Recommended Brake Fluid MK II Front Brake?
- Thread starter Dan1950
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if my memory is still working,... dot5 was originally developed for modern aircraft ? my norton isn't fast enough to spend any serious time in the air, 
so it will have to be happy with dot4.
so it will have to be happy with dot4.- Joined
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I used dot 5 in my 1974 interstate, after a total brake rebuild, starting with a dry system , and using a sleeved 12 mm master. Brakes worked great. Bike is now stored and I have no concerns about corrosion.
I use dot 4 in my 1972 roaster with a sleeved master and the brakes work great. But if I was storing it I'd worry about corrosion.
I use dot 4 in my 1972 roaster with a sleeved master and the brakes work great. But if I was storing it I'd worry about corrosion.
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About two years ago I went through my front brake system, M/C kit, new hose, caliper seals. As for the dot 3-4 absorbing moisture and evenly displacing it is a good thing if you flush the system every two years. If not water will still accumulate at the bottom of the caliper as indicated when I dissembled it and had a hard time cleaning the corrosion from the bottom of the seal grove. Over the years the M/C would leak at the outer ( lever end ) seal from corrosion, or water, brake fluid induced crud.
After reading as much as I could and the fact that a friend has used it and raves about it for thirty years in a 68 Dodge dart I went with DOT 5, and will convert my other bikes and my 63 Ford the next time any brake work is needed. It seams to me that the less a vehicle is used the more DOT 5 makes since.... IMO.
After reading as much as I could and the fact that a friend has used it and raves about it for thirty years in a 68 Dodge dart I went with DOT 5, and will convert my other bikes and my 63 Ford the next time any brake work is needed. It seams to me that the less a vehicle is used the more DOT 5 makes since.... IMO.
Mart UK
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In my view, storing the bike with fresh dot 4 really ought to be fine. The seals will do their job. I think it's riding in the wet and hosing the bike down that introduces water into the system. I try to avoid getting the bars and m/c wet when washing the bike (also try to avoid the guages). I change the fluid every 2 years though.
cliffa
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Apparently it was originally developed for military use, so no need to build a launch rampif my memory is still working,... dot5 was originally developed for modern aircraft ? my norton isn't fast enough to spend any serious time in the air,
jaydee75
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I use Dot 5 in all my bikes. It stays clean and pure, and I don't have to worry about the fungus that grows with Dot3.
I value my original paint too much to risk drip or fume attack by others. One less thing to worry about.
I ride pretty hard and never had the caliper get hot enough to cause a problem with 5. Caution, don't just change to Dot5, it requires complete removal of all old fluids. Best to do with a full rebuild, fill it and forget it.
Jaydee
I value my original paint too much to risk drip or fume attack by others. One less thing to worry about.
I ride pretty hard and never had the caliper get hot enough to cause a problem with 5. Caution, don't just change to Dot5, it requires complete removal of all old fluids. Best to do with a full rebuild, fill it and forget it.
Jaydee
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DOT 5 would be a disaster in aircraft. Since any moisture that got in would not mix with the brake fluid, it would sink to the bottom of the calipers, as kommando already mentioned. Air temperature decreases with altitude. That means that water trapped in the calipers of an aircraft could freeze at altitude. If the plane descends quickly, the ice may not have time to melt. Like I'd really want to try to stop an aircraft with no brakes on a wet or snow covered runway. NOT! Modern aircraft [large] use Phosphate Ester based brake fluid, called Skydrol. It's like super DOT 5.1, but a very nasty carcinogen. Small aircraft use Polyalphaolefin based fluids, meeting Mil Spec H-83282.if my memory is still working,... dot5 was originally developed for modern aircraft ? my norton isn't fast enough to spend any serious time in the air,
Actually, it was developed for the US Army. The idea was to reduce maintenance and failures in military vehicles. They tend to drive off road and sometimes are required to ford streams & rivers. After 10 years of use, the Army gave up on it. They found that water got in, didn't mix and corroded the snot out of all the calipers and wheel cylinders of their vehicles. Racers loved it at first, but found that rapid pumping of the brake pedal causes DOT 5 to cavitate [create air bubbles] with resultant brake fade.
Jaydee75's use of it is reasonable, but even DOT 5 should be flushed out occasionally.
DOT 2 thru 4 & 5.1 are all glycol based fluids. They are hygroscopic, meaning that they attract moisture. That is why these types of fluids need to be flushed [not just bled] every 2 to 3 years. Basically, it's time to change the fluid when the moisture content reaches 3%. You can find a great brake fluid tester on Amazon. I've used one of these tools for years now. See
Amazon Brake Fluid Test Pen
DOT 4 fluid absorbs moisture much slower than DOT 2 [old drum brake spec] or DOT 3. My experience is that cheap DOT 4 fluids don't last as long as the good stuff. If you are going to use DOT 4, buy Castrol or ATE 200. These are top quality fluids & have higher boiling points & last longer than cheap fluids. Don't be impressed if the label says "Synthetic". That's just marketing BS. All glycol based brake fluid is synthetic.
I can flush the fluid on both systems of a Mk III in about half an hour. Since it takes so little time, I do it every year, as a precaution.
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Could always try adding a little blue pill.....
(Just do NOT mention the: 'V' word¬)
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I use DOT 4 front, but DOT 5 for my rear brake, because I have no reservoir, but only 25 cm of clear tube .
DOT 4 will 'sweat' right through crystal tube, and attack the paint:
Like others have said, the fact that DOT 4 absorbs water, is a good thing..
DOT 4 will 'sweat' right through crystal tube, and attack the paint:
Like others have said, the fact that DOT 4 absorbs water, is a good thing..
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If You are using the Stock Norton master and caliper Dot 5 silicone fluid will most likely eat the seals and cost you a fortune for 500ml or worse when the seals fail
using Dot 4 / 5.1 Glycol based is the answer stock seals are compatible , just change the fluid every two seasons
if you buy a modern car manufacturers schedule a brake fluid change at 24 months or 24.000 miles which is perfectly adequate
using Dot 4 / 5.1 Glycol based is the answer stock seals are compatible , just change the fluid every two seasons
if you buy a modern car manufacturers schedule a brake fluid change at 24 months or 24.000 miles which is perfectly adequate
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i knew it was something like that, thanks for the correction.
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Two weeks ago, I was paranoid about my isolastics (which have given years of effective service and there is absolutely nothing wrong with them)....
Now I am paranoid about my brake fluid, which I had not given a second thought about for this entire past riding season, and for at least the last 12,000 miles for that matter (but still inspect regularly).
I wonder what I will be paranoid about next week? LOL
Now I am paranoid about my brake fluid, which I had not given a second thought about for this entire past riding season, and for at least the last 12,000 miles for that matter (but still inspect regularly).
I wonder what I will be paranoid about next week? LOL
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How about ethanol in gasoline absorbing water which condenses on the inside upper surface of the gas tank, leading to pin hole corrosion.
When is the last time you scoped your gas tank?
When is the last time you scoped your gas tank?
cliffa
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Rectifier/regulator?
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That is the paranoia that never dies!! - LOL
But definitely not an area of worry for me anymore - 16 months ago, different story....
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jaydee75
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Balderdash! Silicone is one of the most seal compatible liquids there is. Works for me.
Jaydee
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Derek, brake fluid replacement is more of a Calander, rather than mileage issue. Fluid life varies depending upon how humid your local climate is. Buy one of the fluid testing pens on Amazon and you won't have to worry, plus you won't have to flush it more often than really needed. You can use it on your cars and trucks, as well.
FYI, the anti lock brake controller on your car/truck costs $1,200 to $2,500 to replace [US vehicles cheaper, Euro models most expensive] Old, dirty, contaminated brake fluid is what kills them. Flushing the brake fluid on cars/trucks with ABS is WAY cheaper than an ABS controller replacement [they can't be repaired & you'll rarely find a good one in the junk yard] Recently replaced an ABS controller on a customer's 2008 LS470 Lexus. Repair was over $2,000. If you think you can simply delete the ABS on your car/truck, forget it. The proportioning valve is built into the controller!
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Frankie, I'm not a fan of DOT 5. That said, it will not damage the seals [EDPM rubber] in your brake system. Most cars call for a 24 month brake fluid flush. However, some cars [mostly European makes] have 3 year change intervals, because they specify using only the best brands of DOT 4 fluid.
EDPM Rubber Wikipedia
Regarding paint damage, that's what polyurethane & epoxy paints are for. Simply spray clear polyurethane [Imron, PPG Delta, etc] over your tank and side covers. Norton switched to black epoxy paint for frame parts on the 75-77 Mk IIIs, so no worries about damaging the frame paint on those. Many on this forum powder coat their frame pieces, which is also brake fluid proof. There is no reason to use 1960s paint technology today.
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