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How to bleed NUTT brakes - a guide

Started by justsomedork, September 08, 2023, 09:53:19 AM

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My personal take on adjusting, maintaining and using the hydraulic NUTT brakes that come preinstalled on the RadRover 6+ HS/ST.

**Out of the box:**

The brakes arrived poorly aligned on both my and my partners bikes (RadRover6+ HS, RadRover6+ ST). My recommendation is to fully assemble the bike as normal and adjust the calipers at the end. I discourage the use of the loosen caliper, hold brake lever, tighten caliper method as I have never managed to get the calipers aligned with this method. I suggest aligning the calipers by eye, or with the help of a feeler gauge, try your best to get even spacing between the pistons/pads near the top/middle/bottom. Once the caliper is adjusted, give the brake levers a gentle squeeze and verify that the pads make contact at the same time (or close thereof) and that the pistons retract an acceptable amount.

**Do not forget to bed the brakes** (search for a guide, easy to do).

Now I recommend ordering replacement brake pads, I may have been unlucky or unduly hard on the brake pads but mine did not last as long as better quality pads. Searching for  Avid Elixir pads should help narrow down the field, compare the pad shapes and do some light internet searching to confirm compatibility. You can also buy replacement pads directly from RadPower but they are overpriced for what they are.

**The trickier stuff:**

Since putting about 1000km on the bike I have had a lot of trouble dialing in these brakes, I've had to bleed them twice to eliminate air, had a lazy piston causing brake rub and had poor brake force on and off. If you are experiencing difficulties with your brakes there can be multiple reasons why, here I will try to help give you diagnosis guidance.

\+ Brakes squeal in a light fashion: pad rubbing (caliper misaligned, lazy piston) or pad contamination.

There are good guides for fixing a lazy piston that doesn't rollback properly.

If your rotor or pad are contaminated, remove the caliper from the frame, clean your rotor with brake degreaser, then clean rotor with 99% alcohol, replace your pads with new ones and make sure to bed the brakes (search for a guide).

Brakes may not be bedded correctly.

\+ Brakes squeal extremely loudly and violently: pad contamination.

Remove caliper from frame, clean rotor with brake degreaser, then clean rotor with 99% alcohol. Replace pads before reinstalling caliper (failure to do so may result in rotor contamination) and bed brakes as new.

\+ Brakes feel weak (consistent lever feel):

Pads may be worn down and need replacing. Air may be trapped in hydraulic line. Check to see if pads are close to being worn down to retaining clip that keeps them tensioned inside caliper.

\+ Brake lever mushy, but firms up when pulled repeatedly:

Air is trapped in the hydraulic line and a brake bleed or top-up is necessary.

**and finally, how to bleed NUTT brakes, or how I slowly lost my sanity**: I had to go through so much trial and error to get a proper bleed and good lever feel on these brakes, I will spare you details but please know my pain, I did it so you don't have to.

\+ What you need:

\- A brake bleed kit (that includes 2 syringes, a brake bleed block to stop pistons from firing by mistake, **MINERAL OIL,** compatible connectors and torx hex key). These kits are easy to find on amazon or get yourself a nice one from park tools.

\- 99% alcohol or comparable.

\- Brake Degreaser.

\- Gloves (optional).

\- New pads (optional but a good idea incase you contaminate the ones you have).

\- Small needle nose pliers for brake cotter pins.

\- Paper towels and Q-tips.

\+ The process:

**I have come to understand that a 2 part bleed is necessary to remove air and retain lever pressure on the NUTT brakes.**

1. Remove front or back caliper from bike frame.
2. Remove brake pads from caliper by bending cotter pin. Do not handle the inside of the pads as you may contaminate them, put them down on a clean surface.
3. Insert brake bleed block to prevent piston actuation.
4. Prepare your syringes with MINERAL OIL, (attach tubes with adapters to syringe, then depress plunger fully before drawing oil into syringe). I would say fill the syringes both to about 40% capacity for your first time. If you don't have enough MINERAL OIL you have to restart.
5. Prepare to open brake lever bleed screw (loosen lever clamp and make the lever housing parallel to the ground, have your syringe in hand as well as a folded paper towel).
6. Unscrew brake lever bleed screw while holding paper towel around the screw area.
7. Screw in the connector attached to the syringe. Dab up any errant fluid.
8. Prepare to open the caliper blood screw (paper towel, syringe)
9. Open the caliper bleed screw while holding paper towel around the screw area.
10. Screw in connecter attached to second syringe. Dab up errant fluid.

**Okay now we're going to do what's called a double syringe bleed.**

1. Slowly depress the caliper syringe plunger, slow even pressure, do not try to depress the plunger quickly. You should see the brake lever syringe slowly rising with fluid/air.
2. Once you have depressed the plunger about half way, gently let it hang from the caliper.
3. Move to the brake lever syringe and slowly depress the plunger, making sure not to tilt the syringe, to avoid injecting air. Once completed let the syringe hang gently.
4. Repeat the back and forth process between the syringes until no more air is exiting on either end, making sure not to inject air. Do not pull on the plungers, only push, to avoid accidently pulling air into the line.
5. Loosen the brake lever and tilt it varying degrees as you push from the caliper syringe to try and eliminate any tricky air bubbles.
6. Rotate the caliper to different positions while pushing from the brake lever syringe to try and eliminate caliper side air bubbles that may be stuck.
7. Depress caliper syringe to ensure brake lever syringe has enough oil for part 2.
8. Prepare paper towels, bleed screw and torx key.
9. Unscrew caliper syringe while holding paper towel around area, insert bleed screw and close. Dab any extra fluid that has leaked out.
10. Remove brake bleed block.
11. Clean caliper with alcohol spray or dabbed paper towels, eliminate as much MINERAL OIL residue as possible (Use Q-tips to clean inside the caliper, use sparingly as to avoid alcohol seeping towards piston gaskets).
12. Clean hands with soap and water, alcohol, or any product necessary to remove oil from hands.
13. Reinsert brake pads and mount caliper to frame, adjusting caliper as needed.

**This concludes part 1 of this bleed, now onto part 2:**

1. Make sure the brake lever housing and bleed port are parallel to the ground.
2. Gently depress lever syringe until you feel resistance. Do not over pressure the line as you may cause seal failures or other issues.
3. Pull on lever syringe to check if any remaining air remains.
4. Repeat steps 3 & 4 about 10 times ensuring no air bubbles come out of the hydraulic line.
5. Depress the lever syringe until you feel a resistance from the hydraulic line.
6. Prepare paper towel, bleed screw and torx key.
7. Unscrew syringe and screw in bleed screw while dabbing up excess oil.
8. If no oil is coming out around the screw while you screw it in, something has gone wrong and there is a lack of oil, or an excess of air in the line.
9. Clean brake lever and housing as necessary.
10. Position lever as wanted and secure.
11. Ensure your caliper is aligned, your lever is comfortable.
12. Gently pump the brake, check that pistons are retracting (rolling back) correctly and leaving an equidistant amount of space between pads and rotor.
13. Test the brake at low speed or standing beside the bike to ensure it is safe to ride with.

That's the process from top to bottom. This is the only process that has resulted in non-contaminated brakes with decent (for such horrible brakes) stopping power and brake feel. You may need to adjust the brake lever bite points for comfort (small screw near the base of the lever). Don't feel bad if it doesn't work out the first time, these brakes are temperamental to put it mildly.   

Thanks for reading!

p.s. sorry about markdown errors, 2 lazy 2 fix.