RGS Rear Brake Bleed

[Dellortoman]

I've never bought the "tie back the lever" trick. All it does is pressurise the system and if the M/C seals work as they should, nothing at all will pass them, in neither direction.

Exactly! Thank you Piet. I feel like I've been arguing this point on my own. I struggle to understand why some folks recommend the lever tie back thing. I've argued the case before but it seems those who adhere to this fallacy don't believe me. The only way it could possibly achieve anything is if there's trapped air up against a M/C or caliper piston seal, and that seal leaks, allowing the air to get past it. But if that's the case then you need new seals.

 

[Slartybartfarst]

Exactly! Thank you Piet. I feel like I've been arguing this point on my own. I struggle to understand why some folks recommend the lever tie backion of the thing. I've argued the case before but it seems those who adhere to this fallacy don't believe me. The only way it could possibly achieve anything is if there's trapped air up against a M/C or caliper piston seal, and that seal leaks, allowing the air to get past it. But if that's the case then you need new seals.

Totally agree getting rid of trapped air in a motorcycle hydraulic system by tying back a brake lever is an utter fallacy. The system is closed wheres the air gonna go?

But I did it and it worked and its never taken me 3 bloody weeks 3 sets of seals and a new master cylinder to solve a brake bleed.

I fitted new seals, a new master cylinder with its new seals, I used new unopened brake fluid, Ive been bleeding brakes 50 years, there was no air in my system I can be 99.9% sure of that.

Ive designed and engineered and produced millions (literally) of pneumatic cylinders that sporadically suffer pre build by pass leaks on the lip seals due to storage deformation of the elastomer.

I take my experience of work on small cylinder diameters. Sufficiently small such that deformation of a lip seal forms a cord which constitutes a significant proportion of the total surface compression area.

Maintaining a high load over an extended period on the lip seal in both pneumatic and hydraulic systems forms it to a better set which stops the initial very small but large enough by pass leak such that the system holds pressure enough to seal and get better with use.What we all want from brakes!