Brake fluid and grease question.

Hi,

I am about to change my tires and brake pads for 1st time. I need to get dot 4 brake fluid which is not available in my location, in case of any short fall in brake fluid can top up with dot3 ? and also theres mention of lubricating the wheel bearings with molybdenum based grease after removing the tires, can i use silicon grease or sodium based grease for this operation ? Thanks.
:biker:

Not a great idea to mix Dot3 and 4 fluids, as they have different properties. Any brand of dot 4 with dot 4 OK, same with Dot 3

Silicon/sodium grease is not a substitute for moly grease, dont mix them.

Wheel bearings can use general purpose grease, but only use Moly where specified, IE drive train surfaces

The only grease that's called for anywhere near the bearings is around the seals, and those take plain lithium-based grease. See this thread.

--Mark

+1 on the thread link.
And don't confuse moly paste with moly grease.

longerone said:

Hi,

I am about to change my tires and brake pads for 1st time. I need to get dot 4 brake fluid which is not available in my location, in case of any short fall in brake fluid can top up with dot3 ? and also theres mention of lubricating the wheel bearings with molybdenum based grease after removing the tires, can i use silicon grease or sodium based grease for this operation ? Thanks.
:biker:

Click to expand...

Yes, you can top off DOT4 with DOT3 fluid, but I would only recommend doing that if you are desperate (if fluid levels are extremely low and you cannot get DOT4 fluid ordered in). You should order the Honda recommended DOT4 fluid. [ame="http://en.wikipedia.org/wiki/DOT_3"]DOT 3 - Wikipedia, the free encyclopedia@@AMEPARAM@@/wiki/File:Merge-arrows.svg" class="image"><img alt="Merge-arrows.svg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/52/Merge-arrows.svg/50px-Merge-arrows.svg.png"@@AMEPARAM@@commons/thumb/5/52/Merge-arrows.svg/50px-Merge-arrows.svg.png . DOT3 fluid is hygroscopic (draws moisture out of the air) and degrades quicker than DOT4.

When you change your brake pads, chances are you'll have excess fluid as you have to retract the pistons back into the calipers (clean them first!!). If it were mine, I'd do more than just replacing the pads. I'd fully clean the pistons / seals and fully flush the entire brake system.

Both DOT 3 and DOT 4 share almost identical chemistry and are hygroscopic (attract moisture). DOT 4 also contains borate esters and has a slightly higher boiling temp. For DOT 3 the dry boiling point is at least 401 and the wet 284 degrees. DOT 4 is about 446 and 311 respectively. You can mix both fluids without concern. The higher boiling points are critical to those of you that wish to spend time on a race track. If you are an every day driver DOT 3 works just fine, but you'll want to be sure to flush and replace the fluid every Spring as routine maintainance to ensure maximum performance and ability to absorb heat.

Hojo 70 has the details correctly stated. DOT 3 and 4 are compatible. It's DOT 5 you DO NOT want to use as it's silicone based and won't mix.

I've used DOT 3 with no negative consequences.

Do change your brake and clutch fluid regularly.

Do clean the caliper pistons thoroughly before pushing them back in. If the miles on your bike are 50,000 or more, consider changing out the piston fluid and dust seals.

I've never added grease to a wheel bearing, just a light coating on the INSIDE of the dust seal at installation.

BakerBoy said:

Yes, you can top off DOT4 with DOT3 fluid, but I would only recommend doing that if you are desperate (if fluid levels are extremely low and you cannot get DOT4 fluid ordered in). You should order the Honda recommended DOT4 fluid. DOT 3 - Wikipedia, the free encyclopedia. DOT3 fluid is hygroscopic (draws moisture out of the air) and degrades quicker than DOT4.

When you change your brake pads, chances are you'll have excess fluid as you have to retract the pistons back into the calipers (clean them first!!). If it were mine, I'd do more than just replacing the pads. I'd fully clean the pistons / seals and fully flush the entire brake system.

Click to expand...

Thanks a lot i will clean the pistons well, but leave the fluid change for another time. The bike is only at 38000k and i have no acess to dot4 presently.

Maybe this is a silly question, but why is DOT4 ok to clean the brake pad callipers? Why is it ok to clean the outside of the callipers? What if the DOT4 fluid is used to clean the rims of the ST1300? I am trying to figure out the chemistry of this stuff.

If you can use it to clean the pistons in the calliper, what if it gets on anything else, like dripping onto the rims...just curious.

90210brandon said:

Maybe this is a silly question, but why is DOT4 ok to clean the brake pad callipers? Why is it ok to clean the outside of the callipers? What if the DOT4 fluid is used to clean the rims of the ST1300? I am trying to figure out the chemistry of this stuff.

If you can use it to clean the pistons in the calliper, what if it gets on anything else, like dripping onto the rims...just curious.

Click to expand...

Brake fluid gas just the right chemistry to bind to the paint base. Wipe off the brake fluid, wipe off the paint. Some people (incorrectly) think that makes brake fluid some pretty nasty and harsh to human skin stuff. Nah... it's not that bad. Eggs do the same thing. Now I don't recommend you make an omelet from brake fluid, but don't be deathly afraid of it.

As far as cleaning the Pistons, calipers and forks? Works wonderfully. A little Dot4 and a toothbrush will scrub the road grime and brake dust right off. The forks, rims and caipers have powder coat, impervious to the brake fluid. But don't let them throw that brake fluid onto the bodywork, it's not so resistant. After cleaning the forks rims and brakes up, give them a good bath with soap (grease cutting) and water.

I will toss this in here, although, if the OP can't get DOT4 it's unlikely he can get this: DOT5.1. Not to be mistaken with DOT5, which is silicone based fluid, and useless in an ABS system due to it's foaming characteristics. DOT 5.1 is polyglycol based and has a higher heat rating than 4. It's also pretty expensive compared to DOT4. I've used it in high performance applications where extreme heat is an issue. That being said, I've also used DOT5 in applications also, but this was on fresh systems, with *all* new parts, and no ABS to contend with. DOT5 does not mix with DOT3, DOT4 or DOT5.1. DOT5 tends to foam when subjected to an ABS pump, resulting in loss of braking.
I have, in an emergency, replaced DOT4 with DOT3 with no issues, but have replaced it when I had access to DOT4.
Which reminds me, I need to look at my front brakes, noticed the fluid seemed low today.

I've been using a bottle of Valvoline DOT 3/4.

DeanR said:

I've been using a bottle of Valvoline DOT 3/4.

Click to expand...

DOT 3 and 4 share very similar chemistry, as pointed out earlier. DOT4 has more stringent specs than 3, so it is backwardly compatible. That's why the labels for DOT4 often say DOT3/4. The reverse would, obviously, not be true, DOT3 fluid would not meet the specs for DOT4.