Go Back  Bike Forums > Bike Forums > General Cycling Discussion
Reload this Page >

DOT Fluid Hydraulic Brakes or Mineral Oil?

Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

DOT Fluid Hydraulic Brakes or Mineral Oil?

Old 05-31-20, 04:56 PM
  #1  
Fissile
Senior Member
Thread Starter
 
Fissile's Avatar
 
Join Date: Nov 2007
Posts: 611
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked 14 Times in 13 Posts
DOT Fluid Hydraulic Brakes or Mineral Oil?

I'm wondering what people with hydraulic brakes prefer? Brakes that use DOT fluid or brakes that use mineral oil? If you have a preference, what's your reasoning?
Fissile is offline  
Old 05-31-20, 05:15 PM
  #2  
Troul 
:D
 
Troul's Avatar
 
Join Date: Oct 2013
Location: Mich
Posts: 3,005
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 473 Times in 335 Posts
mineral oil. Ever see what DOT fluid can do to paint, carbon, & rubber parts on a bicycle if you have an "oof 1,000" moment?
__________________
-Oh Hey!
Troul is offline  
Old 05-31-20, 05:19 PM
  #3  
mrblue
Senior Member
 
Join Date: Jul 2014
Posts: 647

Bikes: Canyon, Bowman & Colnago

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 131 Post(s)
Likes: 0
Liked 39 Times in 20 Posts
Originally Posted by Troul View Post
mineral oil. Ever see what DOT fluid can do to paint, carbon, & rubber parts on a bicycle if you have an "oof 1,000" moment?
I concur.

So if mineral oil is less corrosive and, consequently safer for the home mechanic to use, what are the advantages of a manufacturer, i.e. SRAM, engineering their hydraulic brakes to use DOT fluid?
mrblue is offline  
Old 05-31-20, 05:32 PM
  #4  
Fissile
Senior Member
Thread Starter
 
Fissile's Avatar
 
Join Date: Nov 2007
Posts: 611
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked 14 Times in 13 Posts
Originally Posted by mrblue View Post
I concur.

So if mineral oil is less corrosive and, consequently safer for the home mechanic to use, what are the advantages of a manufacturer, i.e. SRAM, engineering their hydraulic brakes to use DOT fluid?
My guess would be that DOT fluid is cheaper.
Fissile is offline  
Old 05-31-20, 05:44 PM
  #5  
Gresp15C
Senior Member
 
Gresp15C's Avatar
 
Join Date: Sep 2014
Posts: 3,456
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 903 Post(s)
Liked 406 Times in 281 Posts
Is there a palpable difference between mineral oil and motor oil that would forbid use of the latter? You could even get multi-grade for winter use.

I'm waiting for someone to recommend wax.
Gresp15C is offline  
Old 05-31-20, 05:51 PM
  #6  
tomato coupe
Senior Member
 
Join Date: Jul 2009
Posts: 1,743

Bikes: Colnago, Van Dessel, Factor, Cervelo, Ritchey

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 1036 Post(s)
Liked 1,347 Times in 561 Posts
Originally Posted by Gresp15C View Post
I'm waiting for someone to recommend wax.
You'd have to bleed your brakes every 100 miles.
tomato coupe is offline  
Old 05-31-20, 05:56 PM
  #7  
Troul 
:D
 
Troul's Avatar
 
Join Date: Oct 2013
Location: Mich
Posts: 3,005
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 473 Times in 335 Posts
not all MO are interchangeable if comparing to glycol DOT 3, 4, 5.1. MO for a bicycle is not equal to household MO. Brake systems that is MO are often "enhanced" by the OEM. So don't go pouring your bicycles brake MO on your dome for a dandruff remedy.

There's a bit more to it, but that is a snapshot of information.
__________________
-Oh Hey!
Troul is offline  
Old 05-31-20, 06:12 PM
  #8  
Fissile
Senior Member
Thread Starter
 
Fissile's Avatar
 
Join Date: Nov 2007
Posts: 611
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked 14 Times in 13 Posts
Just trying to understand why use two types. It's also curious that the makers of the cheapest hydraulic brakes and some of the most expensive, like Hayes, use DOT.
Fissile is offline  
Old 05-31-20, 06:30 PM
  #9  
DrIsotope
Non omnino gravis
 
DrIsotope's Avatar
 
Join Date: Feb 2015
Location: SoCal, USA!
Posts: 8,553

Bikes: Nekobasu, Pandicorn, Lakitu

Mentioned: 119 Post(s)
Tagged: 0 Thread(s)
Quoted: 4898 Post(s)
Liked 1,687 Times in 943 Posts
I have one bike on DOT (SRAM Rival HRD) and one on mineral oil (TRP Hylex.) The only problem I have is that I need to have two bleed kits. They seem to perform exactly the same, and I service them at the same interval, which is to flush-n-fill once a year.

My selections had nothing to do with what fluid was in the brakes-- I was building a 1X bike in the pre-GRX era, so it was SRAM, and they use DOT. When I built my SSCX, the Hylex is the only game in town for dropbar hydraulic without shifters, so mineral oil was it.

They're the same to work with, IMO. If either gets on the pads, they're fouled, so no advantage one way or the other there. DOT boils way higher, but no one is ever gonna get there on a bicycle, so that doesn't matter. DOT is hygroscopic, but even at my annual service interval, the fluid comes out barely a tinge shaded from when it goes in. DOT fluid is significantly cheaper, if you really wanted to split hairs. A 500mL bottle of Motul 5.1 is around the same price of 50mL of Tektro mineral.
__________________
DrIsotope is offline  
Old 05-31-20, 06:32 PM
  #10  
wsteve464
Senior Member
 
Join Date: Jul 2016
Posts: 557
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 157 Post(s)
Liked 70 Times in 61 Posts
Google


https://sram.zendesk.com/hc/en-us/ar...r-mineral-oil-

Why did SRAM choose DOT 5.1 over mineral oil?

  • 4 years ago
We specifically choose DOT fluid for its performance characteristics:
  1. Heat/moisture management: DOT fluid manages heat better. While pure mineral oil and pure DOT fluid both have boiling points around 280C, DOT fluid is much better at managing water, which, over time, always finds its way into any brake system. DOT fluid makes any water in the system part of the fluid, while mineral oil pushes water to the edges. If a fair amount of water migrates into a mineral oil system, water’s boiling point, 100C, becomes that of the system. Our tests showed that even old, “wet” DOT fluid the boiling point never gets below 180C, while a bike brake system rarely sees temperatures over this point. The result: DOT fluid offers more consistent braking performance.
  2. Feel: DOT fluid is less compressible than mineral oil. DOT was specifically invented to be incompressible—a key attribute of any high-performance hydraulic fluid.
  3. Serviceability: Both mineral oil and DOT fluid systems require regular service. Both fluids must be handled the same way: wear gloves, collect your waste fluid, and recycle it appropriately. DOT fluid offers some advantages: For example, DOT refers to the United States Department of Transportation, which means the fluid must meet a common set of standards set by this regulatory agency. DOT fluid can also be cleaned up with water, no solvents required.
DOT summary:
  • DOT fluid is brake fluid – it gives you great performance
  • DOT fluid manages water – any sealed system will have water migrate in
  • DOT fluid and mineral oil must be handled in the same way: Mechanics should wear gloves and properly dispose of it.
wsteve464 is offline  
Old 05-31-20, 10:57 PM
  #11  
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Posts: 23,586

Bikes: Some silver ones, a red one, an orange one and a few titanium ones

Mentioned: 119 Post(s)
Tagged: 1 Thread(s)
Quoted: 3897 Post(s)
Liked 1,327 Times in 820 Posts
Originally Posted by Gresp15C View Post
Is there a palpable difference between mineral oil and motor oil that would forbid use of the latter? You could even get multi-grade for winter use.

I'm waiting for someone to recommend wax.
Yes, there is. Mineral oil is made from longer chain alkanes. It is related to mineral spirits but just bigger molecules. Motor oil is slightly related but it has a lot of different chemicals in it to provide the modification needed to operate in the high heat environment of an engine. It has detergents and viscosity modifiers that arenít compatible with mineral oil that is used in bicycle hydraulic systems.

Originally Posted by Fissile View Post
I'm wondering what people with hydraulic brakes prefer? Brakes that use DOT fluid or brakes that use mineral oil? If you have a preference, what's your reasoning?
DOT fluid is used for various reasons. SRAM has a good discussion of why they use DOT fluid over mineral oil. I think the biggest reason is better water management. Water gets into the systems through seals over time. Water is insoluble in mineral oil but not in DOT fluid. If you heat the two fluids...well, three if you include water...the DOT will heat evenly. The mineral oil will phase separate and the water is at the bottom of the system. Heating the brake fluid will heat the water first and cause it to flash to steam if it gets hotter than 100įC. Now you have a gas inside the brake system which becomes compressible.

Just to be clear, this would be in the most extreme case. But water can expand significantly if it is heated enough. At the boiling point of the oil...280įC...water will be steam at a pretty significant pressure.

The other problem with mineral oil is that it comes in different viscosities. You need to know what viscosity of oil is to be used for a specific brake. If you have a viscometer, you could measure it but thatís not a cheap instrument nor that easy to use. You are kind of stuck using the oil that the manufacturer specifies...and sells, usually for a premium. On the plus side, mineral oil is nontoxic.

DOT fluid, on the other hand, is fairly standard. There are a few of them but DOT 3 and DOT 4 are the most common and are usually interchangeable for bicycle brake applications. It is somewhat hard on paint and somewhat toxic but manageable.
__________________
Stuart Black
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
cyccommute is offline  
Likes For cyccommute:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.