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Location:
Hong Kong
Registered:
November 2003
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what's optimal setting for rear axle control arms?
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Tue, 20 July 2004 15:52
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Hi
Car type is KE70
I just custom made the existing lower control arms to adjustables and the lateral control arm too.
The lower control arms were used to adjust the differential ANGLE so that it is aligned straight in-line with the prop shaft to the gearbox. However I couldn't match the left-right off-set angle, since the axle is off-set from center.
We used a string to wrap around all 4 wheels to check toe, axle left / right bias and found it off-set in reference to the front as much as 1 inch.
Anyway, we adjusted the lateral control arm to match the rear tracks to front tracks.
I would like to ask also regarding my rear axle bending? assuming car faces forward and we're in the car facing forward. My rear left is -0.1 camber - good, no problem here. However, to my dissapointment, my rear right is +0.2 camber.
My rear left also has a little toe in, as oopose to right, NIL.
Alright, I'll leave it here, hope someone can enlighten me on this.
BTW, I took it up a mountain road and found handling improvement on the same road with higher speed.
These are the only thing I've done but don't know what else are they good for?
Many thanks in advance.
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Location:
Madrid - Spain
Registered:
August 2002
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Re: what's optimal setting for rear axle control arms?
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Fri, 23 July 2004 03:41
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Sounds like you have been having fun...
Ideally you want the diff flange to be at the same angle as the gearbox output flange. If the angle is out, it wont make much of a difference, just wear your front bearing a little faster.
Ideally you want the axle on centreline (which it looks like you have fixed with your adjustable panhard rod), zero camber and toe. You could fix the camber and toe by heating up the diff housing with an oxy and shrinking a side untill it line up but they don't seem too bad and you are just as likely to make it worse by heating it up.
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Location:
Hong Kong
Registered:
November 2003
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Re: what's optimal setting for rear axle control arms?
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Fri, 23 July 2004 14:06
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Thanks for your reply gold28
Say, since we're talking, I was thinking "why engines are tilted?"
I think for FR cases the real reason may not be engine power but instead to match the gearbox's output angle straight to the rear axle's input...
i.e. since the rear axle's input is off-set. This requires the gearbox in the front to be slightly off-set as well, hence when bolted onto the engine, the engine has to be off-set a little as well, and may be during the off-set manufacturing time, they found it necessary to tilt the engine to match everything properly.
Any take on this?
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Location:
Madrid - Spain
Registered:
August 2002
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Re: what's optimal setting for rear axle control arms?
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Wed, 28 July 2004 00:23
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I haven't really thought about this before, but at first guess I assume that you would want the crank center line to project through diff center line. This would minimize lateral loads on the diff due to the offset(and power loss/fuel use etc). This would also reduce the lateral loads on the uni joints, increasing service life.
Makes you wonder about those ridiculous 4x4's with huge lift kits installed.
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Location:
Ipswich
Registered:
May 2002
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Re: what's optimal setting for rear axle control arms?
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Wed, 28 July 2004 01:11
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OT: Hey Acoustic - emailed you but didn't hear back... How are you? Am going to be back in Malaysia for about a week in late August/early September, maybe can meet up?
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Location:
Melbourne
Registered:
January 2003
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Re: what's optimal setting for rear axle control arms?
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Wed, 28 July 2004 01:19
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"I just custom made the existing lower control arms to adjustables and the lateral control arm too."
Lateral ? the pan-hard rod ? or the upper trailing arms ?
What kind of joints ? rubber , pillow , rose ? where used .
Most people make the upper arms adjustable , because making the lower arms adjustable , normally make the arm shorter to get the correct pinion angle if the vehicle is lower that standard . Adding to the torque force on the arms and making the wheelbase shorter , not good for handling .
The pinion is offset for a torque equalization of the live axle , this is a direct relation to the torque force applied . Just making a straight line sometimes doesn't make it better , this is more trail and error . I found that going the opposite way worked for more dry weather traction , than wet for instants .
[Updated on: Wed, 28 July 2004 01:19]
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Location:
Madrid - Spain
Registered:
August 2002
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Re: what's optimal setting for rear axle control arms?
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Wed, 28 July 2004 03:08
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Ahh thats cool, so you intentionally build in some offset to counter the torque reaction on the live axle. Makes sense really.
The more you look at it the better an IRS is. 
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Location:
Hong Kong
Registered:
November 2003
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Location:
Hong Kong
Registered:
November 2003
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Re: what's optimal setting for rear axle control arms?
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Sat, 31 July 2004 16:11
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Hi fook
didn't get your email, please send again. yes, must meet up
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Location:
Hong Kong
Registered:
November 2003
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Re: what's optimal setting for rear axle control arms?
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Sat, 31 July 2004 16:16
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yes, lateral control rod = pan hard rod - according to manual
not the upper control arms = upper trailing arms
joints are original, hence rubbers
I only made the lower control arms adjustable, unfortunately I don't know if we set it shorter than original, but I'll take your word for it... I'm really not very good at all this...
For I've got shorter wheelbase now hey, not good hey
Can you describe more / explain about "going opposite" I'm just too new to all these handling issues.... and really needs to know what's going on with what
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