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Oct 22, 2009 | 11:55 PM

#101

sepixlh

Road Master

Joined: Aug 2006

Posts: 751

Likes: 6

From: 500 miles south from Artic Circle

Quote:

Originally Posted by d_slat

I wouldn't wait that long if I were you. It's dot3 or 4 that will eat up the seals in a dot 5 system, not the other way around. And your brakes will likely not fade,but either spring leaks all over or just fail completely when you need them the most. If I were you, i'd drain the whole system out and start over with dot5, and give it a good flush to remove all of the dot3 or 4 you put in there.

There is simply way to test if brake fluid is compatible with fluid in bike.

1. Take small amount of fluid from reservoir and put it into some e.g. plastic cup
pour some new fluid from container into cup.

2. See if they mix, wait for an hour if they are still "same fluid" (=mixed) they are
compatible.
3. DOT 5 will stay separate from other fluids, it stay as different layer...

DOT3 and DOT4 are based to same glycol or glycol/borat, only boiling point is different (401°F vs 446°F). They may mixed in that test. Some 5.1 fluids are same base and may mix in that test.

DON'T EVER NEVER MIX DOT 5 and DOT 5.1 fluids. DOT 5.1 is "conventional fluid" developed cars with ABS brakes, higher boiling point than DOT 4 ( 446°F/518°F).

DOT 5 is totally different it's silicon-based and CAN NOT BEEN MIXED to any other fluids!!!!!
It shoud not absorb moisture/water from air

To be sure best way is flush and clean system and use that fluid that reservoir cover says.
Mixing those fluids results that you don't have brakes at all... then you must rebuild whole system with new seals and maybe also new hoses.

Oct 23, 2009 | 09:39 AM

#102

nwpaironhead

Thread Starter

Cruiser

Joined: Jun 2009

Posts: 217

Likes: 0

From: Summerville,SC

Went to the auto parts store and checked out some bottles of brake fluid. DOT 5 is silicon based. I've seen 1st hand what silicon does to rubber products. DOT 5.1 os not silicon based, and neither are dot 3&4. The manual recommends DOT 5, but I am running an aftermarket master clinder which recommends DOT 4. I have a new brake line on it, and a freshly re-built caliper off of an old superglide. I'll be VERY careful, but for now I'm gonna leave the DOT 4 in it.

I'll update if I run onto trouble.

Thanks!