weird braking issue?

[miguel_costello]

'ello again, apologies in advance for another total newbie question here...

approaching a roundabout today, i got caught behind a woman in a fiat who should have gone, but instead she screeched to a halt in front of me so she could wait for a slow moving truck (which was at least 15 seconds away to the right)....

anyway, i grabbed a ton of front brake in a panic and my bike juddered horribly to a stop, normally it stops quite smoothly, even when stopping quickly.. it didn't skid (i dont think so anyway), which means i guess i instinctively eased off the brake before coming to a halt. is this just the front disc trying to lock up due to me grabbing the lever too hard? i've never experienced a front lock up before so i just wondered if this is what happens, or whether its a symptom of my front brake being knackered in some way.... (i was carrying a pillion which might have added to the juddering scenario)

thanks! maybe i should have put this in the workshop forum....

[Alexio]

If you were carrying a pillion then maybe it was the bike trying to endo a few times, but failing to do so because of all of that extra weight on the back seat? Really I've no idea.

You definitely need to use the back brake just as hard, it would have slowed you down faster, I'm sure you know this and are mostly just curious about the juddering. I've personally never experienced this no matter how hard I brake (and I've had to brake pretty damn hard a couple of times).

Maybe all that extra weight on the bike gave you more momentum than usual making the brake have to work harder and get to the point where it might start to lock up without causing serious stability issues because of said extra weight?
____________________
will never give up his CG. I look at my fuel gauge more as a progress bar than a fuel gauge.
G: With my GSXR I do often effectively use it as a scooter with a clutch in town.
ms51ves3: why does it need 500 miles? Are you teaching it how to be a piston?

[stinkwheel]

Happens on race bikes a lot.

You braked very hard, I bet you downshifted too?

Essentially, the energy stored in your rear wheel was trying to turn the engine faster than it was going causing the wheel to alternately lock and unlock as the engine turns over compression. Because of the slack in the chain drive and the fact that the rear suspension is almost fully unloaded, this translates into the rear wheel chattering up and down.

My supermoto used to do this a lot under heavy braking (high compression, slow revving engine).

Pulling the clutch in would stop it but you don't have time to think of that (and shouldn't, it wont go anywhere, concentrate on stopping). A lot of bigger race bikes are fitted with automatic "slipper clutches" that allow the rear wheel to turn faster than the engine under heavy braking to stop this chatter.

Don't worry, there is nothing wrong, you were just braking VERY hard.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[miguel_costello]

alexio, yeh totally hear you on that one, i know better than to just rely on front brake alone! wasnt even going very fast, maybe 20-30 mph tops. just was expecting woman in car ahead to actually move at the roundabout. there i go, breaking every rule in the book, expecting a car in front of me to behave the way i want....

i kinda figured it was just a physics thing with the extra momentum, i rarely have to brake that hard.. just was worried someone on here might be able to tell me that "get off your bike at once, its the first sign that your disc/pad/master cylinder/etc etc etc is FUBAR"... i'm pretty much a noob at troubleshooting.

here's to keeping my eyes open a bit better! and not relying on the junction prowess of others in front of me....

thanks

[miguel_costello]

stinkwheel: cheers yeh that's what i hoped! cant remember if i downshifted or not, but judging from my "she's going to go at the roundabout before the truck gets here" attitude i must have done. think i pulled in the clutch at the last second as i didnt stall it!

thanks all

[Faraz]

Here is a video of the "chattering" sound.

https://www.youtube.com/watch?v=OQ-E3YSm3Os&feature=player_profilepage
____________________
'56 Yamaha MT-01
'05 Nissan 350z Roadster GT
3 words dude.. Fvck. Yes.