K2 / Proflex Riders Group
General => Tech Forum => Topic started by: rightturnclyde on October 03, 2007, 12:21:46 pm
-
I was thinking about changing out the oil in my Maguras (rim brakes) and using a "water bleed". I am having a difficult time bleeding them (even with the Magura kit) and read on a trials site that water will not hurt the brakes, and provides a livelier response. Plus you can bleed 'em in a bucket which ensure you rid them of air. Has anyone here tried this? I am not that familiar with the guys on the trials sites, and not really trusting their opinions much. Any input, please let me know-
Thanks, Keith
-
Sorry m8, never had to bleed my Maguras in 10 years!
Put a question to the Magura Tech forum, they've been very good to me in the past:
I have heard of emergency fixes of putting anything in except DOT brake oil, e.g. water, cooking oil etc etc.........
Col.
-
No expertise on this subject except that I own Magura's.
I would think that water over the long haul would be a bad idea because it speeds up oxidation on some materials. I may be wrong but just a thought.
See this article. The guy talks about alternative sources of mineral oil. I haven't worked out the cost but maybe you can get it cheap enough to do a bucket bleed.
http://www.peterverdonedesigns.com/bikemineraloil.htm
I am sold on mineral oil based disc brakes.
1) Mineral oil is not corrosive when it leaks or spills.
2) Mineral oil does not absorb water so like Colin said you don't have to re-bleed unless you spring a leak or have parts wear out. Mtbs are high maintanence in the first place so 1 less thing to do a year helps.
I just bought 2 sets (to do 2 bikes) of LX Shimano discs from the Jenson closeout at $108 a set to do a complete bike. That's a steal.
-
I think it is more fundamental than corrosion of metal parts.
Trials riders always ride at slow speed and do not heat their brakes up - at temperate temperatures water is a great compression resistant fluid. Problem is, it boils at 100degrees C and once it boils your brakes will totally fail! Try a longish downhill stretch - even on an XC bike and see how it performs then?!!!!!!!!!!!!!!!!!
Trials riders are hopping from one obstacle to the next with very little pad/rotor friction - the disc moves slowly through the caliper and causes very liitle heat builld up through friction - compressive strength is more important - hence most good trials brakes having very large (larger than normal caliper pistons) for instant grab effect.
Brake fluid - beit mineral oil or Dot boial at 5 - 7 times the heat of water so it is much better in longer DH's.
tell me I'm wrong?
Sprucey
-
you are NOT wrong Sprucey.When the brakes "fail" on cas,its ussually because of the moisture that has been absorbed nto the brake fluid.Thsi boils creating air/steam pockets which compress easily ...no brakes
-
Enh. I am gonna switch over a set of V-brakes from my Marin, which i'm converting to 'cross. I dont have really good luck, and the way the hose popped out of the brake lever, causing this whole bleeding fiasco, I would be sure to have issues again. Just my luck, so why press it? Thanks for the advice, always appreciated. This forum is always so helpful.
Cheers for the New Years - Keith