I need to bleed my Avid Elixirs which I see can take either DOT 5.1 or DOT 4 fluid. I can find DOT 4 easily and really cheap, but the DOT 5.1 supposedly can take more heat. Since I can't find DOT 5.1 anywhere, will using DOT 4 actually make a difference?
Use the DOT 4. I can't recite the specs off the top of my head, but the boiling point of new DOT 4 is higher than that of wet DOT 5.1. Buy the cheaper DOT 4 and bleed your brakes a couple times a year to flush out contaminants. I can think of no technical reasons why you can't add DOT 4 to a system that already contains DOT 5.1. Rob
I've found the best results with Wilwoods Hi-temp 570 racing brake fluid, it's a DOT4 compatible fluid. I've used Avid's fluid and others and I had to bleed my brakes a lot more and the fluid would break down and turn super black. Have yet to see those same issues with the Wilwood stuff.
Actually, the minimum temp specification for DOT 5.1 is slightly higher than 4...but...that's the minimum requirement. There are many DOT 4 fluids with a higher dry or wet boiling point than the minimum DOT 5.1 requirement. There are even DOT 3 fluids that surpass the minimum DOT 5.1 requirement. Keep in mind that there are many other specifications to the different DOT ratings than just dry or wet boiling points. However, I agree with your recommendation. DOT 5.1 and DOT 4 are chemically compatible.
I've often wondered about the brake manufacturers warning against mixing 4 and 5.1, it would seem they could be mixed. Honestly though, if the factory fills with 5.1, I'll spend a little more to add the same.
Good call on adding the same. Flushing may be a slightly different story, but it's best if you're going to add fluid to add the same fluid. If the factory fills with 5.1, then it is a good idea to use that fluid. There's generally a reason for it. It could be some particular characteristics (e.g., viscosity at high or low temps) why they went with 5.1. Also, although different fluids are chemically compatible, and can technically be mixed, they shouldn't. Just the same, generally speaking, different brands of the same DOT rated fluid shouldn't be mixed, either. Not all fluids of the same rating are created equally. Perhaps you're thinking of DOT 5? DOT 5 should not ever be mixed with DOT 3, 4, or 5.1. DOT 5 is a silicone-based fluid and can create problems when mixed with other DOT fluids or used in systems designed for other DOT fluids.
I already checked at Cyclegear. And it says on all the Code/Elixir/Juicy levers that DOT4 is compatible, I was more curious about any difference in performance. Thanks for the replies.
Ok, so I bled the brakes today following the manual provided with the kit (second time I've bled them). I used the leftover 5.1 fluid from the bleed kit. When I pulled a vacuum to bleed the lever body, along with the bubbles came out what looked to be a load of shredded O-ring bits, and now the lever feels very loose and wobbly when it is pushed out away from the handlebars. This isn't the first issue I've had with them so I'm gonna see if I can warranty them, I hear SRAM's customer service is legit.
Yup...... a good quality dot 4 will have a higher rating for boiling temp than most of your 5.1's..... And in the biicycle applciation there is another benefit as well... the Dot4 has a lower viscosity, which should make the brakes feel more responsive Never heard about not mixing dot 4 and dot 5.1.......... But mixing of dot4 and dot 5 on the other hand..... two totally differenet bases for the fluid. Glycol is used in dot3 dot4 and dot 5.1.... while siliocn is used for dot5. For the op... if you do go to a moto shop.... make sure your not getting the dot5, and it is indeed the 5.1..... Dot5 is regularly used in moto, specially harleys....... EDIT....... Lee beat me to the base formulation..... My bad. Double edit. A far as a true performance gian or loss....mixing vs flushing...... we are talking about brakes on a bicycle. Performance changes will be minimal...... and its really hard when bleeding bicycle brakes<if doing properly> to not be actually flushing it out.
Cycle Gear on Lake Forest doesn't sell DOT5.1 so I got DOT 4. Re-bled them yesterday with some different procedure and got much better results. I took my spare set of bars and clamped them in a vice, then attached the brakes to them so the caliper was hanging down. I followed some tips I found in another topic and used the top syringe to pull some fluid from the bottom up and this seemed to get more bubbles out. Another thing that helped was to spend more time tapping bubbles out of the lever and caliper. Overall the combo of DOT 4 and better technique = nicer brakes. Also bled a friends Elixirs with it and learned why you are supposed to bleed your brakes every once in a while...the fluid came out BLACK and full of bubbles. Really sketchy.
Just a bit more info... My fluid of choice is Wilwood EXP. It's a DOT 4 with a dry boiling point of 626ºF. It's available from summitracing.com at a good price. Right now I'm working out of a bottle of Napa DOT 5.1. Napa stores are all over town, so it's a lot easier to find, and it's more economical than buying from boutique bicycle or motorcycle stores.
Another comparision to automotive here...... the volume is sooo low in bikes, contamination happens much quicker..... Even in automotive its reccomended to flush one a year.
Problem is once you open the bottle of brake fluid it starts to absorb water. The shelf life isn't very long, I'm not sure what it is, after you open the brake fluid bottle. I would say to buy a reasonably priced fluid and replace it more often with the opened bottle.
We toss ours after a week...... just not worth it.... but then again my shop uses up a gallon every day or faster..... we do alot of brake flushes
Hmmm, I know of some nitrogen-based sprays that you can spray into a bottle of urethane resin to prolong the shelf life. I wonder if it will work the same for brake fluid.
If you were to evacuate it before adding the nitrogen... It might.... on the other hand brake fluid is cheap anyways
It's not atmospheric gasses that are not the biggest problem; it's water vapor. Shelf life is no more than two years, even unopened.
