M2S R750 rear brakes not working after changing tire?

[johnw]

Looking for some help. I have a M2S R750 and when my son was changing the rear tire that had a flat somehow the rear brakes got messed up. When I squeeze the brake lever for the rear it has to now be pulled all the way to the handlebar and will barely engage the rear brake. I never adjusted brakes , does anyone have any info on doing it?

Also I seen someone posted about Kevlar tires so I don’t get any flats , where can I get some?

 

[cityscape]

That is strange... did the brake lever get pulled while the wheel was off? These are hydraulic brakes, it sounds like they have air in the line but I don't think the caliper can close enough to do that. Unless you loosened the caliper screws.

The only time you need to bleed brakes is when you aerate the lines.... it is a mystery how you got air in the lines unless you actually loosened the line removing the wheel. I have bled tons of brakes in my time but not these, it's way to much to explain in writing here, I would have to read up on these and find out which screws are the bleeders.

Sounds like air in the brake lines if they are hydraulic. YouTube will show you how to bleed the brakes.

 

[ebikejames]

Yeah it’s just air in the lines. This happens when the breaks get pulled with no rotor between the calipers. The pads go in too far and it bleeds some fluid and gets air bubbles in it. There are videos on YouTube about how to add fluid and get it working but you can also have it done at any bike shop.

 

[jbmon]

I had a terrible experience with M2S Bikes. The quality of the bike was extremely disappointing, with issues arising almost immediately. Despite these problems occurring within the first year, the company refused to honor the warranty. Each time I contacted them, I was given a different excuse, and they never returned my calls. The bike's build feels cheap, and I regret purchasing it. I would never recommend an M2S bike to anyone. Avoid this company at all costs!

 

[addertooth]

What was said by ebikejames is true. I will throw in another factor. If the eBike is INVERTED to work on it, air from the handlebar brake reservoir can bubble UP to the brake calipers at the wheel. This air bubble is VERY squishy, and requires a lot of squeezing on the brakes to even get feeble braking afterwards.

Even worse, this tends to make the operator "adjust" the handbrakes to get better engagement. This means that partially compressed air bubble is keeping the pads under constant light pressure, which results in accelerated brake wear (and glazing of the rotors).

If you have done this, you need to do a brake bleed procedure to eliminate the air in the lines and brake calipers to restore normal function. Some people get lucky, and can clear those bubbles by a few minutes of constant "squeeze and release" on the brake levers. This trick does not work across all brands/types of brakes. So, if it works for you, then great! Otherwise, watch some YouTube videos on bleeding eBike hydraulic brakes. It is in your future.