newrider3
newrider3 Reader
5/11/21 3:28 p.m.

Working on control arm brackets for the Ford 7.5" rear axle swap in our Lemons Starlet.

OEM control arm pickup points on the axle have 6" vertical separation, split evenly (both brackets 3" to axle centerline).

The cast-in upper brackets on the Mustang housing we're using are 3.5" to axle centerline.

Assuming all other geometry stays stock, and we don't know enough to second guess the stock Toyota geometry; would I be better off matching the 6" vertical separation between upper and lower control arm brackets (so new lowers would be 2.5" to axle centerline) or adding 0.5" to the total separation to allow the lower brackets to be at 3" centerline? 

My gut reaction is to match the OEM vertical separation, but some suspension tuning quick reference pages say that reducing the c-to-c lever arm length on the lower control arm bracket can be undesirable. Also, going with a longer bracket buys more room for the heim and control arm to articulate before contacting the axle housing.

We are highly unlikely to notice minute changes in suspension tuning on this car, so the simplest answer here is the answer for us.

Thanks!

gumby
gumby GRM+ Memberand Dork
5/11/21 4:02 p.m.

Quick and dirty calculator

It needs Excel, or some equivalent, but the spreadsheet is free.

asphalt_gundam
asphalt_gundam Reader
5/12/21 11:35 a.m.

Quick and dirty answer is don't change the spacing but give yourself adjustment holes down on the lower and down and up on the upper (if one hole down can be done on the upper). This way the geometry can be maintained or adjusted for any desired changes or ride height changes.

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