Thread: I now know why my brakes were pulsing and giving a shimmy

Originally Posted by PhilipA

Over the last few months my brakes have started to pulse and give as himmy at 80Kmh.
Last week I pulled the calipers off and checked the runout on the discs and they were OK, perfect in fact so I bevelled the pads, greased up the sliders etc and put them back together.
Went down to Sydney last night and pulse still there.
So more complete action was called for.
So today I stripped down the calipers, took the saddles off and measured runout on the discs and wheels, then removed the discs to check for thickness variations.
This is what I found.
Attachment 119435

The crack follows the contour of the brake pad leading edge, so I guess is from overheating. Bit of a disappointment as they were RDA discs that were grooved affterwards and I paid a premium.
Regards Philip A

You paid a premium for RDA rotors What were you expecting Quality

If they were grooved then looking at them now they are not grooved, the grooves have been warn away , so it's probably time they got replaced , might be past their use by date. Also people want brake pads that never wear away, the harder the material the more damage they do to disc rotors, better to get softer pads and replace more often and put up with a bit of dust.

What type of pads Phillip?
that disc surface is terrible,,

no funny brake smell at some stage?
I'm thinking sticky piston...

Originally Posted by Roverlord off road spares

If they were grooved then looking at them now they are not grooved, the grooves have been warn away ,

You can't see a groove in the picture?

What type of pads Phillip?
that disc surface is terrible,,

no funny brake smell at some stage?
I'm thinking sticky piston...

Bendix 4X4
Remember that I do some off road.
The pads are only half worn and pretty consistent in width both lengthways and with each other. Both sides had the backing rubber stuff on the piston side cut through and crispy, so they got pretty hot.
It looks to me that it is really my fault as before I found out the real weight of my camper trailer it had no brakes, and I did some steep stuff. It looks to me like a really hot pad cracked the disc as the crack follows the contour of an edge of the brake pad and it is on the caliper piston side of the RH wheel.
I think the pistons are OK as there is no pull under brakes.
But still shouldn't happen.
My brakes used to smell after every downhill pass, even using the gears, when towing the camper which could weigh up to 1000Kg .
Regards Philip A

Hmm, more likely on the highway before or after the offroading,, ?? not much heat generated at slow speeds.. anyway its good you actually found a fault, not finding is always worse!

Originally Posted by Scouse

You can't see a groove in the picture?

I misread the post, I thought O.P bought the rotors and had them grooved (slotted) after he bought them and paid a premium.
Quote:Bit of a disappointment as they were RDA discs that were grooved afterwards and I paid a premium. unquote
Maybe if it said they '' Became' grooved afterwards

Sorry my misunderstanding .

Originally Posted by Roverlord off road spares

I misread the post, I thought O.P bought the rotors and had them grooved (slotted) after he bought them and paid a premium.
Quote:Bit of a disappointment as they were RDA discs that were grooved afterwards and I paid a premium. unquote
Maybe if it said they '' Became' grooved afterwards

Sorry my misunderstanding .

They are grooved (Slotted) rotors, groove highlighted in red.