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poor braking performance?

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bennell09
Renault 5 Driver



Joined: 12 May 2011
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PostPosted: 11:35 - 21 Jun 2011    Post subject: poor braking performance? Reply with quote
afternoon. yisterday i finally got my front brake bled with my new pads in. problem im finding is that the brake is poor! i can pull the lever as hard as i possibly can and i can still push the bike forward but its abit difficult, the pads are brandnew and the disk is correct thickness, i bled the brakes very throughly as i always do so i know theres no problem in the bleeding, the piston moves freely and theres little to no dirt on the caliper. i did the rear brake at the same time and that has alot more bite but i can stil push the bike but with grate difficulty. is this normal with new pads as ive never had to ride a bike with new pads in theve always been new but bedded in
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DrDonnyBrago
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PostPosted: 11:45 - 21 Jun 2011    Post subject: Re: poor braking performance? Reply with quote
bennell09 wrote:
afternoon. yisterday i finally got my front brake bled with my new pads in. problem im finding is that the brake is poor! i can pull the lever as hard as i possibly can and i can still push the bike forward but its abit difficult, the pads are brandnew and the disk is correct thickness, i bled the brakes very throughly as i always do so i know theres no problem in the bleeding, the piston moves freely and theres little to no dirt on the caliper. i did the rear brake at the same time and that has alot more bite but i can stil push the bike but with grate difficulty. is this normal with new pads as ive never had to ride a bike with new pads in theve always been new but bedded in



Is the lever firm or squishy? Sounds like copious amounts of air in the lines if they are anything but as firm as they were before.

New pads aren't quite as good as worn in ones but they are nowhere near that bad, unless you knew they were new most people probably wouldn't notice.

You haven't oiled or WD40'd your discs or something equally daft have you?
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johnsmith222
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Joined: 26 Dec 2008
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PostPosted: 11:46 - 21 Jun 2011    Post subject: Reply with quote
that most certainly is not normal.

Is the lever soft at all or is it hard? It sounds to me like there is air in the system.

On my bike, I find it is best to unbolt each caliper and compress all the pistons and rebleed. I repeat this 3 times on either side to ensure that the trapped air is bled out.
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chillyman0
Nearly there...



Joined: 11 Sep 2008
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PostPosted: 11:49 - 21 Jun 2011    Post subject: Reply with quote
Silly question but you dont have brake fluid or wd40 or something like that on the discs? That wont help...
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bennell09
Renault 5 Driver



Joined: 12 May 2011
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PostPosted: 12:17 - 21 Jun 2011    Post subject: Reply with quote
when i baught the bike the front brake wasnt set up and the rear pads were missing, i pushed the pistons in, cleaned the master cylinder for the front then bled twice as i usually do. i reverse bleed so i inject the fluid from the bleed nipple then when the master cylinder is full i remove the syringe then let the fluid bleed and keep topping the master cylinder up untill its lowered down 3 times but never letting it low enough that air gets in. i use around 200ml per brake. the lever feels very spongy with no leaks throughout the system.

the disks "seem" clean there could be wd40 left on them from when i cleaned the bike up but im not counting on it
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P.
Red Rocket



Joined: 14 Feb 2008
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PostPosted: 12:20 - 21 Jun 2011    Post subject: Reply with quote
What you can try.. overnight, pull the lever in against the throttle and tie it up with elastic bands/rope/bungee cord.

If its the rear...get a brick/heavy as fuck weight and tie it to the rear brake pedal so it pulls it down.

I've found the front brake on my bike was spongy but perfect pads... just tied up overnight and it made a world of difference
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Willson
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Joined: 26 Jun 2010
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PostPosted: 12:27 - 21 Jun 2011    Post subject: Reply with quote
bennell09 wrote:
the disks "seem" clean there could be wd40 left on them from when i cleaned the bike up but im not counting on it


So you mean to say that you've put WD40 on your brakes?

What did you clean the master cylinder with? Did you clean the inside where the fluid goes? Or just the outside?

You should NEVER clean your brake system with anything other than clean brake fluid or brake system cleaner. And you should NEVER use WD40 or anything else that is a lubricant to clean your discs and pads. You can use water on your discs and pads, but nowhere where there should be brake fluid when you've finished. (Behind pistons, your lines, inside master cylinder, etc).

Willson
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DrDonnyBrago
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Joined: 03 Jan 2010
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PostPosted: 12:29 - 21 Jun 2011    Post subject: Reply with quote
bennell09 wrote:
when i baught the bike the front brake wasnt set up and the rear pads were missing, i pushed the pistons in, cleaned the master cylinder for the front then bled twice as i usually do. i reverse bleed so i inject the fluid from the bleed nipple then when the master cylinder is full i remove the syringe then let the fluid bleed and keep topping the master cylinder up untill its lowered down 3 times but never letting it low enough that air gets in. i use around 200ml per brake. the lever feels very spongy with no leaks throughout the system.

the disks "seem" clean there could be wd40 left on them from when i cleaned the bike up but im not counting on it


Sounds like you need to work on stiffening up the lever then mate.

If it is left for a while a lot of the air will find it's way up to the nipples and master cylinder. Have you tried bleeding it from the master cylinder and brake banjos? Apply a little pressure to the lever and quickly crack open and then do up the banjo bolt to let a little fluid out, have a rag placed to catch fluid drips.

Repeat this once or twice then rebleed the calipers.

If you hold the lever down does it start firm then move slowly closer to the bar? This would indicate a pressure leak in the MC so is worth looking for. It is also worth spraying the pads and disc down with some brake cleaner just to remove traces of oil, it would need to be pretty bad to make the brakes that bad but it is always a good idea after a rebuild.
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bennell09
Renault 5 Driver



Joined: 12 May 2011
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PostPosted: 12:49 - 21 Jun 2011    Post subject: Reply with quote
i cleaned my fork bottoms and the frame with wd40 trying to contain as much of the spray as i could but this was 5 days ago. i cleaned the inside of the MC with clean brake fluid alought it wasnt dirt to begin with. the hole braking action feels spongey with no kind of resistance. ill try bleeding the brakes the normal way i.e crack the nipple and keep topping the MC up with fresh fluid if that doesnt help ill remove the caliper and see if fluid is freely moving down the line. ill also try the overnight trick tonight and see if that has any effect. ill get a video or two to see if the keen eyed notices anything i dont.
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DrDonnyBrago
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PostPosted: 12:52 - 21 Jun 2011    Post subject: Reply with quote
bennell09 wrote:
i cleaned my fork bottoms and the frame with wd40 trying to contain as much of the spray as i could but this was 5 days ago. i cleaned the inside of the MC with clean brake fluid alought it wasnt dirt to begin with. the hole braking action feels spongey with no kind of resistance. ill try bleeding the brakes the normal way i.e crack the nipple and keep topping the MC up with fresh fluid if that doesnt help ill remove the caliper and see if fluid is freely moving down the line. ill also try the overnight trick tonight and see if that has any effect. ill get a video or two to see if the keen eyed notices anything i dont.



Just sounds like massive amounts of air in the lines and if there is no resistance in the lever then you probably also have an airlock in the MC. The only real way of getting the airlock out is to do what I said about bleeding the MC from the banjo bolt a few times until you get pressure on the lever before attempting to bleed it in the normal way (i.e. from the calipers).
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bennell09
Renault 5 Driver



Joined: 12 May 2011
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PostPosted: 13:01 - 21 Jun 2011    Post subject: Reply with quote
DonnyBrago wrote:
bennell09 wrote:
i cleaned my fork bottoms and the frame with wd40 trying to contain as much of the spray as i could but this was 5 days ago. i cleaned the inside of the MC with clean brake fluid alought it wasnt dirt to begin with. the hole braking action feels spongey with no kind of resistance. ill try bleeding the brakes the normal way i.e crack the nipple and keep topping the MC up with fresh fluid if that doesnt help ill remove the caliper and see if fluid is freely moving down the line. ill also try the overnight trick tonight and see if that has any effect. ill get a video or two to see if the keen eyed notices anything i dont.



Just sounds like massive amounts of air in the lines and if there is no resistance in the lever then you probably also have an airlock in the MC. The only real way of getting the airlock out is to do what I said about bleeding the MC from the banjo bolt a few times until you get pressure on the lever before attempting to bleed it in the normal way (i.e. from the calipers).


sorry mate didnt see your post. ill give it a go as soon as i get home from work. i think tho.. the banjo bolt on at the master cylinder end has been rounded off Rolling Eyes as im sure i tryed to loosen it for one reason or another. any idea how to get it off if it is stuck in there as its abit of a sensitive area
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DrDonnyBrago
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PostPosted: 13:15 - 21 Jun 2011    Post subject: Reply with quote
bennell09 wrote:
sorry mate didnt see your post. ill give it a go as soon as i get home from work. i think tho.. the banjo bolt on at the master cylinder end has been rounded off Rolling Eyes as im sure i tryed to loosen it for one reason or another. any idea how to get it off if it is stuck in there as its abit of a sensitive area


Hmm has it ever been off whilst you have owned the bike? They are often quite stiff but the threads are usually well protected by the brake fluid and so not completely corroded. You can try and prime the MC without bleeding from it but it is a hell of a lot easier if you can loosen the banjo bolt. If you wiggle the lever with short quick movements you might see air bubbles squirting out of the master cylinder into the reservoir, this is a sign that the MC could have an airlock in it (i.e. it's not pumping fluid so much as it is just compressing it's own little bubble).

Personally I'd try and get the old banjo bolt out in order to replace it. How stripped is it? Could a well fitting surface drive socket get a bite on it?
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bennell09
Renault 5 Driver



Joined: 12 May 2011
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PostPosted: 13:52 - 21 Jun 2011    Post subject: Reply with quote
DonnyBrago wrote:
bennell09 wrote:
sorry mate didnt see your post. ill give it a go as soon as i get home from work. i think tho.. the banjo bolt on at the master cylinder end has been rounded off Rolling Eyes as im sure i tryed to loosen it for one reason or another. any idea how to get it off if it is stuck in there as its abit of a sensitive area


Hmm has it ever been off whilst you have owned the bike? They are often quite stiff but the threads are usually well protected by the brake fluid and so not completely corroded. You can try and prime the MC without bleeding from it but it is a hell of a lot easier if you can loosen the banjo bolt. If you wiggle the lever with short quick movements you might see air bubbles squirting out of the master cylinder into the reservoir, this is a sign that the MC could have an airlock in it (i.e. it's not pumping fluid so much as it is just compressing it's own little bubble).

Personally I'd try and get the old banjo bolt out in order to replace it. How stripped is it? Could a well fitting surface drive socket get a bite on it?


its not been off while ive owned the bike and i cant contact the previous owner to find out if they had. if i recall when i pumped the lever i did see tiny bubbles rise from the tiny hole each time i pumped the brake. so the only way to solve this is by getting the banjo loose. excuse my ignorance but what does "priming" the master cylinder mean mate

thank you
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DrDonnyBrago
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Joined: 03 Jan 2010
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PostPosted: 14:33 - 21 Jun 2011    Post subject: Reply with quote
bennell09 wrote:
its not been off while ive owned the bike and i cant contact the previous owner to find out if they had. if i recall when i pumped the lever i did see tiny bubbles rise from the tiny hole each time i pumped the brake. so the only way to solve this is by getting the banjo loose. excuse my ignorance but what does "priming" the master cylinder mean mate

thank you


Priming the master cylinder means getting the air out and filling it with fluid so that it is actually pumping fluid when you squeeze the lever. Imagine a syringe on it's side with air in it and a small amount of fluid at the bottom, if there is too much air then when you squeeze it you will be pushing air not fluid. If you empty your MC then fill it up and start pumping you are probably not actually pushing any fluid out.

If you cannot get the banjo off then tapping the brake lever in short sharp movements until you can no longer see any bubbles might be enough, certainly should be able to get some pressure built up in the lever that way. Every time you see a bubble it is one less bit of air in your brakes so keep doing it Thumbs Up . Unbolting the MC from the bars (with the res cap on) and moving it around to angle it so the air can find it's way out of the little hole (whilst tapping the lever) might also work.
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bennell09
Renault 5 Driver



Joined: 12 May 2011
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PostPosted: 16:55 - 21 Jun 2011    Post subject: Reply with quote
DonnyBrago wrote:
bennell09 wrote:
its not been off while ive owned the bike and i cant contact the previous owner to find out if they had. if i recall when i pumped the lever i did see tiny bubbles rise from the tiny hole each time i pumped the brake. so the only way to solve this is by getting the banjo loose. excuse my ignorance but what does "priming" the master cylinder mean mate

thank you


Priming the master cylinder means getting the air out and filling it with fluid so that it is actually pumping fluid when you squeeze the lever. Imagine a syringe on it's side with air in it and a small amount of fluid at the bottom, if there is too much air then when you squeeze it you will be pushing air not fluid. If you empty your MC then fill it up and start pumping you are probably not actually pushing any fluid out.

If you cannot get the banjo off then tapping the brake lever in short sharp movements until you can no longer see any bubbles might be enough, certainly should be able to get some pressure built up in the lever that way. Every time you see a bubble it is one less bit of air in your brakes so keep doing it Thumbs Up . Unbolting the MC from the bars (with the res cap on) and moving it around to angle it so the air can find it's way out of the little hole (whilst tapping the lever) might also work.


okay, i did everything you said and everone else and the brake has improved but i can still push the bike with the front locked on but i have to use alot more "push" to move it, first i eventually managed to get the banjo loose and did what you said, after that the brake seemed a touch less soft, then i removed the MC from the bars and moved it around to untrap any air, this made no difference, then i remove the res cap and pressed the lever and a huge bubble came out follwed buy a few small ones, i did this for 20mins untill all the air had been reliesed, this did improve the soft spongy feeling but its still there, i bled the brake 3 times afterwards and pumped the brake afterwards for another 15-20 mins but only with 1-2 tiny bubbles. so lastly i removed the caliper and moved the piston out slightly to make the pads closer and this has improved the braking feeling alot but the brake pads are now constantly rubbing the disk. still all this and i can move the bike with the brake on full? i also cleaned the disk and sandpapered the pads to remove the shine off them during the bleed process, there are no leakes, everything moves freely so ive got no idea. could it just be the fact the pads are new?
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DrDonnyBrago
World Chat Champion



Joined: 03 Jan 2010
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PostPosted: 18:52 - 21 Jun 2011    Post subject: Reply with quote
bennell09 wrote:
okay, i did everything you said and everone else and the brake has improved but i can still push the bike with the front locked on but i have to use alot more "push" to move it, first i eventually managed to get the banjo loose and did what you said, after that the brake seemed a touch less soft, then i removed the MC from the bars and moved it around to untrap any air, this made no difference, then i remove the res cap and pressed the lever and a huge bubble came out follwed buy a few small ones, i did this for 20mins untill all the air had been reliesed, this did improve the soft spongy feeling but its still there, i bled the brake 3 times afterwards and pumped the brake afterwards for another 15-20 mins but only with 1-2 tiny bubbles. so lastly i removed the caliper and moved the piston out slightly to make the pads closer and this has improved the braking feeling alot but the brake pads are now constantly rubbing the disk. still all this and i can move the bike with the brake on full? i also cleaned the disk and sandpapered the pads to remove the shine off them during the bleed process, there are no leakes, everything moves freely so ive got no idea. could it just be the fact the pads are new?



most important question - when you pull the brake lever is it reaching the bar or is it reaching a point where it will goes hard and cannot be pulled any further? Is there any resistance at all in the lever?

If it is reaching the bar and or has no resistance then there is still a lot of air in the system. Does the brake line loop around higher than the MC? If there are other high points in the system (like loops in the line, line splitters etc) then you can get air accumulating here? Did you try bleeding fluid from the brake caliper banjo? You can also get air trapped here that is very stubborn to remove.

Lastly how are you bleeding from the nipple (do you have a one way valve or are you using a tube dipped into fluid?), could it be that when you are bleeding the fluid air is returning back into the caliper? Was is a fresh non shaken bottle of fluid you are using, bubbles take ages to settle out so if the bottle has been shaken then it will introduce air into the system (one of the reasons I don't like back bleeding with a syringe is because it is difficult not to aerate the fluid).


Whenever I install new pads I can quite easily lock the wheel, they really perform rather well even from the start. Don't ride the bike until you get a decent bit of stopping power as it will end badly.

If you try again tomorrow the air will have risen to the highest points, these will be the MC, any high points in the brake line (bad, these are hard to remove - position the MC so that it is the highest point overnight), the banjo at the caliper and the bleed nipple at the caliper.

Bleed at the MC first. Apply pressure to the lever, open the banjo and close it again before you have pulled the lever the whole way down. Pump the lever a few times to get the firmness back and repeat. Do this 5 or six times from the MC banjo, then the caliper banjo then finally bleed from the caliper nipple.
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bennell09
Renault 5 Driver



Joined: 12 May 2011
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PostPosted: 21:24 - 21 Jun 2011    Post subject: Reply with quote
DonnyBrago wrote:
bennell09 wrote:
okay, i did everything you said and everone else and the brake has improved but i can still push the bike with the front locked on but i have to use alot more "push" to move it, first i eventually managed to get the banjo loose and did what you said, after that the brake seemed a touch less soft, then i removed the MC from the bars and moved it around to untrap any air, this made no difference, then i remove the res cap and pressed the lever and a huge bubble came out follwed buy a few small ones, i did this for 20mins untill all the air had been reliesed, this did improve the soft spongy feeling but its still there, i bled the brake 3 times afterwards and pumped the brake afterwards for another 15-20 mins but only with 1-2 tiny bubbles. so lastly i removed the caliper and moved the piston out slightly to make the pads closer and this has improved the braking feeling alot but the brake pads are now constantly rubbing the disk. still all this and i can move the bike with the brake on full? i also cleaned the disk and sandpapered the pads to remove the shine off them during the bleed process, there are no leakes, everything moves freely so ive got no idea. could it just be the fact the pads are new?



most important question - when you pull the brake lever is it reaching the bar or is it reaching a point where it will goes hard and cannot be pulled any further? Is there any resistance at all in the lever?

If it is reaching the bar and or has no resistance then there is still a lot of air in the system. Does the brake line loop around higher than the MC? If there are other high points in the system (like loops in the line, line splitters etc) then you can get air accumulating here? Did you try bleeding fluid from the brake caliper banjo? You can also get air trapped here that is very stubborn to remove.

Lastly how are you bleeding from the nipple (do you have a one way valve or are you using a tube dipped into fluid?), could it be that when you are bleeding the fluid air is returning back into the caliper? Was is a fresh non shaken bottle of fluid you are using, bubbles take ages to settle out so if the bottle has been shaken then it will introduce air into the system (one of the reasons I don't like back bleeding with a syringe is because it is difficult not to aerate the fluid).


Whenever I install new pads I can quite easily lock the wheel, they really perform rather well even from the start. Don't ride the bike until you get a decent bit of stopping power as it will end badly.

If you try again tomorrow the air will have risen to the highest points, these will be the MC, any high points in the brake line (bad, these are hard to remove - position the MC so that it is the highest point overnight), the banjo at the caliper and the bleed nipple at the caliper.

Bleed at the MC first. Apply pressure to the lever, open the banjo and close it again before you have pulled the lever the whole way down. Pump the lever a few times to get the firmness back and repeat. Do this 5 or six times from the MC banjo, then the caliper banjo then finally bleed from the caliper nipple.


the lever does reach the bar with a ample amount of squeeze so there is some resistance but nothing like ive felt before on a front brake its too soft. the brake line raises around 10cm above the MC which loops down to the caliper. i didnt try the caliper banjo i stupidly forgot that Mad . ive been using a tube into a bucket, pulling the lever in a little then cracking the nipple-closing it then relising the lever and repeting untill the fluid pours itself freely so i dont think air can go back into the system like this. i had the bottle sat on the shelf for a day to allow to settle before i used it? tomorrow ill bleed the MC using your banjo method for both the MC and caliper and see if that hopefuly does the trick then ill hang the system so that the MC is attached to the bars and the rest of the system is below the MC then repete the banjo trick and bleed to reliese the air that might be caught in the highest point of the system. youve been a massive help mate hopefuly itll get it fixed tomorrow if not im going to dump all the fluid from the line, MC and caliper and start again
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bennell09
Renault 5 Driver



Joined: 12 May 2011
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PostPosted: 19:00 - 22 Jun 2011    Post subject: Reply with quote
so today, i did everything you said...again , baught 350ml of fluid and ran the entier lot through the system. after around 100ml bubbles stopped showing but i used the rest to be on the safe side. this did make the lever a fair bit more harder to squeeze but i can still get it to reach the bars but i do have to use alot of pull. the actual braking has improved quite alot and i can only just and i mean just push it for 10-15cm then i run out of energy then its off for a rest Laughing so things are improving. ive cable tied the lever to the bar as someone suggest to see if anything improves by tomorrow if not ill get myself a radial brembo and a new nissin caliper
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