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shake when front braking

  #1  
Old 05-19-2009, 11:19 PM
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Default shake when front braking

did a couple searches and pretty much down to the rotors just wanted to see what you guys thought before i ordered some rotors.
when i brake it shakes and it feels like it only does it at certain parts of the rotor because when im going faster it shakes faster and when im going slower it shakes slower and when im going real slow its not a shake any more its more of a bumping along.
so what do ya guys think?
while i got the wheel out im planning on doing
brake pads, brake line(little bit of fraying on one) bearings and cleaning the caliper piston.
anything else im forgetting?
Also for the brake line there are two for the front and only one of them is fraying should i just buy both or pick up a used replacement only for that one if i can?
thanks alot in advance
 
  #2  
Old 05-20-2009, 06:37 AM
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Your rotor is warped. $$ permitting, get some stainless braided lines.
 
  #3  
Old 05-20-2009, 05:11 PM
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Well, there's shaking and there's pulsing. There's a difference.

If the entire wheel/fork assembly oscillating back and forth, I would suspect a front tire or loose stem bearings.

If it's *pulsing" feedback through the brake system itself and you can isolate that, could be a rotor or pads. I'm not a big believer in the warped rotor theory, but you can remove them and check them pretty easily. Maintenance manual tells how.

--Paul
 
  #4  
Old 05-20-2009, 05:25 PM
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You can check the rotors to see if they are waped...put the bike on stands, if you have a dial indicator you can really see how bad/if they are warped, or you can use a wooden dowel(pencil) clamp it to the fork so it barely touches the rotor and slowly rotate the wheel now look closley at the point where the dowel touches the rotor if a gap appears that is 0.20MM or greater on the front or 0.30MM or greater on the rear the rotor/s are warped beyond service limit
 
  #5  
Old 05-20-2009, 08:06 PM
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thanks guys. ya thats a better word for it it wasnt a shaking or wobble more like quick pulsating and this is only when i am putting pressure on brake lever when im riding normally its fine.
 
  #6  
Old 05-20-2009, 11:02 PM
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you can also get the pulsating feeling under braking if your wheel is very slightly out of balance (1/4 oz) even if you don't notice it under normal riding the weight transfer can magnify the feeling

the easiest way to check is to just look to see if you have any wheel weights, very rarely will a sport bike rim with a low pro tire be perfectly balanced without any

if you see a white sticky are in the shape of a small square or rectangle, then you probably had some stick on weights and have thrown them

i'd check those and the brake rotor runout as described earlier and you'll probably find your problem
 
  #7  
Old 05-21-2009, 06:30 AM
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I had a warped rotor on my CBR250RR. It did the exact same thing with the fast pulsing/shake feel in the lever when braking. You could tell it was warped. You could see, quite visibly where the warped spot was on the disc was. The pads were hitting it and causing it to leave a dark mark that didn't match the rest of the disc. I replaced the rotors with EBC Pro-lite rotors.. problem fixed.
 
  #8  
Old 05-21-2009, 11:33 AM
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nice thanks syphen.
 
  #9  
Old 06-09-2009, 03:18 AM
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just if anyone searches this. just replaced the rotors and problem solved
 
  #10  
Old 06-11-2009, 08:48 AM
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How come they were bent in the first place?
Did you drive the bike extremely?
Did you came down from the Himalayas mountain in neutral, just using brakes?
Did you hit something and bend them (or one of them)?
Few years ago, I forgot to take off the disc lock, and the brakes used to make funny noise afterwards... (yes, I have learned the hard way where to put the disc lock on disc: always right behind the calipers if I will go strait ahead, or just in front of the fork if I have to go backwards to get out of parking place...)
 

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