Synthetic DOT 3 Brake Fluid Opinions Wanted

[twr1776]

I saw some of the Prestone Brand and wondered if anyone has tried it. I am going to completely flush out the front and rear systems and wanted to know if there are any pros or cons. I do not think the system has synthetic in it now. 81GS1000L

[Steve]

I'm sure that some time in the past I have probably used Prestone brand, but can not guarantee it.

Virtually any DOT3 or DOT4 brake fluid will work very well in our bikes. Change it at least every two years and you will have no problems. Since braake fluid tends to absorb moisture, only get as much as you are likely to use for the service at hand. If you are going to go to the trouble of flushing the system and replacing the fluid, get a larger bottle, a pint or so, but use a fresh one. Installing fluid from a bottle that has been opened before is just inviting the possibility of problems.


.

[Muser3]

Fluid

What Steve said and I like to change mine every year. I'm retired and have lots of time to do that kind of stuff. Keep the lid screwed on tightly on the container and throw it out every second year or if it is getting yellow. Dot 3 and 4 are very close to the same thing. Dot 4 absorbs water a bit more slowly than Dot 3 and if you stay on top of the situation it doesn't make a lot of difference.
Lee

[twr1776]

Thanks for the replies. The bottle description makes the synth sound superior to the standard types. I just wanted to make sure it was compatible with the original master cylinder innards.

[Steve]

I never have known the differences between synthetic and 'natural' brake fluids.

The big difference is the performance of the different numbers. DOT4 has a higher boiling point than DOT3, so it is considered to be more 'heavy-duty'. If you are racing your bike or maybe have a GK that is ridden in a 'spirited manner' in the mountains (frequent, long braking sessions), you might need DOT4. DOT5 is silicone-based and is not compatible with 3 or 4. DOT5.1 is compatible with 3 and 4, but it rather hard to find. For the few cents difference, I just get a new bottle of DOT4, and don't really pay attention to whether it is synthetic or not.


.

[dardoonk]

Here's a nice article explaining DOT 3/4 & 5 by Mike Nixon at The Motorcycle Project

[bwringer]

I generally grab the small bottles of the synthetic brake fluid. I found a bunch on clearance last summer and scooped up several bottles.

It doesn't make the slightest difference in performance, but it makes me happier than using the store brand generic and the price difference is a mere drop in the ocean of motorcycle maintenance expenses.

It's far more important to flush it out every year or two, even if you're using the plain label. And buy the small bottles to reduce the chances of contamination.

I haven't done this personally, but you can also get brake fluid that's colored blue or red so you can tell when you're done flushing -- use the blue during even-numbered years, then use red in odd-numbered years. Probably handy on cars, but kinda silly on vehicles where the entire braking system is less than three feet long.

[Jaguarjoe]

I never have known the differences between synthetic and 'natural' brake fluids..

It seems to me that all brake fluid is a manufactured product so it is ALL synthetic. Not like motor oil which can be dino based or synthetic.

[dardoonk]

I never have known the differences between synthetic and 'natural' brake fluids.

Since I just put in a completely new brake system, I went ahead and used DOT 5 Synthetic. I've heard it will give a softer feel to the lever, but probably that is offset by upgrading to full stainless lines. Mainly, I wanted to use the DOT 5 because it won't damage everything I just painted.

[Grandpa]

I use the cheapest house brand DoT-3 fluid and change it every year. No problems with braking system of any kind on my GK, which I've had for 8 years now. The GK has 124,000 miles on it and still running, and braking, strong.

I had four successive GS850's before the GK, and each got the same braking fluid treatment. No braking system troubles of any kind. Consistent braking is all I've experienced in 22 years on GS bikes.

Save your money, use cheap DoT-3, and think about better things, like riding your GS.

[Mark whiz]

I've had nothing but bad luck with the synthetic Dot 3/4 brake fluids. I tried the Valvoline version right after it came on the market. I tried it in a car that I had basically purged of the standard Dot 3 and replaced with the Valvoline......................It proceeded to lock up one of my rear discs and ruined a rotor on a car that was less than a year old.

I tried the Prestone in my bike this summer when I rebuilt the calipers and I just could not get any feel back into the system. I purged and replaced it with standard Dot 3 and it is much better now, although it is still a tad spongey.

Two strikes against the Synthetic fluid for me - I'll stick to the "regular" Castrol LMA Dot 4.