R1200RT 2005

My R12RT now has 90k.miles on her andthe front discs are down to 4mm so time to replace them.
New ones are eye watering and I have a set of 05 R1150RT with virtually no wear on them in my spares box. I know the history of the bike they came off. They are 320mm dia and 36mm wide just like my R12RT ones, but they are 0.5mm thicker (when new) and a slightly different bobbin setup.
The bobbins on the R12 discs are not removable, whereas the R1150RT ones are. I also notice that the washer between the disc and the rim is much thinner on the R1150 bobbins.
These small differences add up, but the calipers should be able to cope with these small differences ?

Looking for any pearks of wisfom or anyone who has used the older style discs, or knows a reason why I couldn't use them.

I appreciate that for many there will be a view of "why mess with brakes, just get the right ones" but they are ridiculous money, so if I can do it safely and cheaply, why not ?

My plan this morning is to measure the overall distance between the two discs mounted to the wheel, then fit the r1150 ones and see what it does to the overall measurement.

Thanks all.

Talk to Motorworks and see if they have a bobbin/washer kit to make them work. I know what you mean about eye-watering, I’ve just replaced the originals on a 2010 RT as they were down to 4mm. But the bike was new-to-me and I budgeted for this and will run it for a good few years.

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=35&Ct=HA&SbCt=BA_15_35_HA_50

Cheers have had bits from them before, will give them a shout.
I've had the bike about 5 years now, rescued it from a barn a sorry old state, now has 90k miles on her but still brings a smile to my face.

The replacement Brembo discs for the twin cam are 5mm (min 4.5) replacing 4.5 (min 4) so that shouldn’t be an issue. Good luck finding an economic fix.