis - I think this one is big in an off-road car and potentially it is the reason that you felt a gain in handling from raising the rear roll centre. Controlled front axle flex is generally far more difficult to achieve. The atypical failure of a car with a bunch of flex is when it is in a creek bed, it drives up the bank from an angle, the front does not flex and the back of the car drops to 100% down travel, car flops over. The roll axis compared to the normal plane goes up very quickly as the front suspension heads up the bank and the roll is biased to the rear of the car. In this case roll stiffness helps to overcome how far it unloads so again it feels better and the spring may slow the rate of change but that outside tyre is extremely loaded while the inside is not. The roll axis of an off-road going vehicle should aim for higher in the rear than the front if it is going to be spending any time climbing.

Centre of gravity and roll centre - already covered well above but the relationship between the two will dictate the direction that a vehicle will roll and by how much for a given side load. The side to side centre of gravity is interesting, particularly in the Sierra world where we are working with low weights. I would posit any vehicle would drive better if it were balanced, regardless of direction.

Caster - along with Camber (which we generally can't control) a proper alignment will make any driving experience better. A Sierra is designed for manual steering with a stock caster of -3.5 degrees. A-arm off-road suspension seems to start with almost double that much. I don't think it would be a problem to have a Sierra that wants to self centre off-road. Although the more caster you have the more contact patch on the leading edge of the tyre starts to angle into the turn. That would be interesting to play with on a car with 90 degree approach angles...
Instant centre "antisquat"* - Lower seems better than what most people expect. The likes of Jesse Haines has often commented that his antisquat for high single seat crawlers is down around 50-55% if I remember correctly. Go fast guys are about the same. There are other tunable ways to make the suspension do what you want than by binding it in the design.

high and low speed shock valving - I get this backwards often but low speed valving is for human input control (brakes, steering, accelerating) and high speed valving is for environmental input control (hitting a rock, road variation)? I believe there is plenty of gain to be made here in Sierra land. Instead of developing shocks that work well we were investigating the cheapest shocks possible from other cars that could bolt on with a compromise. I think Ultra4 is the definitive case that shock valving that works for going fast can work in technical trails.

compression travel - Generally underrated
droop travel - Generally overrated

spring rate - As I said above, a spring is only responsible for holding a load at a specific height. In of itself, it is not a tunable device. I subscribe to the theory that every spring should be responsible for the task you want it to do, not several. The springs between the diff and the chassis responsible for carrying the load of the vehicle should be specified so that they do not bind at the bottom of your travel, have a small amount of preload at the top of you travel and hold the vehicle at the static height you require. If it only fills those requirements it is going to be a fairly light spring. Then using dampeners to control vehicle dynamics through valving and using sway bars to control roll stiffness you have a more complete suspension package that allows springs to be application specific.

What is your take on that?

[sideways]

Bravo good sir!

[MrRocky]

Your creek bed example sounds like you are describing a jimny offroad. Front not flexing, rear unloads, car flops over

[Gwagensteve]

sideways wrote:

Gwagensteve wrote:

Having driven my car with no other change than raising the rear roll centre, I can say categorically the car is more capable with a higher rear roll centre.

You've missed the point of what I'm saying. To be very clear, raising the roll centre closer to the COG will improve capability.

What I'm saying is high roll centre irrespective of COG has no benefit to us. There is nothing about a high roll centre that intrinsically makes the car more capable, the added capability is from moving it closer to the COG. Of course it would be of far more benefit to move the COG closer to the roll centre but that's generally impractical.

I'd be interested in driving a vehicle with the roll centre higher than the cog, that would certainly take some getting used to.

A high roll centre has well understood handling negatives but then it depends what you call poor handling, I think we've defined it as good enough to drive normally on the road.

I disagree. (Road) race cars run their roll centres significantly below their COG - because doing so maximises traction to the inside wheels when cornering and separates suspension movement from body roll - body roll being dealt with by COG, spring rate and roll stiffness. There's no way the centre of gravity of a mark 2 escort is level with the centreline of the axle.



The most stable off road cars built, Rock buggies, do appear to run the roll centre well above the centre of gravity. (especially when you consider they typically run water in the tyres)



So I'm pretty satisfied to say for low speed/high angle off road use, raising the roll centre irrespective of any other factor improves capability.

[Gwagensteve]

Zook_Fan wrote:

Considering feel is a big part of how we drive sway bars can make or break our driving experience. Roll stiffness can take away from travel in two cases - the spring is too stiff or it causes binding. I think stock sway bars generally bind at the extremes we want, aftermarket bars have more travel and are tunable.

I see swaybars as more of a workaround due to other compromises - case in point - the obsession the japanese have with designing coil suspension around leaf sprung chassis designs, resulting in inadequate rear roll stiffness. A clean sheet design should be able to be designed without the need for swaybars, but subsequent revisions might make them necessary - two cases in point - the Land Rover coil suspension design was just fine until two compromises were introduced: the design of the discovery roof required it to be made in steel, and fashion dictated an increase in tyre width - raised COG and increased lateral grip meant the suspension design was overwhelmed. Also, the original Lotus Elise did not have swaybars, but as power and grip increased, they were required.

Quote:

Roll axis - I think this one is big in an off-road car and potentially it is the reason that you felt a gain in handling from raising the rear roll centre. Controlled front axle flex is generally far more difficult to achieve. The atypical failure of a car with a bunch of flex is when it is in a creek bed, it drives up the bank from an angle, the front does not flex and the back of the car drops to 100% down travel, car flops over. The roll axis compared to the normal plane goes up very quickly as the front suspension heads up the bank and the roll is biased to the rear of the car. In this case roll stiffness helps to overcome how far it unloads so again it feels better and the spring may slow the rate of change but that outside tyre is extremely loaded while the inside is not. The roll axis of an off-road going vehicle should aim for higher in the rear than the front if it is going to be spending any time climbing.

I don't think the behaviour your'e describing has much to do with roll axis, but lots to do with roll stiffness and roll centre. Pretty much all 4WD's have a lower front roll centre than rear. What you're describing is a car with low rear roll stiffness and high front roll stiffness. This will either be because of engineered in compromises by the manufacturer, as I mentioned previously, or because the owner has built a hektik teal-slack spec linked back end but left the leaves or stock radius arms in the front.

I don't believe the roll axis rises in the front when the vehicle is climbing unless the front is already oversprung for lift or has high roll stiffness inherently and unloads - the suspension "straightens out" - but as has been discussed, a high roll centre isn't inherently a bad thing, it's more that the when the front unloads and straightens out the GOG goes sky high, traction falls and the front end starts to follow the camber of the track rather than going straight up the hill.

Quote:

What is your take on that?

There some of my take.

[Zook_Fan]

Gwagensteve wrote:

I see swaybars as more of a workaround due to other compromises - case in point - the obsession the japanese have with designing coil suspension around leaf sprung chassis designs, resulting in inadequate rear roll stiffness. A clean sheet design should be able to be designed without the need for swaybars, but subsequent revisions might make them necessary - two cases in point - the Land Rover coil suspension design was just fine until two compromises were introduced: the design of the discovery roof required it to be made in steel, and fashion dictated an increase in tyre width - raised COG and increased lateral grip meant the suspension design was overwhelmed. Also, the original Lotus Elise did not have swaybars, but as power and grip increased, they were required.

In both of those cases the net outcome is that mechanical grip has increased over the original suspension design which is an ideal outcome. I believe that a clean sheet design would be foolish to emit sway bars purely for the fact that they provide tuning to the roll stiffness of the suspension for different grip and loading cases. In a light vehicle the passengers can make up 15-20% of the weight of the vehicle and in a four wheel drive we typically place them fairly high. This weight is variable based on the person, whether you have a passenger or you have people in the back of the car too. A sway bar gives you provisions to control the car. Will most people tune that tightly? Nope. But will it make for a better handling vehicle both on and off-road? I think so.

Quote:

I don't think the behaviour your'e describing has much to do with roll axis, but lots to do with roll stiffness and roll centre. Pretty much all 4WD's have a lower front roll centre than rear. What you're describing is a car with low rear roll stiffness and high front roll stiffness. This will either be because of engineered in compromises by the manufacturer, as I mentioned previously, or because the owner has built a hektik teal-slack spec linked back end but left the leaves or stock radius arms in the front.

I don't believe the roll axis rises in the front when the vehicle is climbing unless the front is already oversprung for lift or has high roll stiffness inherently and unloads - the suspension "straightens out" - but as has been discussed, a high roll centre isn't inherently a bad thing, it's more that the when the front unloads and straightens out the GOG goes sky high, traction falls and the front end starts to follow the camber of the track rather than going straight up the hill.

I think there's more to it than roll stiffness. Although as I think on it a large part of this is weight transfer. I still subscribe to my roll axis theory somewhat; I think the plane at which the suspension needs to be analysed is the normal plane, 90 degrees from the vertical. As the front suspension goes up a hill, the front roll centre rises with respect to the rear, raising the roll centre and changing the behaviour of the car with respect to gravity. It doesn't change in regards to the force inputs from the car but it does from environmental forces. It can be overcome through high rear roll stiffness but I don't think that is the cause or really the cure. Does the rear roll stiffness have to be high enough to prevent an unequal displacement of suspension from the front with ~100% of the vehicle weight?

A different question on the same line of thinking, for an on-road vehicle is there a case where you would consider 1 or 2 wheels being off the ground not a failure of the suspension? And do you consider lifting a wheel to be a failure of the suspension in an off-road vehicle or is it more of a non-issue because dynamically we've solved the problem with locked differentials?

[alien]

Zook_Fan wrote:

A different question on the same line of thinking, for an on-road vehicle is there a case where you would consider 1 or 2 wheels being off the ground not a failure of the suspension? And do you consider lifting a wheel to be a failure of the suspension in an off-road vehicle or is it more of a non-issue because dynamically we've solved the problem with locked differentials?

Yes. It's legally defined for on-road. Lane change/swerve testing defines a fail as the car lifting a wheel or hitting a cone. The difference between on and off (largely) is speed. Lane change test is done at 100km/hr. Offroad for the average bear you'd be lucky to hit 50-60 occasionally unless you were belting it down a hard beach or entry track. Sure, locked diffs solve a bit of that problem, but on the road we have LSDs too, so they're much the same solution. The difference however, is that offroad, lifting a wheel off the ground and still maintaining enough momentum to move forward and get it back on the ground again results in progress on the track. On the road, lifting a wheel is EXACTLY the same on almost any front wheel drive - which often cock a back leg when being pushed hard around a corner... But they're operating at the absolute limit of traction at that point. In either situation, the less time a wheels spends in the air, generally, the better =)