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pfi,
From the archive, you may have read this thread which has some sub-frame (S/F) alignment info, and some guesses:
https://www.s2forum.com/forum/techni...01#post2053401
Some believe the S/F alignment does not matter, and perhaps that's true to some extent (you can't know what the alignment rack will dictate and/or there may be enough available adjustment at the ball-joints) or they've just been lucky (their S/F positions were 'good enough'), while some think road-crown ought to be counter-acted/addressed with their fixing. Prior to removal, certainly some recorded measurements will help one re-establish the previous positions, but I don't think those measurements are necessarily going to be exactly equal (otherwise there would be no need for adjust-ability!), just as close as possible to previously.
It may be worthwhile to hire an alignment shop with satisfied B3Q customers; and also be valuable to know what S/F points are fixed and which ones to best gently tap to get the S/F to move incrementally (the one opposite the fixed mount) should the job require their movement (you could then point them out to the mechanic), it may not.
Only on the alignment rack itself (with the car suitably attached) is the mechanic going to 'see' the car's theoretical center-line (TCL), and if the net result of the two S/F positions is satisfactory. The mechanic is going to adjust the rear axle's effective thrust angle (ETA) parallel to and centered on that TCL as best as possible, then with the front axle's total toe split evenly side to side (and the rack and steering wheel centered), he will similarly bring these three together so the rear axle properly trails the front. The degree to which the tracks of the two axles closely agree with and are centered on the TCL of the car (like the other settings) is dependent on how good and how fussy he is, and how easily he can get there, so anything you can do prep wise beforehand (like dis-assemble, clean, anti-seize and re-assemble your steering links and rear links (so they are freed-up for adjustment) will be helpful.
Because the static alignment involves mere minutes of a degree in accuracy, and frangible bushings can allow a good deal of uncontrolled movement (measureable with a simple ruler), I can't help but think new top-mounts and A-arm bushes (and of course kept that way with Strut and Arm-Stops!) would be as important as S/F position, to hold that accuracy steady dynamically; while cornering and braking.
newsh,
That's interesting sir, by quieter, perhaps you mean that you found the S/Flex's transmit less road noise than the standard purple hardness P/Flex's, correct?
John.
Re design, you may have something there sir. The orig. Boge bush (photo in above linked thread) is not only more generous in foot-print, but also has that star-shaped spline on its mating face which no doubt helps it hold (its adjustable) position once gripped by the stretch(?)-bolts. I read that the P/flex bush kit for the B4s rear S/F has S.S. tubes with splined ends; perhaps to do similar?
From the archive, you may have read this thread which has some sub-frame (S/F) alignment info, and some guesses:
https://www.s2forum.com/forum/techni...01#post2053401
Some believe the S/F alignment does not matter, and perhaps that's true to some extent (you can't know what the alignment rack will dictate and/or there may be enough available adjustment at the ball-joints) or they've just been lucky (their S/F positions were 'good enough'), while some think road-crown ought to be counter-acted/addressed with their fixing. Prior to removal, certainly some recorded measurements will help one re-establish the previous positions, but I don't think those measurements are necessarily going to be exactly equal (otherwise there would be no need for adjust-ability!), just as close as possible to previously.
It may be worthwhile to hire an alignment shop with satisfied B3Q customers; and also be valuable to know what S/F points are fixed and which ones to best gently tap to get the S/F to move incrementally (the one opposite the fixed mount) should the job require their movement (you could then point them out to the mechanic), it may not.
Only on the alignment rack itself (with the car suitably attached) is the mechanic going to 'see' the car's theoretical center-line (TCL), and if the net result of the two S/F positions is satisfactory. The mechanic is going to adjust the rear axle's effective thrust angle (ETA) parallel to and centered on that TCL as best as possible, then with the front axle's total toe split evenly side to side (and the rack and steering wheel centered), he will similarly bring these three together so the rear axle properly trails the front. The degree to which the tracks of the two axles closely agree with and are centered on the TCL of the car (like the other settings) is dependent on how good and how fussy he is, and how easily he can get there, so anything you can do prep wise beforehand (like dis-assemble, clean, anti-seize and re-assemble your steering links and rear links (so they are freed-up for adjustment) will be helpful.
Because the static alignment involves mere minutes of a degree in accuracy, and frangible bushings can allow a good deal of uncontrolled movement (measureable with a simple ruler), I can't help but think new top-mounts and A-arm bushes (and of course kept that way with Strut and Arm-Stops!) would be as important as S/F position, to hold that accuracy steady dynamically; while cornering and braking.
newsh,
That's interesting sir, by quieter, perhaps you mean that you found the S/Flex's transmit less road noise than the standard purple hardness P/Flex's, correct?
John.
Re design, you may have something there sir. The orig. Boge bush (photo in above linked thread) is not only more generous in foot-print, but also has that star-shaped spline on its mating face which no doubt helps it hold (its adjustable) position once gripped by the stretch(?)-bolts. I read that the P/flex bush kit for the B4s rear S/F has S.S. tubes with splined ends; perhaps to do similar?
"
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