Bremseveske.

Trenger du hjelp til mekking, tips til deler, spør her.
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TheDuke2
Posts: 642
Joined: 02 May 2005 15:14
Location: Raufoss

Bremseveske.

Post by TheDuke2 »

Fant akkurat ut at det var lite bremseveske i bakbremsen på sykkelen ,bruker den ikke så mye men det er kjekt at det er i orden.
I forbindelse med det lurte jeg på om man kan bruke hvilken som helst veske bare DOT nummeret er det samme?
Jalmar
Posts: 7988
Joined: 26 Apr 2005 07:53

Post by Jalmar »

Man kan blande, men det anbefales ikke. Kan ikke gi deg noen vitenskapelig forklaring, men antar det har noe med egenskapene på f.eks. gammel væske og ny væske o.l.

Hvis det er lite bremsevæske kan det være tegn på lekkasje eller slitte klosser. Sjekk det før du fyller på mer væske. Er det slitte klosser og du skal skifte de vil du da sitte med for mye bremsevæske i beholderen når nye klosser er på plass. Dessuten, hvis bremsevæska di er to år eller eldre, er det på tide å skifte den. Den får lavere kokepunkt under bruk, og det kan være farlig.
1980 Kawasaki Z650SR "Gamle Blå" (I deler for øyeblikket)
2015 Kawasaki KLX250S
2023 Citroen e-C4
2004 Suzuki Liana 4WD
1987 Citroen 2CV Dolly
User avatar
TheDuke2
Posts: 642
Joined: 02 May 2005 15:14
Location: Raufoss

Post by TheDuke2 »

Jeg aner ikke hvorfor det er lite veske der , finner ingen lekasje ,pedalen siger ikke når jeg holder trykk på den ,og klossene er nesten ikke slitt. Kan være noen som har gjort en blunder da jeg hadde den på service da.
Men da drøyer jeg påfylling til i morgen ,da får jeg tak i veske av samme merke. :)
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lassie
Posts: 865
Joined: 01 May 2005 00:17
MC: 08 HD Fat bob
Location: akershus

Post by lassie »

Hei, her er nye om bremsevæske, det er på engelsk, men det går sikkert bra :)

Brake Fluid Facts
by Steve Wall

As a former materials engineering supervisor at a major automotive brake system supplier, I feel both qualified and obligated to inject some material science facts into the murky debate about DOT 5 verses DOT 3-4 brake fluids. The important technical issues governing the use of a particular specification brake fluid are as follows:

Fluid compatibility with the brake system rubber, plastic and metal components.
Water absorption and corrosion.
Fluid boiling point and other physical characteristics.
Brake system contamination and sludging.
Additionally, some technical comments will be made about the new brake fluid formulations appearing on the scene.

First of all, it's important to understand the chemical nature of brake fluid. 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, as Dr. Curve implies, a petroleum fluid. DOT 5 is silicone chemistry.

Fluid Compatibility
Brake system materials must be compatible with the system fluid. Compatibility is determined by chemistry, and no amount of advertising, wishful thinking or rationalizing can change the science of chemical compatibility. Both DOT 3-4 and DOT 5 fluids are compatible with most brake system materials except in the case some silicone rubber external components such as caliper piston boots, which are attacked by silicon fluids and greases.

Water absorption and corrosion
The big bugaboo with DOT 3-4 fluids always cited by silicone fluid advocates is water absorption. DOT 3-4 glycol based fluids, just like ethylene glycol antifreezes, are readily miscible with water. Long term brake system water content tends to reach a maximum of about 3%, which is readily handled by the corrosion inhibitors in the brake fluid formulation. Since the inhibitors are gradually depleted as they do their job, glycol brake fluid, just like anti-freeze, needs to be changed periodically. Follow BMW's recommendations. DOT 5 fluids, not being water miscible, must rely on the silicone (with some corrosion inhibitors) as a barrier film to control corrosion. Water is not absorbed by silicone as in the case of DOT 3-4 fluids, and will remain as a separate globule sinking to the lowest point in the brake system, since it is more dense.

Fluid boiling point
DOT 4 glycol based fluid has a higher boiling point (446F) than DOT 3 (401F), and both fluids will exhibit a reduced boiling point as water content increases. DOT 5 in its pure state offers a higher boiling point (500F) however if water got into the system, and a big globule found its way into a caliper, the water would start to boil at 212F causing a vapor lock condition [possible brake failure -ed.]. By contrast, DOT 3 fluid with 3% water content would still exhibit a boiling point of 300F. Silicone fluids also exhibit a 3 times greater propensity to dissolve air and other gasses which can lead to a "spongy pedal" and reduced braking at high altitudes.

DOT 3 and DOT 4 fluids are mutually compatible, the major disadvantage of such a mix being a lowered boiling point. In an emergency, it'll do. Silicone fluid will not mix, but will float on top. From a lubricity standpoint, neither fluids are outstanding, though silicones will exhibit a more stable viscosity index in extreme temperatures, which is why the US Army likes silicone fluids. Since few of us ride at temperatures very much below freezing, let alone at 40 below zero, silicone's low temperature advantage won't be apparent. Neither fluids will reduce stopping distances.

With the advent of ABS systems, the limitations of existing brake fluids have been recognized and the brake fluid manufacturers have been working on formulations with enhanced properties. However, the chosen direction has not been silicone. The only major user of silicone is the US Army. It has recently asked the SAE about a procedure for converting from silicon back to DOT 3-4. If they ever decide to switch, silicone brake fluid will go the way of leaded gas.

Brake system contamination
The single most common brake system failure caused by a contaminant is swelling of the rubber components (piston seals etc.) due to the introduction of petroleum based products (motor oil, power steering fluid, mineral oil etc.) A small amount is enough to do major damage. Flushing with mineral spirits is enough to cause a complete system failure in a short time. I suspect this is what has happened when some BMW owners changed to DOT 5 (and then assumed that silicone caused the problem). Flushing with alcohol also causes problems. BMW brake systems should be flushed only with DOT 3 or 4.

If silicone is introduced into an older brake system, the silicone will latch unto the sludge generated by gradual component deterioration and create a gelatin like goop which will attract more crud and eventually plug up metering orifices or cause pistons to stick. If you have already changed to DOT 5, don't compound your initial mistake and change back. Silicone is very tenacious stuff and you will never get it all out of your system. Just change the fluid regularly. For those who race using silicone fluid, I recommend that you crack the bleed screws before each racing session to insure that there is no water in the calipers.

New developments
Since DOT 4 fluids were developed, it was recognized that borate ester based fluids offered the potential for boiling points beyond the 446F requirement, thus came the Super DOT 4 fluids - some covered by the DOT 5.1 designation - which exhibit a minimum dry boiling point of 500F (same as silicone, but different chemistry).

Additionally, a new fluid type based on silicon ester chemistry (not the same as silicon) has been developed that exhibits a minimum dry boiling point of 590F. It is miscible with DOT 3-4 fluids but has yet to see commercial usage."
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