Mountain Biking - Hydraulic disc brakes- air in the lines?

I go to my MTB the other day. It has Avid Ultimate disc brakes. I squeeze the levers, they offer little resistance, go right to the handlebars, so that doesn't feel right. But the brakes are working. Then after a couple of minutes, they feel more normal. Noticed that on today's ride too, the brakes seemed odd the first couple of minutes, quickly returned to normal.

I describe this to my LBS, the instant response is 'air in the hydraulics, you have to bleed the air out of the system'. I ask him if this is tricky, he says 'a little', which essentially means that for me it would be like building a fusion reactor out of balsa wood, I'll bring it to them. He says that while the brakes work OK now, this condition does worsen with time.

Comments?

Had your bike been hanging or upside down for a while prior to this?

After a couple of minutes of using the brakes?
I would try bleeding the brakes

Had your bike been hanging or upside down for a while prior to this?

Mine will go soft for a little bit when I have it upside down. I have to give it a few pulls to get it working good again. I don't think its from air in the lines because I have recently bleed both brakes but I'm not sure.

Mine will go soft for a little bit when I have it upside down. I have to give it a few pulls to get it working good again.

:innocent:

Go mechanical.

Bleeding your brakes, while a little time-consuming the first time you do it, is really not all that hard. The bleed kit comes with pretty detailed instructions. The first time worked out great for me. Save yourself the ~$25/brake and do it yourself. (You will need a workstand for this.)

Bleeding is easy if you brakes already have fluid in them. Don't hang upside down, this is generally bad for all bikes containing fluids (ie suspension forks, hydraulic brakes, etc). I had my headshok leak oil after this.

Just get the bleed kit and do this yourself. A workstand is not necessary. Also, follow the instructions. Make sure to keep the reservoir full as you do it, if you suck some air in.... you get to do it all over again!

Be glad you are not trying to bleed a new pair of Shimano hydros. That is a pain. I must have run 25 fills of the reservoir through it and pumped the brake lever for 30 min before they bled properly.

Oh, hydros are that much better than mechanicals. I rode mechanicals for a year prior to hydros, and they are the best thing since sliced bread.

And for god's sake, use the right fluid! I believe Avids are DOT fluid, but don't quote me on this.

Yeah Avid are DOT. You need to get the Avid bleed kit because if the special fittings on the brakes. The kit is pretty sick though super easy and it comes with fluid.

How does one know when the problem is air in the lines? I have hydros (Hayes Stoker Trail) and the left one (which I use nearly exclusively) is getting soft. Bike's pretty new, only a few hundred miles on it. I did have it upside down once to change a tire (before I knew that doing that was a no-no).

What does air in the lines feel like vs. pad wear?

:innocent:

I second that. . .

I flip my bike over all the time with hydros and have no problems... also I believe fliping it over for the fork fluid to lube the seals occasionally is recommended.. how else are you going to change a tire on the trail besides flipping the thing over... I guess don't store it upside down, but leaving it inverted for less than an hour isn't going to hurt anything.

I did have it upside down once to change a tire (before I knew that doing that was a no-no).

Why is that a no-no?