Just stumbled across this by chance, but it appears that high end Shimano race brakes now run a new type of Low Viscosity mineral oil. Apparently the lower viscosity means that it will transfer hydraulic pressure more quickly.
It's not it appears compatible with standard mineral oil systems or vice versa (using the wrong sort may screw your brakes) and I can see there being a lot of potential mix ups.
As a keen pootler with no skills I've never been too concerned with marginal gains (the swap from outboard to inboard banjo nuts apparently gained you 10% activation time, but felt just the same to me) and anyway, I can't afford top tier kit but other will be impressed.
Is this a genuine advancement or just change for change's sake?
https://www.bikeradar.com/features/tech/shimano-lv-mineral-oil-brake-fluid
Saw it in the STW feature when the new XTR came out. Presumed it was just for them and new gens of Shimano brakes. Something about it improving the wandering bite-point issue (which I've not experienced, though my son's Saints are very prone to it)
The new fluid is one part of an attempt to stop the wandering bite point issue. Which I haven't noticed on more recent Shimano brakes anyway. Had one set of XTs where it was noticeable while riding. Interestingly Sram are now having similar issues after switching to mineral oil. Shimano sent out a questionnaire some time ago within the industry to shops or whoever gets these things asking if a new mineral oil would be acceptable to them if it fixed the issue. Apparently the answer came back yes.
The secret fix for wondering bite point was Putoline 2.5wt fork oil.
I'm sure Shimano will tell you it will be death by bicycle fireball if you mix them but there's likely not going to be an issue using new fluid in old brakes.
The secret fix for wondering bite point was Putoline 2.5wt fork oil.
I'm sure Shimano will tell you it will be death by bicycle fireball if you mix them but there's likely not going to be an issue using new fluid in old brakes.
I've not done a full flush and replace with the Putoline HPX yet, but mixed it in with existing fluid - with promising results so far.
My experience was that it was becoming less of an issue anyway, but new problems were emerging (leaky calipers).
I was reading that bikeradar article yesterday, and it seems very mealymouthed. At no point do they really answer "yeah but why", even though the answer would appear, from various sources, to be "because old mineral oil was leading to Shimano's infamous wandering bite point problems"
Fine if they want to do it (just mark the brakes and make sure there's a supply for home mechanics) but I've never had an issue with the existing oil that seemed to be the fault of the oil. My oldest (albeit lightly used) Deore level brakes are from 2003, the only problematic set is one from 2009. The 2003, 2015 and 2020 sets have been pretty close to flawless.
Been using the Putoline HPX R 2.5wt in some M8100 brakes for couple of years - no leaks and wandering bite point disappeared. Shimano coming out with a low viscosity oil sort of vindicates those already using Putoline or Redline Like Water as a fix.
I'm willing to bet that the new stuff will be fine in the old brakes - ultimately the return of fluid when you release the lever pressure is an imprecise science when you've got variations in brake pipe length and routing, so I can't really see how Shimano can be so confident that the new fluid would be disastrous in the old brakes. (And there are Youtube videos of people using water and baby oil at the very least).
The general explanation does make some sense though - really all that can cause it is air in the system, and air could get pulled into the lever piston from the master cylinder if the fluid doesn't return quickly enough. Also probably explains why most people claim that a bleed fixes it - that would minimise the air in the master cylinder so mostly/only fluid rather than air can get pulled in (well pushed when there's a vacuum on the other side) from the master cylinder.
So which hero is going to try it?
Edit: Does occur to me that BH90 hose could be a contributing factor mind, the smaller bore vs BH59 will definitely restrict the return of the mineral oil.
so whats the difference between this new oil, reverb oil, and johnsons baby oil? asking for a friend..
and air could get pulled into the lever piston from the master cylinder if the fluid doesn't return quickly enough.
Only with a previous poor bleed that left air under the diaphragm. NO air should be able to get into the master cylinder
If you imagine a super high viscosity brake fluid you can picture how it would be very difficult to bleed but also that you’d get less feedback from piston to lever of what the brakes are doing.
Conversely a super low viscosity fluid would bleed easily but might put too much vibration through the lever and more importantly might leak past the seals.
And whatever the fluid it has to not react with the seals etc.
A lower viscosity mineral oil makes sense if it’s more like DOT fluid. I’ve often wondered if that viscosity difference is part of why Hope feel so much more nuanced than Shimano?
If you imagine a super high viscosity brake fluid you can picture how it would be very difficult to bleed but also that you’d get less feedback from piston to lever of what the brakes are doing.
Conversely a super low viscosity fluid would bleed easily but might put too much vibration through the lever and more importantly might leak past the seals.
And whatever the fluid it has to not react with the seals etc.
A lower viscosity mineral oil makes sense if it’s more like DOT fluid. I’ve often wondered if that viscosity difference is part of why Hope feel so much more nuanced than Shimano?
I don't think this is entirely true - the viscosity is only relevant when the fluid is flowing, so yes it could affect the bleed, but once you're feeling the fluid pressure through the levers the fluid will have stopped flowing pretty much.
Only with a previous poor bleed that left air under the diaphragm. NO air should be able to get into the master cylinder
Not sure about this - certainly after a good bleed there shouldn't be any air in the system, (hence why floating bite advice was always 'good bleed'), but I find it hard to believe that the system remains air free once the pads have worn and master cylinder fluid has made up the difference leaving a vacuum behind initially...but atmospheric pressure. Otherwise why would you ever need to bleed a system again?
A hydraulic disc erake system is a closed system with a diaphragm to allow for varying volumes. there is no where to get air in. I suspect that cases like you mention is air under the diaphragm in the reservoir getting into the lines. There simply is no where for air to get in unless seals fail. I have multiple sets of hopes, none of them have ever required re bleeding unless air under the diaphragm has got into the lines. I think shimano have very low reservoir volumes making this more likely
Air cannot get in to a closed system There is never a vacuum created in the system. The lever spring does not act to pull the pads back, the piston seal pushes the lever back. The diaphragm moves to keep the system at atmospheric pressure as pads wear
But in the real world TJ no seal is perfect and many flexible rubber-like materials will pass through gas molecules slowly - see how quickly non-foil balloons deflate.
Apparently the lower viscosity means that it will transfer hydraulic pressure more quickly.
Hydraulic pressure will be transferred at the speed of sound within the medium. A brake hose is less than 2 meters long. You wouldn't tell the difference in speed of transfer between different fluids.
Apparently the lower viscosity means that it will transfer hydraulic pressure more quickly.
Hydraulic pressure will be transferred at the speed of sound within the medium. A brake hose is less than 2 meters long. You wouldn't tell the difference in speed of transfer between different fluids.
I only understand the basics of hydraulic systems & braking systems, and hadn't heard about LV mineral oil until stumbling across the BikeRadar article, which is where that came from. Interestingly the article doesn't even mention the wandering bite point.
Shimano sent out a questionnaire some time ago within the industry to shops or whoever gets these things asking if a new mineral oil would be acceptable to them if it fixed the issue. Apparently the answer came back yes.
So Shimano are admitting that it's a problem then are they? I'm rarely up to date with what's going on in the cycling industry (I'm still 3x10 & QR wheels) but it used to be that there wasn't a problem (although you could warranty your brakes if you were experiencing said non-existent problem). The advice on here was often that it was all down to poor bleeding technique.
If the wandering bite point issue is oil related then surely they could make something that was backwards compatible or at least make compatible seals available.
The other thing that seems odd is that the article states (although maybe that it's not as reliable as I thought) that currently only XTR & XT race brakes use the oil with everything else remaining on the old 'flawed' oil.
Everyone does degas their fluid before a bleed, yeah? That seems to help make the bleed and lever feel remain consistent for far longer than anything else I've tried...however, helping get all the air out can take some.time.and persuasion.
On a friends SLX brakes that had a wandering bite point the pistons were slightly sticky. They'd retract enough to not rub and then very slowly move in a bit more. A replacement calliper seems to have fixed it for the moment.
So Shimano are admitting that it's a problem then are they?
Yeah, along with the rattling pad issue. Shimano have put forward some fixes for that too. It's never happened with my brakes though so I don't know what all the fuss is about.
I'm inclined to believe Shimano brakes do allow air in somehow over time. I've had 10-12 pairs of Shimanos over the last 15 years and most have required occasional bleeding, some regular, a few with far too much air way too often to be a bad bleed or already in the fluid. The one exception is GRX, which are the only drop bar brakes I've had. If I ever go to bleed Sram, there's just no air in there.
Thing is, even if it is purely an "air still in after bleeding" thing, that's still a design failure when it's so widespread and so frustrating. It's weird to me this stuff, I'm using 15 year old brakes that don't do this, good brakes are a long solved problem- in fact even the crappest brake manufacturers have managed to solve this problem at least once but some of them just keep reinventing old problems, for a laugh.
