I need to replenish the fluid in my front brake on my Whyte Portobello (Promax Hornet disk brake) after all of the fluid leaked out through my own mistake.

I'm looking at kits like this on eBay, will it will be fully compatible with my Promax calipers etc?

2 Answers 2


The only specific piece that you need to worry about is the threaded hose fitting that screws the tube from the syringe into the reservior port, everything else is identical.

Unfortunately I believe that the Promax Hornet use two different types of threads for their reservoir ports on the lever and caliper whereas Avid only use a single type (if someone can confirm otherwise, you are good to go). So you may only have one fitting that works instead of the required two.

There are many generic sets that come with multiple fittings that are cheaper than the Avid kit and will have the fitting you need. They don't ususally come with DOT 4/5.1 but you can buy this at any automotive store.

  • From contact with another website RE: Hornet brakes "Yes our Universal bleed kit will work win your Hornet brake set. It takes 5mm threads, the same as Avid brakes." I've ordered a bleed set from them - I'm hoping what they claim is correct, I've heard about the different threads elsewhere too.
    – Ben
    Oct 2, 2013 at 22:18
  • What's the difference between DOT 4 & 5.1?
    – Ben
    Oct 2, 2013 at 22:18
  • 1
    Boiling point, DOT 5.1 is much higher. They're compatible but you shouldn't mix them.
    – DWGKNZ
    Oct 3, 2013 at 0:26

Having a brake bleed kit helps do the job quickly and cleanly, but if you're not doing it very often you don't necessarily need a kit.

As long as your bike is setup so there aren't many places for bubbles to get caught, you can just work the lever and tap the lines and so on while the bleed bolts are open, to assist air bubbles rising to the top and out of the system (catching any leaking fluid in a perfectly clean container so you can re-use it).

I have a bleed kit and don't bother using it, my bike generally doesn't trap any air bubbles anyway.

If there are a few small bubbles in the system, the brake lever will still work, it'll just feel a tad spongy or soft. I would just try doing as good a job as you can without a bleed kit, and then if they aren't working as good as they should order a proper kit for your Promax brakes.

  • Problem is my brakes are missing all of their fluid entirely, so it would seem a kit is necessarily - if not just for the sake of ease.
    – Ben
    Oct 2, 2013 at 22:19
  • @Ben With my brakes it isn't necessary to have a kit, it'll just take longer. The air will (slowly) rise to the top and out of the system as you put fluid in. Oct 2, 2013 at 22:21

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