my friends 2005 1200c and most harleys use Dot 5 brake fluid which does not burn the paint if you spill it, and has a higher boiling point.
My 2007 1200c I noticed now uses DOT 4, does anybody know why Harley Davidson switched?

I don't know 100%, but my best guess would be because they have ABS models that use dot 4. Either they want all models to be consistent to prevent mixing of the two or they may be wanting to provide ABS on more models. Just guesses.

There are problems with DOT 5 (silicone) brake fluid. It traps air very easy and is hard to bleed, resulting in a spongy feel. Almost no bikes or cars use DOT5.

my friends 2005 1200c and most harleys use Dot 5 brake fluid which does not burn the paint if you spill it, and has a higher boiling point.
My 2007 1200c I noticed now uses DOT 4, does anybody know why Harley Davidson switched?

Three letters...

ABS...

That's the ONLY reason...really..

Although DOT 5 holds air much better, its not really a factor in the change......its all about ABS technology..

There have been several threads recently about the "downfalls" of DOT 5, but the FACT is, its been around since at LEAST the mid-seventies on Harleys, and there is NOTHING WRONG with DOT 5....FACT.

Cantolina is correct. DOT5 is no problem whatsoever. And it's inert.

I much prefer DOT 5. If I spill some I don't have to :censor myself because it's eating away at my bike! If you do spill some DOT 4 just hose it down real good, haha! Glycol based brake fluid is water soluble. Silicone is not, but it doesn't really matter.

I don't know 100%, but my best guess would be because they have ABS models that use dot 4.

Harley has models with ABS??? it took them until 2000 to stop using single piston calipers, it should be another 10 yrs or so until they get to ABS...

The dealer told me that the ABS system that they are using(i belive bembo, but dont quote me), the manufacture will only let them use dot4, so instead of having two systems in production at the same time(more chance for screw ups) they switched wholesale to dot4.

Yes there is problems with dot 5. It doesnt absorb water. Might sound great, but it lets the water collect at the lowest points. If allowed to build up enough it will cause corrosion. Some systems dont have a bleed valve at the lowest point which means even if you flush it you wont get rid of the water. Also this water setting right next to the pistons, flashes to steam when it gets hot, and locks up the brakes. Either DOT 4 or 5 have their "issues" and strengths.

Harley has models with ABS??? it took them until 2000 to stop using single piston calipers, it should be another 10 yrs or so until they get to ABS...

They have ABS on some touring bikes and police models.

I have had DOT 5 in my 82 FLHS for 24 years without a problem, almost 100,000 miles. I'm sure there is a reason for switching to the DOT 4, but I will stay with the DOT 5.

I have had DOT 5 in my 82 FLHS for 24 years without a problem, almost 100,000 miles. I'm sure there is a reason for switching to the DOT 4, but I will stay with the DOT 5.

I wouldn't change either, converting from one to another is a pain because you have to make sure that there is no traces left of the other fluid or it can for a nasty goop. With either fluid just make sure you change the fluid every 2 years and you should be fine. Its not hard to lay a garbage bag over the painted bits to protect from dot 4. I was just trying to state that one is not neccessarly "better" than the other, just different

Harley has models with ABS??? it took them until 2000 to stop using single piston calipers, it should be another 10 yrs or so until they get to ABS...

They're moving a lot quicker now. They all have closed-loop EFI now too. It would have been unthinkable a few years before.

Also this water setting right next to the pistons, flashes to steam when it gets hot, and locks up the brakes.
Actually, it flashes to steam then you have NO BRAKES, not locked up brakes. You'll rarely see DOT5 on a race bike for that reason (well, in the 883 and Buell series' anyway: not sure about the rest of them race bikes.)

--Chris

...its been around since at LEAST the mid-seventies on Harleys ...
September 7, 1976 was when they switched from DOT3 to DOT5, in the 1977 model year.

--Chris

Actually, it flashes to steam then you have NO BRAKES, not locked up brakes. You'll rarely see DOT5 on a race bike for that reason (well, in the 883 and Buell series' anyway: not sure about the rest of them race bikes.)



Sorry, you are right, should of said vapor locks the braking system

Cool - thought I was on the crack again. I've seen it happen at the track, and it's not pretty.

--Chris

My question is that if DOT 5 was such an "inferior" brake fluid, why did they use it successfully for so many years? It seems that the ONLY reason the MOCO changed back to DOT 4 was for the requirement for the ABS systems. I have ridden bikes with both systems and they both seem to work great especially when compared to older bikes with mechanical drum brakes.

Paul,that's a revelation. Hydraulic discs better'n mechanical drums. WOW! Have you seen the new pointless ignitions?

Roadster There you go again :wonderlan

mechanical drums rocks mon ! havent u ever heard them played on street corner in NYC

Sorry roadster. I keep forgetting that there are allot of newer riders out there that have never ridden the old stuff that was state of the art 30+ years ago. Back then if you had dual leading shoe drum brakes, you had the state of the art for that time . If you ever get the chance to ride some of the older stuff please do. Then you can acquaint yourself with that technology and be able to understand my comment. And. Yea, we werer all thrilled when CDI and electronic ignitions came out too.

We're not supposed to put water in with the brake fluid! Dot 5 does not absorb water out of the air like the others and with a good seal it won't get any unless ...

There are problems with DOT 5 (silicone) brake fluid. It traps air very easy and is hard to bleed, resulting in a spongy feel. Almost no bikes or cars use DOT5.
Is this really true because bleeding the brakes is a pain in the ass.

dot 5 because it dont absorb moisture , it pools in lowest point of system, the calipers, very bad, especially on ABS, the better dot 4 fluids also have higher boiling point , i dumped my dot 5 out of my 06 QUICKLY

dot 5 because it dont absorb moisture , it pools in lowest point of system, the calipers, very bad, especially on ABS, the better dot 4 fluids also have higher boiling point , i dumped my dot 5 out of my 06 QUICKLY
I don't think this is strictly accurate. There may be some variances between brands of fluid, but generally, DOT4 has a lower boiling point than DOT5. And since DOT4 is hygroscopic, it will absorb moisture, from the humidity in the air for example which LOWERS its boiling point even more. DOT5 is hydroscopic, meaning it does not absorb water. The problem with DOT5 not absorbing water is that the water separates out. Since water boils at 100 °C, that will boil before the brake fluid itself, which is what creates problems. Moisture mixing with DOT4 means the boiling point of DOT4 goes down. Since water does not mix with DOT5, the fluid itself keeps a stable boiling point, but any moisture in the system will boil at its normal boiling point, which can lead to brake failure.

http://en.wikipedia.org/wiki/DOT_4
http://auto.howstuffworks.com/question451.htm

--Chris

What the hell is brake fluid? Brakes work by cables. I think you guys got fluid on the brain.

We don't need no stinkin' brakes.

http://www.chrishajer.com/bike/XLF/flintstones.jpg

--Chris