Discs and stuff
I've got both.
After quite a bit of research I bought the 320mm HE kit direct from maker at
http://www.he-motorradtechnik. 250 Euros plus delivery. Available from resellers for a few Euros more, might be more cost effective if you're ordering other stuff. I also sourced a new P4 Brembo caliper complete with pads at a very reasonable price from Carpimoto in Italy.
Taken out to NZ and dry fitted to the '89 r100gs that lives at my parents place. I had to return to UK before I could complete installation so as yet untested. Others seem to like it, particularly with the 4 pot caliper. Nicely finished bit of kit which I reckon will be a big improvement over standard. Unfortunately it doesn't shed any weight v. the solid OEM disc. I had hoped to shave a few grammes despite the increased disc diameter but the adaptor ring, longer bolts and increased disc thickness actually make it slightly heavier. I think the P4 caliper will even things out at bit as it replaces a bulkier 1100 four pot.
I also have a recently acquired r100gs in the UK and this came fitted with the ABM 300mm disc, something that I hadn't come across when researchin brake set ups. This is clamped by the standard P08 caliper. At 1540g I would guess that it is svereal hundred grammes lighter than the standard OEM disc - maybe not a lot given the hefty front wheel but any reduction in rotating unsprung weight can only be a good thing.
Agree with Tufty re the looks - the ABM disc has a more professional look (e.g. anodized alloy carrier v. adaptor ring and longer bolts). It is also a proper fully floating unit (hence the lighter weight). The UK bike also came with a second used ABM disc that had been removed as a precaution - it is a tiny bit loose on the bobbins. Age/usage of this disc unknown and the play is only slightly more than the brand new ABM disc. Certainly no worse than a couple of other FF sets ups I have used/owned & MoT'd. Likely to be resolved with new bobbins in any event but might be something to consider if it concerns you
Braking with the ABM set up is, as you'd expect, an improvement on the well used set up on my NZ bike. (This has the OEM disc & master cylinder mated to a 1150 four pot caliper with braided hose.) Feel is similar i.e. pretty wooden. Actual effectivness is much increased.
Lighter, neater and slightly more professionally finished ABM disc v. larger, likely more effective, HE. (Disc/pad materials will make a difference here of course). Caliper adaptors are both neat and of a good fit and finish. Similar value if you take into account the line and pads included with the pricier ABM.
IMHO either would certainly provide a worthwhile improvment over standard. Well worth doing.
New disc means new pads so I'd might be worth considering replacment 4 pot caliper at the same time, particularly if the original caliper is a bit tired. You could source a used 1150 caliper and modify it but new Brembo P4 is probably more cost effective. I see that ABM also do a caliper. This looks to have 40mm mounts, same as the P4 - and the pads look similar if not the same. If opting for the ABM set up and considering a 4 pot it might be worth doing some research on that. I suspect the ABM caliper would be pricier than the readily available Brembo
Further research is called for into master cylinders:caliper piston ratios to improve the feel at the lever, but that's a whole other story!
Now, where's that Harrison 6 pot...
