Brake caliper flex

[mitch_f1]

Problem is on both sides, and pretty much equal as well in terms of the amount of wear.

I will happily adopt new calipers, if someone funds them ;)

[mitch_f1]

Actually Bryan, what rotors do you run, being that you have virtually perfect pad wear

[manga_blue]

Problem is on both sides, and pretty much equal as well in terms of the amount of wear.

Likewise.

Thanks Terry and GM, ... again. I take your point that there may well be 2 separate but compounding issues with my car.

Need for gainful employment limits my time a bit here. Also the fact that the nearest person I can trust to do a wheel alignment is 2 or 3 hours towing away. So the immediate plan for me is:
1. Order caliper re-build parts and sliders - done.
2. Do some further quickish suspension tweaks plus the usual pre-race check for major issues underneath.
3. Do a detailed check and re-build of calipers. Throw on a fresh set of pads while I'm at it.
4. Drive the nuts off it at Phillip Island at the end of the month.
5. Bring it back and do a serious check of suspension and sub-frame arms, bolts, bushes, etc.

[Guran]

Since Aug 2011, I'm using DBA "Street Series Standard" rotors on the front. I think they were OEM rotors prior to that. Photos of my pad wear are included in the above link. I still have those old pads in the garage and just checked the taper. There's less than 1mm taper from inside to outside, and even less from top to bottom.

[manga_blue]

Time for an update now if it helps anyone. I've done a front caliper rebuild with seals and sliders from MX5Parts.co.uk and then run it at Phillip Island.

This is a '95 NA8 with 195,000kms and 54 track days on it. It was well maintained when I bought it and for the last 6 or 7 years it's had an annual fluid change, originally DOT 5.1 but lately SuperDOT 4. It has used 1-2 sets of pads a year, so sliders have been regreased as often with quality synthetic caliper grease. Pads are HP+, rotors are DBA 4000 slotted.

Before dismantling we tried applying max pressure on the brakes to detect caliper flex. Effectively there was none. The caliper fingers are pretty massive and I'd say caliper flex is probably a myth on these if they're OEM. Radial taper wear must have some other cause.

On inspecting the dismantled calipers the cylinders and bores were virtually as new: no wear or pitting present at all. So the fluids regime worked well. All seals were very good too. Obviously Mazda started out with good materials.

The small slider had zero wear and I'd generally say that it's a waste of money replacing it, unless damaged. It only provides a minor locating function, it's not load bearing and it slides in a rubber sleave anyway.

The original big slider was showing 1/2 thou of diameter wear and, while I couldn't measure it, I assume that the hole in the caliper bracket in which it slides had a similar amount of wear. The consequence of this is that the caliper rocks about 2-3 degrees relative to its bracket. This could explain most of the radial taper pad wear. The rocking was reduced by half when I put in a new big slider.

It's interesting to note that the sliding design cannot cause mechanical wear on the calipers. The slider/bracket interfaces are the only external wear surfaces. This means that if it all gets too sloppy then all you have to do is buy new slider pins and new caliper brackets, but not calipers. As long as you keep changing fluids the calipers could last forever. This is very good since new pins and new brackets are much, much cheaper than calipers.

The Island was not a very good test for them. It's not very hard on brakes there and most sessions had some rain. At Honda I was mostly gently squeezing brakes from about 170m when I usually stand on them from 80m.

Nevertheless there were some big stops on the odd dry lap: 170kmh down to 70kmh from 100m at Honda maybe half a dozen times. Impressions are that brake performance is about 75% back to where it used to be. There's no more weaving but it still seems to get a little localised heating about 1/3 of the way in from the outside edge of the outer pads. This translates into some slightly erratic braking by the time you get close to the turn-in point on the hairpins. Had one run down the escape road at Honda and 2 near misses, one at Honda and one at MG, but that's pretty normal for me anyway.

New front caliper brackets next ...

[mitch_f1]

Have you inspected pad wear for any of the vertical uneven wear patterns?

[manga_blue]

Not yet, mitch, just rotor surfaces Could be a while before I have time to get it too, sorry.

[mitch_f1]

No worries. Was just curious. Glad to hear you got yours sorted though

[sailaholic]

Checked wheel bearings?

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[manga_blue]

OEM, 40,000kms old, but an interesting thought. Will check it. Probably unlikely because it's the same both sides.

[plohl]

Thanks for the write up! My car darts a bit under heavy braking sometimes - more noticeable with the semi's one - might pull them apart and have a look. cheers

[sailaholic]

Brakes direct had a face book post explaining how bearings are often the cause of "warped" rotors. Normally the rotors aren't warped just have pad material laid down unevenly. I'll try and find it once I'm at a computer.

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