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Whatever the problem, squeeling, fade, too much lever travel, too little lever travel, etc., someone will suggest bleeding the brakes.
Is it just urban folklore, or is there some science behind it ?
If there's air in the system, they need bleeding, if there isn't, they don't. Or have I missed something.
My Land Rover's 23 years old. I think I've bled the brakes twice, each time only after replacing pipes or hoses.
I've worked on trucks with 16 gears doing 70 000 miles a year. That's a lot of clutch pedal presses, yet they never need bleeding.
What's different about mountain bikes ?
I'm not. I only bleed my MTB or motorbike brakes when servicing and i want new fresh fluid.
+ 1billion
I only bleed if there is too much travel, or the pistons refuse to go back in during pad replacement. My 2 sets of elixirs are 2 years old, only bled one of them once.
I'm not. I only bleed my MTB or motorbike brakes when servicing and i want new fresh fluid.
Which I suppose would beg the question,
why would you want "new fresh fluid" ?
Dunno what it's all about either. Bleed when fitting and leave alone. Mind you, all mine are Shimano and nothing newer than 775.
it's a homoerotic coolness thing int it..?
what did you do on Sunday afternoon...?
I had to bleed my brakes
yeah, but what did you [i]really[/i] have to do..?
Well, it was bleed my brakes or sit watching the Eastenders omnibus with the wife while we discussed curtains for the back bedroom.. I thought that you would think bleeding brakes is cooler, so I did that instead..
I've never bled my own brakes, even when shortening hoses. In fact the only times I've done it are when I've replaced a leaking piston or calliper.
why would you want "new fresh fluid" ?
Brake fluid absorbs water from the atmosphere. I think most vehicle manufacturers recommend it should be replaced every three years or so.
However, bicycles and motorcycles usually use sealed reservoirs with a diaphragm, so there is no contact between the fluid and atmosphere.
Truck systems are built to be robust and last for years - weight isn't an issue.
Land rovers rely on good luck and a head wind to slow them down. the brake pedal is only there to fill a hole in the floor:-)
But you are not wrong theres a lot of faffing that goes on with mtb brakings.
Its because most people appear to have absolutely no idea how hydraulic brakes work!
Changing the fluid is something you should probably do once every few years as it does absorb water over time although I've got a set of Hope disks that must be ten or twelve years old (maybe more) and are still on the original fluid (and they work perfectly).
I owned some Juicy 3s for a bit. If anyone wants curing of the frequently recurring impulse to bleed their brakes, I strongly recommend you get some of those, you'll be sick of the sight of DOT5 in no time.
Doesn't brake fluid degrade over time/heat cycles? I wouldn't leave the fluid in the car for years and years, but on the Bikes it gets left until something goes wrong.
The XT brakes on the Pitch have never been bled in the 3 years since i bought them new. The Hayes HFX 9s i have on my 456 were bought 4 years ago second-hand; I bled the rear one a few months ago (because of excess lever travel) and the font has never been touched.
On a slightly different note - i spoke to a trials rider the other day, who said he fills his brakes with Water instead of Brake Fluid. Apparently it ruins the seals reasonably quickly, but it makes the brakes incredibly grabby (which i gather is a good thing in trials, where you simply want to lock the brakes on).
However, bicycles and motorcycles usually use sealed reservoirs with a diaphragm, so there is no contact between the fluid and atmosphere.
I was meaning bike brakes really when I asked about the need for "fresh clean fluid"
Your comparing mountain bike disc brakes with a trucks clutch?
One is probably constructed from girders, and bits of left over rail bridge. One isn't.
I have Avids on both my bikes. Therefore I'm used to bleeding brakes. Can't see the problem myself. I could probably now do it blindfolded in 3 minutes flat
I'm not sure MTBers are 'always' bleeding their brakes, it's the default response on most [I]Why my Brakey no Workey"[/I] type threads as I suppose it can't really do any harm to eliminate air in the brakes as a cause of problems, I don't bleed mine that often, if they're working why fiddle, some of them have gone a good couple of years between needing a bleed, and I've not died yet...
Relative to your landy though MTB brakes have nothing like the same size reservoir, the whole system volume is far smaller, and they probably are a bit more sensitive to air ingress?
It's a bit like comparing a fishing boat with an aircraft carrier, they both float but they ain't used for the the same thing and are on hugely differing scales...
On motorbikes you have a clear reservoir. Over time this changes colour... Now i'm not sure if it's the heat cycles, degrading of the fluid, crap that gets in there, or even something like the lining of the brake line... but new fluid is different than old fluid. On motorbikes they recommend changing it every 2 years (generic service interval), i assume there's a reason for this....
"One is probably constructed from girders, and bits of left over rail bridge. One [s]isn't.[/s] is constructed from old filing cabinates in yorkshire"
I could probably now do it blindfolded in 3 minutes flat
Can you video it please, that would be great 🙂
I'd like to know the answer to this.
It happens all the time, a customer requests a brake bleed when dropping off their bike for repair, have a look at the brake, it's normally a combination of pads worn to backing, out of alignment caliper and a serious amount of corrosion around the pistons resulting in sticky/seized pistons. This is far more work than a bleed, resulting in more than "just needs a bleed" bill, much to their surprise.
Avid elixirs are generally ok and dont needs regular bleeding if you get a good bleed in the first place, which never happens first go.
Why are bleeding mountain bikers always on about their brakes ?
I never have had any bother with mine ,and that's with using mainly Avids over the years.
Maybe setting up brakes is beyond some people,but they have a go anyway.
Then they mess it up and have a moan on here.
Then loads of people post up how easy it is and that they should try some other method.
They try again,but really they should have got someone else to do it,as they end up messing it up in a different way.
So they buy new brakes,then come back on here to moan about whatever the brand was that they ditched.
🙂
Your comparing mountain bike disc brakes with a trucks clutch?One is probably constructed from girders, and bits of left over rail bridge. One isn't.
And one get's upto hundreds of degrese under high pressures in reinforced hoses, the other is a clutch, opperates at ambient temperature and needs nothing stronger than plastic pipe to do it's job.
Also MTB's get crashed, turned upside down, shaken etc, a truc spends it's life upright at 56mph on a motorway unless something goes very very wrong.
Maybe MTB'ers are ametures and a fault is likely to be the result of miss-bled brakes rather than profesionaly maintained truck brakes?
My hope's need bleeding, but that's because the hose got ripped off in theboot of the car, again not a probelm a truck often has.
[i]"Truck systems are built to be robust and last for years - weight isn't an issue."[/i]
and
[i]"One is probably constructed from girders, and bits of left over rail bridge. One isn't."[/i]
Well, yes, the mechanical components are going to be more robust on a truck, but the fluid is doing exactly the same job, except that bikes haven't got a servo, so the fluid and seals are working under [i]less[/i] pressure on a bike.
Seals and cylinders wear, and those minute particles of aluminium and rubber end up floating around in the fluid, eventually turning it black, so I can see a need to replace fluid every now and then.
I can't see the need to bleed brakes though, unless there is air in the system.
Why bleed brakes?
You won't get brake fade as quick as you would with old fluid that has gone black from being subject to heat and absorbed moisture, when brake fluid gets hot (enough) it boils it gets bubbles in it thus increasing brake fade - loss of power and lever pulling to the bar.gradually over time through use brake fluid will change colour and turn black no matter what. It's worth while doing and you probably will notice a difference! At a race weekend ill bleed brakes sometimes after 1 run!
Did you get them new? Because I'm on elixirs at the mo and both sets needed a bleed on first pad change as the oem pads are thinner.toys19 - Member+ 1billion
I only bleed if there is too much travel, or the pistons refuse to go back in during pad replacement. My 2 sets of elixirs are 2 years old, only bled one of them once.
I've used brakes from all hands - shimano, hope, avid, magura etc and it's pretty clear they're not a MTB component that 'just works'. They need some tlc - alignment issues, sticking pistons, bent rotors etc all commonly encountered.
I'll guess at:
Mountain bike brakes are manufactured with lower quality/smaller seals than on cars/trucks etc, to keep size and weight down. therefore more likely to persih the seals/wear out and leak, so need bleeding.
Thankyou very much Mr Shimano for not designing brakes which can have seals replaced. Genius idea.
"At a race weekend ill bleed brakes sometimes after 1 run! "
would it not be better to do it right the first time. or perhaps fix the leaks in your brakes.
that is an excessive amount of bleeding.
i agree to an extent they need bleeding more than car brakes - the fluid in a single car caliper exceeds that of the entire fluid system on the bike. but after 1 run ....
Why are mountain bikers always bleeding their brakes ?
I didn't realise they were...
It might be the default fix solution to several different posts each by a different individual.
Does this equate to people 'always' bleeding them?
On the theme of 'why do bike brakes need so much faffing when cars run for thousands of miles without a problem' I've always wondered why we're told to service our forks every 30 hours - they're just trickle down technology from motorbikes surely, and no biker I've asked services his forks anything like that often.
I thought the line was open to the reservior until you pressed the lever pushing the master cylinder and applying pressure to the fluid in the brake line, hence the reservoir can operate. The common issue with bikes is probably that they are much eaiser to put upside down than motorbikes,cars and trucks. I'm sure some designs etc are more prone to issues than others when gravity gets it's wicked way when the lever has no pressure on it.
And one get's upto hundreds of degrese under high pressures in reinforced hoses, the other is a clutch, opperates at ambient temperature and needs nothing stronger than plastic pipe to do it's job.
You won't get brake fade as quick as you would with old fluid...
therefore more likely to persih the seals/wear out and leak, so need bleeding.
I think this could be the answer. there's a lot of misunderstanding about how brakes work and what bleeding them does.
The purpose of bleeding brakes is to get all the air out of the system. If there is no air in there, then bleeding them will achieve nothing.
Air in the system does not cause brake fade. That's caused by high temperatures.
If your brakes leak, bleeding them will not cure the leak.
Does this equate to people 'always' bleeding them?
It was a metaphorical "always".
It was clearly not a literal "always" as that would leave no time for riding, eating, sleeping etc.
It was a metaphorical "always".
It was clearly not a literal "always" as that would leave no time for riding, eating, sleeping etc.
That's not a metaphor that's Hyperbole...
It was a hyperbolic "always".
Curses, I've been outpedanted. 😡
not at all when you mechanic for the current womens dh world cup champion everything has to be 110% for the average rider then yes,i do my own brakes monthly.
Surely that comes down more to being transported arround at all angles in abike bag, and sat on by baggage handlers than an actual need to bleed them after each run? I've bled my brakes after one ride before, but I'd put that down to something being wrong, not bleeding for the sake of it. If the brakes were fine I'd not touch them (if they're already 100% then fiddling with them can only make them worse).
Monthly still seems OTT unless you do a similar ammount of air travel or have faulty brakes.
Beats me. I've had the same set of XT brakes for ten years. Apart from one replacement set of discs, all I've ever done is look at them occasionally and say "Hmm. Nice brakes". Still got the original oil in them...
You do live daaarn saaaarf though wopster, so they won't have had much use 😉
Shit brakes, only time ive beld any of my 3 sets of shimanos was to shorten the hose on 1 the others didnt even need a rebleed after cutting.
not at all when you mechanic for the current womens dh world cup champion everything has to be 110% for the average rider then yes,i do my own brakes monthly.
Hmmm,
I can sort of understand a high frequency of brake bleeds for a WC DH bike not so much because they need it EVERY run, but as an "elimination of faults" measure...
Although I'd have thought having 2 or 3 identical brake sets made up as "looms" to just bolt on between runs (or when needed) would make more sense to me, less downtime, and more time to make sure the bleeding is done 'Right'...
Either way I'd have thought there has to be a sensible balance between miles covered/brake use/type of brake use, and bleeding frequency, bleeding your brakes monthly suggests you put as much wear and tear on your bike in 4 weeks as most people do in 6-12 months, and then you find time to spanner for an Atherton... Kudos!
My brakes are about 4 yrs old, and all I've done is replace the pads and clean them. But I REALLY clean them. Maybe I just have the reliable ones.
I would think a WC DH rider would have enough energy to boil the brakes properly on a run if on marginal equipment(some poor souls are even sponsored by Avid :wink:) If so then they may wish to bleed the brakes often to maintain a consistant feel.
I've been using hydraulic brakes on my mountainbikes since 2004. I've bled one set of brakes - Avid Elixirs that I had to replace the pistons on (I'd worn them down using them to stop on Kielder 100 in 2011).
I had shimano deores for 5 years that never got bled, didn't even require it when shortening the hoses, just a top up of the reservoir. My elixirs on two bikes are fine after years with the exception of the rebuild.
I've had two brake bleeds in roughly 5 years. I had some old style M800 saints which got bled when they were new. I had to take the off the bike when I broke a lever. They are lying in a cupboard somewhere, they still work.
I replaced them with some Shimano M785 XT's. They got a bleed when they were put on the bike a year ago. Not a dickybird since. Working perfectly.
If so then they may wish to [s]bleed the brakes often[/s] [b]throw themselves onto the nearest tree[/b] to maintain a consistant feel.
Based on my brakes, thowing myself into the nearest tree was the most relaible and least painfull way of stopping with Elixirs.
they're just trickle down technology from motorbikes surely,
the forks on my R1 have substantially more than 5ml of oil in the lowers lubricating them... Marzocchi open baths (which were famous for not needing attention and the latest have a 3yr warranty with no specified service interval) are closest to most motorbike forks in having substantial oil volumes lubricating them.
Cant remember last time I needed to bleed one of my own brakes. I change the fluid every couple of years as thats what I do with my motorbike, as part of a maintenance schedule in the same way I service my forks, inspect bearings etc.
In Verbier last summer another punter's (shimano) brakes were coming all the way to the bar. About 2 years old and untouched from new. I changed the fluid for him and the stuff that came out looked like puddle water, brown and full of visible particles and contamination. Fresh fluid and bingo brakes transformed.