Maz wrote:
OK, let me ask you another way........what's wrong with DOT 4 or better yet 5.1
Nothing at all - the Land Rover and Citroen seem perfectly happy with it - but I'm equally perfectly happy with 5.
I have to say I've never seen dirty Dot5 when I've done a pre-emptive flush. Here of course there's generally little humidity which may be a factor. I recall the state of the Dot4 in several Guzzis and Laverdas when I lived in the UK and before I switched to Dot5.
I'm seriously interested in understanding why some bikes seem not to like it and others have no issues, though. The only corrosion I've ever had in a Hydraulic circuit was the slave clutch cylinder on a Volvo - that was Dot4.
As you point out H/D use Dot5 and giver the septics propensity for law suits - There has to be a reason (other than paint) they keep using it if brake loss is an "issue". Apart from the colour, naturally.
Maz wrote:
and warn against ever moving from 5 to mineral without changing seals, hoses, etc.......
My guess is that 90% of problems is due to incorrect flushing so the fluids mix. Dot4 seems (from my personal experience) to keep (esp hydrophylic?) shite in suspension, whereas Silicone lets it (forces it to) precipitate out.
I've always changed to Dot5 when doing something else (i.e fluid change was not the driving force) - normally new hoses or a complete circuit rebuild (new seals and stripped M/C and callipers). And once done I've never had an issue. This said I do not ride on the brakes.
Would you switch from Mineral to Veggie oil lubrication without a full flush?