Hydraulic disc brake query for those in the know

[Northernraider]

Ok so I replaced my hybrid bike at the end of last year with a more robust mountain bike I bought from gum tree, it's a carrera model and is quite good for a second hand bike. It's done me ok up till now with no problems given I'm not a diehard cyclist and I'm only on it once in a while so it spends most of its life on the rear bike carrier.

I took it off a few days ago and the wheels would not turn .....the brakes were locked on solid.

Now this is the first bike I've ever had with disc brakes and despite being reasonably good with vehicle mechanics I never even gave the braking system on the bike a second glance when I bought it .....but it looks like it has hydraulic brakes which surprised me. So there was no way to adjust the brakes off that I could see but they were jammed solid.

Anyway I loosened the bolt where what I thought was a cable off and that's when I realised it was a hydraulic tube when a little fluid came out .....but this seemed to free of the brakes so by accident I solved the problem

I did the same to the back wheel and great stuff...brakes free again and actually working better than they had before.
No sticking etc after being used.

Anyway I was out for a ride etc and no probs came back put bike back on the rack and I've not looked at it since.

Took it off today to fit a handlebar height extension and the brakes were jammed on again.
So I did the same again and they free off.

But why are they jamming on ?

If I keep releasing the pipe and letting a spot of fluid escape there will end up with none.
The brake pads don't seem to be seized or anything as after I've slackened the pipe and tightened up again the brakes will work no probs ...

Any ideas?

Could it be the sun ?

I've had a couple of spells of rain here and there but these bikes should be able to cope with that without brakes seizing etc right?

I'm confused


And also where do you top up brake fluid and is it the same stuff as a car?

I

 

[Lenny HB]

Sounds like the calipers are seizing probably needs a strip down and clean & new seals. I wouldn't risk car fluids would be expensive if it's not suitable.
Bleeding and and adding fluid is done arse about tip, from the bottom.

This video explains it.

 

[Northernraider]

Sounds like the calipers are seizing probably needs a strip down and clean & new seals. I wouldn't risk car fluids would be expensive if it's not suitable.
Bleeding and and adding fluid is done arse about tip, from the bottom.

This video explains it.

Jings that doesn't look anything like what's on mine.

 

[Lenny HB]

Jings that doesn't look anything like what's on mine.

What do you expect with a Halfords own brand bike.

 

[Lenny HB]

This any good.

http://i1.adis.ws/v/washford/cycling_how_to_bleed_avid_or_sram_brakes/mp4_720p

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[Northernraider]

What do you expect with a Halfords own brand bike.

It's a good bike that for the 100 quid I gave for it. Think it was about £400 new and had hardly been used.

I'm not Chris hoy lol it gets me where I want to go with it. No point buying a fancy one


Anyway you cheaters with the electric ones can't take the pee out of anyone lol

 

[Lenny HB]

Just to make you feel good just done a Google and everyone appears to complain about shit Carrera brakes with the best option being to change them for Shimano ones but that will probably cost more than you paid for the bike.

 

[Northernraider]

This any good.

http://i1.adis.ws/v/washford/cycling_how_to_bleed_avid_or_sram_brakes/mp4_720p

Hmm still look nothing like mine but as I don't have any of that stuff required to bleed them I'm probably just aswell getting it done at a bike shop.

I'll see if I can hold off till I'm in aguilas again and use that shop I got to fit my chain etc last year

 

[DBK]

In theory when the lever is released the piston the lever is attached to returns far enough back it uncovers a small hole which allows excess fluid to drain back into the reservoir. This means it shouldn't be possible for there to be excessive pressure in the pipe leading to the caliper. However, there will be some pressure as the reservoir is covered by a diaphragm so a slight pressure is maintained all the time.

You could try giving the system a good bleed but if that doesn't work check the levers are fully returning and the caliper pistons can move. Take the wheel off and check with a screwdriver they can be forced back a bit. They may be corroded. The pistons also have a diaphragm which seals in the fluid and helps the piston return.

My experience of hydraulic disc brakes led me to specifying mechanical ones for my bike.

 

[Lenny HB]

Anyway you cheaters with the electric ones can't take the pee out of anyone lol

I've got a Specialized Rock Hopper as well & so has the boss.

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[Northernraider]

Just to make you feel good just done a Google and everyone appears to complain about shit Carrera brakes with the best option being to change them for Shimano ones but that will probably cost more than you paid for the bike.

The brakes were always ok before and have to say even now they are good once I open and close that bolt on the pipe.
Never realised they were so bloody complicated though. Car ones are less hassle than all that nonsense

 

[gus-lopez]

Have you taken the hand brakes off ?

 

[Northernraider]

In theory when the lever is released the piston the lever is attached to returns far enough back it uncovers a small hole which allows excess fluid to drain back into the reservoir. This means it shouldn't be possible for there to be excessive pressure in the pipe leading to the caliper. However, there will be some pressure as the reservoir is covered by a diaphragm so a slight pressure is maintained all the time.

You could try giving the system a good bleed but if that doesn't work check the levers are fully returning and the caliper pistons can move. Take the wheel off and check with a screwdriver they can be forced back a bit. They may be corroded. The pistons also have a diaphragm which seals in the fluid and helps the piston return.

My experience of hydraulic disc brakes led me to specifying mechanical ones for my bike.

I can see why ....the last bike was good apart from I was always getting punctures ...I thought this one woukd be hassle free lol.

That said though I think I've used it 5 or 6 times since January so probably not the best.

 

[Silver-Fox]

My experience of hydraulic disc brakes led me to specifying mechanical ones for my bike.

Funny you should say that.

The Daughter used to do four cross and down hill.
Never liked disc brakes, we used to change to mechanical ones ie brake blocks and rough the wheels up with a grinder.

 

[DBK]

Funny you should say that.

The Daughter used to do four cross and down hill.
Never liked disc brakes, we used to change to mechanical ones ie brake blocks and rough the wheels up with a grinder.

My bike has disc brakes but they are mechanically operated, Avid BB7s. One of my sons had an MTB with hydraulic discs and it needed fiddling with after every trip! I'm sure you can get good ones though.

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[Lenny HB]

My bike has disc brakes but they are mechanically operated, Avid BB7s. One of my sons had an MTB with hydraulic discs and it needed fiddling with after every trip! I'm sure you can get good ones though.

Both our Scott e-bikes & our Specialized ordinary bikes have Shimano hydralic discs. The Specialilzed are 12 years old and have never been touched, my Scott one of the levers started to get a long travel when I had a software update done they fixed it without even mentioning it, been fine since.

 

[PORKSTER]

Needs bleeding your need a proper bleed kit and not automotive fluid

 

[andy63]

Hi tam.. your symptoms are common enough with some types of hydraulic brakes on bikes... I've got a giant.. the hydraulic system is a closed system and if there is a rise in temperature the brakes will lock on..
There is usually a facility to adjust them.. but if they are adjusted up say in winter in summer they will lock up and require winding back..
Same can happen on say a long decent where you are on the brakes a lot.. the heat can cause the brakes to bind..
If you have to re bleed them its often easier to push the fluid through from the calliper end with a syringe rather than the reservoir end..
Andy..

 

[Northernraider]

Hi tam.. your symptoms are common enough with some types of hydraulic brakes on bikes... I've got a giant.. the hydraulic system is a closed system and if there is a rise in temperature the brakes will lock on..
There is usually a facility to adjust them.. but if they are adjusted up say in winter in summer they will lock up and require winding back..
Same can happen on say a long decent where you are on the brakes a lot.. the heat can cause the brakes to bind..
If you have to re bleed them its often easier to push the fluid through from the calliper end with a syringe rather than the reservoir end..
Andy..

It does sound like that's the problem as it was fine till it got warmer and calipers dint seem seized

 

[pappajohn]

Wish my leccy bike had disc brakes.
Front is a regular rim caliper but the rear (motor hub) is an internal mechanical band brake.... As much use as t!ts on a bull.
Better off reverting to childhood biking and stick both feet down.

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[andy63]

It does sound like that's the problem as it was fine till it got warmer and calipers dint seem seized

It's happened with mine regularly tam .. it hangs under the plastic car port roof and if its hot and i lift it down to use the brakes are often on...
my reservoir has adjusters and i can alter the volume and release the pressure.. I believe there used to be two types... those with a closed system and the other type was vented.. but im only familiar with what ive got and that's about 20 years old now
Andy..