GTD rear control arms

[Simon]

Is that the right term? the arm that attaches the top of the rear upright to the chassis next to the gearbox?
Anyway, I'm making up some with rose joints (l/h and r/h thread) at each end. I've worked out the exact length I want to keep the uprights absolutly vertical, but how much adjustment do I need for a road car. I'm trying to work out how far out The joints need to be to enable me to adjust them in. Obviously I don't want the joints to have too much thread showing.
Have I explained myself clearly? I know a picture is worth a thousand words, but I'm not at home right now.
Thanks

Simon

 

[Paul Thompson 'Hooligan']

If you make the arms so that they are correct standard length centre to centre when the joints are both unscrewed approx half an inch, you'll still be able to adjust the arm length longer or shorter from stock by about an inch.

Just remember to keep say 1.5 x dia of rosejoint thread dia within the threaded insert as a minimum.

Don't forget to use quality joints and allow and use lock nuts to secure both ends. I've seen arms with no lock nuts!:stunned:

Oh and re the quality, they ain't cheap but having a joint break is not fun! - I know as I've been in a car approaching Avon Rise at Castle Coombe when a rear offside lower trailing arm joint broke at about 130mph under braking. Touch brake pedal and wheel moved back locking completely = skid. Lift off brake pedal and risk not slowing down.... It definitely focusses ones attenttion!:laugh:

 

[Terry Oxandale]

Unfortunately, once you get a lock/jam nut installed, the amount of adjustment becomes even smaller (after being safe with the 1.5X mentioned by Mr. Thompson). The good thing is you'll not want any positive camber (or I can't imagine you would), so that leaves all your adjusting for a range of 0 to -?.