Outer Limits 4x4 Board

Ok tech heads, we all know about anti squat right and we all know that running your links parallel to each other helps right So when and what degree of angle differance does there start to be a noticeable differance in squat.
Also we all know that longer links seems to help with antisquat, so what is clasified as a long link, Or does it depend on chassis leingth, overhang behind diff, height of truck, weight up front, weight in rear, coil rate, tire side wall ect ect, of each truck.

I want some genuine replies. 8)

Stangerover explained it all for me and worked out how long to make the links and where to run them too.

It seems to work really well so give him a call or pm him.

bloody good topic. I think that anti squat has got so much to do with a rigs capabiltiy it isnt funny. It really makes the difference when driving uphill between a rig thats stable and you can get into the throttle and one that either hops or tips over backwards.

Theres so much involved in this that is hard to know where to start but there has been some good threads on pirate on the topic.

I think that the less antisquat the better which means parallel and horizontal links. The longer the links the better cause it means that the amount of anti squat that you have remains stable when your suspension unloads when you point up hill.

There are trade offs though. A lot of comp rigs in the US run a lot of antisquat and tight limiting straps which seems to work really well for the rock racing type of comps.

Ive only been out driving my rig once since i changed the rear link setup to end up with a lot less anti squat and it worked unbelievable. Its now way better than it was before, the difference is incredible.

Sam

On pirate they talk about how to work out the percentage of anti squat and people say that about 50% to 80% anti squat is a good number to work with.

Then there are the other crowd that believe the higher amounts of anti squat is better cause it gives you better hook up of the tyres when you accelerate (like a drag car which runs high amounts of antisquat) when you plant the throttle.

I think the best plan is to understand what anti squat is and what it does and then stick your head under different rigs, get a feel for how much anti squat they run and then see how they perform.

Dobbin runs a fairly high amount of anti squat where as antunac has a lot less. Overkills new rig doesent have much and tjpetes old rig did have a fair amount (mainly because of its lift).

Im still trying to work out what is best but there is just so many different things you can do to a suspension setup to affect how it works it makes it hard to see whats happening. But thats the beauty of 4wding.

Sam

I am hoping mine will be better too as b4 the links were pointing at eachother and on big hills the thing always wanted to lift wheels and flip.
The links are longer 5 degrees to the ground and almost parallel to each other.
The other prob I used to have was to shorter wheelbase, to heavy behind the rear diff and to light up front.

I think there is alot that contribute to antisquat, eg balance of rig, leinght of chassis even tire pressures.

I think that a good test is to drive up a loose steep smooth hill. Something that you almost have to winch. Before if I drove up it with some wheel spin the rear would start to cycle up and down. When I first put the big tyres on it was really bad. It would do it even on the silghtest incling if I drove with some wheel spin. Now with the better setup links it doesent move. I can just play with the throttle and steering the the rear doesent move at all. This is good cause it keeps the load off the drive train, keeps everything really smooth and makes it a lot harder to break stuff. Its also a lot more fun cause I can use more throttle and not break stuff.

If you want to see something with loads of antisquat you should see BJs rig. Like a monkey phucking a football as soon as he points up hill.

Sam

The info in the box onthe left is always the current information. So its got your current avatar, title, total post count etc and its the same on all your posts no matter when you posted them.

Sam

"CHEEZY" are you listening to wat sam is telling you ?????
or just inadvertantly looking around your screen !!!!!!!


nice topic change !!!!

Sam how would this thing go for anti squat ? ?

http://www.jeepsunlimited.com/forums/sh ... did=337534

Pretty good judging by this pic from the link you posted:


Double triangulated is good for eliminating axle steer, too

Hard to tell. You really need to look at the vertical spread of the chassis mounts cause a couple of inches difference at the chassis makes a lot of difference. I think the biggest issue with that rig is that its so tall. I would think that on the steep climbs and ledges that it would want to fall over.

Sam

Strange Rover wrote:
If you want to see something with loads of antisquat you should see BJs rig. Like a monkey phucking a football as soon as he points up hill.

Sam

YEAH

ROFL, ive never seen a mokey fucking a football, but i imagine it to be similar

Sam,
If you put smaller diameter and narrower width tyres on your rig with its current suspension configuration does it still perform better than stock geometry or does the decrease in available traction from the tyres change how much antisquat you can/could use?
How much weight have you got on the rear axle and whats your split fr/rr?
I was about to make some cranked rear arms but stay with stock geometry but am now thinking about your advise for lengthening the rear links...
Any advise?

Cheers
Daryl

Does anti-squat apply 2 leaf sprung rigs and can it b changed

softer or harder leafs

different spring rates

spring lengths

shackle length/angle

With playing around with anti-squat percentages, you also have to take into account instantaneous centre positioning, which can be a bastard to try and work out on a rig with a body and running gear in the way of your tape measure / straight edge, etc.. Easy to work out on the leaf sprung trucks with the ladder bar style torque rods, though..

Ok hypolux asked if it afected leafs and we got a yes answer to it afecting all the listed parts. So how do you figer out the antisqaut on leafs Also dose running a trouqe rod afect the antisqaut

derangedrover wrote:Sam,
If you put smaller diameter and narrower width tyres on your rig with its current suspension configuration does it still perform better than stock geometry or does the decrease in available traction from the tyres change how much antisquat you can/could use?
How much weight have you got on the rear axle and whats your split fr/rr?
I was about to make some cranked rear arms but stay with stock geometry but am now thinking about your advise for lengthening the rear links...
Any advise?

Cheers
Daryl

Going back to a smaller diameter tyre (say a 31) would decrease the amount of anti squat I have dramatically because with the smaller tyre the tyre/ground contact point (which is the point where the power is applied to the ground) is so much closer to the rig and is therefore so much closer to the instantanious centre of the links (which is where the power is applied to the chassis. Therefore the line joining the two points is so much more horizontal which giver less anti squat because as power is applied it doesent try to lift the chassis as much.

So it comes back to how much anti squat you think you need. Because having some anti squat is a good thing because it helps getting the power to the ground. Take drag racers. These machines run alot of anti squat because it gives them so much more grip for the launch. I would guess that v8 supercars would run a lot of anti squat as well for the same reason.

Now the steeper the incline, the more the rear suspension unloads, which gives you more rear lift, which in turn gives you more antisquat. Now at some point (of steepness of climb) the amount of antisquat that you started with will become to great and it will then get unstable and the rig will start to hop which is bad.

For example take two identical rigs, one with moderate anti squat and one with very low anti squat. You come to a moderately steep, loose dirt hill climb. For the guy that has very little anti squat to drive it he has to really get into it with the throttle say full noise second gear to make the climb with heaps of wheel spin where as the guy with more anti squat can just idle up the climb in first gear because the anti squat is helping him. I have this exact hill and it really is amazing to see what sort of rigs drive it easily and what has trouble. But take these same two rigs to a steeper climb with more rock and grip and throw in a ledge and a big hole on one side then the rig with more anti squat may become unstable and start to hop on the climb and wants to lift a front wheel and fall over backwards when it gets to the ledge and drops a wheel into the hole. Where as the guy with the little anti squat is still stable on the climb (and can still use heaps of throttle if he wants cause the thing wont start to hop) and when he gets to the ledge with the hole keeps all four wheels on the ground (doesent lift a front wheel) and drives it as well.

So IMO it does depend on what sort of stuff you drive but if you have problems with the rig hopping on loose climbs or lifting front wheels on off camber climbe or ledges or wanting to fall over backwards on the really steep stuff then you may have too much anti squat. (now the down side with less anti squat is that you will find it harder to do the more slippery less steep climbs like loose dirt or mud)


Oh yeah - this is all just my opinion.

Sam

hypolux wrote:Does anti-squat apply 2 leaf sprung rigs and can it b changed

softer or harder leafs

different spring rates

spring lengths

shackle length/angle

With leavs you got two things to worry about. You got axle wrap and anti squat.

Axle wrap is caused by the axle not being very well located. Main cause is soft springs. So soft springs, long springs, going to spring over axle will cause axle wrap. All these things are bad.

Increasing anti squat on leafs is caused by a highly angled rear shackle, going to spring over axle, and putting a track bar that is rigidly connected to the diff and is connect to the chassis with a vertical shackle. A long shackle will affect things to some degree (but IMO not directly but it iwll affect the setup when the suspension unloads on climbs, meaning a short angled shackle will turn into a not so angled shackle on a climb reducing the anti squat where as a long angled shackle will stay angled more as the sus unloads).

Sam

Just my $0.02 worth for those that may not have a good grasp of these concepts. Apologies for repeating any other's comments.

Weight is transferred to the rear wheels during forward acceleration. This tends to cause the rear to squat.

The geometry of rear links can be arranged so that during forward acceleration, some of the vertical load is carried by the links. This is called anti-squat.

100% anti-squat occurs if the vertical load carried by the links is equal to the weight transferred during acceleration and the rear height will not change. If ant-squat is greater than 100%, the rear will lift.

It makes no difference to traction if more or less vertical load is carried by the springs or the links. Essentially it is the weight transfer during forward acceleration that increases traction at the rear wheels. However anti-squat can change the height of the centre of gravity and therefore the amount of weight transfer. This is the most controversial point with regards to anti-squat.

Anti-squat can be measured (on level ground) as the ratio of the height from the ground to the instantaneous centre (of the upper and lower rear links viewed from the side) to the height to an imaginary line drawn from the point where the rear tyres contact the ground to a point at the front wheels that is the same height as the centre of gravity. Anti-squat is 100% if the I.C. is located on this imaginary line and less than 100% if it is below the line.

The I.C. (in the side view) is found by extending lines through both end joints of the upper and lower links to their intersection point. This is the point where the forces (tension in upper link, compression in lower link) can be resolved into horizontal and vertical forces. It is called the instantaneous centre because it is the point which the axle rotates about as it moves up or down relative to the chassis.

It is important to remember that the location of the I.C. changes continuously as the suspension moves (therefore called "instantaneous" centre). Longer links benefit because the change in the location of the I.C. is less than with short links.

IMHO the most credible supposition expressed on pirate for the advantage of high anti-squat coupled with a tight limiting strap is that as the rear lifts against the strap the effective spring rate becomes very high and the rig pitches around the rear axle rather than the centre of gravity thus making it more stable when climbing.