Attention: TDR Forum Junkies 
HEMI®Dart
TDR MEMBER
I found this at Fritz's Web Page: I did not write this. 
#ad
In a previous posting written by ???? (don't remember), they were complaining about a shimmy in their Ram 4x4 after striking bumps in the road.
I suggested that the front end alignment has either too little or too much caster, thus causing a caster shimmy. He did not like my response and changed his concern from a "shimmy" to a "bounce" (big difference), and insisted it was the shocks. Maybe it is, I haven't driven it. He also said the alignment "checked out". Here's the problem:
Alignment programs (and service manuals I believe), give a wide acceptable range for front caster on the 4x4 Rams. I believe the range is 2 degrees to 5 degrees (if that's not correct, it's pretty close). The problem occurs when the alignment tech (independent or dealer) tells you that the measurements "checked out fine", just because they were in this broad range of acceptance.
Caster readings that fall on either end of the scale are subject to caster shimmy, even though they are "acceptable". I had to align some 30 trucks and attend a 9 hour "Dodge Ram Chassis Dynamics Diagnostics" training session (fancy name, ehh?), before finding out that 3 degrees to 4 degrees is the optimal caster setting for 4x4 Rams that eliminates caster shimmy.
Below I will post what specifications I set Ram trucks to. First I want to give a little more info on correct Ram alignments so you can see if you had a job well done,
The eccentrics on the lower control arms ARE NOT for individual wheel caster adjustments (even though our alignment machine says they are). The eccentric sleeves in the upper ball joints are for adjusting individual camber and total cross caster (difference in caster between two front wheels). This is why replacement eccentrics are positionable in eight different ways.
Once camber and cross caster are attained with the eccentrics, the lower control arm eccentrics are then used to swing the caster readings into specifications. The two eccentrics must be swung in the SAME direction in EQUAL amounts. If they are not, it will create a setback condition (one front wheel further forward than the other).
FYI - Comparing between the two front wheels, caster will cause a pull to the smaller value and camber will cause a pull to the larger value. A truck set up with caster pulling in one direction and camber pulling in the other direction, can lead to a wandering truck; even though it is "in specifications"!!!!!!
If the eccentrics on the lower control arms of your truck are not pointing the same direction, the alignment was done incorrectly and the axle was "twisted" or "forced" into position to attain the acceptable values (seen them from the factory this way, go figure).
A correct alignment will set the truck up with a slight negative cross caster (truck has slight pull to left) to compensate for right hand road crown. Camber will be equal side to side slightly on the negative side. This will help maintain acceptable camber when hauling heavy loads, as the truck tends to lift in the front when towing. Camber will then fall slightly positive when towing.
Just because the alignment shop says "it's in specifications", that does not mean it is set up for proper performance and handling!!!!!!!!!
Specifications (my personal settings for every Ram I align): all specs below are in degrees.
Left Wheel Right Wheel
-------------- ----------------
Caster 3. 2 3. 5
Cross Caster -. 3
Camber -. 10 -. 10
Cross Camber 0. 0
Toe - standard specs, (maybe a little out if you tow a lot, they will pull in as the front end lifts up).
Brent
ASE Certified
Gold Certified Chrysler tech
[This message has been edited by HEMI®Dart (edited 03-01-2001). ]
#adIn a previous posting written by ???? (don't remember), they were complaining about a shimmy in their Ram 4x4 after striking bumps in the road.
I suggested that the front end alignment has either too little or too much caster, thus causing a caster shimmy. He did not like my response and changed his concern from a "shimmy" to a "bounce" (big difference), and insisted it was the shocks. Maybe it is, I haven't driven it. He also said the alignment "checked out". Here's the problem:
Alignment programs (and service manuals I believe), give a wide acceptable range for front caster on the 4x4 Rams. I believe the range is 2 degrees to 5 degrees (if that's not correct, it's pretty close). The problem occurs when the alignment tech (independent or dealer) tells you that the measurements "checked out fine", just because they were in this broad range of acceptance.
Caster readings that fall on either end of the scale are subject to caster shimmy, even though they are "acceptable". I had to align some 30 trucks and attend a 9 hour "Dodge Ram Chassis Dynamics Diagnostics" training session (fancy name, ehh?), before finding out that 3 degrees to 4 degrees is the optimal caster setting for 4x4 Rams that eliminates caster shimmy.
Below I will post what specifications I set Ram trucks to. First I want to give a little more info on correct Ram alignments so you can see if you had a job well done,
The eccentrics on the lower control arms ARE NOT for individual wheel caster adjustments (even though our alignment machine says they are). The eccentric sleeves in the upper ball joints are for adjusting individual camber and total cross caster (difference in caster between two front wheels). This is why replacement eccentrics are positionable in eight different ways.
Once camber and cross caster are attained with the eccentrics, the lower control arm eccentrics are then used to swing the caster readings into specifications. The two eccentrics must be swung in the SAME direction in EQUAL amounts. If they are not, it will create a setback condition (one front wheel further forward than the other).
FYI - Comparing between the two front wheels, caster will cause a pull to the smaller value and camber will cause a pull to the larger value. A truck set up with caster pulling in one direction and camber pulling in the other direction, can lead to a wandering truck; even though it is "in specifications"!!!!!!
If the eccentrics on the lower control arms of your truck are not pointing the same direction, the alignment was done incorrectly and the axle was "twisted" or "forced" into position to attain the acceptable values (seen them from the factory this way, go figure).
A correct alignment will set the truck up with a slight negative cross caster (truck has slight pull to left) to compensate for right hand road crown. Camber will be equal side to side slightly on the negative side. This will help maintain acceptable camber when hauling heavy loads, as the truck tends to lift in the front when towing. Camber will then fall slightly positive when towing.
Just because the alignment shop says "it's in specifications", that does not mean it is set up for proper performance and handling!!!!!!!!!
Specifications (my personal settings for every Ram I align): all specs below are in degrees.
Left Wheel Right Wheel
-------------- ----------------
Caster 3. 2 3. 5
Cross Caster -. 3
Camber -. 10 -. 10
Cross Camber 0. 0
Toe - standard specs, (maybe a little out if you tow a lot, they will pull in as the front end lifts up).
Brent
ASE Certified
Gold Certified Chrysler tech
[This message has been edited by HEMI®Dart (edited 03-01-2001). ]
