fireroasted

iTrader: (3)

For the gurus and track rats that have rebuilt their calipers any number of times can you help identify if the need to rebuild the piston seals and dust boots could be a cause for brake shudder?

I have a 9 and last year put on a set of DBA4000 rotors. Until them the stock rotors with proper fluid and DTC70 pads gave excellent braking performance on track (CA). Even my first track day with the DBA4000 gave shudder. I went back to my reseller, but they couldn't help. Installed the correct direction and hardly any wear, and then I tried several different pads, both new and used, as I have many sets. Same thing.

I did notice one of the dust boots is torn, and I think I learned from this forum that is likely due to not using the pad shims to protect against some heat. At the track I switch them so much that I stopped using the shims.

I am trying to figure out if I need to change rotors again, or if I actually need to rebuild the calipers.

Smike

iTrader: (8)

Have you had the rotors milled (turned)?

If there is a pad deposit or lateral run out - would make sense they you'd have it with different pads used. Pad deposit or LRO wont scrub away; just gets worse or not change.

Off chance you have some lateral run out. DBA 99% of the time is on top of their product....but like anything manufacturing; you could have a bad set.

Correct on dust boot. Not really from no shim or shim, but heat from tracking. Ti shims do a better job in heat management. I'd get new boots and inspect the piston for wear.

fireroasted

iTrader: (3)

thanks smike, I read a lot of your posts trying to research this in this forum.

I have not had them turned, and some of the info I read indicated that wasn't possible or recommended because of the slots. At the very least a special machine shop was needed. I just wasn't sure if that was a good troubleshooting step or not. I am willing to get them done, or bring them back to Stillen for inspection. The rotors or setup did this on the first track day of use unfortunately. Never had shuddering prior to using them.

Do you think the seal or dust boot could some how cause shudder, even if no leaking is apparent anywhere from the piston? Is it logical or possible the shudder could be caused by seals or boots rather than a rotor issue?

Smike

iTrader: (8)

Pad material deposit if it started at the track. Need to turn them. A good shop should be able to.

RevRevGone

What bedding procedure do you use?

I was having a problem with brake shudder with my stoptech rotors after 4 1/2 months, removed the pads sanded them and rebedded the pads and the shudder went away.

fireroasted

iTrader: (3)

I used the standard process on the yellow sheet that comes with the DBA in the box. Its the usual heat up slow partial, go faster, slow harder, then to nearly a complete stop, etc.

I do, or did switch pads frequently, which I am started to learn could cause to the pad build up and shudder. I am going to take them to a shop down the street and at the very least prove that they are or are not run out. Get the turned if needed.

The sanding idea sounds interesting and something worth getting good at between pad changes. I usually run a track set and a street set, because of the noise. Any track guys have opinions on that? I don't want to have to switch rotors for on off track too. That seems over complicated.

Below are some pics of the condition. They have very few miles and very few track days, maybe 3 or 4. You can see the weird 'gasing' at the end of the slots.

Here you can see both outside faces and how there is a trail of whatever at the slot exit.


These are the same rotors inside face.


Here is a close up of an inside section.

fireroasted

iTrader: (3)

Just to update. I had a shop turn them for 16 bucks a piece. It was just a regular lathe machine, and not a milling machine. Not sure how exact the process was, but they did wobble in the machine quite a bit. The shop let me inspect the process. very casual place.

Freeway Auto for any SoCal guys, at the 5 and Avery exit.

We'll see how they do and how long before they warp again. They didn't last long if all before this problem so I don't think I'll be getting 'expensive' rotors again unless I go all out for 2 piece. Might just go cheapo's, and then not be surprised at warpage.

Anyone know the minimum thickness for DBA 4000s that you can't turn them anymore?