Glycol Based Brake Fluid???

[newold81]

I'm going to drain the fluid from front brake system of my 81' GS850G.
I've got a leaking seal on the right side caliper.

Which leads me to my question.
The shop manual specifies glycol based brake fluid.

Is this written in stone?
Since the brake system is being completely drained, can a more modern, silicone based fluid be used?
Or should I stick to the glycol based brake fluid?

Thanks for the help.

Tim

[Nessism]

Dot 4 is the safe choice. I think you can use 5.1 as well, but using DOT 5 silicone based fluid requires a full tear down and clean out. I suspect it would be best to change your brake line as well (which is something that you should do regardless if your bike still has the original rubber lines). DOT 5 also is known to lead to a more spongy lever feel. I don't understand why anyone would want to use that stuff other than for vehicles that may sit for years at a time.

[DPage]

I agree with Nessim, using DOT 4 is plenty good for these brakes, considering the state of technology available when they were made.

As another idea, how about this - put fancy nitrogen gas in your tires, or maybe copy what they once put in the space shuttle tires (argon/neon mix or who knows what?) I doubt if you would see any meaningful improvement when you get on the street.

You'd be surprised what happens when you rebuild what you've got with normal brake fluid and OEM parts - a big improvement, I'll bet.

[Steve]

I don't understand why anyone would want to use that stuff [DOT5] other than for vehicles that may sit for years at a time.

That's not good for them, either. Because DOT5 is silicone based, it does not absorb water, like glycol does. Because of that, any moisture that does find its way into the system will pool at the lowest point. In the case of our front brakes, that would be behind the pistons in the caliper. In the rear brake, probably at the back of the swingarm, just before the brake hose rises to the caliper. With all the water pooled behind the piston, it is most susceptible to heat buildup. If it gets hot enough, it can turn to steam. Talk about MUSHY brakes.

Systems with DOT5 need to be flushed more often than systems with DOT3 or DOT4.

.

[TooManyToys]

The reason DOT 5 gets it's reputation for sponginess becasue it's almost impossible to get all the air out. Our dyno lab used to go crazy with the one dyno that required it. Bikes have enough air issues with DOT 3/4.

DOT 4 will give you better fluid boil resistance as long as you change it on a regular basis. Its ability to absorb moisture is higher then DOT 3 so after ~2-3 years you are at the same boiling point.

[bwringer]

Just to add to the above, it's unknown whether Suzuki's seals (understanding that you're going to install new seals) are compatible with DOT5 fluid. (By the way do NOT bother with aftermarket seal kits -- they're overpriced, dangerous junk. Use OEM Suzuki components only.)

To sum it up, there's absolutely NO reason to switch to DOT5 fluid, and lots of good reasons to stick with DOT 3 or 4.


The silly numbering system drives me nuts because people automatically start thinking that the higher number must mean it's better. It's not better -- it's completely different stuff, and actually inferior in many ways.

Some good info:

http://stoptech.com/technical-support/technical-white-papers/brake-fluid

In sum, just use a DOT4 fluid in your GS, change it every couple of years, and fuhgeddaboutit.

[newold81]

(By the way do NOT bother with aftermarket seal kits -- they're overpriced, dangerous junk. Use OEM Suzuki components only.)

I ordered the caliper seal kits from Old Bike Barn (p/n 7600-096).

Would these be considered OEM?

If not, where do I purchase OEM kits?

Thanks,
Tim

[TooManyToys]

Just to add to the above, it's unknown whether Suzuki's seals (understanding that you're going to install new seals) are compatible with DOT5 fluid. ......

That is not a problem as any rubber compound that was formulated for glycol will be fine with 5. So if you have a bike that is staying in the living room as a show piece after your wife walked out, DOT 5 could be a good choice.

[newold81]

So, I'm still a little confused.

I've looked around and the only glycol based brake fluid I can find is DOT 3.
All the DOT 4 is silicone based.
So, do I use the DOT 3 glycol based fluid, or DOT 4 silicone fluid?

Thanks,
Tim

[jwhelan65]

So, I'm still a little confused.

I've looked around and the only glycol based brake fluid I can find is DOT 3.
All the DOT 4 is silicone based.
So, do I use the DOT 3 glycol based fluid, or DOT 4 silicone fluid?

Thanks,
Tim

I use the DOT 4 with no issues on my both my GS"s, replacing the lines and making sure the system is clean in clear is most inportant.

[derwood]

Dot 4 is not silicone based fluid
dot 3 and 4 are polyethylene glycol based fluid and are compatible with each other.
dot 5 is silicone based and does not play well with the other two.
dot 5.1 I think is a dot 5 spec fluid (boiling point) but is glycol based, i have never used it.

Dot 5 does not absorb water so it's boiling point does not degrade over time like poly glycol based fluid, because of this characteristic corrosion can be an issue because water will collect in pockets over time. It is more difficult to bleed as it absorbs (?) air more than the others. But, dot 5 will not eat paint.

Dot 3 and 4 hold water in suspension this lowers the boiling point over time, it also eats paint.

I dont beleive that the rubbers in the system are incompatible with either fluid, it is the toxic cocktail is that mixing Dot 5 with any other fluid makes that causes the rubbers to swell. even any residual fluid remaining in the system after flushing.

I use dot 3 or 4

[JimmyR]

When I bought new fluid from my local Suzuki dealer (and they are a little unusual in that they actually know a lot about bikes) they said to use DOT4 rather than DOT3. All new Suzukis use DOT4 and it is perfectly safe to use in our bikes.

Now I know DOT4 and DOT5 are completely different and not to mix them, but I use DOT5 in my Harley's PM brakes and those brakes are amazing - definitely not spongey! No they are not stock Harley brakes but are supposed to be used with DOT5 like most Harleys. I only wish my Suzuki brakes were as good as the brakes on my Harley. I've had the bike 5 years and the first thing I did was put the PM brakes on. They have never been spongey.