Topic: How about DOT 5.1 brake fluid? (dont' want to open a can of worms)

[Raul CB750K1]

As I was tired of my locking rear brake and my weak front break, while replacing the chain and the rear shoes I plan to replace the front pads and master cylinder too -with a modern CB Seven Fifty M/C-. The M/C includes a mechanical switch so I plan to use a single line from the M/C to the caliper, probably braided.

I bought a bottle of DOT5.1 because it seemed cool not having to worry with damaging paint. And then is when I read all the issues with DOT5 silicone-based fluid in the forum. I decided I rather be more careful when replacing the fluid that undergoing all that flushing and woes of the DOT5. For some reason I assumed DOT5 and DOT5.1 were the same, but then I discovered that DOT5.1 is compatible with DOT3 and DOT4, only with a higher boiling point.

Am I right? Can I use DOT5.1 without having to flush the system of DOT4?


Thanks in advance


Raul

[CB750F2]

Raul, DOT 5.1 is not Siicon based. Check out this site http://www.apracing.com/roadcar/brakefluid/data.asp?code=cp4510
Regards Pat

[MRieck]

Raul, DOT 5.1 is not Siicon based. Check out this site http://www.apracing.com/roadcar/brakefluid/data.asp?code=cp4510
Regards Pat

Yes. Actually...DOT 4 is more than enough Raul./

[Clyde]

No problems,DOT 5.1 is interchangeable with DOT 3 or 4, just more expensive
Just flush it through as if you were doing a regular fluid change.
Clyde

[eurban]

Yeah but does it absorb water like DOT 3 & 4? Does it eat paint light DOT 3 & 4 do?  DOT 5 may have its own issues but it does neither of those things . . . .

[CrisPDuk]

It may not strip paint like DOT 3 & 4 Eurban, but it does tend to dissolve the seals in the braking system, especially on older stuff like ours

Don't know about you, but I'd rather stick to being careful with my paint when I've got the cap off my M/C, than find out my brakes have no seals left next time I come to need them

[Raul CB750K1]

Thanks guys. I bought the bottle assuming it was DOT5 because I wanted to "upgrade", but then I read all the feedback in the forum and decided I would stick to the old "tried and true" brake fluid. Then I found DOT5.1 and DOT 5 are not the same, so if DOT5.1 and DOT3 and 4 are compatible I will use the bottle straight away.

As I said, I don't want to open a can of worms here. Generally I replace the brake fluid every three or four years -or when it becomes brown, whatever comes first-. The way I change brake fluid is the same than the way I paint my house: I use masking tape, plastic cover and cover almost the whole bike but the master cylinder. It proved useful the first time, when I pumped the lever and a big squirt came up the reservoir and onto the tank -fortunately protected by the plastic. I also wear googles and vynyl gloves. When the brake fluid touches the vynyl it starts to burn your hand, it's amazing how the vynyl reacts with the brake fluid.

As I said, taking all those precautions is an annoyance, but once every four years is not that much.

I will post pictures when the M/C replacement is done. I had a spare Suzuki GZ250 M/C, but the reservoir is slightly tilted -to compensate the tilt of the handlebars- and the mirror thread is in the clamp, not in the reservoir body, so I decided to go for a CB Seven Fifty M/C because the reservoir is flat and the mirror threads are in the reservoir body. I can buy braided lines here but finding the threaded plug can be a problem. I was thinking about using a banjo bolt on the caliper and using a direct line from the M/C to the caliper without using the caliper pipe.

[Ibsen]

http://www.vtr.org/maintain/brake-fluids.shtml

[eurban]

It may not strip paint like DOT 3 & 4 Eurban, but it does tend to dissolve the seals in the braking system, especially on older stuff like ours

Don't know about you, but I'd rather stick to being careful with my paint when I've got the cap off my M/C, than find out my brakes have no seals left next time I come to need them

Two years with DOT 5 and no issues yet.  Did a complete system rebuild when I switched. . . . . The point I was trying to make was why buy expensive DOT 5.1 fluid for our bikes if it still eats paint and absorbs water just like DOT 3 and 4?  Perhaps it doesn't but I would doubt it as it is compatible with these fluids.  Its performance chacteristics might be better but unless you are racing this would be a waste.  If Raul already has the stuff and it is truly compatible then by all means make use of it.  However if you are going to the store to purchase new brake fluid for your stocker then why spend the $?

[Raul CB750K1]

The point is that I bought 5.1 assuming it was DOT5, thinking it was silicone based. Had I known 5.1 was compatible with DOT3 or DOT4 I would have bought DOT4, the higher boiling point of 5.1 is not something I think I need. I have read good and bad feedback about DOT5, and after reading all of them I have decided to stick to DOT4 -will use the 5.1 as long as I have already bought it-. That's why I said I didn't want to open a can of worms and make this thread a DOT5 vs DOT5.1 debate.

What I am more excited about is how much difference will the modern master cylinder and the single brake line make.


Thanks again everybody!!!!

[crazypj]

DOT 5.1 is compatible with DOT 3 & 4  but is more expensive.
Its overkill unless you use brakes hard (only once ever had brakes burn out/fail, switched to dual disc the next day) I just re-built it with stainless line, new DOT 4 and Girling race pads about an hour before it happened.  I was younger and faster then 
 I will use it next time I re-build brake system as it does have advantages over DOT 5.0 silicon (actually LESS maintainance) You only need to change fluid with 3, 4 & 5.1, with 5 you have to strip and clean out system as any condensation collects a the lowest point  (I've already replaced calipers on 550 because of this issue) Draining and flushing system as you would with conventional fluid doesn't work with silicon as it floats on the water which doesn't get flushed out, just builds up over time and makes pistons rust and calipers corrode. As far as I'm concerned, DOT 5 silicon is evil stuff
PJ

[eldar]

And how is that different from dot3? It attracts water and causes corrosion and rust too. Fact is that all brake fluids should be changed every couple of years.

[crazypj]

Dot 3, 4, 5.1 absorbs the water.
 When you change fluid the amount of fluid with water contamination is now diluted throughout the entire system. With DOT 5 silicon the water 'builds up' over a period of time if you don't remove the pistons to clean out anything at the lowest point

[eldar]

I wonder how many people have had that issue though with water build up. I never have and I do not shy away from rain so maybe the trick to keep the seals in good shape and to start with a dry system. I must say that I do not miss that corrosion build up I got almost every summer with DOT3.

[crazypj]

I wonder how many people have had that issue though with water build up. I never have and I do not shy away from rain so maybe the trick to keep the seals in good shape and to start with a dry system. I must say that I do not miss that corrosion build up I got almost every summer with DOT3.

Have you stripped calipers and pulled pistons yet?
It isn't going out in the rain, its water molecules in the air

[eldar]

I usually flush everything yearly and have never found water with dot 5 or synthetic fluid.
Dot 3 though had me cleaning the caliper every year and using a brush to remove corrosion buildup.

[crazypj]

I usually flush everything yearly and have never found water with dot 5 or synthetic fluid.
.

my point exactly, the water stays at the bottom so you cant see it.
If all your seals are in such good shape due to annual re-builds, how did the water get in there with the DOT 3?
PJ

[dusterdude]

im going to try to put to rest the "seal eating capabilities" of dot 5.i had dot 3 in my panhead for about 4 years or so and then i flushed out the dot 3 and put in dot 5,the dot 5 has been in the system for 15 years or so and i have had no problems whatsoever.

[eldar]

DOT3 attracts water and seems to require better seals. It always caused drag so I had to clean every year inside the caliper. They synthetic I use never had an issue. I cleaned things and used the same seal and put in the new synth and it was in for 5 years with some of those years being the bike sitting in storage. No corrosion and no water and still worked fine.

I changed it when I got the bike out of storage and it was fine and I changed it when I got a new brake line. I now change every couple years mainly to keep things clean cause after all, I only have 1 front brake and I want to make sure it is in tip-top shape at all times. I am sure I could go longer but piece of mind is more important than seeing how long my brake fluid lasts.

I also like to clean my disk and pad every year to prevent squeal and that works pretty good for me.