weird brakes

Jacques_nasi · Jan 5, 2008

Ok, i dont know if anyone else may have had this, but here goes:

The other day we went out for a quick ride, a couple of fast corners, hard braking and nothing unusual, I did about two high wheelies and at about two corners later no brakes at all!!:exclamation:exclamation (Front brakes)

Scary to say the least but luckily I had enough run-off next to the road to avoid a crash, lucky for me no hedges!!!

Squeezed the lever 3 times, still nothing and all of a sudden back to 100%!!

Took the bike back home, brakes working fine, then did a quick inspection, all fine, did some bleeding with some air coming out at the top bleeding nipple, and a little bit at each caliper! brakefluid resevour is topped up.

the strange thing is, everytime i've done a wheelie or two the brakes seem to go all spongy, I'm baffled!!!
:dunno:dunno

BB1000 · Jan 5, 2008

Dont do wheelies then mate.....bikes were ment to be on 2 wheels....hth

carbon kid · Jan 5, 2008

EEK-sounds like the pistons were shoved back when you landed the wheelies, something like that happens to racers.
CK

Sprocker · Jan 5, 2008

Battlebiker said:
Dont do wheelies then mate.....bikes were ment to be on 2 wheels....hth

:stupid ...I hope you had run off room in your underpants too :lol

rsvsteve · Jan 5, 2008

Check to see if your discs are glowing red hot, if so it could be brake fade due to extreme braking :devious. Seriously though if your brakes are failing it could be inferior pads not being able to cope with the heat generated if your giving it some stick m8 :confused.

Sure Badger has an answer to this one ........:hail Badger.. If all else fails m8 get it checked out , it wont cost much :thumbup

LEGS · Jan 6, 2008

As CK says i would also suggest that it's the pistons being pushed back in the calipers when you land the front wheel ( a little hard maybe ? ). Three or four pumps of the lever and all's well again :thumbup

This is what caused James Toseland's crash at Monza'a parabolica in WSBK last year.

Badger · Jan 6, 2008

Sounds to me like the pads are getting pushed back by violent landings, is the front end giving a pretty violent shake when you set it back down, if it is then the ferocity of the shake/wobble is pushing the pads away from the disc, so when you go to use the brake the pads are not near the disc, resulting on no brakes until you pump the lever often enough to bring the pads back to the normal position, the only way to cure this is to make sure your landings are more gentle.

The other possibility is if the angle of the wheelie is acute enough you might be allowing air into the lines due to the fluid moving away from the feed hole at the reservoir, unlikely, but still a possibility to consider.

Jacques_nasi · Jan 6, 2008

I must say that all the landings are gentle, with no head shakes.

I also thought of the possibility of brake fade, but shouldn't your brakes slowly get weaker, and not all of a sudden just not be there, I've ridden my old ZXR harder for longer on the brakes with nothing like that!

Badger · Jan 6, 2008

Jacques_nasi said:
I must say that all the landings are gentle, with no head shakes.

I also thought of the possibility of brake fade, but shouldn't your brakes slowly get weaker, and not all of a sudden just not be there, I've ridden my old ZXR harder for longer on the brakes with nothing like that!

The brakes on the track get far more abuse than you are ever likely to throw at them on the road, so brake fade is not a problem on these bikes, i suggest you strip them and make sure they are moving freely (clean the pistons and the whole caliper), bleed it thoroughly, you need to make sure all components are functioning the way they should firstly, if you still have a problem after that, then it is a matter of methodically checking the system.

DaveRSV · Jan 6, 2008

The pistons being pushed back tends to happen after violent tank slappers rather than wheelies. Have to say that I'm with Battlebiker, don't do wheelies! Great way to get banned for dangerous driving and there's two tyres for a reason.

Personally I'd go for air getting into the lines as the fluid level tips to stay horizontal. My brother's 675 did it a little while ago. The fluid wasn't full to max and just leaning in corners (verified stationary and leaning the bike over) allowed air to get into the lines.

1) Don't do wheelies
2) If you must make sure the fluid is always up to max
3) if 2 above applies watch you don't spray brake fluid everywhere when you push the pistons back to fit new pads! :thumbup

Jacques_nasi · Jan 6, 2008

Thanx guys, will let you all know what happens:thumbup

weird brakes

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