Are front brakes overated? [Archive]

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Str8 Jacket

2nd April 2009, 15:30

My lil FXR has had a dodgy master cylinder for a little while now. The brake has been bled plenty of times, the line is fine and there is nothing else wrong with the brake except for the master cylinder, which is obviously dodgy.
As Murphy's Law dictates my front brake completely failed on my way home today - We were always going to be replacing the master cylinder (thanks to Bren) tonight. When I got home, 5 mins later my brake was working, albeit not very well.

So this got me thinking, what makes the brake fail one minute and then work again the next? Has it got something to do with the seals, pressure what? This is not the first time it has done it so I have been a bit paranoid have been keeping my revs relatively high so I can drop down and use the engine braking to help me stop in a hurry if I need too. Also I have started using the back brake which has been a foreign concept to me for awhile! What the heck would you do if you were on a bigger bike or just not expecting this at all?!? :eek:

bungbung

2nd April 2009, 15:34

Murphy's Law dictates my front brake completely failed on my way home today

Murphy's Law dictates bad things unless you get that sorted out.

It's not worth the risk

mattian

2nd April 2009, 15:38

When you have to stop quickly. You will not want your front brake to fail:shit:. get it sorted asap.

Str8 Jacket

2nd April 2009, 15:40

For the record:

we were always going to be replacing the master cylinder (thanks to bren) tonight.

bungbung

2nd April 2009, 15:47

My lil FXR has had a dodgy master cylinder for a little while now.

Sorry, didn't read your post correctly.

Cause?

Lack of sealing (bore, or piston), air bubbles

Quasievil

2nd April 2009, 15:55

Could have some dirt or something in the line, may have a issue with the pistions on the calipers, thats what I would think if its irregular, seals and things would be consistant in that the performance would always suck.
thats my un mechaniclly minded opinion anyway

Str8 Jacket

2nd April 2009, 15:58

Sorry, didn't read your post correctly.

Cause?

Lack of sealing (bore, or piston), air bubbles

All good! ;)

yeah, there are always tiny bubbles rising to the air when fiddling with the master cylinder. No major though, only $45 to replace!

AllanB

2nd April 2009, 16:12

only $45 to replace!

Famous last words....... hopefully not.

If only I'd replaced it before I ran that 5 year old over.....

If only I'd replaced it before smacking up the rear of that 2009 BMW.....

If only I'd replaced it before ripping off my 'bits' on the speedo on impact with the BMW...........

FROSTY

2nd April 2009, 16:14

Piston seals are fucked.
Not a good plan riding with no front brakes long term but shit happens sometimes.To be honest you are the first person who I've heard to have SUDDEN and unexpected brake failure for internal reasons.
Your front brakes supply up to 75 percent of your available brakes
That said I think new riders should practice NOT having front brakes. The brakes themselves are unlikely to fail but their effectiveness can be reduced to fark all if theres diesel on the road or a DEEP load of roadworks gravel.

Str8 Jacket

2nd April 2009, 16:30

Famous last words....... hopefully not.

If only I'd replaced it before I ran that 5 year old over.....

If only I'd replaced it before smacking up the rear of that 2009 BMW.....

If only I'd replaced it before ripping off my 'bits' on the speedo on impact with the BMW...........

As soon as I knew it was fucked I ordered a new one. It had been fixed last weekend and was working absolutely fine all week so I had'nt been concerned about riding it - with caution! I also practiced stopping without using my front brake at varying speed often this week, its a small bike so alot easier to manouvere!

quallman1234

2nd April 2009, 17:27

Still probabaly wasn't the smartest thing, but hey every does these things!.:girlfight:

vindy500

2nd April 2009, 17:29

I also practiced stopping without using my front brake at varying speed often this week, its a small bike so alot easier to manouvere!

try it in the wet :)

Number One

2nd April 2009, 17:35

Geebus woman! I hope that gets sorted pronto - as to your question...overrated hell no! I love my front brakes I wouldn't want to be without them and hate the feeling of them not working so good let alone worrying about them working at all. Hope you get it sussed chicky

Squiggles

2nd April 2009, 18:18

If its the master cyl im thinking its letting air in, so you get nothing, but after a few pulls it'll prime and then you're back in business

Str8 Jacket

2nd April 2009, 18:49

Yeah, it was wierd.
It didn't really 'pump up' there was no sponginess at all, the grab point would just move closer and closer to the bar untill it didn't grab because it hit the bar before it grabbed.

Its sorted now tho, bleeding it was a prick and a half and just wasn't working until we figured out the lever wasn't giving full stroke in place. - we took it off and used an allen key to push the piston in instead and she was bled in a whizzle. :Punk:

Front caliper rebuild is on the to do list too.

R6_kid

2nd April 2009, 18:53

Are front brakes over rated?

Physics says NO.

reofix

2nd April 2009, 18:54

maintain your bike properly... competent people ... proper parts... anything else is deathwish country

R6_kid

2nd April 2009, 19:03

maintain your bike properly... competent people ... proper parts... anything else is deathwish country

We can't stop here, this is .... whoops wrong quote!

imdying

5th April 2009, 21:30

Str8 Jacket

6th April 2009, 07:24

You want to know the technical details of why this unit died? Sure, send it down and we'll give it the same analysis that we'd do for the feds when someone claims there brakes 'failed' and they crashed causing an accident. Or why they die in general?

I guess I now know what was wrong with mine... the lever wasn't giving full stroke in place when bleeding it. we took it off and used an allen key to push the piston in instead and all good...
My guess is an air bubble was "stuck" on there somewhere that we just had'nt managed to bleed out properly due to the above. Im thinking that I probably have 2 perfectly good master cylinders but I chose to put the "bling" on it anyway. Every good bucket need bling! :niceone:

Katman

6th April 2009, 08:43

If a small piece of dirt is floating around in the bore of the master cylinder it is possible for it to lodge in the lip of the seal causing the brakes to suddenly fail.

That is why it's good practice when replacing brake pads to open the bleed nipple when forcing back the caliper pistons so the fluid (and any foreign particles) is drained off into a bottle instead of being forced back up into the master cylinder.

Str8 Jacket

6th April 2009, 10:21

If a small piece of dirt is floating around in the bore of the master cylinder it is possible for it to lodge in the lip of the seal causing the brakes to suddenly fail.

Cheers. Why did my brakes start working again a few minutes later though? Im guessing that once the seal has been broken that it cant just magically repair itself again can it? Or if the dirt was to move again then the brakes would work again? :blink:

Katman

6th April 2009, 10:31

Cheers. Why did my brakes start working again a few minutes later though? Im guessing that once the seal has been broken that it cant just magically repair itself again can it? Or if the dirt was to move again then the brakes would work again? :blink:

Yes, if the dirt dislodged itself without damaging the seal then the brakes would start working again.

Str8 Jacket

6th April 2009, 10:33

Yes, if the dirt dislodged itself without damaging the seal then the brakes would start working again.

Kewl, now that makes sense!

munterk6

28th April 2009, 23:29

pfft..brakes are for learners :zzzz:

HDTboy

29th April 2009, 07:02

You should try riding one of my (1985) bikes, they came from the factory with no [piss poor] front brakes.
Still managed to keep up with a late model CBR600 though, so front brakes must be overrated.

koba

29th April 2009, 07:44

You should try riding one of my (1985) bikes, they came from the factory with no [piss poor] front brakes.
Still managed to keep up with a late model CBR600 though, so front brakes must be overrated.

1985! Brakes were awesome on some bikes by then!

I've always thought of old HEAVY british thumpers with cable operated single leading shoe front brakes as bikes with bad brakes!

tychver

3rd May 2009, 21:03

Ever ridden a CB250RS?

It was one of the first cheap bikes Honda made with a front disc, and as such is actually worse than the old drum hondas. Back in the mid 80s it was a common mod to swap them off for a honda drum front end, or an entire twin disc RD350LC front end if you could find a straight one.

driftn

4th May 2009, 08:18

AAHHH about this time last year I actually thought to my self "yeah stuff it i'll ride my bike with no front breaks".

Shouldnt have done that as ended upside down in some bodys front yard.

Front breaks are a very important piece of the puzzle.

jonbuoy

4th May 2009, 08:31