Xt M8000s, the rear has had a wandering bite point from new. Never really bothered me actually, apart from a couple of scenarios, but anyhow i digress.
Putonline hpx r 2.5w fork oil has eradicated the problem. Big in germany apparently, says the internet
[s] Putonline hpx r 2.5w fork oil[/s] [b] a successful brake bleed [/b] has eradicated the problem.
FTFY
I've got a litre of it sat waiting for my next pad and rotor change, which will be soonish. Quite interested to see how it works.
Not so. Did one bleed the week before, same method as I always do, didn't work. Flushed the system and tried the new oil, worked like a charm. Nice try though 😬
People always act like it's user error and Shimano don't have a massive problem with wandering bite points that they've failed to acknowledge or eradicate.
I had the problem with some brand new Saints years ago and I persisted with them for ages because I thought I was doing something wrong. Then I had the same again with some Zees. Now it's common knowledge and it's mentioned in loads of bike reviews that feature Shimano brakes.
Nice idea with the fork oil but I won't be able to try it as all my Shimano brakes are long gone.
Link in original post doesn't seem to work...
I don't mind trying new things but I'm not sure id be messing with my brakes.
If I have an issue a quick top cap bleed or full bleed usually sorts it.
But don't let me stop you, let us know how you get on.
What’s the thinking behind the fix? Any 2.5wt susp fork oil ok?
What’s the thinking behind the fix? Any 2.5wt susp fork oil ok?
It doesn't really make sense to me, I can't understand how two fairly similar fluids can affect the bite point. I'd be willing to bet that the issue will eventually come back as it's caused by a design flaw.
In my experience, it’s almost always a bleed issue. I used to Shimano to shops and did tech support at races occasionally, so have a fair bit of experience. Early M8000 and M9000/20 had design issues, but they were sorted and subsequent models (and previous like Saint, Zee and M785 for example) did not have the problem. It was a very specific symptom - totally random lever strokes every time. What people usually complain about is the brake pumping up - big stroke on initial pull, and shorter for subsequent pulls - that’s a classic bad bleed symptom, and very different from the issue Shimano had. Since there was widespread talk of a wandering bite point issue, people have since understandably attributed bad bleed symptoms to something else. Very possible for the odd unit to be faulty, but it has not been a widespread problem for several years. Bad bleed technique is though. A “lever bleed” on a brake with air in the calliper, hose and master cylinder gets some air out of the master cylinder, but the lever pinging just breaks up bigger bubbles elsewhere into smaller babbles that are harder to dislodge, leaving the brake fluid like Cremola Foam. Shimano recommend not touching the lever until late in the procedure (bleed up - preferably a few times, followed by a gravity bleed and then dislodge the last trapped bubbles in the master cylinder by flicking the lever). The fact that it’s generally the rear brake with a longer hose that doesn’t have a vertical route from calliper to lever would also imply a bleed issue, since the callipers and master cylinders are identical in design front and rear.
Perhaps the 2.5 wt oil allows the air bubbles to move up the system more easily and so doesn’t hold onto air pockets?
Shimano brakes are easy to get a mediocre bleed, but difficult/time consuming to get a great bleed. With a mediocre bleed you’ll get the brake pumping up under multiple pulls.
I agree it's a bleed issue not the fluid.
It’s almost as if people don’t read what I have written. What a time to be alive.
How so?
Been using Shimano brakes across several bikes for maybe ten years or more.
Never any problems.
I bleed them an easy and specific way and it works every time.
Go me.
Same issue for me. M8000 rear brake on a brand new bike came delivered with the wandering bite point issue. I bled it properly, Never had a problem since.
Im sure it helps. Mostly as presumably thinner fluid would flow out faster and carry air bubbles with it. I've watched air bubbles rise back into the system while gravity bleeding.
However, Shimano bleeds seem to be a dark art. I tried everything to get decent lever feel on my rear 9120, took it to the lbs incase it needed warranty. Did a mini bleed straight after getting it back from the shop as it still didn't feel great and got so much air back out.
I'd try it on my m9020's if I could get that putoline shipped over here as they need something doing. Fast lap yesterday though...I guess that's what happens when you're always "late on the brakes" 😉
I agree that there is a design flaw but that's around the fact that some Shimano brakes can be very difficult to bleed fully.
People always act like it’s user error and Shimano don’t have a massive problem with wandering bite points that they’ve failed to acknowledge or eradicate.
This.
And no it has not been fixed. Bike reviews still mentioning it. I've got the latest SLX and XTR brakes, worst so far for wandering bite point.
If it's a bleed issue Shimano need to make their brakes easier to bleed. Don't see this cropping up with other brake companies.
I was a mechanic in a shop when I had my Saints and Zees. Give me any MTB brake available to mankind and I'll bleed it with my eyes closed. Except Avid Juicy's. Those will be thrown off the nearest cliff.
If it’s a bleed issue Shimano need to make their brakes easier to bleed. Don’t see this cropping up with other brake companies
Exactly this^
Regardless of anything else, it shouldn't be borderline impossible to get a good bleed on a simple brake. Other brakes with a little air in the system will still function and not have a lever that travels random distances on every pull.
Cons
- There are still more capable trail bikes
- Inconsistent bite point on Shimano brakes. Again
Recent Pinkbike review of Ibis Mojo.
The lever feel, adjustment, power and stopping performance of the XTR brakes is very much liked. And with 203mm rotors coming front and rear there were no worries on the steeper trails around the Alps. But, like a broken record, the wandering bit point is there on even the highest end brakes
Review of Antidote Carbonjack.
Shimano SLX brakes: Marin put its money into smart choices such as the four-pot disc brakes with a 203mm rotor up front for extra stopping power when that geometry gets you in too deep. Unfortunately, the wandering bite point that afflicted mostly the rear brake took the shine off the otherwise impressive performance, with an unpredictable lever feel when you need it to be consistent
Marin Rift Zone review
mudeverywhere
If it’s a bleed issue Shimano need to make their brakes easier to bleed. Don’t see this cropping up with other brake companies.
"Bleed issue" doesn't mean "you've bled them wrong", people often say it like it does but it can also mean "these have some issue with bleeding that means it's damn nearly impossible to get it right every time, and even Shimano techs will sometimes get a bad result BUT really importantly not every time, you can do literally the same thing and have it be perfect 9 times and bad the 10th".
And that seems to be pretty much definitely what it is here. It's just not reasonably explainable by user error.
Bearback, just wondering (no pun intended....) if the brake that you mentioned is the one that was in the shop the other week? If so, I spent a lot of time getting air out of the system (current Shimano brakes seem really bad for holding air and one can literally spend 5 minutes getting air out of the reservoir). To be honest I wasn't blown away by how the lever felt either but with further discussion in-house it was decided that it was fine, but maybe there is an issue if you got more air out? I know the bladders are really weak on Shimano's current brakes. We've seen several with dead bladders as a result of people pushing the pistons back into their bores without cracking open the lever bleed screw. I'm not saying that this is the issue here, just an example of current Shimano brake issues, along with disintegrating pistons.
People always act like it’s user error and Shimano don’t have a massive problem with wandering bite points that they’ve failed to acknowledge or eradicate.
As above, it seems to be a bleed issue. They are tricky to bleed. Using a different fluid might make them easier to bleed or it could just be a matter of luck.
That @howsyourdad1 and others have bled brakes to their satisfaction with a different fluid is great but it is just a data point on Shimano's design problems.
I've had Shimano brakes try to kill me on multiple occasions. None of that nonsense has recurred since moving to other manufacturers' brakes.
I've had mid-run, out-of-nowhere occurrence of zero free movement of the brake lever accompanied by weakened application (because of ServoWave). Seldom a laughing matter as I'm using my brakes at speed and committed to my lines.
I've had a m/c develop a leak on me on stage 1 of an international enduro (a Shimano supported event so they subbed in a brand new m/c M8000 that was never as good as the M988 it replaced)
I've had micro-weeping piston seals contaminating brake pads multiple times. When you first get this, you buy new brake pads which get contaminated and if you're really slow on the uptake you buy more when those get contaminated the next day - all of which was good money you could have put towards brakes that function.
I've had the general "bite point moves around a bit" problem ad nauseam on individual problem callipers that is fixed forever when you substitute a known good calliper.
I've investigated problem callipers and found loose aluminium swarf and impacted swarf in the pistons that snags and tears at the seals.
So I am done with Shimano brakes.
Normal form for tinternet is for somebody to pipe up that I'm evidently tosh at bleeding brakes. Nah. That's not it.
If Shimano brakes have problems with Shimano fluid (the only fluid they warrant) then Shimano brakes are not good enough for me to bother with.
If the Putoline fluid does indeed fix all the Shimano brake problems then it is a scandal. You can get good individual Shimano brakes with fewer problems out of the box. If you get a bad one, it is worth one competent bleed to see if they come good but after that you're better off ripping them off your bike and spending your money again.
I have experimented with hybrid setups. I've run Formula Cura callipers with Shimano m/cs and Formula mineral oil. This was exceptionally good until the pads wore and the m/c volume proved inadequate. The Cura callipers have the same cross-section area as Saints. The fluid is much lower viscosity like the Putoline. But that was still too much dicking around for me when it is so much easier to plug in a set of Curas, levers and all.
If the Putoline fluid does indeed fix all the Shimano brake problems then it is a scandal.
The only functional difference from the perspective of bite point will be the viscosity (the boiling point might also differ, but that won't affect the bite point when they're cold.) A less viscous fluid should make bleeding easier. That points to the problem being that they are difficult to bleed.
I had a wandering bite point. Cured it by overfilling them (bleeding with worn pads), then pushing the pistons back in to eject the excess fluid out of the reservoir. That ensures that there is no air in the master cylinder reservoir. Just like that, no more wandering bite point.
I don't often come across shimano brakes but pretty much any brake I bleed is a process of sucking sir out as well as pushing fluid in. Does anyone do this with Shimano?
I know people really didn't like the old avid juicy but I still use a bleed technique very similar to the two syringe system they used.
I don't have a horse in this race but I'm still curious as to the cause.
I binned the bleed methods that was recommended by Shimano. I bled the brakes up then down then up again. It definitely gave a more solid lever feel. I used the same technique on my Magura brakes too.
+1 on a good bleed sorting.
We have/had same issue on Magura MT5's if the bleed isn't perfect. It sometimes just took a second run through of fluid and solved.
Normal form for tinternet is for somebody to pipe up that I’m evidently tosh at bleeding brakes. Nah. That’s not it.
Judging from the responses on here that's still the case.
Normal form for tinternet is for somebody to pipe up that I’m evidently tosh at bleeding brakes. Nah. That’s not it.
Judging from the responses on here that’s still the case.
Not quite. They are tricky to bleed and if you don't get all the air out of the system, you will get the wandering bite point problem.
thanks for the varied responses.
I have come to the conclusion that the putoline works as it gives you a higher chance of a successful bleed.
I have used gravity bleed method (like the marshy one) and have done it exactly the same way every time. I put the bike in the same position, i use the same method, everything is as near as identical as possible. I've done it this way for saint brakes, deore brakes, old m785 xt brakes, it has always worked. I have always used shimano oil, used the same bike stand, in the same part of the garage, which is always 15c 🙂
This b#stard m8000 didn't work however. i must have bleed them 10-12 times since owning them, exactly the same method. First go with the putoline and it works. maybe luck, but I am 99.9% certain that i have not bled them differently. The brake is crisp and solid, it's perfect, and has been for 3 weeks. So based on my case study of one, it is the solution to wandering bitepoints.
Not quite. They are tricky to bleed and if you don’t get all the air out of the system, you will get the wandering bite point problem
At this point I don't even care. Even if you're right it shouldn't be like trying to solve a rubik's cube to make your brakes work.
I had a wandering bite point. Cured it by overfilling them (bleeding with worn pads), then pushing the pistons back in to eject the excess fluid out of the reservoir. That ensures that there is no air in the master cylinder reservoir. Just like that, no more wandering bite point.
And I've tried that and many other tricks on problem brakes to no avail. I'm a mech eng and I've designed hydraulic systems (that self-bled at the slave, incidentally). I've assembled and bled many a slave cylinder. I'm sympathetic to all the design intricacies of a multi piston brake. But when it comes to spending my own time chasing out issues, there is a time after which I was happy to declare enough was enough and move on.
Bleeding with two syringes isn't particularly clever with these systems. The friction in the top syringe means you put pressure across the m/c diaphragm and if you plunge the top syringe you get an even bigger pressure differential. When you detach the syringe the diaphragm pings back, ejecting the excess fluid or ingesting air, depending on which way you had it loaded. Shimano have it about right with their funnel. A top bleeding reservoir open to atmosphere is a very good thing for bike brakes with their small master cylinders (you can replicate this with two syringes by just removing the plunger from the top syringe).
Don't get me started on the various i-Specs. What a crock. No compatibility between generations so any update of gears forces an update of brakes and vice versa. Limited range to get things where you need them. Utter, utter pish. Then you have a general policy of Shimano making their band on shifters not sit nicely alongside their own brakes.
Besides being the absolute dregs of the barrel when it came to bite point problems, when the M8000 XT brake came along it became apparent that Shimano had not the slightest clue. A narrow band onto the handlebar? WTAF? Lovely twisty forces being reacted through a very small and bendy interface. Now, of course, they have corrected that totally obvious and execrable mistake and invented a new thing. Reversing course is not the sign of a design team that know their arse from their elbow.
As I say, I'm done. I did my time.
A top bleeding reservoir open to atmosphere is a very good thing for bike brakes with their small master cylinders
You have to get all the air out of the reservoir because bikes are often laid on their sides or upside down, so you can get air into the master cylinder. You can't have the reservoir open to the atmosphere or the fluid would leak when you turned the bike upside down, so you need a diaphragm to separate the fluid from the atmosphere. That diaphragm makes it tricky to get the air out of the reservoir, hence the overfilling trick - that's a simple way to ensure the reservoir is completely filled without any air bubbles.
SLX 675 user here, it's kinda an inbuilt response that I just pump my brakes each time I use them (as in every time I brake), maybe it's just me but it's kinda funky not knowing where their bite point will be, adds a bit of Russian roulette to each descent.
A narrow band onto the handlebar? WTAF? Lovely twisty forces being reacted through a very small and bendy interface. Now, of course, they have corrected that totally obvious and execrable mistake and invented a new thing. Reversing course is not the sign of a design team that know their arse from their elbow.
Yep, this one is ridiculous when you think about it. "Ooh look, we've invented a solution to a problem we only just created with the last generation brakes". Of course no other brake company would be silly enough to to have a clamp so narrow.
First go with the putoline and it works. maybe luck
Likely. There's no way of knowing if you get all the air out of the system, so perhaps this time you did. I have definitely done a bleed before, got unsatisfactory results, then done it again (same method) and got better results.
Personally i think it is unlikely that is was luck. Kind of why i started the post, as hopefully it will help someone.
Here’s the stuff in the uk anyway (saves €20 postage)
[url= https://www.tweekscycles.com/uk/putoline-hpx-r-suspension-fluid-246923/?sku=PUTHPX5-1&istCompanyId=56f52ebf-49f3-492a-9cbb-cb6ab0fc1bf0&istFeedId=33b89177-5114-4491-9c2a-09a3a7cb23b2&istItemId=wilxtpaqi&istBid=t&gclid=Cj0KCQjw4cOEBhDMARIsAA3XDRjn9Cf4g0yayACVGOlVagAQib_-mC3BQ5iQiNvQaGCLqTfJZracDXIaAheOEALw_wcB&gclsrc=aw.ds ]Putoline from Tweeks[/url] (damn, 2.5w out of stock!)
Search also turned this forum discussion up. (pg 3)
Maybe its mainly a low temperature thing?
Sounds like a useful workaround for those really struggling OP.
But I have to agree with Sillyoldman (great response), that there's a confusing mix of technique and luck in resolving the issue with most units I've owned.
I'm sure there are a few really duff ones, but all of mine have responded well to a bottom-up bleed (or three) and I suspect the majority of observed cases are due to the above-mentioned design flaw which makes it quite tricky to get and maintain a good bleed. And Shimano pushing the funnel/lever bleed so strongly hasn't helped the public perception.
My Zees are still my favourite brakes ever, even though my Codes have been less temperamental.
Its not the bleed - Many examples of magazine reviews featuring wandering bite point on bikes that have come straight from the factory.
Its a product of the design - specifically the interaction of the servo wave mechanism in the lever and the caliper seals. Brake power is determined by the ratio of the size slave piston in the caliper compared to the master piston in the lever. With a normal brake power is limited by the need for the pads to sit far enough away from the rotor. If you have too big of a size difference between the 2 pistons then the lever wont push enough fluid to move the pads far enough and they will rub on the disc.
Servo wave is a clever way to get round this problem. The Cam mechanism causes the master piston to move further at the beginning of the lever throw and then ramps up the power at the end of the stroke where the pads bite down. Using this method the shimano lever can push more fluid than a regular design which means it can have a larger piston ratio and more power while still maintaining good pad clearance.
The downside of this is that the Caliper seals have to work harder in between applications of the brake in order to return the pads to the starting point. (It is the springiness of caliper seals that is responsible for returning the pads)
So a wandering bite point can happen to any brake but the design of Shimano brakes makes it more likely and more noticeable.
Personally I think the power increase is worth it. I had a particularly bad set of XTRs once that I bought second hand. I was able to vastly improve them by swapping out the caliper seals and pistons. Unfortunately due to Shimano not selling spares I had to buy a complete set of XT calipers to do this.
Its not the bleed – Many examples of magazine reviews featuring wandering bite point on bikes that have come straight from the factory.
Its a product of the design
Ah, so great idea in theory, fails in practice?
I had yet another failed rear XT9000 last week, but the only brake I could get locally to ride the next day was a new SLX 2-pot. The Zee on the other hand that replaced the previous failed front XT9000 I've never had an issue with. And the XT's were warranty replacements...
@ndthornton The factory bleeds aren’t particularly thorough IME, and far worse on bikes where the line has been fed through internal frame routing and reconnected. They always work better with a further bleed once hose length has been set for the bike they’re going on etc.
Reviews are by journalists rather than mechanics - they often get it wrong!
The servowave mechanism exaggerates bite point softness and vagueness due to the cam action on the mechanical advantage - that’s why the lower end brakes and most of the road brakes are known to be easier to get a firm and consistent bite point on - they lack the servowave (or in some cases have a less pronounced cam action.
As I say - there are bound to be occasional issues in such prevalent brakes, but in most cases the symptoms aren’t due to a design fault IMO, but due to inadequate bleeds and/or poor bleed techniques.
I suspect that the alternative oil is less viscous and so allows bubbles to move up and out of the system more readily.
Deore have Servo Wave don't they?
Just wondering why they seem to be the most reliable of the decent Shimano offerings. The set I had were faultless for five years - and I'd got them secondhand.
