Too much F/ brake lever travel
Posted: Tue Sep 22, 2015 6:32 am
Long story "not so" short !
Front brake system bled every which way & NO air present , yet I have 50mm of lever travel until it's firm & it should be only about 25mm !
Both Calipers have just been rebuilt with new S/steel pistons & all new seals & new Pads. Master Cylinder rebuilt with a ( Japanesse make) 'Tour Max' rebuild kit label # 280069 , underneth this label could be seen another label numbered 08-0217 ....I found this strange but all internal M/cylinder parts appeared to be the same as OEM so I continued.
Also I installed all new Copper banjo bolt sealing washers throughout complete system, & used new Dot 4 Oil .
I was very careful in my assembly proceedures not to nick/damage any seals ..... I inverted the M/cylinder 90 degrees to bleed that & also released the hose splitter unit so I could swing it during bleeding to vent any possible air entrapment there . I used a clear hose connected at one end to an elivated catch jar this hanging 250mm above the calipers with it's upper end emmersed in oil within that jar the other end of the hose connected to an inline vertical mini Non-return valve ...the hose (which is now pre-filled with oil ) continuing down to the 12 o/clock positioned Caliper Bleed Nipples which had each been prior wrapped with 4 turns of PTFE tape to prevent any possible air ingress there.These then bleed in the conventional fashion .
When I then couldn't seem to get the lever firm enough I tried my other method of "reverse pressure bleeding the system" i.e. pushing fluid back up into the Master Cylinder this via the pressure release vent hole ...I do this by using a very large 75 ml Syringe ( 3 times M/cylinder volume ) this is filled & connected directly to each bleed nipple. I did this a few time via each Caliper & did not see any air exit into the Master Cylinder. I could & did during this process, swing the hose splitter to & fro & continually move & tap all lines to aid in moving any lodged air bubbles . I also pushed & pulled brake fluid both back and forward in the system trying to move any trapped air that way too.
With either method I could not get or find any additional trapped air after the initial bleeding. The crazy thing is.... if I cable tie up the lever in a compressed state for several hours then release the held pressure.... it then feels great ...as it should feel ! but within 5 minutes it magically reverts back to the 50 mm travel.....
I think the problems is most likey in the Master Cylinder but what it is within....I now have no idea ( has anyone here used the same Tour Max kit with the same numbers ???? ) I would very much value any input or idea's you may have. THANKYOU , Johny Brando.
Front brake system bled every which way & NO air present , yet I have 50mm of lever travel until it's firm & it should be only about 25mm !
Both Calipers have just been rebuilt with new S/steel pistons & all new seals & new Pads. Master Cylinder rebuilt with a ( Japanesse make) 'Tour Max' rebuild kit label # 280069 , underneth this label could be seen another label numbered 08-0217 ....I found this strange but all internal M/cylinder parts appeared to be the same as OEM so I continued.
Also I installed all new Copper banjo bolt sealing washers throughout complete system, & used new Dot 4 Oil .
I was very careful in my assembly proceedures not to nick/damage any seals ..... I inverted the M/cylinder 90 degrees to bleed that & also released the hose splitter unit so I could swing it during bleeding to vent any possible air entrapment there . I used a clear hose connected at one end to an elivated catch jar this hanging 250mm above the calipers with it's upper end emmersed in oil within that jar the other end of the hose connected to an inline vertical mini Non-return valve ...the hose (which is now pre-filled with oil ) continuing down to the 12 o/clock positioned Caliper Bleed Nipples which had each been prior wrapped with 4 turns of PTFE tape to prevent any possible air ingress there.These then bleed in the conventional fashion .
When I then couldn't seem to get the lever firm enough I tried my other method of "reverse pressure bleeding the system" i.e. pushing fluid back up into the Master Cylinder this via the pressure release vent hole ...I do this by using a very large 75 ml Syringe ( 3 times M/cylinder volume ) this is filled & connected directly to each bleed nipple. I did this a few time via each Caliper & did not see any air exit into the Master Cylinder. I could & did during this process, swing the hose splitter to & fro & continually move & tap all lines to aid in moving any lodged air bubbles . I also pushed & pulled brake fluid both back and forward in the system trying to move any trapped air that way too.
With either method I could not get or find any additional trapped air after the initial bleeding. The crazy thing is.... if I cable tie up the lever in a compressed state for several hours then release the held pressure.... it then feels great ...as it should feel ! but within 5 minutes it magically reverts back to the 50 mm travel.....
I think the problems is most likey in the Master Cylinder but what it is within....I now have no idea ( has anyone here used the same Tour Max kit with the same numbers ???? ) I would very much value any input or idea's you may have. THANKYOU , Johny Brando.