by bigger im assuming that your just talking about the size of the disc, which wont have much to do with the rear locking up before the fronts
its when the rear calipers are too small (in piston area) compared to the front that they lock up not when they are too big

id say they would be fine when using 120y fronts bias wise, but wouldnt suggest keeping 120y brakes if you have the need for a r31 diff anyway

120Y front not maddat rear .....ROCKET rear end....lol

the rear is totally stock R31, the front 120y is temp,
im still trying to understand how to change to skyline fronts to keep them uniformed.......not sure in what strutto use,
help be good on that subject

you dont have to use r31 fronts, pretty much all single piston calipers will keep about the same brake bias

or if you want to get tricky you could measure the r31 front piston size and then can use other single piston calipers that have roughly the same size piston

personally i'd choose what sorta struts you want to use then just go with brakes that will fit onto them

but if you really want to fit r31 front brakes
best way of doing it would be
bluebird front struts, shortened to take r31 or 240z inserts with smaller 1200 sized spring perches welded on or coilovers
then r31 brakes bolt straight on
and you use all the same stuff as stanza struts to bolt them into a 1200, plus a pair of sheer load spacers to properly locate the strut...can get these from datsport

but r31 brakes arent that great from a wheel fitment point of veiw
they are only a 250ish mm disc with a single piston caliper but you need at least 14s to clear them

thats a great lot of info there mate .....thanks

i have tryed a bit of playing around with r31 strut and put 1200 purches on looks good plenty of clearence for wide tyres,

im will be using skyline standard rims for the time being

so if i buy a pair of sheer load spacers thats all i need?

if you have all the stanza struts fitting gear
lcas, balljoints, steering arms and stuff

could also just use r31 struts, but then you have positive camber unless you have camber tops adjusted as far in as they car go
then you might just get some neg camber, maybe

can the neg camber be used at the x-member, intead at the top!

im not up with tech side of things but im learning

you greatly widen your track if you do that with isent sutch a bad thin for a track car but means a afir bit of body work for road worthy..

yeah extra track from the strut swap plus extra track to get camber isnt really the best thing for a street car (he says as he thinks " thats exactly whats been done to my street car")

much easier, in the long run, to just use modified bluebird struts
r31 struts are only really an advantage if your wanting to run 17s or something like that with a fair positive offset as you have more clearance to the wheel/tyre than you do with bluebird ones

it a bit like stuck between a rock and a hard place on this front end stuff,