Rear brake pad wear

[cinquecento]

On the outside (the inside is OK) of the rear disks (both left and right hand side of the car), the pad only seem to be applying pressure to the outside of the disk. Contact between pad and disk from about 1 inch from the outside of the disk does not seem to happening.

Interesting enough, last week end at the growl I noticed this happening to a few cars, and even saw one Griff where there was rust where pressure has not been made.

Thought about warped (curved) disks... but the fact the the inside of the disk is shiney seem to me to indicate the disk is OK.

Pads look new (only had the car a couple of months) so I am not too sure if they are new and just need bedding it..

Any ideas?..

[tvrgit]

if i read you right, the inboard face of the disk is all shiny, but the outboard face is only making contact on the outer circumference, with a rusty strip outwards from the hub?

I think the standard Griff rear brakes are a sliding caliper with the piston on the inside - so the inner pad is pressed against the disk then that pressure slides the caliper to pull the outer pad against the disk. If the sliders are sticky (with a combination of grease and brake muck) the the slidy bit is impaired, so the piston pad (the inner one) does all the braking, and wears twice as fast as it should.

Could this explain why the pads look new - ie previous owner has changed them, but not freed up the sliders?

[GreenV8S]

If the sliders are worn then the pads splay apart under heavy braking i.e. the pads don't remain parallel to each other, or to the disc. This can cause the wear patterns you're seeing. You may also find the calipers twist forwards so all the braking occurs at the front of the pad. This isn't visible on the disc but will show up in uneven pad wear.

[cinquecento]

Guys..

MANY thanks..

I had a look this afternoon.. sliders move freely... but didn't check the lateral play for movement..

Will do!!

Again.. many thanks.. appreciate your input..

[cinquecento]

Under the car on the weekend....

Indeed the sliders are worn: there's quite a lot of play especially in the rear.

Numbers are:

The disk assembly is part number: Ford V89 BB21 315AA
Pad Asembly 67321 052/5
Slider has no part number
Slider dust cover AR256 (front slider)
Slider dust cover 6720464 (rear slider)

The problem is I live in Sydney and most Ford dealers have never seen nor heard of a Ford Sierra. Any ideas what other Ford models would have the same brake assembly used here.. Alteratively, what other brakes assembleys would share the same sliders. Is is likely I just need to replace the sliders.. or could the brake assembly where the sliders sit in need replacement too?

Thanks

[griffter]

cinquecento said:

The problem is I live in Sydney and most Ford dealers have never seen nor heard of a Ford Sierra. Any ideas what other Ford models would have the same brake assembly used here.. Alteratively, what other brakes assembleys would share the same sliders. Is is likely I just need to replace the sliders.. or could the brake assembly where the sliders sit in need replacement too? Thanks

I seem to remember seeing mkIII Grandas (that's what they're badged in the UK) in Aus, and I'd be fairly certain the calipers are a similar if not identical design. The car might be badged a Taurus or Taunus or something? Around 1985-1995 vintage. There was a Girling caliper used on some Audis (80, 90 & 100) which is very similar too. Best bet is to take the slider in to the garage and get them to match a replacement. I can't remember if it separates from the caliper/bracket or if it's integral though.

[Aaron C. Reskew]

Check that the raised locating pips on the pads are aligned with the cutouts in the piston.
This often gets missed when fitting new pads, causing the pad to sit at an angle to the disc.
The piston rotates or screws in and out for fitting new pads.

[cinquecento]

Since the last post, have looked at the sliders (they are OK) and generally looked around...but still no luck.

Here are some photos.. interestingly both sides of the disc make contact at the top.

[stringbag]

That just looks like what happens with new pads for the first couple of hundred miles.
You said that you have just bought the car - how many miles have you done?

[cinquecento]

Just done 2000km... (2000 fantastic km that is!!)

I had considered the bedding in idea (as the pads do look new)..however the shiney strip hasn't got any bigger (wider)..

[stringbag]

I can't quite make it out in the pics - is the actual contact area on both sides of the disk only the last bit of the disk - near the edge. I can see the outer face wear band is near the edge, it the inner face the same, or is the wear band the opposite way around ie near the centre of the disk?
If that is the case, then the bracket that holds your caliper on is bent (or the bolts are bent), canting the calpier away from 90deg to the disk.

[nztrev]

I have some spare calipers in NZ if your still having grief,almost looks like your calipers are not to the outer of the disc's,assuming the pads are right.I'll also dig out some pad specs that you can get down under if that helps.

[cinquecento]

Stringbag.

Yes.. the pads are only touching on the (outside) edge of the disk..

I can try to measure the caliper bracket to see if it's bent..may be difficult to guage it really accurately.. nevertheless I'll give it a go.

NZtrev

Thanks for the offer..

Pads are OK.. they are also off a Volvo/Jag... and readily available here. Capliers may be different.. not too sure what they are off. Having said that, I am really scratching my noggin to think that the calipers are out of wack..

Many thanks for yr off..I'll let you know...

BTW...great to know of another "local" TVR fan