Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Solved 'BUMP' or 'JUDDER' When braking.

Discussion in 'Technical and Troubleshooting Torque' started by TheHorseChild, Oct 16, 2016.

  1. I've been riding around on my SV650S Recently when I started to notice that the bike was acting strange while applying the front brake.

    About a week ago I had a little incident where I had a minor rear end collision; AKA, I went into the back of a VW UTE, it was a relatively slow collision, I didn't drop the bike, only a scratch on the fender. I don't know if this bent the disc or the wheel...

    I've been doing some tests today to try and figure it out.
    1. The bike when rolling with engine off is smooth, no bump or judder. This leads me to believe it's not a issue with the wheel.
    2. Engine off, 25kph when I gently squeezing the brake I feel it hit a bump or judder in a single spot, it's not over the entire disc or discs.
    3. emergency brake from 60kph, I don't feel it at the beginning but as the bike starts to slow down it becomes very severe, Same thing though, it's only in a single spot.
    4. I've looked at both the discs, I can't seem to find any high or low spots in the discs, they don't look bent.

    My next plan of attack is to wait until my front stand arrives and try to see if I can hear any grinding.
    If anyone has any idea, advice would be greatly appreciated!
  2. give both sides of the discs a light sand with something like 400grit wet n dry to remove any stuff off the surface. (should be able to do without front stand)
  3. You've buckled one or both of your discs.....
    • Agree Agree x 1
  4. Would there be a way to find out exactly where the buckled point is? There's no obvious point on the discs where it's bent.
  5. You need to get them redressed(some tire/brake shops have special disc brake grinders), or replace them entirely if they're bad.
    You can probably find some buckle by holding a straight edge against the disc.
  6. I'm going to try this with a ruler now.
  7. Are you sure its not a stuck link in the chain?
    If the disks were warped it should be pulsing whenever the front wheel is spinning (or at the slightest of braking) and get worse with speed as the pads are always touching the disk.

    Where do you feel the pulsing coming from, the actual lever, handles or the frame via your backside?
  8. easier spinning the wheel and checking for runout.

    any local bike mechanic or shop will have a front stand and can probably do this cheap or free

    the getting worse with temp suggests it is crap on disc, like resin transfer.
    or could be expansion of disc with heat making buckle worse
  9. The pulse, or 'bump' is only there when applying the front brake, not the rear. It feels as if it's coming from the front wheel.

    I've cleaned the both the discs, what am I looking for when I put the bike on a front stand?
  10. I've put a steel ruler up against both the discs with a flashlight behind the ruler to see any light coming though any small spaces, It seems that the left hand side disc has a 0.5mm-1mm bend in it, could this be something that I could fix?
  11. Looks like I'm just going to have to ride through this for the week.

    I was wondering as the bend is so small, could it be possible that it will wear itself back into shape?
  12. Brake really hard for the next 5000km :)
    • Funny Funny x 1
  13. Go up and down my street 1,000 times while braking hard from each direction? That would work too!
  14. I'd get them machined. It's cheaper than new discs
    • Agree Agree x 2
  15. are those the correct sizes for the SV650S?
    Generally how much life does a set of discs get?
  16. Yeah look replace discs and the bike should feel great, just did this with the wife's bike which had a severe shudder as well. Perfect now.
  17. Check your head stem bearings Dude.........also if you've damaged your forks somehow you may get judder.
    If you think it's your discs get your front wheel off the ground and spin it and gently apply brakes, you'll see "tight spots" but I'll bet it's not discs.
  18. Or it might be your discs.
    • Funny Funny x 1
  19. choose your bike
    Search By Bike Model - Test

    disc life, depends on how aggressive the pads are, and how aggressive you are.
    new discs, may as well get new pads too, unless your old ones have a lot of meat (still need to flatten them so they don't score new discs)