Has anybody tried a higher Dot rating than 4 . My rear brake on my 2017 supersport is basically a chocolate fireguard. And bleeding doesnt last 5 minutes
The DOT rating won’t make any difference ie if you go to DOT 5.1 rather than 4. Yes DOT 5.1 has slightly a higher dry & wet boiling point than DOT 4 but I suspect your rear brake fluid isn’t getting anywhere near hot enough to boil even with the DOT 4, unless the routing of the brake line is too close to the exhaust.
You need to get to the root cause of the issue. Maybe it’s due to seized pistons, glazed pads, leaking master cylinder piston, air in the line, etc. Perhaps the brake line is passing too close to the exhaust and perhaps the fluid is overheating and reaching boiling point in which it becomes ineffective. Without addressing the root cause you’ll never cure the issue.
The rear brake can and does work, sure, it’s not going to stop the bike from 50mm h or higher without the use of the front brakes but it can be made so it does lock the rear wheel or cause the rear abs to engage.
BTW never mix DOT 5 brake fluid with DOT 3, 4 or 5.1 it’s silicon based not glycol based and the 2 fluids won’t mix you’ll just render your brakes ineffective.
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