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The following link is what Bendix have to say about disc brake shudder. https://www.bendix.com.a...explained-and-how-fix-it
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I guess that article leads to the obvious question for Warren, is the shudder through the steering wheel or the brake pedal?
That article does remind me of the big text on the bit of paper that comes with the DBA rotors that spells it out clearly that you must fully clean up the hub face before fitting new rotors. I have always exercised the caliper pistons and slides when changing rotors and/or pads but I bet plenty don’t. When I rebuilt the 120 Prado calipers for the Hilux they really needed a good work over externally on slides, pins etc but were like new internally. Whoever owned the Prado before it was wrecked appeared to have had brake fluid and pad/rotor maintenance done but had ignored the outside of the calipers. The brake place I got the kits from showed me the pins that needed linishing and the other spots that get ignored in general servicing. |
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400 grit emery has cured my FG of this several times. It's usually outgassing pads causing surface contamination.
It always amazed me how many VR/EF era Falco-dores needed their front rotors machined because they were warped. I would watch the disc lathe doing its thing, noting how it was an even scraping of material - when you'd expect a rythmic 'chuff-chuff-chuff' if they were in fact warped. I proved this several times on the lathe at work in the mid 90s - brakes that would shudder still came up perfect on the dial gauge. Taking a layer off would cure them - but in reality it was only getting to a clean surface. Then I realised it only needed rubbing with emery to cure it.
Just in the last 12 months I've cured an FG, VE & 2 WKs from "warped" rotors using 400 grit emery.
I have a fairly significant hot-spot period for the brakes - coming off the freeway at either end of my commute, into traffic lights, which are usually red. I've learnt to stop a bit early (say 5-6m), and gently roll up about 1/2 metre at a time every 1-2 seconds for about 4m, to allow the whole surface of the rotor to cool, and to put that cooler surface under the pads again. If it's going to be a long stop (like when it's just gone red) I'll use the hand brake & neutral so the pads aren't jammed hard against the rotor. Doing this has given me a much longer period between emery treatments. |
Cheers,
Mick
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On my dirt bike I got real bad brake squeal and this was due to what I washed he bike down with, so I had to rub the disks and the pads back to get rid of the noise. it looked like a build up on the rotors.
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Originally Posted by: castellan  On my dirt bike I got real bad brake squeal and this was due to what I washed he bike down with, so I had to rub the disks and the pads back to get rid of the noise. it looked like a build up on the rotors. I remember reading years ago in Sidetrack mag that you can’t change from sintered metal pads to organic or vice versa. I can’t remember why now though.
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Originally Posted by: wbute Originally Posted by: castellan On my dirt bike I got real bad brake squeal and this was due to what I washed he bike down with, so I had to rub the disks and the pads back to get rid of the noise. it looked like a build up on the rotors. I remember reading years ago in Sidetrack mag that you can’t change from sintered metal pads to organic or vice versa. I can’t remember why now though. I still have the original front brake pads in it.
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Some interesting concepts in the brake components matching and bedding in.
Bremaxx brake pads are coated with a thin layer of Quikbed Organic material, this helps to ensure that the Bremaxx brake pads are correctly bonded to the new rotor surface for maximum braking efficiency.
Bremaxx recommend 8 x firm stops - 80 kph down to 20 kph for bedding in of rotors to new pads.
Most manufacturers will nominate the bedding in process.
Mismatching aftermarket pads to rotors- 650 C ceramic pads to 450 C rotors is troublesome. The concept of braking is the conversion of mechanical (kinetic) energy to Heat and some engineer somewhere is paid a lot of money to get it right as a match pair rotors to pads. The co-efficient of friction of pads has to be matched to the capacity of the rotors to dissipate heat.
Just because it fits does not mean it will perform as intended.
I also stay away from cross drilled and slotted (aftermarket)rotors. OEM high performance rotor are cast with holes in them and not drilled after manufacture only cleaned up.
Cross drilled and slot are weak (fracture) points vulnerable to the heating and cooling process for cracking. Clawed rotor are "less" vulnerable.
Domestically driven brakes may not highlight mismatches, however harshly, work/towing load and trackday applications will.
Its a process of elimination :-
* wheel balance
* wheel alignment
* Pad change
* rotor Change
* bushes/steering geometry
I have seen a pad change fix everything and nothing!
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