Norco Six with shuddering vibration howl
I'm hoping someone can help me out here - I've got an 04 Norco Six, which I love, and it has Hayes brakes on it. I got the pads replaced on the back a little while back, and then had a minor issue with the brakes gripping all the time, so a bike mechanic drained a little bit of fluid out to release the pressure, and they have been braking nice ever since, except one issue: the howl, squeal, shudder and vibrate under mid to heavy braking..
light braking isn't a problem, but as i ease into the more usable, heavy range, they start to really shudder. It's bad enough to the point of being uncomfortable, not to mention the noise..
Can anyone suggest what I might do to fix this??
Thanks in advance, Lucas.
replacing Norco suspension bearings
I've ridden 2 Norco Shore's that both eventually developed the same issue you're describing. The issue is probably coming from the rear pivots of your suspension (the ones by the rear hub) as you squeeze the rear brake. Have you ever replaced those? Try putting your bike in a stand, spinning the cranks, and then grabbing the rear brake while keeping one hand over the rear pivot on the brake side. If you feel any vibration, that is most likely the culprit. Changing the bearings is easy if you have the right tools, and a pain in the ass if you don't. If you're not mechanically inclined, I'd suggest skipping the rest of this message and take your bike to a shop to have the bearings replaced.
If you're going to do it yourself, you need a good workbench mounted vise, a complete socket set, and off course the necessary allen keys to unscrew all the hardware that holds all the pivots in place. When placing the frame parts in the vise, cover the clamping surfaces of the vise with a rag so you don't damage the frame.
First, go buy some standard cheap skateboard bearings from a skate shop. Then take all the preload pressure off your shock and remove the rear wheel. Then unscrew the bolts that hold the rear pivots, taking care to observe where all the washers go so you can put it back together. Next remove the seatstays from the rest of the frame, again watching carefully where all the spacers and washers go.
Now take the largest size socket that will fit against one of the rear bearings, put it in the vise, and crank the vise so that the socket forces the bearing out. Now find a socket that is the same size as the outer bearing race from the new bearing. Make sure that the socket is large enough so that no pressure will be on the baring seal, or else you'll damage the bearing as you press it in. Place the new bearing beside the seatstay in the vise with the socket beside it and crank down on the vise, pressing the new bearing into the seatstay. Repeat for the other side, and then replace the seatstay and all the little washers the way you found them.
You can use this same method to replace all the bearings of the rear suspension. The only bearing that is not a skateboard bearing is the big one by the bottom bracket. You'll have to get this one from a bike shop or a bearing house, and you'll need much larger sockets for this one.
Hope that helps.
Thanks for the super-information answer, its much appreciated.. I'm thinking perhaps that is exactly the cause, as it start happening after the rear end was played with by a bike mechanic, trying to get the gears to shift properly on the rear derailleur. He succeeded, but the whole rear end was wayyy out of alignment, and hence it required a lot of elbow grease and effort to actually bend the thing straight again, perhaps in this process its speeded up/expedited/catalysed the bearings on the back showing signs of wear and tear.
I've learned my lesson, buying a 3 year old bike, and won't be repeating my actions again!! (Anybody wanna buy a 2004 Norco Six with super t's, vanilla rc, hayes brakes and some other really nice bits?
Double-metric mtb man
Well, there are a couple other things to try first. I've got Hayes on my ride and they can get noisy. I'd say to make sure the calipers are properly centered first, and then try a little elbow grease on the rotors and pads before you take apart the rear end of the bike.
I'm assuming you've centered calipers before, I won't describe that here....but
Try taking some fine emery cloth to the rotor and rub the entire braking surface using a figure-8 motion, both sides. Clean the rotor with isopropyl alcohol. Remove the pads from the calipers and sand them (remove any glaze that may be on them) and then clean them wit isopropyl alcohol as well. Re-install the pads into the calipers (don't touch the braking surface with your fingers) and re-fit the wheel. You'll need to bed the pads a bit again (I found it only takes about a half dozen stops to get them back again unless you're really aggressive with the sanding).
You should find them a lot more quiet. I did it to mine once and have had no issues since (except when I've messed with the caliper alignment).
Once done, you'll need