DOT5

Up here in Denver we're dry as all heck, so I've never had a problem, however how does water get into the sealed fluid even if you live in a damp environment? If no fluid is leaking, no air or water can enter the system.

RonKZ650 wrote:

Up here in Denver we're dry as all heck, so I've never had a problem, however how does water get into the sealed fluid even if you live in a damp environment? If no fluid is leaking, no air or water can enter the system.

That's a good question. And I don't have the answer.

But I do know that water does in fact somehow accumulate over time in the caliper piston area, especially when DOT5 is being used, making it all the more important to routinely flush the system with fresh fluid.

That's exactly why I quit using DOT5 in my KZ900-B1 (LTD), dual front calipers and rear caliper. This at least affords some relief via water absorption ability of non-Dot5 types. And of course should also be routinely flushed, say every year or so.

Good Luck!

Rumor has it that DOT5 makes any non-oem brake pads squeal like heck. :laugh:

Have DOT 4 in my H-D and noticed a few weeks ago that the paint (or whatever the coating is on the front master cylinder cover) was peeling. Turns out the screws vibrated lose and that DOT 4 was seeping out and destroying the paint. Sure am glad I noticed that before the tank and fender took a hit. I'm not familiar with the DOT 4+. Is it compatible with DOT 4? Thanks.

DOT3, DOT4, and DOT4+ are all compatible.

to maintain either one of the fluids right. they both should be flushed out at least once a year.
use what you like.

Flush often, ok. Sounds good. This forum is great! After rebuilding the forks, replacing plugs, and caps, I'm closer to having the bike fully restored.

if the master cylinder diaphram is in good shape it should be sealed but if it has deformed over time it will allow air to be pulled into the system and since glycol based brake fluid is hygroscopic in nature it will draw some moisture out of the air and cause contamination over time so for that reason the major manufacturers recommend you replace your brake fluid every two years and they recommend changing your brake lines out as well as the will erode under extreme circumstances but in 20 years of doing this for a living i could count on one hand how many people do that. by the way the master cylinders are vented to the atmosphere. they aren't totally sealed like some people think.

I am in about as humid area as you can get,,Houston, I have used dot 5 in the brakes for several years without any problems, nor I have I ever flushed it.
A friend put it in his bike about 10 years ago, and when he took it apart for a rebuild the system was perfect.

my 2 cents worth, go with the 5

The master cylinder is vented to the air, but only the outside of the diaphram. The inside, where the fluid is, is not vented, it's sealed completely. I wouldn't doubt water could possibly form from extreme cold temperatures, maybe condensation could build up inside the system possibly. I change the fluid only whenever I have to rebuild a master cylinder or caliper. That adds up to (1) master cylinder, (0) calipers. I know it's a sin, but yes I have 20-25 yr old Dot5 in all my Kawasakis and they all work just fine.

yes your right but on older units sometimes through bad installation or age they will deform and allow air past. a sure sign of this paint that is missing from the master cylinder.

For Your' consideration. the O rings and piston seals in master cyls are of a rubber designed to be compatible w/brake fluid. Perhaps you or others have experianced instances where in fuel or refrigeration incorrect application has resulted in swelling/premature deterioration of said. to be fair, I've only experianced 3 or 4 incidents where rubber failure caused stuck bits, and they might have had other factors involved.still, I prefer dot 3-4, and flush semi-annually or when discoloured.G