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Rear Brake Squeal


DiscoClax
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Hi all,

I replaced the stock rear rotors with DBA slotted ones last weekend. New Bendix 4WD (AFM) pads went in at the same time. These are the same pads as I have always run (now on my third set) without any previous issues at all. Problem is that after the first two or three brake applications they start to squeal. Didn't happen initially, but as the pads started to bed in, this issue started to happen. Doesn't occur when dead cold, and improves if I've been motoring down the freeway for a while off the brakes and they cool right off. Gets progressively worse as the brakes warm up and starts happening at higher speeds. And I'm not talking " Oh, that's a bit annoying" type squeal. I'm talking "People in the next suburb looking out their windows with their fingers in their ears" type squeal. Driving me totally nuts. I change into low-range for carparks now so I can stay off the brakes as much as possible. It's really embarrassing and annoying in the extreme. I haven't had a chance to off-road on the new brakes yet, they've only done about 1,000kms of mainly highway work so far. Pistons are retracting properly, can't see anything obviously wrong with the brakes. Seems to be the LHS ones only, as well.

I've tried putting anti-sieze compound on the edges of the backing plates and contact areas of the top retaining spring plates, and even chamfering the leading edge of the pads. No joy. No better. Still being deafened. I've avoided using an anti-squeal compound on the backs of the pads so far as that's always somewhat messy and coats the pistons and seal in gunk (and doesn't always work). Note that I don't have the pressed metal shims fitted (which appear in the EPC), but then I never did.

Someone please help... My usual fixes haven't worked. :(

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Either back to stock rotors or try another make of pad if you want to stay with those rotors.

Or fit the shims and use a little antisqueal lube on the pad backs.

Thanks for the advice Paintman. Finally got a few minutes free to have another crack at the brakes and put anti-squeal on the pad backings today as you suggested. De-glazed the pads at the same time with a bit of emery, just in case. Net effect: bugger all. Still screams like a rabid banshee as soon as the slightest warmth gets into the pads. Starting to run out of options... :( Still trying to track down where I can get the shims. Toying with the idea of going to a Bendix Heavy Duty pad to change the interface frequency, but they're overkill in the rears and may not come into their operating temp during normal driving. Almost sounds like the brake shields are now going off as well, just to add even more noise to the equation... Aaaaaargh :ph34r:

There's a product that you can spray onto the discs which makes them temporarily more abrasive, allowing the pads to de-glaze and bed to the rotors quickly. I'd never heard of this product before today but it was recommended by a respected source (who was also highly sceptical before trying it himself in a multitude of customer cars with very good results). Has anyone had any first-hand experience with this sort of product?

I've tried the new generation Bendix pads with the Titanium stripe recently, which are supposed to aid bedding in and give good pedal feel and bite from new (like the miracle spray above). They were (and are) excellent and live up to all of their claims. Unfortunately the pads I got were from older stock, and don't have the stripe.

P.S. I put slotted rotors on there for improved performance. Esp after water crossings/mud baths where the pads bite hard immediately, rather than after a few heart-stopping revolutions. Also stops rocks, etc jamming in the pads and causing damage to the rotors or pads. I've had plain, slotted and cross-drilled in the past and have found slotted rotors easily best for off-road use (and on-road for that matter). Apart from that, it extends the thermal operating range of the pads under extreme duress - ie. less fade.

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IIRC genuine Ford pads used to have an abrasive coating to help clear any glaze or high spots when used with old discs. As to whether it works or not I have no idea.

Is it possible that the discs are running out of true & the squeal is a result? If you have access to a dial gauge might be worth a look. It is also possible to improve disc runout by moving it to a different position on the hub. I assume that you thoroughly cleaned the mating surfaces & DIDN'T put any sort of lube on the mating surfaces?

If the pads with the stripe don't squeal I'd be inclined to cut your losses - and embarassment when evrybosy looks to see what's making the noise - and fit them instead!

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  • 3 weeks later...

Alright, time for an update... some advice, and a plea for help, in that order.

Update:- Tried the spray on abrasive compound. Well, that made a huge difference... several dB louder. Then I stripped off all of the spray stuff, "machined" the rotor with 220 grit wet&dry (1st gear, one wheel in air), PBR squeal-stopped the backings and cleaned everything again. Much better... for a few kms... then returned over time to the previous levels. :( I can't blame the spray-on stuff, it was obviously only accelerating the bedding in process (as it's designed to do) as my squeal levels now are as they were after the spray. Run-out checked as as perfect on the LHS, but there is small amount visible on the RHS (minimal, though). No lube on the discs. Note that the mountings were cleaned with a brass brush when fitting the discs to the hub. Both sides squealing.

Advice:- Then I contacted DBA on-line help. Their local sales manager called me the next day and we had a nice long chat. He then had a chat to his counterpart at Bendix to try and nut this out. Long story short, their recommendation is don't use Bendix 4WD brake pads if you are actually going to use them off-road semi-regularly, or tow, etc. Use the Bendix Heavy-Duty variant instead. The 4WD pads are more of an on-road pad formulation and can be susceptible to squeal. The HD ones suppress squeal much better and cope better with off-road use. Also the advice was that I was pushing it up hill with a stick to solve the issue without the factory backing shims (which I've never had).

Desperate plea for help bit:- Despite my best efforts to source these backing shims here in Oz, I can't track any down. The OS suppliers don't seem to want to deal with us Antipodeans as I cannot get a response from any of them.

Is there any kind-hearted forum member that would be willing to source some of the bits I need and ship them across? I'll cover all costs, include a forum donation, plus cover the cost of a few pints of that warm beer substitute you guys seem to enjoy as this classifies as thirsty work. :)

Wish list-

Axle set of items 20 and 21 on the attached pics of the rears and item 21 on the fronts (I'm converting from solid to vented front brakes and need the longer retaining kit for it). Ideally I'd like enough bits to do the car twice (ie. so I have a spare set) given that they're low-cost, light items.

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Can't locate the part number for the front axles shims - Ralph, where are you?

Les.

Hi Les,

I don't know if anyone does shims for the front. :unsure: Nothing I could find in EPC. Be a bit tricky to do with a four-pot caliper maybe? If there is one I'd certainly like to have a set as I don't know how the fronts will go for squeal, and I'm a bit gun-shy after my experience with the rears and these rotors/pads. :ph34r: Please don't waste too much time on it though.

Cheers.

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  • 1 month later...

Update time... but firstly a massive, heartfelt, and sincere thanks to Les - who kindly sent me the goodies required to fix this issue. :) :) :) :)

Final fix appears to have been changing to Bendix Heavy Duty pads (with Titanium stripe), giving the calipers a good clean, fitting the anti-squeal shims and a new pad retaining kit. The shims I got seemed to be for a slightly different set of pads (I run DB843 type pads), so I tweaked them to fit and to line up with the pistons properly and then lightly glued them to the pad backings with anti-squeal (but not under the piston contact area) just so they won't fall out.

Have now done over a thousand kms over the last few days, much of it off-road with only a few little half-hearted squeaks on one occasion during a long tortuous downhill grind whilst the pads were still bedding in. The joy of braking with confidence in silence is something I will not underestimate again.

Faith restored in both DBA and Bendix for their excellent products. Very happy now with the braking performance. Long may it continue...

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