Quantcast

stupid question about dot

dhkid

Turbo Monkey
Mar 10, 2005
3,359
0
Malaysia
why do you have to change dot fluid when it get all merky coz of boiling? mine gets merky after about 3 weeks of everyday riding. gets annoying to change them all the time. oh yea, is there someone who can proove that minerall oil works in dot systems with no problem? besides saying that someone you know has ran them for 3 years with no problems ect.
 

8it

Chimp
Apr 6, 2003
91
0
NYC
Something might be wrong with your set-up. You shouldn't be going through that much hydro fluid that frequently. What kind of brakes are you using, are you using the right kind of fluid for your set-up? Are your brakes loosing power? Try to provide a little more details and maybe one of the monkeys can help you figure it out or you can take a trip to your local bike shop. Good luck
 

dhkid

Turbo Monkey
Mar 10, 2005
3,359
0
Malaysia
eh, every detail? here it goes. my brakes are hope minis. 9 in rotor in front, 5 in the rear. stock mini pads. power suck really bad, the brake has been bled over and over agian, same ****. and the feel is solid so air in the system is out of the question. about the pads, i can get them to work really nicely if i sand them down to make them rough but they hardly last a ride. and then the power is really ****ty agian. about the fluid boiling all the time, i live on a hill, 2700 ft ASL, so everday i go to work by bike, the road down is 5.1 km, i dont drag al the way down, but just at the last km, my brakes boil or are pretty close to boiling. so i dont think there is anyway aorund my problems. oh yea, about the power, i am getting new pads, galfer ones. so if it still suck, new brakes!!!! oh yea, my trip to the LBS is every day coz i work there.
 

Biscuit

Turbo Monkey
Feb 12, 2003
1,768
0
Pleasant Hill, CA
What fluid are you using? Specifically?

I had a very similar problem with my hopes a few years ago that made me hate them. Turns out there is a big difference between dot 5 and dot 5.1 fluid. One is glycon based and one is silicon based (I think).

Basically, the wrong fluid will gradually eat up your seals, causing air leakage and contamination. It gets worse and worse till your brakes litteraly don't last a ride. You could try sending them back to hope for new seals, their customer service is top-notch.

Another possibility is whatever fluid your using could be contaminated. Brake fluid readily absorbs water from the atmosphere. If you've left your fluid bottle open, it will get water in it, and boil extremely easily.

As for using mineral oil, whats the point? The fluid that hope recommended to me works great, is cheap, and available at any auto-shop. It's a synthetic, in a gold bottle, I believe made by valvoline (not positive though). Try that.

And, check your hose for kinks. Even if it appears fine on the outside, a kink can cause a breakage on the inside, leading to bad brakes.
 

dhkid

Turbo Monkey
Mar 10, 2005
3,359
0
Malaysia
i just bought a botol of motul 5.1 brake fluid, gonna flush out the system when i can find a hose to fit over nipple. might contact them for that rebuild. see what happens.
 

mack

Turbo Monkey
Feb 26, 2003
3,675
0
Colorado
I have been running mineral oil in my grimeca system 8 brake since february without any problems at all. Not that it works any better or anything, just that i have a shimano lever (mineral oil) and grimeca rear caliper (DOT).

I left some DOT fluid in an open bottle for about half a year now, and its all congealed at the bottom. Kinda strange.
 
Are your brakes the old Minies or are they the newer Mono Minies? If they are the old minies I had the same problem but I was able to fix them. The problem arises from the Minies not having a bolt to secure the upper half of the calipers (near where the brake line is connected). In most cases if you look at your caliper closely while holding onto the brake you can see the caliper halves separating, thus letting air into the system. To fix this all you need to do is buy a couple of small hose clamps from Auto Zone and install it around the upper portion of the caliper and tighten them down as much as possible. If your worried about looks, Speed Goat Cycles used to sell a machined bracket for the hope minies. Problem solved.

If your brake is a Mono Mini I don't know what to tell you.
 

snoopz666

Monkey
Dec 24, 2004
248
0
now residing in kamloops
mack said:
I left some DOT fluid in an open bottle for about half a year now, and its all congealed at the bottom. Kinda strange.
this is because bake fluid absorbes water over time, this is why you should only buy small bottles and not use old fluid.

dhkid said:
why do you have to change dot fluid when it get all merky coz of boiling? mine gets merky after about 3 weeks of everyday riding. gets annoying to change them all the time. oh yea, is there someone who can proove that minerall oil works in dot systems with no problem? besides saying that someone you know has ran them for 3 years with no problems ect.

k this is x posed from a thread i repiled to a while ago about DOT fluid

odds are that you have dot 3 brake fluid in your system, this means that at 400degrees(F) it will boil. now this is when the fluid is brand new, since brake fluid is hydroscopic(absorbs water) over time the boiling point (BP) goes down. now i had to look this up but a just 4% water content the BP drops to 280 degrees(F). i remember reading an article in decline that said that at ~300 degrees (F) most brakes loose most of their power(although i remember that the tests done where them testing the brakes to the very limit). but by that time your fluid has got that hot it will boil gas will be produced and you will loose all of you braking power(lever pulls to the bar).

* although this is true this will only happen in the most extreme circumstances. to remedy this you can get DOT 4 brake fluid that boils at 450d degrees or if you really want DOT 5.1( i know hope comes stock with this). it boils at something around 525 degress.

**in the hope manual it says not to mix 5.1 and DOT 4. this is true if you want the highest BP possible but no harm will come to your brakes if you mix the two. now if it was DOT 5 and 4 this is true because DOT 5, unlike DOT 4 and DOT 5.1 which are a glycol ether / borate estermix, is silicone based and will eat the seals.
so next time you decide to bleed them try 5.1 it should help your braking performance alot. especially since your getting the new pads.
 

dhkid

Turbo Monkey
Mar 10, 2005
3,359
0
Malaysia
they are the old minis, and i am using dot 4 right now. i dont think i have problems with air getting in the system. but that might explane why the brake fuild dissaperes. has anyone ever had brake fuild come out of the calipers insead of air going in?
 
dhkid said:
they are the old minis, and i am using dot 4 right now. i dont think i have problems with air getting in the system. but that might explane why the brake fuild dissaperes. has anyone ever had brake fuild come out of the calipers insead of air going in?

If fluid was coming out then it would be wet on your caliper,pads,rotor,etc.....
You would notice that
 

Biscuit

Turbo Monkey
Feb 12, 2003
1,768
0
Pleasant Hill, CA
dhkid said:
they are the old minis, and i am using dot 4 right now. i dont think i have problems with air getting in the system. but that might explane why the brake fuild dissaperes. has anyone ever had brake fuild come out of the calipers insead of air going in?
Actually yes! On a pair of hopes I had!

What happened to me, was I had to buy a new 1/2 caliper to transfer it from a intl std to a boxxer mount. When putting on the new 1/2 caliper, I didn't notice the tiny little o-ring that goes around the "fluid hole" in a tiny little detent.

If that o-ring is either worn out or missing, your caliper will leak.
 

dhkid

Turbo Monkey
Mar 10, 2005
3,359
0
Malaysia
just changed the fuild, see how the ride goes tomorrow. i am thinking about mono minis, or m4s or if i give up on hopes, juicys.
 

Brian HCM#1

MMMMMMMMM BEER!!!!!!!!!!
Sep 7, 2001
31,464
36
Bay Area, California
Don't use DOT 5 in Hopes. Only use a high quality DOT 3-4 or 5.1. As mentioned above the older minis did sometimes have an issue with leakage at the caliper from braking forces.
 

DirtyMike

Turbo Fluffer
Aug 8, 2005
14,307
894
My own world inside my head
Ok this is a question for me........ 2 degrees one automtive one deisel tech...
Ok DoT 3 DOT4 and DoT 5.1 are all glycol based <Master certed AUto Tech Btw i answer this question a couple times a week> Mineral oil will destroy not only your brake system but your warranty. DoT5 is a synthetic based fluid and is usually purple. WIll suually find i on high end luxuray vehicle high Xtra high performance vehicles and Crotch rockets. Hope Mini's and Hayes recomend using DoT 4 or better.... DOT 3 will break down and Boil Way to easy. NOw as far as what your talking about Have you called Hope yet?.. they had a few warranty issues with the Mini's. i have gotten more than a few set totally replaced for free<Works at Bike shop in off time> Oh yeah teh DoT3 DoT4 and DoT5.1 will eat the paint/PC/anyting right down to the metal someimes you wont see it till you wash it. As far as teh Pads needing to be sanded try a different brand or maybe a different compound might get a beter result... i knwo alot liek Kol stops See is someone offers a Sintered Pad for the ones you are running. little harder on teh rotors But they wont harden up like the factory pads sounds like your on teh right track though with the 5.1 very high Boiling point but remember with anything glycol based it starts absorbign water as soon as you open it right from the air if the bottle has been open and not used up in a week Throw it out even with the cap on it has already absorbed enough water to lower the boiling point dramatically
All three of the DoT gylcol based are Very Prone to this no matter how high of a quality fluid it is.. Its just the nature of the fluid type... Call hope though tell them whats happeneing Might get a Free set of brakes
________
The Cliff Condos Cosy Beach
 
Last edited:

dhkid

Turbo Monkey
Mar 10, 2005
3,359
0
Malaysia
ok, its been about a month since i changed my brake fuild. good news is that it doesn't fade anymore and the caliper doesn't leak oil. bad news is that the oil has turned merky again and the brakes feel a bit squishy. so whats wrong now? :(