Brake Rebuilding & Silicone Brake Fluid Dot 3 vs Dot 4 & 5

I Just what to see what you guys are doing when it comes to brake fluid when you rebuild your brake systems. New bikes seem to come from the factory with Purple fluid in them. Is it true for brakes that sit with for long periods of time the silicone repels moisture from the system.

If you were to replace the kits in all your calipers and master cylinders and install new Stainless Steel lines would you stick with Dot 3 or go to Dot 5 fluid. Thanks for your input

 

my cap says DOT4 so I would at least put that back in. The purple is Dot 5. The higher the rating the higher the boiling or flash point I can't remember which it is. Be safe and go with at least Dot 4 If you only had the choice of 3 or 5 go with the 5.

Hmm well after reading Chacal's link I guess 5.1 seems the best LOL!! I did not know about the 5 being a silicone based. It makes alot of sence now why when we had to replace one of my friends brake lines on his HD we bought the Dot5 home immediatly poured it in and had a heck of a time getting getting the brake lever to feel firm. after sitting overnight we bled them again and the level feels better.

 

I am upgrading my system (with all new components, thanks Chacal) and will be running DOT 5. The stuff I picked up (Bell-Ray) has a slightly higher boiling point (compared to my current grade and brand), doesn't eat paint and is hydrophobic. I will echo that this is taking place after a complete system rebuild so no traces of the old brake fluid will be present in the new lines. I understand that this condition is key to a sucessful upgrade.

 

Re: Brake Rebuilding & Silicone Brake Fluid Dot 3 vs Dot 4 &

DOT 5 won't gather moisture. All the moisture that gets into the system will sink to the bottom (caliper) where it can cause corrosion. And moisture will get in. And if you collect moisture at the caliper and get good an hot it will boil causing brake fade.

Dot 3, 4 and 5.1 will absorb moisture, so when you flush the system the water comes out with the fluid. The water in DOT 5 will continue to sit at the bottom of the caliper.

I'm also not certain about seal compatibility.

For my money, I'd stick with DOT 3 or 4 and change it every year.

If you want to improve the braking system talk to Chacal about some braided lines.

 

More than you ever wanted to know about brake fluid:

http://www.motorcycleproject.com/motorc ... fluid.html

 

OK So If I go back to DOT3 I noticed that in a few of my bikes that I have flushed new fluid into. I just checked them and found the fluid is turning color again, Light tan in color. Is something in there doing this or is it a natural thing that brake fluid does? I'm going to flush those bikes again this weekend.

 

Re: Brake Rebuilding & Silicone Brake Fluid Dot 3 vs Dot 4 &

The fluid turns color as it picks up moisture. Once it is honey colored it's time to replace it.

 

Re: Brake Rebuilding & Silicone Brake Fluid Dot 3 vs Dot 4 &

And when it gets the color of Coca-Cola you know it's past due for a change.

 

Chacal, thank you kindly for the tutorial, I think I'll use the 5.1 ATE SuperBlue I just bought (the Seca 750 m/c is a pain to access!). Anyone want a pint of Bell-Ray DOT 5? For sale cheap!

 

DOT-4 & 5 were developed to be used in Anti-Lock Systems.

The later formulations withstand the high-speed cycling without expanding to the heating of the Fluid generated by the high-frequency of the Anti-Lock Brake System applying and releasing great pressure to the Brake Fluid.

We don't NEED to use DOT-4 or 5.
But, if replacing all the Fluid in your system with it will get you to Flush and Bleed the Brake System; have at it!

Flush-out all the Old Fluid and a good measure of the new Fluid to insure that you aren't mixing the two grades of Fluid.

 

i have always used dot4 brake fluid in my motorcycles, it has a higher boiling point, and from what ive found it tends to be cleaner to work with.