|   Hope Mini Noise | ScottN
Mar 31, 2003 1:50 PM | | My wife's bike has a set of minis on it and they (the rear specifically) emits a horrible high-pitched scream when they come on. No matter how hard you are on the levers, they still scream. I replaced the rear pads with EBC greens, re-shimmed the caliper a bit differently and sanded the pads and cleaned the rotor down and they still screech horribly.
Anyone have any ideas? I did a search on this site and didn't see much (I didn't go back too far though). If it helps, we live in Arizona and the bike is a SC Juliana Superlight.
Sn |
| Move to Buffalo | JimC.
Mar 31, 2003 2:03 PM | | j/k, Hey Scott, here's Mike T's FAQ on squealers, maybe a tip for you in there? Good luck, I got the same on the front with new pads on Sunday. Hmn. cheers to you both, Jim
Brake Squeal
Given the right place and time, all brakes including disc brakes, squeal. This is normal and we can't get away from it. Usually your brakes will, or should, be quiet and it's certainly normal for them to squeal if they get wet. But they should not squeal all the time and if they do there are some things that you can try to stop the infernal noise.
1. The first thing we should check is that the slave cylinders are mounted correctly regarding the relationship of the rotor slot to the rotor. The rotor should be in the center of the slot and the slot should run parallel to the rotor. Take some time to eyeball your setup and view it from as many angles as possible in a good light. Get down there with a flashlight and really be critical of the setup. Shim the slave cylinder as necessary to get it as good as you can. Yes you may use unequal numbers of shims under the mounting arms to get the setup as close as possible.
Consider scraping paint off the insides of the fork and frame mounting tabs to get a perfect surface.
Magura has a new tool - the Gnann-o-mat ! This is a facing tool for International Standard disc brake frame tabs. This will work on any front fork or rear frame IS mount and it is compatible with any make of IS disc brake (hydraulic or mechanical). This tool is a much needed tool by the dealers. This will allow dealers to achieve perfect alignment and set up with any IS disc brake. In addition, it will greatly reduce or eliminate disc brake squeal. It is a tool that every shop selling disc brakes should have.
2. We should also be certain that the pads and rotor are free of contaminants. It's easy to get things like brake oil and chain spray lubes on the pads and rotors and these will cause you all kinds of problems. Believe me it's easier to keep the parts clean than to get them clean! Be very wary of any kind of lubricant or contaminant around your brake parts. Yes it's ok to wash your bike with soapy water and for it to get on the brakes. I do mine all the time and it causes no problems. There may be some squeal until the pads dry out - apply the brakes a few times to do this.
3. Spoke tension can play a part in disc brake squeal too. Spokes must be of high tension so if you have squeal this is one area that you can check.
4. Frame harmonics. Oh here's a biggie! Many frames tend to vibrate from frequencies set up by the friction of the disc brakes. The frame itself or parts of the frame like the rear triangle can start to vibrate like a tuning fork. My own frame at certain times lets out a low "Nnnnnnnnnnnnnn" noise but it only does this on high humidity days. Go figure!
How do we cure this? I don't think we can really. If the frame was made with a different gauge tubing, different stays or whatever then maybe it wouldn't vibrate. But how will we know? Maybe you can try, as a temporary test, taping some thick rubber or weights to the seat stays or frame tubes to see if this makes a difference. It's not a fix but at least you'll know what the problem is.
I'm not an engineer but I think that brake squeal is an individual bike thing. Your brakes might squeal on your bike but not if you fitted them to your buddy's bike.
Obviously squeal comes from the pad to rotor interface and a different pad material would change the friction characteristics and therefore the squeal. But.......is there a different pad material for your brakes?
5. Last but not least - sometimes pads "glaze over". This is molten pad material that solidifies on the pad surface and can cause squeals and other weird squealy type noises. To get rid of it, remove the pads, lay some medium grit sandpaper on a flat surface, rub pads on sandpaper just until shiny surface is just gone, blow off the dust. Don't touch pads with fingers! I'd be cleaning off the rotors with Isopropyl Alcohol too. You'll have to break-in the brakes all over again - no big deal for removing your squeal. Hey I'm a poet! |
| re: Hope Mini Noise | Dougal
Mar 31, 2003 2:52 PM | | There was a post here a while back about ebc gold pads. Apparently they stopped a squealing mini that nothing else would.
I'd also take one of two approaches. Often these work when nothing else will:
1. Douse the rotors in brakleen.
2. Drag them down a hill and get the rotors nice and hot.
Dougal.co.nz |
| Have you done the gnannomat thing? | Shylock
Apr 1, 2003 6:15 AM | | ....if not , consider getting the Hope tool: 60 bucks and reportedly works like charm. ( my fork was given the Hope treatment last night)
That could cure your squealing if your rotors aren't properly aligned in the caliper.
However, with one exception, everyone I've talked to with minis complains about the squeal, so ear plugs might be the solution.
Feel the gin |
| Bingo! | JimC.
Apr 1, 2003 9:33 AM | | we did 3 SC bikes in Vancouver recently with Codman's (kindly lent G-mat)and all were significantly out in the rear. Codman also remarked that in Montreal, SC bikes seem to have rear IS tabs out of line more than most other bikes. Betcha that might at least help.
That said, major LBS here says ALL of the bikes should ahve it done, none of them are correct.
Jim MCM #11 |
| Bingo! | Dougal
Apr 1, 2003 8:15 PM | | $60?
A machinist should be able to do it for about a third of that. A little work with a crescent wrench and a file works out about 100% cheaper.
That said, many hydraulic brakes allow the pistons to swivel around to find centre, easily taking up minor misalighment.
Brakes with a fixed pad and mount (like all mechanicals but avid and early maguras) need a straight mount.
I guess that's why magura made the tool.
If I owned the tool and charged to use it, I might also say every bike needed it!!
Dougal.co.nz |
| Bingo! | Marktw
Apr 2, 2003 8:38 AM | | This is interesting. I am building an SC Superlight and checked with SC and with two reputable local Shops in Portland. (Fat Tire Farm and River City Cycles.) SC says their frame tabs (at least now) are aligned during production and especially an ano frame shouldn't need it. (no paint build up.) Fat Tire farm says they have only had to use their gnannomat tool to actually make cuts on two frames out of hundreds. |
| Fat Tire Hacks nm | Jaybo
Apr 8, 2003 12:55 PM | | NM |
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