lta01 wrote:are you sure that you are not suffering with slightly more seal stiction than usual in the calipers, especially with the pistons being stainless rather than chromed finish ?
I have experienced this before with stainless pistons. It can show up as the calipers having slack on the discs which you can feel by rattling them on the sliding bolts.
Quick way to rule this out....remove the calipers one at a time from their mounts, pump lever very gently until piston moves out and just stays out..put back on disc carefully...should now be a tighter fit. Do this on both sides, then try lever again.
No improvement, I would say master cylinder problem, if it has improved, either leave as is if drag is not bad, otherwise disassemble calipers, remove seal, clean groove carefully and rebuild with plenty of lubrication around the seal.
Hope this helps
Ita O1 Thankyou very much indeed ! You were 100% accurate in your diagnosis . I'd never heard mention of this before...great pick-up !! & it will be definately Deposited in my Memory Bank. I have relayed this issue to my suppliers & hopefully they will contact Rhino (the manufacterers ) in the UK ... hopefully they'll take it on board & ensure they use 2000 grit wet & dry + Wd 40 to obtain a mirror like Piston O/D finish 'before' they leave the Lathe, so other un-suspecting victims like me don't go Stir-Crazy ! Also, I pointed out that the Piston to Pad interface should have also a Heat barrier coupon machined & secured to the open end of the Piston to eliminate Heat transfer to the brake fluid if there being used with Sintered pads.
Thanks again for your kind help & thanks to the other people that took the trouble to chip in. Goodonya Boy's ! Johny Brando.