Brake Fluids

[thrasher]

What are the advantages of DOT 4 brake fluid over DOT 5?

I have an 2004 Road King that uses DOT 5. What was the reason they are using DOT 4 brake fluid now?

[LittleBear]

Dot 4 can be used with ABS, Dot 5 cannot.

I think when they started putting ABS on the cop bikes, they changed all bikes to Dot 4. Just a guess though.

I prefer Dot 5. Non corrosive to paint. Dot 4 will eat paint.

[swmnkdinthervr]

Do not mix the two...it will lead to brake failure!!! They react to each other and will gel if mixed!!! Even if you don't wreck it can be time consuming and costly to fix...make sure if you change completely flush out the other fluid.

[Geezer-Glide]

If you have DOT 5 in your bike now, don't switch. The biggest advantage to DOT 5 is it doesn't absorb moisture like DOT 3 and 4 do.

LB has it right. The ABS systems can not use DOT 5. DOT 5 is sylicone based, and does not eat paint. DOT's 3 and 4 do eat paint. FAST! (Don't ask me how I know) Since the cop only bikes had ABS, it was no big deal to keep those with DOT 4. Once the ABS came out on the new baggers and the v-rods, it made sense economically to change the entire fleet back over to DOT 4.

[thrasher]

Thanks for replies, guys. This is excellent information.

I knew better than to mix the two and about DOT 5 not eating paint, but I didn't know that the rationale for the change was for ABS brake systems. I also didn't know that DOT 5 didn't absorb moisture like DOT 4 and DOT 3.

I think I'll stick with the DOT 5 fluid.

[LittleBear]

Originally Posted by thrasher

Thanks for replies, guys. This is excellent information.

I knew better than to mix the two and about DOT 5 not eating paint, but I didn't know that the rationale for the change was for ABS brake systems. I also didn't know that DOT 5 didn't absorb moisture like DOT 4 and DOT 3.

I think I'll stick with the DOT 5 fluid.

It does not absorb moisture like Dot 3 and Dot 4 so the water that gets into the system pools in one spot and can corrode the inside of the caliper. That is why it should be flushed with fresh every year or two depending on you millage.

[thrasher]

Originally Posted by LittleBear

It does not absorb moisture like Dot 3 and Dot 4 so the water that gets into the system pools in one spot and can corrode the inside of the caliper. That is why it should be flushed with fresh every year or two depending on you millage.

Oh, okay... I understand.

[Red Rider]

Originally Posted by Geezer-Glide

DOT 5 is sylicone based, and does not eat paint.

I can attest to this. I got DOT 5 all over my bike (and my garage) when I changed bars and tried to bleed the brakes alone.

[Type O]

dot 5 boiling point 550
dot 3 ( ) 287

each number is a higher boiling point and yes 5 is syn