Caster & Camber 1928 Cadillac - Insert Shims - Why

[Ken Andersen # 21420]

According to the workshop manual, in order to adjust the castor of the front axle, shims of various thickness are inserted, between the axle and the base of the front springs.  The thicker end of the shim needs to be placed to the rear side of the axle.  Can any one advise why the castor needs to be altered in this way.

[JIM CLC # 15000]

07-23-06
KEN, On any vehicle with solid front axle, Even present day trucks, in order to have easy steering and to be able to have the vehicle come-back-stright-after- making-a-turn is to insert a tapered shim between spring and axle.
You may have to use serval size shims before you get the ones that feel right to you.
HTH to answer your question.
Good Luck, JIM
P.S. Just re-read your post. IF you like the way your car steers now, forget about the tapered-shims.

[Ken Andersen # 21420]

Dear Jim,
Thanks for the info Jim. When I pulled the axle apart to reco it, I noticed the shims. The previous owner had a proper 1 & 3/4 shim on each side, and then on top of that he had another piece of plain steel around 3/8 inch thick.
I was just wondering why they are put with the thick end at the rear of the axle and not the front.  Is this something to do with the angle of the king pin?    Why was this problem ( of the fixed solid axle) not addressed in the factory? Is it a matter of experimentation until you find the right angle, or is there allowances that you make for tyre wear, king pin wear etc.
Could do with as much info as possible. I am hungry for info on my girl

[JIM CLC # 15000]

07-24-06
KEN, IM not an expert on wheel alignment of solid-axles but do know that the caster is adjusted using shims between axle and springs, and, yes, the shims controls the angle of the king-pins. Suggest you pose your question to Hunter and or Bear companies, makers of alignment machines.Or, call a spring/Frame repair shop.
HTH, Good Luck, JIM

[Warren Rauch]

 From tht Serviceman  July15,1927  Front Wheel Shimmy and Its Remedy I will give you this articles top 8 reasons and the part about caster. First the top eight in order of how easy they are to correct. 1) tire inflation, 2) Front wheel alignment (toe-in)3)Loose front wheel bearings, 4) Loose steering connections (tie rod& pitman arm),5)Steering gear adjustment (gearbox),6)Stabilizer adjustment (on front spring)7) caster angle,8)Wheel and tire Balance.
  Caster Angle---The caster angle or inclination of the spindel bolts has an important effect on the front wheel shimmy. Too much casterwill cause shimmy, whereas too little will make the steering wander. The caster angle (both Cadillac and Lasalle) is approximately one degree. Although there are devices for measuring caster angle without diassembling the axle, the most satisfactory procedure is to change the caster by inserting tapered shims or wedges between the springs and the axle and then try the car on the road.To decrease the caster angle ,insert shims with the thicker edge toward the front. After inserting the shims always check for wandering and low -speed shimmy as well as for shimmy at high speeds Warren

[Ken Andersen # 21420]

Dear Warran & Jim,
Thanks guys for the infor, I am now a bit wiser as to the reason of inserting these shims, and what they do.