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I had a puncture today and due to having to faff around with a dodgy inner tube where the valve core kept unscrewing each time I unscrewed the pump head, the bike was upside down for about 30 minutes.
When I checked the brakes after righting the bike, the front lever went straight to the bar but pumped up to normal after 3 or 4 pulls (the rear lever was fine but has done the same in the past); the brakes functioned exactly as usual from then on (including coming down out of the Mendips). They're SLX brake and about 5 months old (came pre-bled but I just cut the hoses without re-bleeding).
Is this an indication of air in the system or normal behaviour? Pumping the lever back up felt the same as finding the bite point after having pushed the pistons back in but the front wheel never left the bike.
If I do need a bleed I assume that I could just ziptie the levers back overnight and top up the system from the lever.
On a related point, I have an old 1 litre bottle of Shimano mineral oil that probably 4 or 5 years old. There's no indication of a use before date on the bottle and it's been stored sealed and in the dark (as per the instructions); can I use this to top up or bleed?
Does suggest there is air somewhere in the system, zip tieing levers back will fix for a period of time but I'd do a proper bleed.
Had this on a few of the newer Shimano brakes, can often be resolved by doing a quick bleed of the lever, as per Shimano instructions
Ta
Any thoughts on the old mineral oil? It's clean, sealed and out of the light and still seems to be doing its job in the brakes I bled with it years ago and didn't tough again.
I bought it because a couldn't stomach paying £9.99 for 50ml (and a plastic tube) when you could get 1000ml for £16; it could turn out to be false economy though if it needs binning.
I bought a set of xtrs new from my lbs and they need pumping a few times but still lever throw cones closer than liking to bars.
Reminds me I should go back and get the guy to bleed them foc.
Any thoughts on the old mineral oil?
should be fine it's not hydroscopic like like DOT fluid