How often do you need to bleed the hydraulic disc brakes?

[stockae92]

Just wondering how often do you have to bleed hydraulic disc brakes for a cross country bike?

Nothing crazy and no heavy AM or DH bike, just cross country bike.

[caballero]

once installed and bled, I'd run them until they change feel, become spongy or contaminated.

Maybe replace fluid once a season.

[mattr]

I do it yearly, once the bike comes out of winter storage. Gets a complete once over. Pretty much strip down, clean and rebuild with new parts (where needed) and new grease/lubricant/copperslip.
During the year (if they were filled properly when last done) they are effectively a sealed system, new pads might be needed, but nothing else.

Training/winter bikes i generally just leave them until they either break or i have an issue. So maybe every 2 or 3 years.

They still never need bleeding. Just new fluid.

What brakes do you have anyway?

[TheRookie]

My old M765's weren't touched for about 4 years, other than 3 sets of pads.

No real need to change the fluid in a sealed system either.

So if you want to bleed (flush the fluid, no mileage in just checking it's 'full') that's fine, but you shouldn't NEED to.

[stockae92]

The reason I am asking is that the front brake (older XTR disc) of my MTB is losing feel. I am wondering if I should buy a bleed kit (if i have to do it often), or just take it to the LBS if I only need to do it once every 5 yr

[bikemaniack]

In my opinion,brake fluid shp=ould be changed in normal riding twice a year<not only bleed,but totally changed. I heard,that very good riders(not only pros),changing fuid twice a month.

[afalts]

I have xtr's and flush the fluid every month. It gets dirty. Do I notice a difference? Not really. But the first bit of fluid that comes out of the caliper is always quite murky. fwiw, I ride my mtb about 30-40 hours per month in mostly dusty conditions with a couple muddy rides per month. Part of the reason all my bikes have shimano brakes; quick and easy to bleed with the funnel and a drain hose at the caliper.

I consider it preventative maintenance. Same with servicing lowers on my fork every 2-3 weeks. There, I do notice a difference however. Nothing like fresh slick honey!

[kode54]

good to know. i myself thought that a sealed hydraulic is good for several years...but i suppose it depends on the riding conditions and moisture in the air.

[TheRookie]

Most the muck that appears in the fluid is just contamination that is already inside the system and makes no actual difference

[afalts]

Source/proof?

Working as a mechanic for over 10 years it has always been told to me through various trainings and discussions that it is due to dirt/brake dust (and moisture too) seeping in through the moving pistons in the caliper. Yes, sometimes fluid comes gunky from the factory, which is why every bike I build get a flush before riding.

[TheRookie]

No more proof than any other hypothesis.

If water/gunk/muck is getting in past the calliper seals, why is the brake fluid (under significant pressure when braking) come out........a lot more......makes no sense to me.

[Oswald]

Seems like a waste of time to me. Just do it when the brakes start to feel different.

[afalts]

I hope you're kidding - but considering the number of mechanicals I see at races, I'm not surprised. By then it could be too late if you are in the middle of a long race/ride. It's called preventative maintenance for a reason. Not 'wait until something goes wrong' maintenance.

[mattr]

Once a month is called paranoia.

[CGT]

Once a month is called paranoia.

This.