pinion angle question

[uninformed]

hey all,

i'm lead to believe that the rear a-frame set up on rover's (defenders,rangies, early disco's) is a parralleagram, so when the axle travels up and down the pinion angle doesn't change (if much)

is this true?

what happens to the pinion angle if you lengthen the rear trailing arms in the same plane as originals? does it change the geomertry/pinion angle through travel?

cheers, serg

[Ruffy]

As long as you lengthen both the upper and lower.
The rear arms swing through an arc from there pivot point. The pivot point of the longer lower arms isn't detrimental. What you need to do though is make the pivot point of the top arms or a frame be at a point which lets the diff pinion swing through an arc of which the centre point is the output drive flange. Therefore the length, angle and height of the mounts are quite critical if you want to keep you pinion angle correct.
I hope all that makes sense.
Cheers Dan

[uninformed]

thanks,

sort of understand. but i ment only lengthening the trailing arms not the stock upper a arm

cheers, serg

[Ruffy]

If you lengthen the lower arms and not the top arms the the ratio will obviously change and the pinion angle will alter as it swings through its arc. As long as the pinion angle is correct when the cars is at its normal ride height then you probably wont notice any difference.
Cheers