Servo wave
Shimano Brake wandering bite point cure...sort of
Posted by: UFO
Servo wave
Is that a new Xtr lever? That design looks like it would be more durable than my current XT levers.
This is ooooold, M980 series, back when 10sp was a thing. I have these paired with MT520 4 piston calipers and they have been wonderful. These have even been the first Shimano levers where I've found the bite point adjustment to actually do anything
Honestly, what you're feeling is air. When you pump the lever once and then pump it again that bubble is temporarily compressed and the bite point happened sooner.
A good bleed will fix it. For a (possibly short) while.
If you've ever bled the brakes on a car after replacing a caliper or master cylinder, you know what I mean. The way brakes "pump up" is exactly like what the wandering bite point feels like.
Last edited by: Kenny on May 17, 2021, 7:13 p.m., edited 2 times in total.
Posted by: Kenny
Honestly, what you're feeling is air. When you pump the lever once and then pump it again that bubble is temporarily compressed and the bite point happened sooner.
A good bleed will fix it. For a (possibly short) while.
If you've ever bled the brakes on a car after replacing a caliper or master cylinder, you know what I mean. The way brakes "pump up" is exactly like what the wandering bite point feels like.
Of course that makes sense. I wonder if that wandering bite point has any relation to how we store our bikes? I hang mine by the front wheel. Will that make any air in the master cylinder move into the piston area? While storing upright won’t?
Posted by: andy-eunson
Posted by: Kenny
Honestly, what you're feeling is air.
Of course that makes sense. I wonder if that wandering bite point has any relation to how we store our bikes? I hang mine by the front wheel. Will that make any air in the master cylinder move into the piston area? While storing upright won’t?
I have stored my bikes:
Hung by the front wheel
Flat (like in the orientation you ride one)
Upside down
Hung by the back wheel
In my experience: have not noticed a wandering bite issue that was caused by any orientation. If I have a brake that needs a bleed anyway, anything other than storing the bike in a normal position will make it worse. So if you're hanging it by the front wheel and it needs a bleed as a result, it would have anyway.
re: orientation of bike during storage
upright is no problem but sitting on its side in the truck the lever goes to bar and same with hanging from the new storage rack by the front wheel, I been putting off a bleed cuz the lever alwasy comes back right away when the bike is upright but clearly its time for a bleed, I can't say I've noticed a wandering bite point otherwise
I have an old Manitou X-vert super on a touring bike that will leak fork oil if hung by the front wheel so it gets hung by the rear wheel
Posted by: Kenny
Honestly, what you're feeling is air. When you pump the lever once and then pump it again that bubble is temporarily compressed and the bite point happened sooner.
A good bleed will fix it. For a (possibly short) while.
If you've ever bled the brakes on a car after replacing a caliper or master cylinder, you know what I mean. The way brakes "pump up" is exactly like what the wandering bite point feels like.
The thing that gets me is what is it about Shimano brakes that makes them uniquely have this problem? Where is that bubble?
I was able to achieve rock solid bite points on every brake before or since, but the Shimano brakes I've had all maintained a wandering bite point to some degree. The first few years and sets of having them like a lot of people I recreationally bled them constantly.
Removing the brake from the bike and hanging it completely vertically and doing a ridiculously careful bleed fixed the problem- for a few rides.
Where has the engineering gone wrong with this brake? I wonder if Shimano will ever face the reality of users experience and fix the issue.
Last edited by: Hepcat on May 19, 2021, 11:21 a.m., edited 1 time in total.
So for those with wandering bite point, how fast do your pads retract when you let go of the lever? My front brake is rock solid and never changes but my pads retract lightening fast, my rears retract slower and have the wandering bite point. My rear is bled perfect, there's no air. If I let the brake relax for a moment then grab the brake, its a rock solid on/off feeling but if I release and grab again super fast the lever grabs further out and so on until the throw is basically non existent. The pads aren't retracting fast enough so when I grab again I'm introducing more fluid into the line. Take a look and see for those with the problem.
Posted by: T-mack
So for those with wandering bite point, how fast do your pads retract when you let go of the lever? My front brake is rock solid and never changes but my pads retract lightening fast, my rears retract slower and have the wandering bite point. My rear is bled perfect, there's no air. If I let the brake relax for a moment then grab the brake, its a rock solid on/off feeling but if I release and grab again super fast the lever grabs further out and so on until the throw is basically non existent. The pads aren't retracting fast enough so when I grab again I'm introducing more fluid into the line. Take a look and see for those with the problem.
The wandering bite is a lever issue, so kinda doubt sticky pistons are contributing. It sounds like you just need to clean the pistons on your rear brake, my rears usually need a good clean at about twice the rate of my front, because they get used way more.
Last edited by: mammal on May 26, 2021, 8:24 a.m., edited 1 time in total.
Posted by: mammal
Posted by: T-mack
So for those with wandering bite point, how fast do your pads retract when you let go of the lever? My front brake is rock solid and never changes but my pads retract lightening fast, my rears retract slower and have the wandering bite point. My rear is bled perfect, there's no air. If I let the brake relax for a moment then grab the brake, its a rock solid on/off feeling but if I release and grab again super fast the lever grabs further out and so on until the throw is basically non existent. The pads aren't retracting fast enough so when I grab again I'm introducing more fluid into the line. Take a look and see for those with the problem.
The wandering bite is a lever issue, so kinda doubt sticky pistons are contributing. It sounds like you just need to clean the pistons on your rear brake, my rears usually need a good clean at about twice the rate of my front, because they get used way more.
yeah I clean mine every pad change, that being said Ive had these calipers for a few years now and Im wondering if the pistons are starting to wear.
wouldn't you see scuff marks on the piston bores if they were wearing ?
isnt servo wave just a way of changing the pivot point of the lever for more power ?
I hung that Manitou from the front wheel and it puked all the oil,
while scoping oil amount on line the manual sez don't hang it upside down !
Posted by: XXX_er
wouldn't you see scuff marks on the piston bores if they were wearing ?
isnt servo wave just a way of changing the pivot point of the lever for more power ?
I hung that Manitou from the front wheel and it puked all the oil,
while scoping oil amount on line the manual sez don't hang it upside down !
Scuff marks no, but deviation in tolerance from wear yes.
Also my point with the servo wave was that the bits that make up the servo wave are plastic and wear over time, so it wears, the piston can come out further than it should and cause problems hypothetically
I have shimano saints m820 on one bike and the newest slx brakes on another. After countless hours of research and many more bleeding I finally gave in and asked my lbs, mechanic told me it might be the olive had been pressedsideways. Before that i tried all methods of bleeding, using weird oils, shimano oil; ultra low viscosity oil; putoline oil, none fixed my problem, i even took apart my caliper and rebuilt it in an oil pool. Turns put you just have to make sure that when you are inserting the cable into the lever: it has to be dead straight, quick bleed after changing the oil and you get the best brakes there are.
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