Honest ! I’m not just trying to start Trouble - Dot 3 / Dot 4 vs Dot 5.1

[DeadEye]

All things being equal - which they aren’t - other than dot 5.1 brake fluid having a higher boiling point , would there be a problem doing the brake fluid flush with Dot 5.1 fluid on all the bikes… isn’t the Fancy new Formula better  ?

PS: NO silicone based fluid 5.0 here !!!

Thanks,
Don

PPS: Yes , I keep asking the question until I get the answer I want to hear ! :)

[9Mary7]

(I might have seen this question somewhere else)

[Groanup]

THIS ARTICLE 

may answer some questions.

[RogerC60]

1 hour ago, Groanup said:

THIS ARTICLE 

may answer some questions.

Use caution. In one paragraph that article states that DOT 5.1 is not compatible with ABS, and in the next paragraph says it is compatible with ABS. Whenever I find internal inconsistencies in an article I throw it in the trash.

[Lowndes]

Dang it DeadEye, look what you done started.  Now how you gonna put THIS fire out??

[JCtx]

Why not just use what the bike says on the brake fluid reservoir cover? That's what I always do. BMW even says to use DOT4 LV (low viscosity) now, but I use plain DOT4, which is exactly what the bike came with, and what it says on the reservoir cover. And I don't deviate from engine oil viscosity either (I use Castrol Power1 4T 5w40). I did the brake bleed job yesterday, and used Prestone Snythetic DOT4, just like the first time when bike was new (but 2 years old, with 0 miles). All you need is a $6 12-oz bottle you can buy at Walmart. Anyway, in theory, you could use DOT5.1 fluid, but the braking system wasn't designed for that, so if you need higher boiling temperatures than regular DOT4, just buy a racing DOT4 fluid, like Motul. Similarly, my 2020 wasn't designed for DOT4 LV either, and I don't ride in winter, so zero incentive for me to switch. Finally, you didn't state your reasons for considering DOT5.1, so if you explain why, this could be a more informative thread. Bottom line is unless you're tracking your bike, there's no reason to consider anything other than regular DOT4.

[Dave_in_TX]

8 minutes ago, JCtx said:

Why not just use what the bike says on the brake fluid reservoir cover? That's what I always do. BMW even says to use DOT4 LV (low viscosity) now, but I use plain DOT4, which is exactly what the bike came with, and what it says on the reservoir cover. And I don't deviate from engine oil viscosity either (I use Castrol Power1 4T 5w40). I did the brake bleed job yesterday, and used Prestone Snythetic DOT4, just like the first time when bike was new (but 2 years old, with 0 miles). All you need is a $6 12-oz bottle you can buy at Walmart. Anyway, in theory, you could use DOT5.1 fluid, but the braking system wasn't designed for that, so if you need higher boiling temperatures than regular DOT4, just buy a racing DOT4 fluid, like Motul. Similarly, my 2020 wasn't designed for DOT4 LV either, and I don't ride in winter, so zero incentive for me to switch. Finally, you didn't state your reasons for considering DOT5.1, so if you explain why, this could be a more informative thread. Bottom line is unless you're tracking your bike, there's no reason to consider anything other than regular DOT4.

If your 2020 R1250R wasn't designed for DOT4 LV, why does the BMW parts fiche for your bike  show DOT4 LV?

 

And if DOT5.1 isn't suitable for ABS systems, why does a google search for "dot 5.1 abs" show several brands of DOT5.1 with recommendations for use in ABS systems?

[JCtx]

My '20 bike wasn't designed for DOT4 LV, and that is a fact. Vehicles designed for it says so on the reservoir lid, like my other vehicles. That BMW is recommending it now (which I clearly mentioned on my first line you quoted above), is a different story. At any rate, the only reason to consider it if if you ride in very cold weather, which I don't, so I'm not going to use it. But to each his own. Anyway, it's a similar situation with engine oil, where just one viscosity doesn't always cover all conditions. So it's okay to switch if conditions warrant the change, especially if an alternate viscosity is approved elsewhere in the world.

[Dave_in_TX]

BMW has been recommending low viscosity brake fluid (based on parts fiche) at least as far back as 2016 and BMW still hasn't changed the reservoir cap on the 2023 models. I don't think you can make the assumption that just because your cap doesn't say low viscosity that the system was designed for regular viscosity.

[DeadEye]

If you Google around, one characteristic of Dot 5.1 is lower viscosity for ABS applications ???

I did track a couple of cars, Miata, MINI and thought nothing of using Dot 5.1 for the first flush and for ever after !

WHY Now:

The local BMW club offers a spring time Track day, and I’m considering attending.

I’ve been to the track they use many times in a cage - but I won’t be treating it the same on a bike !

Im a chicken @#$&  so I’ll be on the brakes A Lot, why not have an extra measure of security ?

( no ABS on my bike )

 

Where is an engineer when you need one !

I Imagine the difference to be  like motor oil.

20W-30 :

- you can buy the cheap stuff

- quality with premium additives

- full synthetic 

They all work but do you fell better with « The Good Stuff » in your baby ;)

 

Don

 

[DeadEye]

22 hours ago, RogerC60 said:

Use caution. In one paragraph that article states that DOT 5.1 is not compatible with ABS, and in the next paragraph says it is compatible with ABS. Whenever I find internal inconsistencies in an article I throw it in the trash.

Indeed, 

for Dot 5.1

In the  water absorption section it says it worse

in the cost section it says it’s better !

 

[JCtx]

On 3/27/2024 at 5:19 AM, Dave_in_TX said:

I don't think you can make the assumption that just because your cap doesn't say low viscosity that the system was designed for regular viscosity.

Well, you're making the assumption that just because you can use it, it was designed for it. Bottom line is it was designed for extreme cold weather, which my bike will never see, so I have zero reason to even consider it. But those who use their bikes in those conditions, can safely use it, according to BMW. End of discussion.

[Dave_in_TX]

1 hour ago, JCtx said:

Well, you're making the assumption that just because you can use it, it was designed for it. Bottom line is it was designed for extreme cold weather, which my bike will never see, so I have zero reason to even consider it. But those who use their bikes in those conditions, can safely use it, according to BMW. End of discussion.

I'm not making any assumptions (well, i am assuming it could have been designed for either low vis or regular). You're the one making them, assuming that even though BMW recommends  low viscosity and has for many years, it was designed for normal viscosity simply because it doesn't say low viscosity on the reservoir cap.

[DeadEye]

Ok, ok I’ll just go out and buy a couple of bottles of Dot 4 fluid  And do them all together.
Brake fluid flush « party » At my house !