Brake Fluid!?!?!?!?!?!?

[bulletproofcycle]

I am replacing the brake fluid in my GS because I am switching to braided lines and was wondering where I should get my fluid from.

At the dealer they have a small bottle of DOT 4 motorcycle fluid for $8.50 CAD and at Wal-Mart the have a way bigger bottle of synth DOT 3 & 4 (made for both) for half of the dealer cost.

What should I buy? Does the car DOT 4 fluid resist temperature as well as the motorcycle stuff ?

[Phaedrus]

If it were me, I'd buy the DOT4 from the bike shop. It will be slightly higher quality I am sure, and able to withstand higher temperatures. And since you are getting the new lines, why do something half assed and put less than high performance fluid in high performance lines?  :dunno:

Being that it is just the GS - and not a rocket ship   - I am sure you would do fine with the cheaper stuff. But I think as long as you are upgrading your lines, why not upgrade your fluid as well?

[scratch]

Braking is kinda important. Kinda like tires, why would you skimp?

[500rider]

Once the bottle is open, it goes bad relatively quickly so there is not much point in getting more than you need.  

[The Buddha]

Dot 5 from an automotive shop or a performance shop or god forbid ... bike shop ... Used it for 5-6 years, its great, doesn't eat paint, you need to suck the old crap out but hey your system is already dry ... so I'd use 5 ... not 5.1 ... 5 silicone based ...
Cool.
Srinath.

[dgyver]

You can use either DOT 3 or 4. DOT 4 has a slightly higher boiling point. No big deal. I use DOT 4 since I am hard on brakes and tracks have a lot more braking requirements. I used DOT 3 for many years without problems.

Do not use DOT 5 unless you want to completely clean out the entire brake system. There is a lot fluid left in the caliper and master cylinder. It is worth risking mixing them.

[ninja_steve]

get some motul rbf  

[ukchickenlover]

Do not use DOT 5 unless you want to completely clean out the entire brake system. There is a lot fluid left in the caliper and master cylinder. It is worth risking mixing them.

What would happen if you did not completely remove all of the dot 4 fluid?

[dgyver]

I think it thickens when they are mixed.

[scratch]

Ah, yes, they coagulate (thicken), potentially blocking the passages of the brake fluid. Bad, very bad.

[makenzie71]

It doesn't matter where you get the stuff.  Brake fluids are produced by only a few manufacturers and they're restricted legally or physically from making it very different so it's all the same within variety.  The only difference you can get from changing brand is different addatives, and sometimes not even that.  It's just like engine coolant.  It doesn't matter who's name is printed on the bottle...they all got it from the same place, basically.  Get the bottle from wally-world, it'll work fine (I've been doing it for years)...but don't get a huge one, it's rather pointless.  Just get a little more than you think you'll need.

Personally, I've always used castrol products...because I like their bottles better than anyone elses (less messy).

[RedShift]

DOT 3 brake fluids are mixtures of glycols and glycol ethers. DOT 4 contains borate esters in addition to what is contained in DOT 3. These brake fluids are somewhat similar to automotive anti-freeze (ethylene glycol) and are not a petroleum fluid. DOT 5 is silicone chemistry.

If it were me I'd stick with DOT 4 and buy a small bottle.  If you run out, get another bottle from the same source.  As commented already, though DOT 5 has a higher boiling point, the risks outweigh the advantages.