Rider_of_Bikes
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Sent from my GT-I9505 using Tapatalk
Sent from my GT-I9505 using Tapatalk
I would have thought that the o-ring seals would give before the plastic piston, and the reason it's plastic is purely from a cost/weight POV - a simple injection moulded part vs a more expensive machined metal one, and plastic is less milligrams of overall weight for marketing purposes (although the difference is probably negligible in reality).I'm keen on these too, but have one concern over this.
Is the plastic piston a fail safe, albeit a flawed one?
Is there a way that, in the event of say a crash, it would flex to allow some bypass of the piston. If this piston were ally, would this be creating another problem.
(Mine are going off to get rebuilt today, as they are only a few months old)
My plastic pistons are even thicker further along, at one of the narrow sections, but your suggestion is still valid. The pistons hole for the plunger is tapered, it retains the ball of the plunger somewhat.Sounds like the OEM fix is in play then, F-R... although I'm still keen to see whether the home brew aluminium piston is a viable alternative.
Edit: I was just looking at Jesterarts pictures, and I see that the modification to the piston is at the lever end, so maybe it is the plunger pushing against the plastic piston that slowly 'flares' it out and jams it in the bore? If so, does the modified piston simply delay this process further but not actually solve it?
View attachment 332566
Still don't know what to call the seal, you're right, they're like 95% of automotive master cylinder seals, a directional seal. I'm sure I've had a master cylinder apart that had quad rings in it.I would expect the brake handle would bend or flex before you would blow or by-pass one of those seals, they are the same type of seal as in a master cylinder of a car foot brake.
I think the main culprit of the piston jamming would be heat expansion aided by the mushrooming of the piston making the piston to bore clearance tighter and then you have that pissy little spring that loses tension over time. From what I have read somewhere else the new piston is .7mm smaller in dia than the original.
reckon you'd be on the money, although there are a lot of PTFE variants - you'd have to think it would be a low cost version that is easily moulded, rather than something selected as best fit for purpose.good job link.....
does anyone know what the piston is made of...
teflon or some other teflon based product ?
0.7mm or 0.07mm?? Just a decrease of 0.7 is huge in the case of any piston/bore set up. And in the case of the brake bore, it would now be the equivalent of throwing a sausage down a hallway.I would expect the brake handle would bend or flex before you would blow or by-pass one of those seals, they are the same type of seal as in a master cylinder of a car foot brake.
I think the main culprit of the piston jamming would be heat expansion aided by the mushrooming of the piston making the piston to bore clearance tighter and then you have that pissy little spring that loses tension over time. From what I have read somewhere else the new piston is .7mm smaller in dia than the original.
To your point, i suspect the new piston is designed to eliminate the most serious issue. I still have money on plastic expansion.Sounds like the OEM fix is in play then, F-R... although I'm still keen to see whether the home brew aluminium piston is a viable alternative.
Edit: I was just looking at Jesterarts pictures, and I see that the modification to the piston is at the lever end, so maybe it is the plunger pushing against the plastic piston that slowly 'flares' it out and jams it in the bore? If so, does the modified piston simply delay this process further but not actually solve it?
View attachment 332566
Maybe they measured the new recessed area ? Someone should measure a new and old piston with a micrometer and it should reveal what's happening.0.7mm or 0.07mm?? Just a decrease of 0.7 is huge in the case of any piston/bore set up. And in the case of the brake bore, it would now be the equivalent of throwing a sausage down a hallway.
Jesterarts, are you rebuilding this weekend? Do you have a decent set of vernier calipers or a micrometer?Maybe they measured the new recessed area ? Someone should measure a new and old piston with a micrometer and it should reveal what's happening.
90% most likely rebuilding this weekend. Still waiting on the DOT fluid.Jesterarts, are you rebuilding this weekend? Do you have a decent set of vernier calipers or a micrometer?
I have a set of vernier calipers you van borrow. They work but not sure if they qualify as decent? They weren't expensive.Jesterarts, are you rebuilding this weekend? Do you have a decent set of vernier calipers or a micrometer?