IRS or non IRS

[Immortality]

No. IRS squats (under load) which makes it hard to create weight transfer and depending on the IRS design when it squats it introduces camber which reduces the tire contact area.

 

[losh1971]

That makes sense.

 

[Deuce]

fixed

Cheers,
I was going to fix it after seeing losh's post at the same time. But didn't obviously.

 

[keith reed]

Have a look under a VU onwards ute and you will notice the difference straight away.

 

[losh1971]

Have a look under a VU onwards ute and you will notice the difference straight away.

That's interesting because VT and VX were terrible cars to tow with.

 

[NORTI]

That's interesting because VT and VX were terrible cars to tow with.

VX S2 changes weren't so bad

 

[_R_J_K_]

Why is it better in drag racing? I would have thought less wheel spin in an IRS?

Live axles are much easier to manufacture in different sizes and take more abuse than CV shafts. It's also much easier to modify and change the rear track and put your own mounting points on the axle tubes. There's also a few ways to centre it - watts, panhard, triangulation etc.... Basically you can make the diff fit the car instead of having to make the car fit the diff like you would with an IRS cradle. They also don't go around corners which is why it's not really that important that each wheel moves independently. Then there's them constantly keeping a 90 degree angle to the pavement like Immortality said.

The squat can be good and bad depending on how the angles of all your arms are setup, but yeah, if the car is slammed and no changes have been made to compensate, the amount of camber that will be introduced is usually detrimental. Other side of the coin is that squat puts weight on and digs the rear tyres into the ground.

Motive did a good video about removing anti-squat from Nissan subframes by moving arm pickup points down slightly. I believe the Traction Mod from MCA for 86s/BRZs is also similar to this. From about 8:00 onwards.

 

[Immortality]

That's interesting because VT and VX were terrible cars to tow with.

Part of the problem with towing is the way a trailer is loaded. Get to much tongue weight on the back of the car and it's going to tow like **** regardless. I've pulled some heavy weights with the Calais and it towed fine but always worried about the total weight and controlling it

Something else to try with an IRS Commodore is to hold the brake and apply some power and see what the back end the car does. Normally the back of the car will squat, the more power you apply the worse it gets.

 

[Deuce]

Other side of the coin is that squat puts weight on and digs the rear tyres into the ground.

Um, my thoughts was that the driveshaft rotation, through the diff, was effectively lifting the wheels up away from the pavement, and the gravity and weight is what is dropping the car down.
On the flip side, say a 70's Mopar with leaf sprung solid axle will fit slapper bars or caltracs, and the rotation force of the diff forces the tyres into the pavement harder and in turn lifting the car up during hard launches.

 

[Immortality]

Yup. with IRS when you apply power it is effectively turning the wheels up into the car against the springs.