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Specifically, it happens:

On steep stuff when the brakes are under fairly constant load (you are braking on steep stuff) and you quickly let go and brake again, whether to give your fingers a slight rest, or to let your rotors cool a bit, but it's the quick "let go and brake again" where the engagement point moves out further. But on such steep stuff, you can't just "let go the brakes", because you'll fly off the hill, tumble down the slope into a tree. You usually have the brakes under significant load, constant braking...but as you let go and squeeze, the engagement (bite point) moves further and further out.

In the winter, in cold temps, it happens much easier, without as much steep stuff and the engagement point will move further and further out until, when it's cold enough, the lever basically doesn't move at all, it's fully "out" and you just touch it and your brakes are engaged. The big problem here is your finger doesn't generate much leverage when the engagement point is all the way out...so it's absolute crap for controlling the bike. When it gets to like -20, the brakes are just on/off switches...again, the lever only takes like a "hair" of travel before the brakes engage, basically all the way out.

On the steep stuff, as you have to "let go and brake" as the engagement point moves out, you get less and less ability to control the bike through the brakes, because again your leverage is poor.

When I thought about it, I remembered some old Formula brakes I had back in 2013 that did the same thing. It's almost like a "closed" brake system at those times...If you remember back in the early days, there were some "open" and "closed" hydro brake systems. The closed systems couldn't adjust for heat and had to be constantly adjusted during the ride...it's like that...but you can't adjust them.

Anything other than this is usually a bad bleed. Soggy levers/bleed is easy to identify. When a lever goes to the bar and has to be "pumped up" to deliver power...there's air in the lines. That is NOT the shimano wandering bite point.

It's seems pretty obvious it's related to a port/orifice size and the fluid not being able to flow/backfill or something. My Hopes don't do it. I ride a LOT of real steep stuff though and this just made Shimano brakes unacceptable. If you are on more level ground, you may never notice this trait.

Shimano techs KNOW there are issues with the brakes...but they don't offer any solutions. They acknowledged the fact that they can weep through the pistons and they said "just remove the pads when the bike isn't being used". I mean...that's just telling me it's a **** system, no I'm not removing the pads every time I'm done riding because I don't know exactly when I'll use that bike again.

And if there was a part that you could replace that simply wears out, that'd be fine, but shimano doesn't make replacement parts for their levers. They make disposable brakes and as such, they have basically gone to the bottom of my list, as in absolute last resort. I wanted to like them, I LOVE the servo-wave power delivery for said steep riding...but they screw themselves over with the issues and no replacement parts. IDK if the newest shimano brakes maybe finally solve this problem...but I don't have it on Hope T4 levers (or my maguras) and there's no reason for me to go back to shimano anymore.
So...what you're telling me is I been salty at brake bleeders when it's the brake's fault? My rear tends to act like air in the lines about 2/3 the way down the hill. I thought the shop monkeys were being apes. Apparently, Shimano just sucks at brakes.
 
So...what you're telling me is I been salty at brake bleeders when it's the brake's fault? My rear tends to act like air in the lines about 2/3 the way down the hill. I thought the shop monkeys were being apes. Apparently, Shimano just sucks at brakes.
Possibly, yes. That place is steep enough and sustained enough for it to rear. A bad bleed means a soft lever that goes too far towards the bar. This is the opposite, a firm lever that goes further and further out, both resulting in significantly diminished braking.
 
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Aren't the Hope rotors not floating in the "rattle around side to side and make tons of noise" way that moto floating rotors are? As in, the hopes have some expansion room radially but don't freely move side to side?

Even if they were amazing, I am not sure I could tolerate the noise of a true floating rotor on a bike.
It's quirky - and debatable how well it works. When they are cold they are pretty tight. When they heat up they expand and can move a little.
 
So...what you're telling me is I been salty at brake bleeders when it's the brake's fault? My rear tends to act like air in the lines about 2/3 the way down the hill. I thought the shop monkeys were being apes. Apparently, Shimano just sucks at brakes.
It's possible you have air penetration, so air penetrated after the shop did the bleed. This can be either from the caliper or lever.

I got to say that I can overheat the brakes so they lose power and the lever feel does not change. Super careful about bleed process to avoid potential air penetration in the future. Learned the hard way.
 
It's possible you have air penetration, so air penetrated after the shop did the bleed. This can be either from the caliper or lever.

I got to say that I can overheat the brakes so they lose power and the lever feel does not change. Super careful about bleed process to avoid potential air penetration in the future. Learned the hard way.
shimano ones?

I do roast my rx4's and aside from fading and needing to pull harder, they don't seem to ever change.
 
Darrington was pretty much brakes the whole way. Idr the vert. More than home, which is 1500 ft. The Cura 4s and 220 rotors didn't change a bit top to bottom. I was impressed.

We need more boring around here...
Ya ain't wrong. But for the love of Dog, not THAT flavor of boring.
 
Darrington was pretty much brakes the whole way. Idr the vert. More than home, which is 1500 ft. The Cura 4s and 220 rotors didn't change a bit top to bottom. I was impressed.


Ya ain't wrong. But for the love of Dog, not THAT flavor of boring.
Honestly they are pretty great. Ice techs on some and rt76 on others.
I have some hope 160s. If i had bigger ones in red id probable run them, but I ain't paying for them when an rt76 cost like $17.
 
From what I know and understand from how the system works, the shimano's WDP® is due to the flow rate mainly. When you release the brake, the oil starts to flow back up the line. With viscosity, there's a resistance to this movement which increases the time where the oil/piston returns to the base position. If you brake while it's still going up, the calliper's pistons aren't fully retracted so you end up adding oil from the reservoir to the line as the levers's piston is in the original position. The addition of this oil is what changes the bite point.

With Poisseuille's Law,
Image

Image

If we reduce, the viscosity. Flow rate increases. Resistance decreases. Meaning a quicker retraction and much lower different bite points.

This explains why the wdp is practically nonexistent on the front brake compared to the rear brake. (The length of the hose is much shorter for the front). Bad cold weather performance aswell, with higher viscosity.

I have used LHM+ (18Cst), shimano's oil(8Cst) and currently(2years) on likewater(4 Cst). Using LHM+, I almost had a big crash as I had the initial bite point close to the grip as I knew the second pump would be higher. On a section, I expected the bite point to be in the farthest bite point but it had fully retracted. And the pull was nowhere near the bite point. Switched back to shimano oil but I still didn't like it. So went with redline which made it far more predictable and WDP is almost gone. I don't have bite point issues but spongyness on the rear(saint) compared to my front( mt520) which I don't like.

My front brake is just obscenely sharp and strong, a sram's hamfist user's worst nightmare, a literal light switch. You pull the lever, FEEL it touch the rotor and the lever stops moving.

I assume that the spongyness and small amount of WDP is naturally due to lenght of the hose and exacerbated by it as I never cut the hose when I installed the saint. + some damage to the line.

I'm also on 180mm rear and 203mm front. The difference could take a small part aswell in the issues but it's mostly a power and overheating thing I see on the long steep descents here in the alps.

One day I'll take the lever and calliper apart to clean along with a proper length hose.


Another point is that it's much easier to get a better bleed with lower viscosity oils as the bubbles move easily in the system. There was a big difference when I did LHM+ to shimano and when I did shimano to likewater, I spent a while just pulling the levers and bubbles still kept coming.
 
This explains why the wdp is practically nonexistent on the front brake compared to the rear brake.
Well no, it doesn't, because it isn't. IME it affects both brakes equally and it sure as hell is NOT "practically nonexistent" with the front.
 
Well no, it doesn't, because it isn't. IME it affects both brakes equally and it sure as hell is NOT "practically nonexistent" with the front.
And the lines wouldn't be the main restriction. Its not the flow back from the cylinder that is the problem, it is the flow of excess into the reservoir (if indeed this is the actual root problem).
 
in my opinion most of the problems come from the brake caliper. Ceramic pistons and greater pad clearance than cause inconsistency. Servo wave further increases this problem by constantly changing the leverage.
 
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