Anti Squat / Anti Dive

[Z()LTAN]

When using a 4link calculator that is designed around a rear 4link setup on a front 4link, do you reverse the antisquat figures? As if the rear was in reverse?

[Micka]

Just treat it as if it is the rear.

[uninformed]

the 2 things you need to know when doing AS are COG and Wheelbase. The 3 things you need to know for AD is COG, wheelbase and Front-rear brake bias....dont forget to look at your figures through bump and droop on Triage'd calculator.

are you saying that you can get your front links exactly the same as the rear. That is length, heights, seperation, angle etc?

[Z()LTAN]

Unfortunately no, with as low as i want it im running into clearance issues with the engine and chassis. The figures are much the same but link lengths, angle and separation differ slightly.

Im just trying to get my head around the fact that the front and rear diffs are torquing in opposite directions but the effect on the links/squat/antisquat are the same.

[MikeH]

It's confusing to me too. I thought about it for a while and played with some models with pins and cardboard.
with the front diff think about the direction he force is acting under acceleration, it's trying to pull itself away from the centre of the vehicle when you are on the power.
the rear is pulling itself away from the centre of the vehicle under brakes and pushing itself toward the centre of the vehicle under acceleration. so the results of the calculator are the opposite in some ways when you are dealing with the front.

so if you dial a lot of "traditional squat" into your front diff it will "squat" under heavy braking and do the opposite under heavy acceleration.

where I get lost is in deciding the relationship between "actual squat" in the front and rear axles. as in how much to put into each.
a traditional 2wd race car you want as much grip on the rear as possible to accelerate and the fronts just do their own thing.
but if you do that with our lack of a centre diff you end up with less steering traction because the inside front wheel is being forced to spin in every corner. End result is a vehicle that is only using one wheel to steer under power and wont go around corners. There is a really big budget 4x4 around which does this badly and he is just starting to address the problem.

COmpounding this is that once the inside front starts to spin it doesn't take much to keep it spinning, so all the torque goes to the rear axle and you suddenly go from one-wheel-steering-understeer to two-wheel-drive-style-oversteer still with only one front wheel steering. In some long fast corners this was an oscillation which was really weird to experience.

I found myself tending to stab the brakes to get some weight on the front wheels to commence the turn and loosen the rears then get on the gas before the weight rebounded off the fronts. At least I think that was what was going on. (to add even more confusion there is no such thing as brake bias when the transfer case is also transferring your front wheel braking torque to the rear wheels)

so after all of these conflicting forces I'm pretty much lost, I'm leaning toward setting the rear up neutral and trying to give the front as much grip as possible, when you add some weight transfer into the mix it should end up relatively neutral with a good chance of going where I point it in the tight stuff.
Perhaps someone who has actually got their head around all of the calculations can chime in. I may be way off track.

[-Scott-]

I'm very much a N00b when it comes to squat/anti-squat, so feel free to ignore this (that's if you've bothered to read this far. )

With my lack of knowledge, I found MikeH's post quite interesting (and well written for this N00b - thanks). But it did get me thinking about how traditional (road going 2wd) race cars tune their suspension to keep the driving wheels on the tarmac i.e rear drive will lift a front wheel, front drive will lift a rear wheel.

Obviously, road racers aren't as interested in travel as an off-road racer, so perhaps that environment is simply too different, but should a 4wder be leaning towards a fwd setup rather than rwd?

[brooksy]

I think in your last paragraph Scott you nailed the limited relevance to circuit racing (2wd) to offroad. The suspension cycle has a big bearing due to the COG changes depending on the vehicles travel. The other telling factor is the terrain or more to the point the changes in terrain.
On bitumen the variables are limited, in offroad especially what we are more so leading towards with the OP's question, large changes in terrain, the simple adjustments have to accommodate large variables. The thing is with the Combined suspension & terrain variables you need to accept that what you do is a compromise not a definitive result.
With the front setup with regard to suspension geometry or link placement I can only suggest keep in mind that the forces are obviously acting against the links & travel arc. If you can have the travel arc at ride height at a neutral position relevent to link travel arc this is always going to prove itself a huge benefit. It will make climbing characteristics as well as high speed loading much simpler to predict as it will help reduce or eliminate initial reverse of direction loading. From that point keep your Roll Centre in mind.


brooksy

[TheBigBoy]

I think in your last paragraph Scott you nailed the limited relevance to circuit racing (2wd) to offroad. The suspension cycle has a big bearing due to the COG changes depending on the vehicles travel. The other telling factor is the terrain or more to the point the changes in terrain.
On bitumen the variables are limited, in offroad especially what we are more so leading towards with the OP's question, large changes in terrain, the simple adjustments have to accommodate large variables. The thing is with the Combined suspension & terrain variables you need to accept that what you do is a compromise not a definitive result.
With the front setup with regard to suspension geometry or link placement I can only suggest keep in mind that the forces are obviously acting against the links & travel arc. If you can have the travel arc at ride ride at a neutral position relevent to link travel arc this is always going to prove itself a huge benefit. It will make climbing characteristics as well as high speed loading much simpler to predict as it will help reduce or eliminate initial reverse of direction loading. From that point keep your Roll Centre in mind.


brooksy

X2 although some extremes work better in some situations with 4x4s. keeping it predictable is very important.

[Z()LTAN]

Ive been keeping the links at flat and as long as possible to reduce link arc, everything is very tight through the axle arc.

Ive been aiming for around the 85-90% anti squat so the effect on the suspension under brakes/acceleration is minimal. I do however have the ability to change the squat percentages from around 60-120% by moving some link holes.

[brooksy]

Also remember the calculator is not the "be all end all" of suspension setup & is often stated by many as just a "Base guide" to a suspension setup. Squat & Dive can be combated by shock tuning as suspension rate, real world travel percentages, bumps, etc isn't considered in the numbers which is why it is really only an initial step (be it an important one). So don't be concerned about chasing an exact figure, the calculator is there only to help make sure you are on the right track.


brooksy

[Micka]

Also remember the calculator is not the "be all end all" of suspension setup & is often stated by many as just a "Base guide" to a suspension setup. Squat & Dive can be combated by shock tuning as suspension rate, real world travel percentages, bumps, etc isn't considered in the numbers which is why it is really only an initial step (be it an important one). So don't be concerned about chasing an exact figure, the calculator is there only to help make sure you are on the right track.


brooksy

^^^^^^
This is probably the most important part of getting your head around using the link calculator.