Working on my brakes, can I use either DOT4 Regular or Synthetic?

[MedicAndy]

I had a patient a couple of weeks ago show up in our ED who presented himself with some very impressive road-rash and a couple of skin patches missing between his arms, shoulders, and back. (No worries, he did get to go home several hours later).

Either way, he told me that he was out riding on his motorcycle when without any notice the front brakes locked up. He told me that something didn't feel right with his brakes during his last couple of rides that he was on. He stated that the brakes seem to "drag" at times. His bike was totaled , and he told me that he was done riding.

Which brings me now to my bikes. I noticed about three month ago when I took the GSXR out for a ride that the front brakes on that bike were almost frozen up, and it was really hard to push her out of the barn. This bike had been sitting for several month, so I assumed that the brakes would free up again after I ride her for a minute. And the front brake did free up again, and all seemed fine. I tried to ride this bike again today (she has been sitting again for many weeks), and the front brakes were frozen up again. However, instead of trying to looses the brakes up again, my road-rash patient came to mind, so I decided to pull the front calipers to see if I could find the issues.

I had the bike at a shop about a year ago, and they installed new front and rear pads, and they also installed new brake lines and flushed the brake fluids. I assumed that the issue more then likely had to be the master cylinder, since I had new brakes installed maybe 500 miles ago......





To my surprise, both front calipers were really hard to remove from the rotors, and I saw immediately what the issue was... The brake calipers pistons were so dirty that they were all frozen in place and stopped working all together. My first thoughts were that I was glad that I didn't meet the same faith as my patient did with sliding down the highway due to my front brakes locking up.








I never worked on brake calipers before, so I spend two hours on youtube and so far so good! I also ordered me a Suzuki brake caliper rebuild kit, which will be here on Monday. I was able to blow the pistons out with the use of my air compressor. I was stunned after I saw on how dirty and corroded the pistons were, and the outer o-ring seals were also in really bad shape.

Either way, I got everything cleaned up with some brake cleaner, steel wool, and my dremel tool. I hope that I can re-use the pistons, but I won't know if they leak due to the metal surface scarring. I guess that I will find out if the calipers leak after I get everything back together.

















The picture below shows the pistons metal pitting. I hope that the pistons seals won't leak because of the pitting....




Now finally on to my question..........

My 1996 GSXR, per Suzuki requires DOT4 brake fluid. I can't find any information if the brake fluids needs to be synthetic or non-synthetic? I read some Suzuki forum blogs, and from what I read, I should be ok to use either synthetic or non-synthetic brake fluid. I "think" that it is ok to just add synthetic brake fluid even if my bike only requires non-synthetic fluid, since the 96 GSXR doesn't have a ABS system. (I think that bikes with ABS must use DOT4 Synthetic) I'm planing on purging the brake fluid on the GSXR with the DOT4 Synthetic fluid, if my 1100 Sports are also ok with synthetic brake fluids?


As most of you know, I own a couple of 1996 & 1997 1100 Sports, and the brake fluid required on those bikes is also DOT 4. The manual does not state if it must be non-synthetic, so would it be ok to also use a synthetic brake fluid with the 1100's braking system?





I like to standardize the type of brake fluids that I use to only one, so I could choose to only use synthetic brake fluid, if I could also use synthetic for my 1100 Sports, or I can go with non-synthetic brake fluids, if the 1100 Sports don't like synthetic brake fluids?

Andy



 

[wirespokes]

Maybe someone will confirm this (or prove it false) but as I recall, all DOT4 is synthetic. At any rate, I've used the DOT4 synthetic in brake systems I had no idea what was in there with no issues.

Part of the job when replacing brake  pads is cleaning the pistons before pushing them back in their bores. When the pads wear, the pistons extend and of course they get grungy. So they need to be cleaned up before sending them home.

Minor pitting usually isn't a problem. I can't tell how bad (deep) the pits are, but a lot of the time, the damage is on the outward side from the seal. Those seals are sunk into the bores a ways.

[Zoom Zoom]

Dot 5 is syn. Dot 5.1 is not. If your bike calls for dot 4, you would not want to use dot 5, but you could use dot 5.1. (Crazy huh?)

Dot 4 has a higher boiling point than dot 3, (which would also be compatible with 4). I don't know what the numbers are though. With regard to dot 5: I don't know if any rubber parts need to be changed in the system, but they, (4 & 5), should not be mixed. I have also heard not to use dot 5 on ABS equipped bikes, but I don't know why.

I realize this sounds cliche', but I would simply use whatever the system was designed for and call it good.

John Henry

[kballowe]

Putting the term "Synthetic" on a bottle of DOT 3, 4, or 5.1 brake fluid is like putting "Fat Free" on a bottle of water.

DOT 3, 4 and 5.1 are polyethylene glycol based and are "synthetic", by definition.
DOT 5 is silicone-based and does not mix with the polyethylene glycol based fluids. 
Be very careful not to intermix DOT 5 with anything else.  It can be an expensive mistake.  Do not mistake DOT 5 and DOT 5.1.

Run on over to the store and get the no-name-brand DOT4 brake fluid and forget about all of the marketing hype.

 

[Mike Tashjian]

Check the seal bores carefully and use new brake fluid for lubrication to install the seals and pistons.  The pistons should move pretty easily when you have them in.  And remember that the square cut seals flex as you apply the brakes and help retract the pistons just a bit as you release the brakes.  If they are dragging too much, excessive heat produced can damage the pads and or rotor and boil even new fluid.  The last fluid I bought was dual rated 4 and 5.1.  I see Bosch brand is rating 3,4, and 5.1 all together and compatible with all regular fluids.  So you should be able to just buy one like that for all regular service and top offs.  And yes, 5 still is the odd man out and not compatible with any other fluid.   Mike 

[Wayne Orwig]

What kballowe said.
it is all synthetic. Dot 5 is silicone (does not play well with others).

I suspect those pits in the pistons will be outside the seals.

[MedicAndy]

Thanks for all of the great informations you guys replied back to me with! I got some conflicting statements about which type of brake fluids I should use with what bike or my 1100 Sports, so I'm glad that this issue has now been properly addressed, and I don't need to worry anymore with either looking, buying, or using the wrong type of fluid! I'm off from work today, so I will have time to reinstall the calipers and then flush the brake lines with the DOT4 synthetic brake fluid that I already bought for my GSXR. I will from here on out buy me the Bosch DOT4 brake fluid that Mike was talking about, which will then eliminate the question of which fluid to use within what bike, or furthermore what car, since the Bosch fluid will take care then of everything that I am riding or driving......

Thanks again,

Andy

[PeteS]

The main advantage of Dot 5.1 vs Dot 4 is higher boiling temperature. If you planned to do track days with your bike 5.1 would be the best choice, otherwise 4 is fine. You do have to flush it out every few years because it does absorb water which may be the cause of those pits.

Pete

[zenand]

Just my 2 cents on these posts,before you bleed out the system clean out the master cylinder resevoir and make sure BOTH of the little holes in the bottom are clear and not clogged with crap. In my experience if one of these is clogged it can cause the brakes to stick on

[lrutt]

If the brake system is fully clean and flushed, there should be no harm in switching to 5. I've done that in countless bikes (77 Lemans 850, 73 Norton, 84 Yamaha, 76 Honda, 78 Honda, 53 MG TD) with zero problems after many many years. Love the 5 as it won't destroy point and does not absorb moisture.

[Zoom Zoom]

Putting the term "Synthetic" on a bottle of DOT 3, 4, or 5.1 brake fluid is like putting "Fat Free" on a bottle of water.

DOT 3, 4 and 5.1 are polyethylene glycol based and are "synthetic", by definition.
DOT 5 is silicone-based and does not mix with the polyethylene glycol based fluids. 
Be very careful not to intermix DOT 5 with anything else.  It can be an expensive mistake.  Do not mistake DOT 5 and DOT 5.1.

Run on over to the store and get the no-name-brand DOT4 brake fluid and forget about all of the marketing hype.

 

I guess I was on the right track, but with a poor understanding.

Thank You for explaining it. 

John Henry

[kballowe]

I guess I was on the right track, but with a poor understanding.

Thank You for explaining it. 

John Henry

You assume that I actually know this thing.
hahahahahahahahaaaa aaaaa

 

Your explanation was spot-on.  I simply had to add my five cents' worth.
 

[PeteS]

If the brake system is fully clean and flushed, there should be no harm in switching to 5. I've done that in countless bikes (77 Lemans 850, 73 Norton, 84 Yamaha, 76 Honda, 78 Honda, 53 MG TD) with zero problems after many many years. Love the 5 as it won't destroy point and does not absorb moisture.

True silicone doesn't absorb moisture but it doesn't mean water won't get into the system. It just forms droplets within fluid.

Pete

[MedicAndy]

I installed the rebuild calipers yesterday and then flushed the old brake fluid out and replaced it with the new DOT4. The front wheel (when up on a wheel stand) is almost completely free-spinning now, and I can most definitely feel a big difference by just pushing the bike out of the barn now. I now have to flush the fluid on four of my other bikes, since the color of the brake fluid on those bikes is far from being clear! But all of the 1100 Sport brakes work great, so I won't need to rebuild any of those bikes calipers.

Thanks again for all of the great replies!

Andy