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DOT 5 brake fluid?

  • Thread starter Thread starter ap72
  • Start date Start date
A

ap72

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Okay, so I know braking isn't normally a performance thing.. but I think it kinda is this time.

My rear brake fluid kept boiling (I ride a lot of hilly back roads and use the brake A LOT), and since it was the cheapy DOT3 fluid that I use on cars when doing brake jobs it didn't suprise me when it couldn't take the heat of the motorcycle caliper (it gets a lot hotter). So I wend down to the local auto parts store and picked up some DOT 5 fluid (twice the boiling temerature rating). On our bikes it says "only DOT 3 or 4" or something to that extent, and on the DOT 5 fluid it specifically says not to mix them (I did flush the entire system quite thuroughly).

Before I go crazy on the brakes has anyone else tried this and have you had any problems?- if none please let me know about that too (for peace of mind).
 
HI

DOT 5 brake fluid is generally a silicone product and is not recommended unless the system is specifically designed for it.
 
Yep, I run Dot 5 in my 1100e. As long as you flush the system real good it shouldn't be a problem. Total brake power may not be quite as good as Dot 3 or 4 but you can spill Dot 5 all over your painted pieces and not worry which is why I switched. Just don't forget you made the switch and top off with Dot 3.

I've never had a problem with any kinda brake fluid boiling over, so don't know if it will solve that problem for ya.
 
If you run DOT 5 you need to flush the system at least once a year. Silicone does not suspend water like the DOT 3 and 4 fluids resulting in a collection of water at the low point in the brake system when the bike sits for a period of time. This can result in corrosion of the brake line from the inside (or damage to the caliper) and ultimately failure of the line. I believe we've had at least one member who has experianced this.

Also, the DOT 5 fluid tends to give a more "mushy" feel to the brake.

Hap
 
why not try running some valvoline synthetic (gold bottle) dot3 / dot4. it sez it excededs dot 3 and 4 specs but can be run with dot 3 or 4 fluid. it's worth a try before totally switching. i ran it in my 550 on a track day and didn't notice any problems like boiling over and i got my rotors nice and toasty.

also you may want to try to use a little more engine breaking and front brakes, to help keep the back a little cooler, this way you are less likely to warp the rotor from excessive heat. also take the back pads off and scuff off the the glazing with some sand paper on a flat surface, that has probly built up from so much use, that way you will get better bite and less heat cause you won't have to press as hard.

-ryan
 
Or just use DOT 5.1 which is not silicone based and higher temp.
 
ap72 said:
.......My rear brake fluid kept boiling (I ride a lot of hilly back roads and use the brake A LOT), and since it was the cheapy DOT3 fluid that I use on cars when doing brake jobs it didn't suprise me when it couldn't take the heat
Click to expand...

Had you flushed or bled the system prior to your boil overs? Could it have been older fluid that had some absorbed H2O to begin with?

Personally, I'd go with the DOT 4, and if a high quality set of brake pads is available, those as well.

saaz, I have not heard of the DOT 5.1. I'm probably behind the times:wink: . Anyone know if we've got that here?
 
Last edited:
I flushed it several times and the boiling problems persisted- though it was cheap DOT 3 fluid, maybe I'll switch to the Valvoline if the brakes feel too mushy.

Where is a good place to get great brakes pads from? I assume it'll be mail order, but I want some new pads for the front (the rears have new pads now) and I'd like to get some good ones (brakes are the most important part of any viehicle).
 
I put tires over breaks, but there is quite a race between the two. EBC pads are pretty good, about $25 a pop, so $50 for the front. One brake upgrade that will help with soft brakes is new brake lines. I like the braided stainless steel myself. After about 5 years the rubber lines are shot, I didn't realize how bad they got untill i played with the brakes on an 05 Honda rancher, get a nice hard handle with them, the 01 Rancher will go to the bars an only get a fraction of that hard.

Odd about the comments about the DOT 5, I've been told the opposite, that because it dose not attract water the system will stay dryer. The DOT 3 will pull water from the air and add to boilling problems. I'm not an expert but the DOT 5 thing dosen't sound right to me. If you run DOT 3/4 then change the fluid every year, better to not let to much crap build up and give you problems.

You might want to pull apart the rear calipar and clean up the pistons. Something just dosen't seem right about getting the brakes THAT hot. Engine braking is a wonderful thing, and I would sudjest that, your engine can take the heat (it's not to much work for an engine really).
 
quakeholio said:
Odd about the comments about the DOT 5, I've been told the opposite, that because it dose not attract water the system will stay dryer. The DOT 3 will pull water from the air and add to boilling problems. I'm not an expert but the DOT 5 thing dosen't sound right to me. If you run DOT 3/4 then change the fluid every year, better to not let to much crap build up and give you problems.

You might want to pull apart the rear calipar and clean up the pistons. Something just dosen't seem right about getting the brakes THAT hot. Engine braking is a wonderful thing, and I would sudjest that, your engine can take the heat (it's not to much work for an engine really).
Click to expand...

You are correct about the DOT 5 not attracting water. Because the DOT 5 does not attract or mix with water the water tends to pool in the low point of the brake system, resulting in corrosion at that point.

I also agree about the rear brake...something is not right. Maybe the pads are dragging?

Hap
 
Hey, Firstimer, I looked at the link to your 550. Wow! My 19 year old daughter rides an 82 GS550L. It looks like you have made the mods I am going to make to her bike. Can you give me the Make of your header, airfilters, and ignition components. If you could pass on the carb jetting that ended up working, it would be GREATLY appreciated. Thanks!
Dan
 
first timer said:
why not try running some valvoline synthetic (gold bottle) dot3 / dot4. it sez it excededs dot 3 and 4 specs but can be run with dot 3 or 4 fluid. it's worth a try before totally switching. i ran it in my 550 on a track day and didn't notice any problems like boiling over and i got my rotors nice and toasty.

also you may want to try to use a little more engine breaking and front brakes, to help keep the back a little cooler, this way you are less likely to warp the rotor from excessive heat. also take the back pads off and scuff off the the glazing with some sand paper on a flat surface, that has probly built up from so much use, that way you will get better bite and less heat cause you won't have to press as hard.

-ryan
Click to expand...

I agree with Ryan on this one. I have had nothing but good experiences with the valvoline semi-synthetic. It isn't nearly as fussy as the DOT5 but has a higher boiling point than regular DOT3. I flush clean fluid through my toys pretty regularly, especially the off-road ones. I had DOT3 in the front and the valvoline in the rear on my 4-wheeler. After a year the valvoline still looked like new while the cheap stuff was a nasty brown. Perhaps not a scientific test, but it made a believer out of me.
 
I've used silicone dot 5 since '80. Worked well for me.
I've heard of some seals swelling however and this causes the pistons to stick. I guess over a longer time the silicone softens/swells the seals.
I'm going with the 5.1 stuff with my next rebuild.
 
I used to use the silicone stuff years ago when it really was much better, but even then it did have its negative points. Since the higher performance normal fluids have come out I have not bothered.
 
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