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Just wondering how hard a fully bled Shimano 4 pot brake lever should feel?
I’m 99.9% certain that I’ve got all the air out. I’ve bled several times using different methods, taken the callipers off the wheel to get a vertical drop from the lever etc and even drained all the fluid out of one of them at one point. Both levers have a consistent feel but I couldn’t help noticing/thinking that when out in the cold they feel slightly more solid and it got me thinking that there must be air in them that has contracted in the cold… it can’t be air, it just can’t!
So they bite well enough and there is a solid feel but if I squeeze harder once the pads are engaged I can definitely pull the lever in further by about 10mm and it feels springy rather than spongy so I’m thinking there is a rubber diaphragm offering the resistance. Yes? 🤞
so I’m thinking there is a rubber diaphragm offering the resistance. Yes? 🤞
Nope, the diaphragm in the reservoir is there to compensate for expansion due to heat, but is cut off from the brake circuit as soon as you pull the lever. It can’t handle any pressure, if it does see pressure it just leaks fluid right away (this may be from experience of trying to faff with fluid levels)
I've found it tricky to bleed 4 pots.
Gotta rotate that caliper upside down, downside up and all the places between to dislodge any air out of the 2 Pistons opposite the hose and bleed side.
Well I’ve had the callipers off again and bled everything - not a single bubble to be seen. I had the callipers upside down, on their sides etc etc but no air came out at all. 🤷♂️ my guess is that they are definitely fully bled. 👍😎🙂.
I’ll nip into a LBS when I get some spare time and try the levers on a few in store to compare. Mine must be OK though.
I’d say that extra movement after the pads engaged is just flex in the system like the actual lever bending and flex from the lever clamp on the bar, also the hoses will expand slightly in use too.
The lever is most definitely moving further towards the bar by about 5mm and I’m not squeezing hard enough to bend the lever. It could be flex elsewhere in the system though hence my original question. Maybe the pads compress slightly - resin Shimano D03. There’s significantly more resistance once the pads engage and I’m squeezing harder than I would if braking so perhaps this is just normal - I’ve got nothing to compare it to as the only other bikes in the house have rim brakes.
normal. Movement and the amount of fluid displaced is tiny. A bit of compression in the pads, flex in hoses etc and you have movement at the lever
Is this happening on the trail or just in the stand? I always feel that Shimanos have an odd trait of feeling softer in the stand than when riding (assume because of the cam helping the power without the level moving far)
Actually now you mention it that is exactly what I am experiencing - went out today after yesterday’s bleed and they felt a lot more solid than they did on the stand in the house. I’m convinced there is no air in anywhere and both levers feel identical to support this. They do feel fine though so 🤷♂️