Author Topic: DoT 5.1 Brake fluid what specification do you use ?  (Read 613 times)

Offline Macabethiele (Ted)

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DoT 5.1 Brake fluid what specification do you use ?
« on: August 25, 2020, 01:01:58 PM »
Although I'm unlikely to be building back the brakes this year I've been pondering in bed during the wee hours about what grade of brake fluid to put in my Honda CB400F2 - as a recent Insomniac (last 3 years or so) I try to utilise "trying to get to sleep time" to full advantage.

I use DoT 5.1 in all three of our four wheeled vehicles as I believe its the best option at a reasonable price.
I'm interested to hear views departing from OEM spec.
Honda CB400F2 under restoration
Jeep Grand Cherokee WJ
Jeep Grand Cherokee WK
Mercedes R129 SL500

Offline Macabethiele (Ted)

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #1 on: August 30, 2020, 07:46:59 PM »
So no dissenters / views  on brake fluid specifications probably not an issue on motor cycles then or I have posted in the wrong section. :-\ :-\
Honda CB400F2 under restoration
Jeep Grand Cherokee WJ
Jeep Grand Cherokee WK
Mercedes R129 SL500

Offline Nurse Julie

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #2 on: August 30, 2020, 09:17:03 PM »
DOT 5 Silicone is what we use in all of ours now Ted.
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Macabethiele (Ted)

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #3 on: August 31, 2020, 12:52:39 PM »
DOT 5 Silicone is what we use in all of ours now Ted.

Wow I didn't think anyone would be using Silicone based brake fluid in a motor cycle presumably that is for using in a system that has no remaining Glycol-based fluid such as Dot 4.0.  Are the existing seals suitable or do you have to upgrade for Silicone based fluid? 

I believe Dot 5.1 is a synthetic Glycol-based fluid with slightly higher boiling point than Dot 5.0 but is still hygroscopic whereas Silicone isn't of course.
Honda CB400F2 under restoration
Jeep Grand Cherokee WJ
Jeep Grand Cherokee WK
Mercedes R129 SL500

Offline Nurse Julie

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #4 on: August 31, 2020, 01:05:25 PM »
DOT 5 Silicone is what we use in all of ours now Ted.

Wow I didn't think anyone would be using Silicone based brake fluid in a motor cycle presumably that is for using in a system that has no remaining Glycol-based fluid such as Dot 4.0.  Are the existing seals suitable or do you have to upgrade for Silicone based fluid? 

I believe Dot 5.1 is a synthetic Glycol-based fluid with slightly higher boiling point than Dot 5.0 but is still hygroscopic whereas Silicone isn't of course.
All our bikes have had the complete braking systems overhauled with new seals etc fitted, so no mix or contamination from the old non compatible brake fluid.
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Macabethiele (Ted)

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #5 on: August 31, 2020, 02:47:28 PM »
DOT 5 Silicone is what we use in all of ours now Ted.

Wow I didn't think anyone would be using Silicone based brake fluid in a motor cycle presumably that is for using in a system that has no remaining Glycol-based fluid such as Dot 4.0.  Are the existing seals suitable or do you have to upgrade for Silicone based fluid? 

I believe Dot 5.1 is a synthetic Glycol-based fluid with slightly higher boiling point than Dot 5.0 but is still hygroscopic whereas Silicone isn't of course.
All our bikes have had the complete braking systems overhauled with new seals etc fitted, so no mix or contamination from the old non compatible brake fluid.

Looks like I will be using Dot 5.0 in the Honda as it will be either new parts or new seals at the very least.
Honda CB400F2 under restoration
Jeep Grand Cherokee WJ
Jeep Grand Cherokee WK
Mercedes R129 SL500

Offline Piki

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #6 on: September 01, 2020, 08:56:02 AM »
DOT 5 Silicone is what we use in all of ours now Ted.

Wow I didn't think anyone would be using Silicone based brake fluid in a motor cycle presumably that is for using in a system that has no remaining Glycol-based fluid such as Dot 4.0.  Are the existing seals suitable or do you have to upgrade for Silicone based fluid? 

I believe Dot 5.1 is a synthetic Glycol-based fluid with slightly higher boiling point than Dot 5.0 but is still hygroscopic whereas Silicone isn't of course.
All our bikes have had the complete braking systems overhauled with new seals etc fitted, so no mix or contamination from the old non compatible brake fluid.
A few months ago I changed my brake fluid to 5.0(base silicone) I actually just did a drain of the old liquid and changed the brake fluid pump mechanism...... did something wrong? Should the brake liquid pipes have changed, too?

Offline florence

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #7 on: September 01, 2020, 10:12:30 AM »
DOT4 works perfectly well.  I think I have also used DOT3

Offline Macabethiele (Ted)

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #8 on: September 24, 2020, 12:22:21 AM »
DOT4 works perfectly well.  I think I have also used DOT3

I agree the older specification brake fluids all work okay but if you want to avoid the build up of water in the fluid caused by hygroscopic action imho the best options are later fluids unless of course you religiously change your brake fluid on an annual basis.

The amount of water absorbed by most brake fluids depends on many factors including atmospheric moisture content of the ambient air, unused new fluid storage, winter bike storage conditions & heavy braking causing fluctuations in fluid temperatures. I am minded to agree with NJ that Silicon based 5.0 is the best option especially for classic bikes that do not always get a lot of all year round use as it is not hygroscopic.
Honda CB400F2 under restoration
Jeep Grand Cherokee WJ
Jeep Grand Cherokee WK
Mercedes R129 SL500

Offline K2-K6

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #9 on: September 24, 2020, 08:44:26 AM »
"I agree the older specification brake fluids all work okay but if you want to avoid the build up of water in the fluid caused by hygroscopic action imho the best options are later fluids unless of course you religiously change your brake fluid on an annual basis."

My understanding of this topic is that the fluid (silicone) isn't subject to water ingress but the brake system still is.

Dot4 etc as described,  will ultimately contain distributed water which is the reasoning for periodic change to purge and restore it's manufactured boiling point,  plus sensitivity of some complex systems to internal corrosion.

Silicone based systems ultimately collect any water accumulation at the lowest point as the oil is lighter in sg,  so should still be routinely purged to avoid lowered boiling point conditions at the calipers.

With the above consideration,  it seems strange to bleed systems by pushing fluid in from caliper end as some advice given out on the great wide web. Can't immediately see why you do that.

Offline Bryanj

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #10 on: September 24, 2020, 08:46:08 AM »
Not sure if its true but have read somewhere that the 5 boils at a lower temp than 3(when 3 is new)

Offline K2-K6

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #11 on: September 24, 2020, 09:31:26 AM »
https://en.m.wikipedia.org/wiki/Brake_fluid

Information posted above is quite informative,  and lucid, in discussing this. I hadn't looked before,  but it seems to give decent appraisal of using silicone and why such a system would have any contaminate within it.

Also description of difference between 5.1 and 5 regarding silicone content and incompatibility or not.

Offline Macabethiele (Ted)

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #12 on: September 24, 2020, 11:32:05 AM »
https://en.m.wikipedia.org/wiki/Brake_fluid

Information posted above is quite informative,  and lucid, in discussing this. I hadn't looked before,  but it seems to give decent appraisal of using silicone and why such a system would have any contaminate within it.

Also description of difference between 5.1 and 5 regarding silicone content and incompatibility or not.

DoT 5.1 is not silicone based and can be mixed with all older Dot fluids fluids except silicone based fluids such 5.0.
DoT 5.1 is what I use in all my cars but will probably go for 5.0 for the Honda CB400F2.
Interestingly some cars now have none water based coolants that are more heat efficient than water/Ethylene Glycol based-  the new generation coolants  can be used retrospectively but every trace of water must be removed first. They make a special flushing liquid to remove every scrap of water - not cheap designed more for very high performance vehicles - very good for reducing engine corrosion from coolants. The flushing agents can cost around the same price as the waterless coolant itself so its an expensive conversion unless you have a fully stripped down engine to start with.

https://www.carparts4less.co.uk/p/evans-vintage-180-waterless-coolant-5ltr-993778061?gclid=CjwKCAjwh7H7BRBBEiwAPXjadrsC2OuV8WAb6mrckteD9t9qdPQ0b1HSdV3u2VPmC68ITog6DG-8rhoCrgMQAvD_BwE
« Last Edit: September 24, 2020, 11:35:30 AM by Macabethiele »
Honda CB400F2 under restoration
Jeep Grand Cherokee WJ
Jeep Grand Cherokee WK
Mercedes R129 SL500

Offline K2-K6

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Re: DoT 5.1 Brake fluid what specification do you use ?
« Reply #13 on: September 24, 2020, 12:06:15 PM »
Yes I know that the two 5 denoted fluids are not the same.  It's more that it causes confusion that somehow those responsible for naming the two have contrived to muddy the water by apparently  putting one as a derivative of the other with the   .1 iteration. 

They really should have given one of them a different primary category to avoid potential conflicts.

 

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