DIY Chassis Squaring and Suspension Alignment

[pheyden]

In putting my own car back together, particularly as it had all new "adjustable" suspension components, I realized that I need to develop a protocol for the various checks to be performed.

Below please find a downloadable PDF file with the ideas and procedures that I developed for my own project. I hope that is is of some help to others.

http://www.scuderiatopolino.com/Suspension%20Set%20Up.pdf

Updates have been completed. Thanks for your patience.

[RaceSport]

Your topic could have not been more better timed Paul!
At present i am in the stage of doing just this on my other car (The IMP).

Regarding the rear camber angles..Could not the pivot points be lowered or raised according to the inner and outer holes..
I am talking off the back of my head here but my other marque of racer which is of parallel configaration has a removable rear crossmember to which the rear trailing arms bolt onto!
To reduce neg camber you raise the inner bolt hole and if necessary lower the outer which makes the suspension arm and wheel sit upright!
The method is to weld substansial washers over the holes to calculated(?) position then redrill out !

I should have re-studied the rear suspension of my 850 Coupe first,but i remember the design is a bit more sophisticated incorparating shims and such like(?)., but i feel the physics of the application are the same!

On another matter it is ironic that i was about to buy ply sheets amongst other items to lay on the workshop floor to level out in the way you have described.

At present i am besotted in building a replicar of a Costin-Nathan Spyder or Nathan Astra chassis, although in aluminium rather than marine ply...Due to a dodgy woodwork teacher at my Secondary school my woodworking skills are inhibited!
All this is but a pipe dream at present ,but the Imp is on course for 2010 like your Fiat . To which the 850 Coupe is peeping out from its cover awaiting excitedly to be breathed on again!

David L

[pheyden]

David,

In a "semi-trailing arm" or "swing arm" design the angle of the bearing carrier surface at the outer end of the arm is dictated by what the designer of the vehicle had in mind for a "design ride height". Particularly with a swing axle design if you go to a lower ride height you will get more negative camber. This is why on the 1000TCR Abarth went to the Pendolare rear suspension in which the chassis pick-up points were relocated both longitudinally and vertically, AND the carrier bearing ride angle was also modified.

If it were a unequal length A-arm suspension then you could modify the upper or lower a-arm length to achieve some adjustment of camber. Further you could modify the inside pick-up points to alter the roll center. In a swing axle car the roll center is essentially fixed where the ring and pinion meet. The Pendolare system, and to a lesser extent my own Tubolare implementation of rear suspension, tries to come to a happy compromise with reduced initial camber and also with reduced camber thrust during suspension movement. If you look at the write up of the pendolare remake you will see how much Abarth actually moved the hangers for the rear a-arms.

Wishing you a great 2010.
Paul