Kalvinder Dhillon Posted December 7, 2021 Report Share Posted December 7, 2021 Hi has anyone fitted a new oil pipe for a TR6 oil pressure gauge ? Would you happen to know if I need to bleed the pipe first ? Quote Link to post Share on other sites
Lebro Posted December 7, 2021 Report Share Posted December 7, 2021 No need to bleed the pipe, pressure at one end will be the same at the other end whether the pipe is full of oil or full of air. Bob Quote Link to post Share on other sites
Rob Salisbury Posted December 7, 2021 Report Share Posted December 7, 2021 15 minutes ago, Lebro said: No need to bleed the pipe, pressure at one end will be the same at the other end whether the pipe is full of oil or full of air. Bob Simple question, Why doesn't that work for brakes? Cheers Rob Quote Link to post Share on other sites
JohnC Posted December 7, 2021 Report Share Posted December 7, 2021 1 hour ago, Rob Salisbury said: Simple question, Why doesn't that work for brakes? Because the volume of air changes as it compresses. Not an issue for the gauge as the pump just keeps pushing more oil in until pressure is equalised. If the same happened in the brake or clutch line you’d get less movement at the business end for the *limited* amount of movement at the pedal. JC Quote Link to post Share on other sites
Kalvinder Dhillon Posted December 7, 2021 Author Report Share Posted December 7, 2021 Thanks Lebro Quote Link to post Share on other sites
Rob Salisbury Posted December 7, 2021 Report Share Posted December 7, 2021 9 hours ago, JohnC said: Because the volume of air changes as it compresses. Not an issue for the gauge as the pump just keeps pushing more oil in until pressure is equalised. If the same happened in the brake or clutch line you’d get less movement at the business end for the *limited* amount of movement at the pedal. JC So less movement at the pads or shoes, but the same ultimate pressure? .... not sure I'd trust spongy brakes to have the same efficiency as a solid pedal, and I have to say I've always bled oil pressure gauges when they've been disconnected, just seems the right thing to do. Cheers Rob Quote Link to post Share on other sites
Lebro Posted December 7, 2021 Report Share Posted December 7, 2021 Not the same ultimate pressure, because the master cylinder has only a finite amount of movement, & one stroke of it may well not be enough to reach the required pressure. This is why pumping the pedal seems to improve the braking, but no substitute for getting all the air out. The pressure gauge however has an infinite supply of oil to squeeze the air to the same pressure as is coming from the pump. So bleeding the pipe is pointless. Bob Quote Link to post Share on other sites
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