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Post by radwan on Aug 7, 2017 21:34:37 GMT
Hi all Wanted to ask, what is the intended brake fluid for my 1996 900 SS CR? Would Motorex 5.1 be ok? And I know this might seem like a silly question, but is it recommended to fill the fluid to the Max line or below? Thanks so much!
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Post by samadhi on Aug 12, 2017 1:26:48 GMT
Hello radwan, DOT's 3, 4, or 5.1 will work, as they are all glycol-based fluids. I use Motul 5.1, because I have had great experience with it, provides better performance than 3 or 4 (higher wet and dry boiling point than the other two) and it's red, so it can be seen through my clear Tygon rear brake cylinder reservoir for some added "bling" DOT 5 is silicone-based fluid, and may eventually cause eventual failure of the braking system and catastrophic results. DO NOT USE IT. As far as the amount to use: After properly flushing, and making sure there are no air bubbles, I make sure the fluid is between maximum and minimum lines. This way, it has room to expand when hot. I personally have never had an issue, but I don't speak from track experience, only aggressive canyon riding. Cheers.
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Post by Iconic944ss on Aug 17, 2017 10:35:24 GMT
Some Expert Q&A:
Shazaam! on DOT 5.1 Brake Fluid
The DOT specification for DOT 5.1 brake fluid has a higher minimum dry boiling point/minimum wet boiling point (527°F/347°F) than the DOT 4 spec (446°F/311°F), but these are just minimum specs.
Several DOT 4 fluids exceed DOT 5.1 specs. For example, expensive Castrol SRF (590°F/518°F) is used by Formula One teams, ATE Type 200 and Super Blue Racing (536°F/392°F), and Motul RBF 600 (593°F/421°F). Golden Spectro Supreme DOT 4 (520°F/367°F) comes close.
So DOT 5.1 fluid is not necessarily better, particularly after absorbing moisture. Most of us don't change our brake fluid very often so wet boiling point numbers are more important. On the track, brake fade is the main concern so we change the fluid more often and use a higher dry boiling point fluid. Generally, the higher the dry boiling point, the faster the fluid absorbs moisture from the air, Castrol SRF and the ATE fluids excepted.
If you don't change your brake fluid once a year or so, the absorbed moisture in the fluid corrodes expensive brake bits. So, do it this spring.
Castrol SRF is the best, hard to find, four-times more expensive than the others, and used by every Formula 1 team in existence because it’s boiling point drops very little as it absorbs moisture. (590°F/518°F)
Motul RBF 600 is next best and reasonably priced. Same dry boiling point and the next-highest wet boiling point. It tends to absorb water more quickly than the others so it seems to be best suited for racing applications where the fluid is changed very frequently. Keep in mind that any fresh dry fluid will be better than wet Motul because it will have a higher temperature boiling point. (593°F/421°F)
This suggests to me that ATE is the best all-round brake fluid.
BMW recommends ATE brake fluid for their street cars because it, like Castrol LMA (446°F/311°F), absorbs moisture very slowly. The advantage over LMA is that ATE has a much better wet boiling point. You can use this in your street bike and forget about it for a year or so. An excellent choice for a weekend track bike which also sees regular street duty.
ATE Super Blue and ATE Type 200 and are the same fluid. The theory is to alternate them and you can tell from the color when you have flushed all the old fluid out. In practice however, once a can is opened it should be used-up quickly. It’s not a good idea to save fluid from an opened can for color change reasons. (536°F/392°F)
As a point of reference, Motul 5.1 is 518°F/365°F.
Do you know if there are any compatibility issues in swapping from DOT 4 to 5 or visa versa?
Shazaam!
DOT 4 fluid can be replaced by DOT 5.1 fluid and vice versa.
DOT 5 fluid is different. It is silicone-based and cannot be used in Ducatis that use Brembo brake and clutch master and slave cylinders. It will damage the natural rubber seals. It is dyed purple to give a visual warning against accidental use.
Nelly!
Shazzams post is pretty much spot on. The high spec DOT4's usually come out better than 5.1, but for all round performance vs. cost 5.1 takes some beating. Motul DOT5.1 is my regular service fluid and i use it in all brake and clutch systems. Motul RBF600 has now been superceded by 660 which is pretty much a match for SRF but works out about double the cost of the 5.1 One other characteristic of 5.1 is it's thinner than DOT 4 which can help with bleeding, or so i find anyhow. DON'T use DOT5....as Shazzam! mentions it's silicon based. It doesn't mix with DOT 4 or 5.1 and plays havoc with the seals in Brembo equipment.
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Post by Iconic944ss on Aug 17, 2017 10:43:12 GMT
Hi all And I know this might seem like a silly question, but is it recommended to fill the fluid to the Max line or below? Thanks so much! I think the main factor in this is how worn your pads are; if new then filling to the max line allows for more pad wear.
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