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Discussion Starter · #1 ·
About the change my '03 ST brake fluid. Grabbed a can of DOT 4 fluid and saw it's synthetic, that's all the store had in DOT 4. I've never used synthetic in a motorcycle brake system. The can says OK for all systems, and for use with non-synth fluid. Does it hold true for motorcycles? Thanks.
 

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I think as long at it says "compatible with conventional brake fluids" you'll be fine.

I've been using Valvoline Synthetic fluid for years.
 

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5.0 is synthetic.

I'd suggest using DOT 5.1. It is compatible with other non-synthetics. I've seen it in use in some 650 class race bikes and works a treat.
 

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Very Informative Information

Unless it's specified, I would stay away from any 5.0 brake fluid.
Most brake fluid is glycol-based, 5.0 brake fluid is silicone-based and cannot be mixed with any glycol-based brake fluid.
Check this non-professional site:http://www.motorcycleproject.com/motorcycle/text/cows-brakefluid.html
If your not sure about what brake fluid to use. Then you REALLY need to READ this Very Informative information that Bruce C. has posted. I learned a little more than I already knew myself about Brake Fluid.
 

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I don't think the OP was confused about which brake fluid to use. He bought DOT 4 and was asking if the fact that it was labeled "synthetic" made any difference. He did not say it was silicone.

DOT 4 is DO4 regardless of labling.

Dolson is right on about 5.1. It is also approved for ABS systems.

What concerns me in this thread is that no one has mentioned that the brake system should be flushed yearly. The OP mentions an 03. I hope the fluid has been flushed in the interim, and not just replenished.
 

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I don't think the OP was confused about which brake fluid to use. He bought DOT 4 and was asking if the fact that it was labeled "synthetic" made any difference. He did not say it was silicone.....


Have to disagree with using 5.1 however - that is intended for race systems with VERY short lifetime.
Yes - it has higher DRY BP's - which make it attractive to the racer. That element alone is the major asset of a brake fluid - especially one under intense usage - like racing - where the brakes are extremely active.
BUT - that comes with a price - it is much more affected by water-absorption. That makes no difference to the racer, who is going to refresh for each session. But not good for a street bike.
The BP is rated on fresh 'dry' fluid - when water is absorbed - even in tiny amounts, the BP is reduced drastically.
DOT4 is plenty for street bike - and even some DOT3 can have excellent specs than can even exceed some 4's, even with some water incorporated.
i.e. is fresh (dry) 5.1 better than fresh 3?
Absolutely!
In the real world, that is not the case and 'wet' DOT3 will actually have better BP's than 'wet' 5.1.
In this case just because racers use it does NOT make it better for your street bike.
 

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Have to disagree with using 5.1 however - that is intended for race systems with VERY short lifetime.
Yes - it has higher DRY BP's - which make it attractive to the racer. That element alone is the major asset of a brake fluid - especially one under intense usage - like racing - where the brakes are extremely active.
BUT - that comes with a price - it is much more affected by water-absorption. That makes no difference to the racer, who is going to refresh for each session. But not good for a street bike.
The BP is rated on fresh 'dry' fluid - when water is absorbed - even in tiny amounts, the BP is reduced drastically.
DOT4 is plenty for street bike - and even some DOT3 can have excellent specs than can even exceed some 4's, even with some water incorporated.
i.e. is fresh (dry) 5.1 better than fresh 3?
Absolutely!
In the real world, that is not the case and 'wet' DOT3 will actually have better BP's than 'wet' 5.1.
In this case just because racers use it does NOT make it better for your street bike.
But, Do you have any direct experience with DOT 5.1 to back up what you are saying?
Personally, I've been using DOT 5.1 since it came out, change normally, usually with pad changes without issue.

How was your testing done? Open container? Closed system? What methodology did you use for your testing?

http://en.wikipedia.org/wiki/DOT_5.1

http://www.stoptech.com/tech_info/wp_brakefluid_1a.shtml

These are just a few that contradict what you are saying and everything I've seen says that for any given amount of moisture DOT 5.1 still has a higher dry AND wet Boiling Point than either DOT 3 and 4.
Since all non-synthetic, Glycol Ether based brake fluid is hygroscopic I'm failing to see your point or how you can say that DOT 5.1 is more hygroscopic than DOT 3+4 especially since DOT 5.1 can easily be considered a enhanced DOT 4.
It is labeled and noted as DOT 5.1 because it is really a DOT 4 that meets or exceeds DOT 5.0 specifications.

The only down side is that the cost is a bit higher than DOT4 but that is minimal and certainly not in the cost of a pure racing brake fluid which I think you are confusing DOT 5.1 with.

Upside of using DOT 5.1 not to be confused with DOT 5.0 is:
1. Compatibility with DOT 3+4 and ABS systems.
2. Higher Boiling Point dry or wet than DOT 3+4 that meets or exceeds DOT 5.0 specifications.
3. The same hygroscopic properties as DOT 3+4 so the same servicing intervals apply. (being hygroscopic is a good thing. Since the system will absorb moisture over time I'd rather have the molecules of moisture in suspension than not.)

Down side:
1. Very slightly higher cost than DOT 3+4. But not enough considering service intervals to be worth mentioning.

That said, if one is happy with the performance of the brake fluid specified for the application, meaning you are not hard enough on the brakes to get fade, by all means keep using it and servicing it as said at 1 year intervals no more than 2.
If you are getting fade like I was you might consider a change to DOT 5.1.




 

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Discussion Starter · #9 · (Edited)
Thanks for the feedback.

I don't think the OP was confused about which brake fluid to use. He bought DOT 4 and was asking if the fact that it was labeled "synthetic" made any difference. He did not say it was silicone.

DOT 4 is DO4 regardless of labling.

Dolson is right on about 5.1. It is also approved for ABS systems.

What concerns me in this thread is that no one has mentioned that the brake system should be flushed yearly. The OP mentions an 03. I hope the fluid has been flushed in the interim, and not just replenished.
True there. I've used synthetic engine oil in motorcycles for years, but never synthetic brake fluid so this is a first. I get the drift that synth is OK to use. The brake system was flushed previous to this time, though I'm a couple of months behind schedule.
 

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Discussion Starter · #11 ·
OK, got it changed and what a hassle.

Tried something different and used a "One Man Brake Bleed Kit" and couldn't get the bubbles to stop and the lever to firm up. Went and got a Mity-Vac and still couldn't get it right.

I went back to the old tried and true of pumping the brake lever while opening/closing the bleed valve (as I usually do). That worked, shoulda started there and saved the dough.
 

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I can't understand why anyone would change their brake fluid every season other than to make peace with their own peace of mind or the lack of better things to do.

Do you change it out in your cars every 6 months to a year?
 

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I can't understand why anyone would change their brake fluid every season other than to make peace with their own peace of mind or the lack of better things to do.

Do you change it out in your cars every 6 months to a year?
Every year on EVERYTHING I own. Or with a pad change too if that gets into the year. Brake fluid is cheap.
 

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5.0 is synthetic.

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I think you mean DOT 5 is silicone based, and not gylcol based like DOT 3/4/5.1. Being silicone based, it's not hygroscopic, so it won't absorb moisture. Most of the brake fluids I have used have been synthetic, so I'm not sure why people are worried. Synthetic and silicone are two totally different things.

If you don't have ABS in your bike, I suggest a Super DOT 4 fluid, such as ATE Super Blue/ATE Typ 200. It has a higher dry and wet boiling point than most of the 5.1 fluids. They also claim a usage life of 3 years, compared to 1 year.

I've used Motul 5.1 and ATE Typ 200 in some of my past cars, and both were great.
 

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I can't understand why anyone would change their brake fluid every season other than to make peace with their own peace of mind or the lack of better things to do.

Do you change it out in your cars every 6 months to a year?
Most manufacturers recommend a brake flush every year. Especially vehicles still using dot 3.
 

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I think you mean DOT 5 is silicone based, and not gylcol based like DOT 3/4/5.1. Being silicone based, it's not hygroscopic, so it won't absorb moisture. Most of the brake fluids I have used have been synthetic, so I'm not sure why people are worried. Synthetic and silicone are two totally different things.

If you don't have ABS in your bike, I suggest a Super DOT 4 fluid, such as ATE Super Blue/ATE Typ 200. It has a higher dry and wet boiling point than most of the 5.1 fluids. They also claim a usage life of 3 years, compared to 1 year.

I've used Motul 5.1 and ATE Typ 200 in some of my past cars, and both were great.
You are absolutely right. I got my synthetic and silicone twisted.

5.1 as is also known in some circles as Super 4 is Synthetic glycol based and 5.0 is silicone based.

As I said 5.1 is known as that as it has the same dry and wet boiling points as the 5.0 silicone based but has the same base and makeup as a 4.0.

Check the links I provided in the previous post it will explain and lead to other links.

As DaveM said, we like all newbies to read the stickies at the top.

Don
 

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Think of it this way, you want your brakes to perform at their best don't you!!!
So follow the makers recommendation and change your fluid as per service schedule, this is written by a manufacturer in consultation with the brake supplier to offer you the rider the best possible advice and most reliable condition, they would be failing in their "Duty of care" to advise stretching the service schedule past 12 monthly changes.
They have conducted testing in all climates/conditions/usage and come up with the best possible advice.

I always use ***** brand of DOT4 and never have any issues with braking, I have used my bike on a trackday with 40C heat and thrashed all day without a hint of fade. Then again I flush/change my fluid every 12 months. I have had huge experience within racing circles and they change every race!!!!! (cars) it is a small cost compared to a life!!!!!!!!!

As for swapping to a different brand/rating I would excercise caution as I have known ***** brand to attack the seals and seize the pistons in the calipers and crack all the discs through heat distortion, new rotors and seals fitted and old fluid back in no issues, please excercise caution as these are life and limb components!!!!!!!!!!!!!!

FYI on the grounds of the fluid being Hygroscopic, this will only happen if the fluid is exposed to air. The design of every brake M/C I have seen, has a rubber bellow incorporated into the resevoir lid this allows air in above the bellow, and not into the fluid, this allows fluid transfer into the calipers to account for pad wear.

Given this is a Forum for all to read, and some people are not familiar with workshop techniques and look here for the best advice, It would be rather confusing when reading about DOT3 this and DOT 5 for that, so I would advise "If your unsure CONSULT the OEM Manual" or take it to a workshop. I would not rest easy myself if someone mis-understood something regarding Brakes and became a casualty of their own mis-led/understood ventures with fluids.

I'll say it again, If your not sure!, take it to someone who does.

Just my 2c
Regards
Ozzyfzr
 
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