ST185 Brake Warping

[Roundy]

hey guys quick question

I have had shocking luck with warped rotors since i 'upgraded' them to slotted rotors.

I think i might know why but i just want to check up on it.

When i took my stock rotors off, i noticed that there are 2 extra holes in them for a screw/bolt to the hub, however it looks like they have sheared off AGES ago and subsequently there were no bolts/screws in there so i didn't think anything of it.

Can anyone confirm there are meant to be 2 extra bolts there to hold it to the hub? If so could that be the cause of my drama's? the set i have on atm warped going UP and across the top of Bells Line of Road

Cheers
Nathan

[3sfe]

There are meant to be 3 screw holes on the oem discs but these are only there to asset you to take them off, by screwing bolts into them it pushes the disc off

[allencr]

Just like 3sfe wrote.

Those holes have left rust spots on the hubs. They may not look like much, but that rust spot is higher then the hub surface and I think that
it distorts the rotor when torqued down & its holes don't match the lumps.

[Roundy]

thanx for that guys! +ve rep for both of you!

so will sand it off/make sure the holes line up with it!

[wagonist]

How old are the discs?
What pads are you running?
Have you checked the rotors are warped by taking them to a brake shop? There could've been a manufacturing fault.

For my ST205 discs, when the slots get too full with brake dust, they start to grab on the pad, and this will also shake the wheel under braking, making to feel like the rotors are warped. I also have an issue with the pads being off the inside of the machined face, but this is caused by the rotors not being on a car they were meant for.

Can I get some rep now too? LOL

[Roundy]

the rotors are probably 2 months old, can't say how many km's they have done, at the very least probably 5000k
running Ferodo DS2500, not the kindest of pads, but not the harshest either.

the first set was definately warped, sent them back for warranty and they said it was mounted wrong (probably those rust spots not in line with the holes) They machined them and sent them back, so they are in my garage atm and hopefully going on tomorrow (unless what u are saying is right)

These rotors i haven't checked for warp no, it has been getting progressively worse since that trip to sydney, i will have a look during my lunch break, but i think the slots are still fairly deep.

You get rep if u are correct

Cheers
Nathan

[Hen]

Take a look at this article.

There is also a bunch more interesting brake stuff on the site

Hen

[Roundy]

hmms that is pretty interesting, maybe i will put the stockers on with the re-surfaced rotors and switch back to the Ferodo's for track days and what not!

however if what he says is correct i will still get the problem!

[allencr]

http://www.stoptech.com/tech_info/wp...rakedisk.shtml
I think this Carrol Smith piece is BS, even though I like & respect everything else of his I've ever read.

When a driver reports a vibration under hard braking, inexperienced crews, after checking for (and not finding) cracks often attribute the vibration to "warped discs". They then measure the disc thickness in various places, find significant variation and the diagnosis is cast in stone.

NO ONE is going to say that a variation in disk thickness is the same as warp/runout, and any variation in disk thickness will show up at any speed, not just hard braking at high speed.
The warp/runout is masked a low speeds by the caliper sliding on these single side calipers, and by the fluid movement between sides on a twin/opposing piston caliper. Heavy braking puts too much pressure on the slides for it to move easily and on the pistons in the twins, so that's when youl'll feel it in the pedal & steering.
If there was a thickness problem, it would show up at .5 KPH with a grab, release, grab or shudder feel through the pedal and shake the whole car.
I can be very wrong, and Carrol Smith died in 03.
http://en.wikipedia.org/wiki/Carroll_Smith