DOT5 vs DOT3/4

[UnderDog]

Quick question for you all. I was thinking about looking at an '89 for sale nearby. The listing says the brake fluid was replaced with DOT5. Has anyone done the switch to DOT5 fluid? Are there any concerns about using DOT5 on an older bike?

 

Thanks in advance...

[MiCarl]

DOT 5 is not compatible with DOT3/DOT4.

 

To do it properly the system needs to be completely cleaned and I believe the seals need to be different too. DOT5 has its own quirks and isn't generally used except in some special circumstances. You're prudent to be concerned.

 

You're sure it's not DOT 5.1? That should be compatible with a DOT3/DOT4 system.

[GS51]

Here's a Link that may help explain the differance

if ot were me I would stay with DOT4 i talked to brake manufacture and they said to stay with the DOT4 unless you plan on fulshing the system every month or so DOT 5 was designed to be changed often.

 

http://www.motorcycleproject.com/motorcycle/text/cows-brakefluid.html

 

 

Gary

[V7Goose]

I would stay far away from that bike. It is always possible the owner actually knows what he is doing and all is good, but just not worth the risk for me. Run Run

Goose

[UnderDog]

Thanks everyone. Apparently I'm not as crazy as I thought. I've emailed the owner a couple times, and each time a little more info comes out that just doesn't sit right with me.

 

Pity, though, as I am in the market for a bike, preferably a Venture, and this one is nearby. I'm not finding a lot of other options nearby at the moment...

[Wizard765]

What is DOT 4 synthetic? Is that OK to use?

[twigg]

What is DOT 4 synthetic? Is that OK to use?

 

Yes, it's all about the fluid boiling point.

 

Those fluids are designed for the race track, where extremely high temperatures are generated .... Your Venture brakes will fade and die long before they ever reach that point.

 

If your bike specifies DOT 3, or DOT 4 there is no need to out think Yamaha. Just use what the book tells ya to use.

 

Most systems will happily run either DOT 3 or DOT 4, it's way more important that you bleed it properly and change it annually. I know the book says every other year ... make it part of your spring routine, your brakes will love you.

[Freebird]

I use the DOT 4 synthetic and I know from watching people change the fluid at maintenance day that a of others do also. It works fine.

[Daveand Barbie]

Real DOT 5 is silicone based and not compatible with anything else. I have been using it in my antique sports cars for 20+ years for the sole reason that it will not absorb moisture like the non-silicone brake fluids will. I wouldn't use real DOT 5 in anything I planned to drive hard because the boiling point really isn't that high. Castrol makes a really good product in their DOT 4 LMA brake fluid, which is available at all the discount stores as well as parts places. LMA means "Low Moisture Absorption". I use it in all the bikes as well as the street cars.

 

The newer DOT 5.1 synthetics like the Valvoline are seeming to get some pretty good reviews, but I don't have any real experience with it.

 

I really don't think that this person is using real DOT 5 in the bike unless he found a bottle on a friend's shelf and decided to use it. Over the counter cost is 3 to 4 times tha cost of normal brake fluid. From your posts, it doesn't sound like this owner is quite that sophisticated.

[MiCarl]

My understanding is that the only non synthetic brake fluid is DOT 1 (castor oil). I don't think you can find it any more.

 

DOT 4 is DOT 4 whether the marketing department puts "synthetic" on the label or not.

 

DOT 3 and DOT 4 (and I assume DOT 5.1) are glycol based. DOT 5 is silicone based. Silicone reacts with glycol producing a sediment. Sediment is bad in braking systems. That's why DOT 5 should never be used with a system that has any DOT 3/4 in it.

[greg_in_london]

DOT5.1 is an upgrade on DOT3 and 4.

 

Some people are not bothering to list the difference between DOT5 and 5.1 anymore and I am sure I have seen bottles which just say DOT5 and that it is compatible with other fluids.

 

If someone actually sourced DOT5, silicone based fluid and swapped it all out, then they made a choice that everybody else would disagree with and I'd look twice at buying from such an 'enthusiast'. I'd say it is more likely that he used widely available glycol based 5.1 and can't quite understand what it is that you are asking.