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Brake pulse under low speed and sintered pad advice.

Discussion in 'Technical and Troubleshooting Torque' started by Tam, Mar 29, 2011.

  1. I used to use Goodrich sintered GH pads on my 2001 R6. Awesome feedback and braking. Currently have modulation in 06 r6- you know, the on and off I think every single rotation- in low speed braking -its really annoying, but not under speed - the pulsing goes away. I have not determined if I am getting the 'pulse' through the lever yet.. and cause yet to be actually determined. Hot spot or warp, not sure. I had advice that changing brake pads may make this issue disappear. Not really a problem as I intend to go to a sintered pad anyway and get rid of the pads in it... Anyone had this before???

    Also has anyone got a review on metalgear sintered pad, or anything other than goodrich? They are darned expensive.
  2. Yes, and there are a number of things that can do it.

    A slightly warped disk can be like that. A disk can wear and warp in such a way that it straightens out at 'normal' operating temp, but you notice a slight warp when it's cold.

    The disk can start to get a light coat of surface rust while parked, and often it doesn't rust evenly, so some parts will have a heavier coating than others, and it goes away when you scrub the rust off.

    Foreign stuff can get on the disk that can change the level of friction in one spot or area. You get splashed by a car passing through a puddle, and there's something in the water - like soap or oil or ... insecticide or...

    You go to great lengths to make sure that while cleaning the bike, you don't get WD40 or polish / wax on the disks, but mistakes happen. CRC make a thing called DiskClean, which should rip most oils and stuff off, but if you get something really nasty on it - like axle grease or chain-lube, it may need the disk removed and chemically cleaned, or machined or even replaced.

    You can glaze the pads and the disk surface, and then more normal use will wear that glaze off, but it may not wear off evenly. A bit of a light clean-up of all the disk surfaces with some fine grade wet & dry can fix that, but be very sure to do the same job all the way around on each surface. You could end up making it worse if you don't do it evenly.

    There are probably other things as well, but those are the ones that come to mind.
  3. I had this issue appear on my FZ when I put in new pads a few months back, it still happens at low speeds even after 9,000kms of bedding in.
    The technicians at work have told me it's due to slight movement of the pad inside the caliper.
    I have EBC sintered pads, the original pads had no issues, next time I'll be spending the extra to get original OEM pads.
  4. As far as I'm aware, you need to machine the rotor, everytime you change new pad.
  5. Nope .
  6. No. Unless there's an issue, you shouldn't need to machine a disk. Bike disks are only just as thick as they need to be, and if you start machining more than about 0.5mm off them which is very little anyway, they'll be under thickness and overheat and warp way too easy.

    Some car companies demand that disks be machined each time a pad goes in. Means they sell more disks. BMW actually demand you replace the rotors every time you change the pad. If you don't (and not many do) then you haven't actually followed the logbook servicing schedule, and if any warranty issues come up, they can use that as a dodge to get out of replacing your 30k engine and gearbox.
  7. Oh I see. BMW's case is extreme, I can't believe they are such bullies to their customers.
  8. Got any evidence for this? Sounds like unfair practise..
  9. Got told about it by a bloke who'd been the state service manager about 15 years ago. They're a bit selective about who they pull that shit on - usually people with more money than sense, little mechanical aptitude ... dare I say females?

    They also (State head office in Newstead) got pinged by Micro$soft for about 75 pirated copies of windoze and orifice... Cost then a 75k fine, plus legals, plus the full license fee for every product. Not so many coke and champers parties for a while after that. LOL.
  10. Consumable wear and tear items, including brake rotors are not generally covered under manufacturers warranty, I know with Yamaha they aren't.

  11. That's what I thought as well.
    Seems like that particular BMW centre was playing funny buggers.
  12. Disks and pads are consumables, and are covered by warranty against defect in materials and manufacture. They are not covered against normal wear. So far so good. So in a high end model, you add a specification (in very small print) that when the pads are changed, you should change the rotors as well. So people roll over, or don't even look at the bill, they just sign. If you tell them to stop being silly, and just slot a new set of pads in with the existing rotors, they make tut-tut noises but do it. Then three weeks later your 18 speed gearbox with artificial intelligence fails. So it's done 80k on a 100k warranty, and you claim, because they cost $16k. Then, the company says it doesn't have to honour the warranty unless you have followed the maintenance schedule. And guess what? You haven't...
  13. Interesting point but I have a warp/modulation which appears systematic - I think it is every single rotation which would explain away the disc pad movement. As it feels very regular.
  14. That does sound very much like a warped disk.
  15. agree wholeheartedly, it describes the same symptoms my bike had before I changed the rotors.
  16. yeah, it does... its just that I have had warps that you can feel under medium brake.. aka 60 - 0 this is only around 10kph-0.

    Looks like I will be getting a pencil test on them soon. Thanks for the wonderful ideas and thoughts.
  17. I find it hard to believe that a gearbox failure can be attributed to disc rotors not being changed. It may be printed in fine print, however, in a court of law it would not stand up. I deal with warranty proceedures on a daily basis, I have a very strict code of conduct I must adhere to. The practices you mention are old school bully tactics that most reputable dealers buried long ago.
  18. If you hold the brakes on lightly you will feel the brake lever pulsing at low speeds like 10 kph with warped disks. Usually you will feel them less as you squeeze harder.

    What you describe sounds like warped disks to me.

    BTW BMW don't require you to change disks when you change pads, at least not BMW Motorad anyway, maybe their cars do.
  19. Yeah, it was cars not bikes, and yes, it's not a good way to do business. Don't know if it's still going on.

    Of course a brake maintenance decision doesn't impact gearbox life. The point was that 1/3 of the people who bought 5 & 7 series boomers in the 80s and early 90s didn't look at the bill, told the shop to do what was required, and just signed the invoice. Another 1/3 had no idea, and just got browbeaten into it. The remaining 1/3 went "Hold on, that isn't right." I think if they went and complained to trade practices or someone, bm backed down real quick, but those who didn't bother, found themselves paying for things they shouldn't have. Point was, an awful lot of people just accepted it, or didn't even look.

    And yes, that dealership in newstead was the state headquarters, and they were a bunch of coke snorting champagne swilling high-lifers, in the 80s. The suit and tie part of the shop, anyway. Their dodgy business practices were as legendary as their new model viewings with Dom Perignon and a real live string quartet playing Handel in the background...

  20. Hiyall... FYI : for future reference...

    I changed to sintered brake pads. Modulation through braking fixed. (not to mention better braking all round)