Kinematic issues .... continued.
04-16-2008, 10:55 PM
#1
Rennlist Member
Thread Starter
Kinematic issues .... continued.
My recent thread on the kinematic angle was prompted by several issues, the net effect of which is to make its adjustment a reasonable DIY if an alternative is not readily available - which is my case: the most pressing of these issues was the discovery that the RR KE eccentric was loose and flopping around ......
Why and how that unusually designed eccentric came loose led me to a solution that may be of some interest.
Background: an alignment done using the KE gauges at a dealership resulted in the LR camber link being at max. length to achieve a minimum camber of -1.5 deg .... but the KE gauges read an acceptable < 1.5 SKE. ROW Sport spec is -1.3 (1, 20'), suggesting that there should at least adequate eccentric travel to make the wheel stand more upright. Clearly not correct, but close enough, so I accepted that as a reference point since the RR toe, camber, and KE were completely screwed up.
Anyway, the RR KE eccentric came loose after having made the corrections discussed previously: to make a long story short, we reset the KE eccentric again and locked it down at a local alignment rack after equalizing both rear cambers at -1.5 deg:: that eccentric was loose again by time I made it 10Km home , and the RR camber was -2.2 deg
.
After hoisting the car, and removing the wheels, it became apparent why the KE link was loosening. Rather than using a conventional eccentric as used in the toe and camber links ( to the left in the close up below), it uses a disc with a keyway ---- and a horizontal slider in back that traps a locknut: this slider was sticking within its rear channel, leaving the front adjuster to move the through bolt off a perpendicular line from the face, ie., " cockeyed " in the channel. Such a bolt will vibrate loose in minutes ..... and it did!
Both KE adjusters were removed today, and the keyways for the rear sliders were buffed with a scotchbrite pad ( with contortion, one finger can reach inside this area
), and the contact side of the slider was lightly lubed with a synthetic grease. Once reassembled, the adjuster now moves smoothly on both ends, moving the arm in or out .... and locks down absolutely square to the disc face!!
At this point, the KE links are set such that the camber links have adequate adjustment - so setting camber will be tomorrow nights work: to do that, the car has to have wheels on, be dropped and rolled around - then back in the air with wheels off to reach the camber eccentric: repeat several times ....
To better visualize how the KE link influenced the suspension - and perhaps to see why the KE eccentric bound up, spare parts were assembled to create a RR set up;
Rather than make this post even longer, the effect of increasing the effective length of the KE link is that both caster ( KE effect) and camber decrease - and increase the height of the suspension by straightening the caster angle towards vertical: what happens is that the hub both rotates forward and moves downwards simultaneously. At this point, I suspect this to be the reason that caused the sliding style eccentric to bind in its channel - one is lifting the car by cranking on a single 38mm eccentric disc. If a jack were used to unload the suspension when adjusting the KE, perhaps this would never have happened; however, I saw no mention of this in the WSM's, so it is entirely speculation.
Anyway, here are the pics which may explain better than the above.
Why and how that unusually designed eccentric came loose led me to a solution that may be of some interest.
Background: an alignment done using the KE gauges at a dealership resulted in the LR camber link being at max. length to achieve a minimum camber of -1.5 deg .... but the KE gauges read an acceptable < 1.5 SKE. ROW Sport spec is -1.3 (1, 20'), suggesting that there should at least adequate eccentric travel to make the wheel stand more upright. Clearly not correct, but close enough, so I accepted that as a reference point since the RR toe, camber, and KE were completely screwed up.
Anyway, the RR KE eccentric came loose after having made the corrections discussed previously: to make a long story short, we reset the KE eccentric again and locked it down at a local alignment rack after equalizing both rear cambers at -1.5 deg:: that eccentric was loose again by time I made it 10Km home , and the RR camber was -2.2 deg
.After hoisting the car, and removing the wheels, it became apparent why the KE link was loosening. Rather than using a conventional eccentric as used in the toe and camber links ( to the left in the close up below), it uses a disc with a keyway ---- and a horizontal slider in back that traps a locknut: this slider was sticking within its rear channel, leaving the front adjuster to move the through bolt off a perpendicular line from the face, ie., " cockeyed " in the channel. Such a bolt will vibrate loose in minutes ..... and it did!
Both KE adjusters were removed today, and the keyways for the rear sliders were buffed with a scotchbrite pad ( with contortion, one finger can reach inside this area
), and the contact side of the slider was lightly lubed with a synthetic grease. Once reassembled, the adjuster now moves smoothly on both ends, moving the arm in or out .... and locks down absolutely square to the disc face!!At this point, the KE links are set such that the camber links have adequate adjustment - so setting camber will be tomorrow nights work: to do that, the car has to have wheels on, be dropped and rolled around - then back in the air with wheels off to reach the camber eccentric: repeat several times ....
To better visualize how the KE link influenced the suspension - and perhaps to see why the KE eccentric bound up, spare parts were assembled to create a RR set up;
Rather than make this post even longer, the effect of increasing the effective length of the KE link is that both caster ( KE effect) and camber decrease - and increase the height of the suspension by straightening the caster angle towards vertical: what happens is that the hub both rotates forward and moves downwards simultaneously. At this point, I suspect this to be the reason that caused the sliding style eccentric to bind in its channel - one is lifting the car by cranking on a single 38mm eccentric disc. If a jack were used to unload the suspension when adjusting the KE, perhaps this would never have happened; however, I saw no mention of this in the WSM's, so it is entirely speculation.
Anyway, here are the pics which may explain better than the above.
Last edited by Garth S; 04-17-2008 at 04:32 AM.
04-17-2008, 01:06 PM
#2
Drifting
Love reading your write ups, thanks! I get a lot of satisfaction analyzing a problem and figuring out what is needed to correct a problem, sometimes outside the box. Sounds like you do too. Cheers.
