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front disk rotor

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by teodons, May 7, 2010.

  1. I've got my bike in a workshop for its 6k maintenance and just got told that its front disk rotor is warped by a few millimeters. They said it should be replaced pretty much straight away and that I shouldn't ride until the problem is fixed. They said it can cost from $100 on the low end to $280 on the high end for a new one.

    Just wanted to ask and make sure this makes sense and that I'm not getting ripped off price-wise. For what it's worth, I have noticed recently that when I apply the front brake, it "pulsates" [like ABS on a car] whilst coming to a stop.

    How would the front disk rotor have become warped in the first place? Is it a serious mechanical fault? Something routine? Complete bike nub so I've really got no idea.

  2. The price sounds about right, but I would be worried if it had warped after only 6000 klm...

    What type of bike is it?

    As to the causes, not entirely sure, usually they wear out & get thinnner/weaker.
  3. It's a 2006 Honda VTR250.
  4. That's really surprising. It's not the quite of bike that would get ridden hard enough to get that sort of heat into the rotor to cause warping.
  5. cant you just get it machined,
  6. I know that the guy I bought it from has had one bad spill [he told me as much] and it's got a large scratch behind the seat to prove it. The guys at the shop think that enough trauma from the spill could have caused this. I don't know enough about the underlying mechanics to say either way =x
  7. Hey mate

    When you pick the bike up next week ask Earl (service Manager if you haven't met him) to show you the problem rotor. Might want to call him on Saturday to say you are interested in understanding the nature of the problem and seeing the faulty bit might help. Just so they don't chuck it out before you pick up the bike :) Then when you go get the bike spend a few minutes with him and get him to show you the warping.

    Then take it home, photograph it and post up some pics so we can see what is wrong :cheeky:

    Fun Ha!
  8. Pulsating sounds like a warped disk rotor.

    If you have a warped disk and you apply the brake gently the warp applies pressure back to the pad and up the line and you can often feel it. Also if you apply the brake a little harder you will sometimes have the warpage cause the pad to grab and release slightly which depending on your springs may translate to your bike diving slightly the releasing giving you a nodding sensation. Remember this doesn't always happen and only likely to happen at low brake pressures as once you grab a handfull the pad will grab hard whether warped or not.

    The garage is actually likely to have a gague which measures the amount of warpage and should therefore be able to show you what the measure is and your handbook may tell you the level of acceptable warpage. If it isn't in your owners handbook it should be in the garages workshop manual.

    Most disks on cars are thick enough to machine effectively cutting the high spots off and bringing the disk back to square but some (most?) bikes cant do this as the disks are thinner. My disks can't be machined.

    Price sounds about right (low end price sounds cheap to me) but I would ask if it's possible to machine them. I would also be concerned about warping after only 6000Km but I guess a drop can do it. In my manual it warns against knocking the disks as they can be warped by a knock even to the extent of saying if you take a wheel off, put the wheel of blocks to keep the disk of the ground to avoid an chance of a knock.

    If you are up for new disks, there are heaps on Ebay that might suit your bike and may be cheaper (although as I said your low end price sounds cheap to me) . Can't speak for the quality but at least one person I know bought them cheap and is happy.
  9. Yea, I'll ask them to hang on to the old one.

    Thanks GreyBM, that's very informative. I also tried Googling for this yesterday, and read a bunch of threads about cars and bikes. In all the car threads, it seems they suggested machining as an option.

    I especially noticed the pulsating [nodding sensation] when coming to a stop for signals. I leave the full 3 second gap most of the time, and brake early-ish whilst coming to a stop. So the long stopping distance meant I was using the brakes softly, which then emphasised the pulsation.

    Over the phone they told me the warping was "a few millimetres" so I'm not sure how much exactly. I'll ask on Monday and compare with what's in the manual.

    The ones he actually ended up buying for me were $200.
  10. Sounds about right mate, discs are costly things as well... Probably bent in a smash. Buy a new one and don't let anyone machine it anything like that. Not sure if they make after market discs for that model either, but you can't afford for them to go wrong or fail....
    Good on the guys who picked that fault up as well, it shows they actually took the bike for a ride...
  11. Just bend it back with a large shifting spanner - i do it all the time to my MTB disks.

    Thats a joke, get the new disk...
  12. Hey Teo - Have Hills MC fixed up your rotor yet?

    Fun Ha!
  13. They were supposed to receive it yesterday, but it didn't arrive. I'm now hoping they'll get it today and I'll be able to pick it up tomorrow. At this stage just waiting for the new rotor to get here =[
  14. Grr. This is frustrating.

    Today [Thursday], they received the one they'd ordered earlier but it turned out to be the "wrong one". They're blaming the vendor, saying they got sent the wrong part. They've now placed another order with a different vendor, asking for overnight delivery. This new one is also coming in from Melbourne. I'm told that front disk rotors for a VTR250 are somewhat rare and they haven't been able to track one down in stock anywhere in Sydney, which is why they keep having to order from out of state.

    Very disappointing for me, since I've now been bike-less for a week. I'd decided to leave it with them instead of riding with a warped rotor, and also due to the inconvenience of having to pick it up and drop it off again when the rotor got here. I hope the wait is worth it x_x
  15. After all that waiting, they finally got the correct rotor on Friday and installed it the same afternoon. I picked it up this morning and the pulsating brake problem is completely fixed. Just a spot of bad luck, getting the wrong one first time around, but shit happens I suppose. As well, I completely forgot to ask for the old rotor to post pics because I was so eager to get riding again >.<