Panhard V No panhard rod.
#101
Posted 10 February 2008 - 12:04 AM
If you think about what happens when you lower the mount for the top arms or lower the whole rear suspension you should see how it forces the roll centre higher.
M@
#102
Posted 10 February 2008 - 10:59 AM
#103
Posted 10 February 2008 - 11:37 AM
M@
#104
Posted 10 February 2008 - 07:16 PM
#105
Posted 14 February 2008 - 09:31 PM
#106
Posted 14 February 2008 - 10:25 PM
#107
Posted 14 February 2008 - 11:08 PM
That's you is'nt it Darren.......wondered how long it would take you to get on here, hahagday guys, may have missed some of your points. jst letting you know. i use an adjustable watts linkage setup in my lx 4dr, and i highly recomend fitting some form of panhard or preferble watts linkage if your seeing track work. one problem with running either setup is. as was mentioned it lowers or tricks the car into having a lower rear roll centre. this will cause the front end of the car to sometimes react not in a psitive nature coz the roll centre is still wrong at the front. im working on correcting this in my own car.
Dave
#108
Posted 15 February 2008 - 09:25 PM
--------------------
Updates to come, watch this space........
Location: Perth
F@#$ing 'urry up !
Welby
#109
Posted 15 February 2008 - 11:03 PM
Dave
#110 _CHOPPER_
Posted 17 February 2008 - 02:25 AM
#111 _82911_
Posted 17 February 2008 - 08:13 AM
Practicallity and packaging almost always dictates that the CofG is higher at least in the front of a sedan anyway, which is what most of this is about.
A car with the CofG and roll centres at the same height will be very hard to drive "on the edge" it will be twitchy and unpredictable. Schumacher could probably handle it, but the rest of us would smudge it into the fence on the first high speed turn.
#112 _CHOPPER_
Posted 17 February 2008 - 09:55 PM
#113 _82911_
Posted 17 February 2008 - 11:18 PM
Rear @ 8" above ground.
with a ride height of 4"
Will take plenty of custom fabrication work to get them there though.
Realistically, if you can get the front anywhere above ground level @ 4" ride height you are doing well.
Rear put a panhard or Watts in it and that will define your roll centre height for you.
#114 _CHOPPER_
Posted 18 February 2008 - 12:56 PM
#115 _CHOPPER_
Posted 18 February 2008 - 09:38 PM
#116 _82911_
Posted 18 February 2008 - 10:07 PM
That is your "roll couple" and if it is too angled down in either direction it causes non linear weight shift and poor transitional handling. In short the car will handle like shit.
Too far down at the front will tend to understeer. and vise versa for the rear, unless of course you prop the offending end up with super hard springs...... Which is why most Racing Toranas run greater than 1000lbs up front.
#117
Posted 18 February 2008 - 10:19 PM
Dave
#118 _CHOPPER_
Posted 18 February 2008 - 11:26 PM
So the ideal solid rear suspension for an LH - UC would be a parallel 4 link with an adjustable watts linkage?
So assuming that:
(1) I'm happy with the spring/shock/sway bar combo and
(2) A tyre pyrometer indicates consistent temperatures across the tyres and
(3) I'm not using a mini/full spool or detroit locker
then adjusting the rear roll centre would then be the best way to alter understeer or oversteer?
#119 _82911_
Posted 19 February 2008 - 07:05 AM
Dave,
1000lbs or greater will almost always be required in a racing Torana. Why? Because it is near impossible to get the roll centre up high enough (closer to the CofG actually) so as you can drop the spring rate below that.
Chopper,
Yes the parallel with Watts is ideal.
I wouldn't make a roll centre change to dial out understeer/oversteer unless it was a BIG push.The problem with using roll centres to adjust car balance is that a small change in height can yield a large change in handling characteristics. The other reason you should use bars and springs to tune your under/over steer is that you are only changing one thing at a time when you make a bar change. When you make a roll centre height adjustment it changes the roll couple angle so the jacking effects are altered at BOTH ENDS of the car.
Is it getting complicated again?
#120
Posted 19 February 2008 - 09:33 AM
Adjustable bars would make all this much easier, but there is a few items ahead of them on the shopping list at the moment.
#121 _CHOPPER_
Posted 19 February 2008 - 11:52 AM
It still makes sense Greg. Just trying to work out what can and can't be done.Chopper,
Yes the parallel with Watts is ideal.
I wouldn't make a roll centre change to dial out understeer/oversteer unless it was a BIG push.The problem with using roll centres to adjust car balance is that a small change in height can yield a large change in handling characteristics. The other reason you should use bars and springs to tune your under/over steer is that you are only changing one thing at a time when you make a bar change. When you make a roll centre height adjustment it changes the roll couple angle so the jacking effects are altered at BOTH ENDS of the car.
Is it getting complicated again?
#122
Posted 19 February 2008 - 10:40 PM
Front @ 4" above ground.
Rear @ 8" above ground.
with a ride height of 4"
That seems to be the figures that keep popping up with guys who race these cars around circuits so that's certainly the sort of figures I would be shooting for.
Some go for a slightly higher than that.
M@
#123
Posted 19 February 2008 - 10:53 PM
best thing you can do is mount lower mount of the shock and the spring as close as possible to the outside lower ball joint, then you could reduce the rates.
#124 _82911_
Posted 19 February 2008 - 11:11 PM
Motion ratio on a Torana is 2:1
Meaning that a 1000lb spring will yield a wheel rate of 500lbs.
Keep in mind though that 1000lb is still a conservative number as I run 1600lbs in the front of my XU-1, and it turns well.
M@, the reason behind those numbers is that is what is achivable without a MAJOR re-engineer of the whole front end... (serious stuff as you know)
Hey Mick..... is the Commo consistent on both lefts and rights? Or does it understeer on one and oversteer on the other?
#125
Posted 20 February 2008 - 09:19 AM
Hard to say, at Phillip Island it understeers at Southern Loop and Siberia, both left handers, but there aren't really any comparable right handers,Hey Mick..... is the Commo consistent on both lefts and rights? Or does it understeer on one and oversteer on the other?
At the end of the day, I figure there are Commodore Cup cars with panhard rods going around P.I. in under 1.48 which is good enough to be on the front row of a state level I.P. grid so the panhard rod isn't too much of a limiting factor. Not as much as the driver anyway....
3 user(s) are reading this topic
0 members, 3 guests, 0 anonymous users