DOT 5 ???

I'm sure this question has been answered before, BUT rebuilding both F/R Master Cylinders on my 77' KZ1000A. Can I use Dot 5 Brake Fluid?

Also, Anyone recommend a good "brake fluid resistant" paint? I have a can of Dupli-Color Brake Caliper Paint, but says it chemical resistant? You would think it would somewhat impervious to brake fluid.

Don't do it! Ed

I have been using Bel-Ray DOT 5 brake fluid in all of my bikes since back around 1978. I even changed over to it in my then new 1986 GSXR750, and RG500 Gamma without completely flushing my brake system of whatever the factory put in. Never had a problem with the brakes on them. I do bleed most of the brake fluid out every two or three years if I am still riding the bike.

I crashed my KH400 racer big time back in 1978, and sprayed the Bel-Ray DOT 5 all over my fancy custom painted tank when it fractured the master cylinder banjo bolt in the crash. I didn't catch the spray of brake fluid on the tank until I got home Monday night. Didn't even dull the clear coat when I cleaned off the tank.

That same bike has been in storage, and the same brake fluid has been in there since 1981 or so, and the brakes still work as good as when I last rode the bike. DOT 5 brake fluid does not attract moisture like DOT 3 or 4 does!!

I've used DOT 5 brake fluid in my Z1s since 1976 with no problems to date.

Zinc cromate paint is impervious.

I'll explain "DON'T DO IT."


You said you rebuilt your master cylinders, but that doesn't mean you have purged all the DOT 3 or 4 brake fluid from the brake lines and from the calipers.

DOT 5 is not compatible with DOT 3 or DOT 4 brake fluid, and mixing DOT 5 with either of them will cause brake system problems. This is because DOT 5 is silicone based and DOT 3 /DOT 4 are not. DOT 5 has a very high boiling point and for that reason is frequently used on the racetrack. The demands of racing create more heat than those of street riding. DOT 3 or DOT 4 brake fluids work perfectly well for street riding where the demands are not nearly as great. DOT 5 will not hurt normal automotive / bike paint. DOT 3 / DOT 4 will ruin paint faster than you can say OOOOPS.

In addition to being incompatible with DOT 3 / DOT 4 fluids, DOT 5 has another drawback for many street riders. It is NOT hygroscopic. DOT 3 / DOT 4 ARE hygroscopic. What this means is that any moisture entering a brake system is absorbed by DOT 3 / DOT 4 fluids, but is not absorbed by DOT 5. At first glance this would make DOT 5 appear a better choice because moisture in brake fluid lowers its boiling point, so you don’t want moisture to mix with the brake fluid, right? Well, actually it depends. The problem with DOT 5 being non-hygroscopic is that the moisture still enters the brake system but instead of being absorbed and evenly distributed through the brake fluid it collects as “puddles” of water. These puddles or globs of water generally end up in the low spots within the brake system (such as calipers), and if they remain there, they can cause rust. Racers do not care about this because they are changing brake fluid very often, so these puddles don’t have a chance to form. The same is true of some street riders, such as Dr. Gamma. However, the brake fluid in street bikes may go for very long periods between fluid changes as many folks neglect this important maintenance, so these puddles can form and can cause problems. Also, to some extent it depends on the climate where the bike lives; the puddles will be worse in a rain forest than in a dessert.

Some folks do use DOT 5 on the street, and if they completely flushed the old DOT 3 / DOT 4 fluid from their brake system and change their brake fluid frequently it should work well for them. If, however, they mixed the DOT 5 with the DOT 3 / DOT 4, or if they go for long periods between brake fluid flushes, they may find their brake systems have been affected. This may not show up until they change their fluid and find traces of rust. Ed

I'm a dot 5 user. It doesn't tear shit up.

If you want to use Dot 5 ........ The entire brake system needs to be removed, broken down, 100% cleaned out and rebuilt......other wards, virgin

You cant mix the fluids. Just a little bit will fk it up.

Wasn't planning on taking the master cylinders apart as with the calipers. Was just going to empty the masters of the Dot 4 brake fluid, then use my mini vac to pull the remaining fluid out of the lines and calipers. Then all I would do is then refill the masters with Dot 5 and bleed the fluid throughout the whole brake system. Think this should work just fine.

What Ed says is technically correct, however even though dot 3 and dot 5 are not compatible, many guys have simply done the obvious, and that is remove the vast majority of dot 3 from the master cylinder, add dot 5 and continue bleeding until you are sure dot 5 is all coming out. Sure you waste fluid, but big deal, I had dot 3 eat paint off my master cylinders long time ago and switched to dot 5 when it was first released, whenever that was, but it was back in the mid 80s I believe. I never have had any problems. The old big round master cylinders like used 77 and prior generally don't leak, the newer 78 up trapezoid shape had orings that leaked after they got old so dot 5 worked fine for many guys that prefer not to have worries over paint.

Thanks Ron, That's kind of what I thought !

Dot 5 fluid does not mix with Glycol brake fluids and Dot 5 is lighter too. This means that no amount of normal bleeding will ever remove all of the glycol fluid from a system changed over to Dot 5. The old glycol fluid will pool in the calliper because it is heavier and not come out the brake bleeder fitting. This will cause corrosion problems in the long run.

Don't know how you folks bleed your brakes. But I always take the calipers loose and place them higher than the master cylinder on a bench with a piece of metal between the pads then start to bleed them.

I never finished college, but I found out that air rises to the top in fluid (ie brake fluid) You cannot believe how quick you can bleed a set of brakes that way!!!

Guess thats why I never had a problems switching over from DOT 3 to DOT 5.

I used to change over to a pair of single braided lines, drain the master, push the pistons all the way back into the calipers to get most of that nasty DOT 3 fluid out, then start bleeding the system. Not bad for a stupid parts person!!!!