Rotational Grinding Noise, left rear wheel
 

I've got an 04, MT. Changed the brake pads a month ago, and last week started getting a grinding noise from the left rear wheel.

The noise is in time with wheel rotation, becomes inaudible above 20-25 mph, and goes away when I brake.

I pulled the wheel and found no gap between the pads and rotor, and took a lot of force rotating the caliper off of the wheel. Pulled the caliper, removed the piston, which was in surprisingly good shape, lubed, reassembled, re-installed...twice...no change.

The piston is compressed into the caliper enough that the caliper slides easily back over the rotor.

I checked the parking brake adjustment nut under the center console, and loosened it, but no change.

I've seen reference to adjusting the parking brake at the caliper, but can't find a procedure to actually do it. Is there an adjustment other than the under console nut?

After my last attempt, I put the wheel back on, left the car up on jack-stands and listened/observed as my wife ran the engine in gear up to about 2k rpm. There is still a very faint grinding sound, but also an occasional "thunk" (not every rotation, maybe every 10 seconds or so).

I'm starting to think wheel bearing.

Any other things to check?

First thing thst came to mind is your caliper slide pins are siezed up. I would take them out, inspect and regrease them. My second thought is your rotor is some how not flush. I would take off the rotor and then make sure everything goes back together properly. Good luck.

Make sure you retract the pistons properly and that you align the pin and the groove properly. Once I had a problem with the parking brakemechanism binding from not retracting it completely...and it acted like the brake was dragging. I removed the pads and retracted the piston completely and it worked correctly after that

Does anyone know the brake master cylinder BORE size?

Thanks for all the info. My '8 needs new front pads. I only autocross occasionally and the '8s brakes are certainly not my limiting factor :) So I'll stick with OEM pads.

Thanks again!
Chris

^ The OEM pads are really very good. Mazda did a lot of things right with this car, and the brake system is one of those things.

I AutoX my car at least once a month year-round, drive it on weekends, occasionally drive it to work and back, and have now done 2 track days. The OEM brakes have performed very well for me at my level of skill. The track days did force a flush and fill afterwards, but that is to be expected. I only experienced a bit of fade at the end of each day (2nd to last lap both times). New fluid and re-bedding brought everything back in line with the OEM pads and rotors both times.

I have only pondered track pads this month since I have a track day at Eagle's Canyon next month, which features very long straights followed by 90 degree turns. I am going to incrementally upgrade to Hawk HP+ pads on stock rotors with Motul 600 this weekend in preparation for ECR next month.

This thread has been tremendously helpful to me, and I look forward to applying more and more if it as I progress as a driver. Thanks!

Glad to hear you're upgrading the fluid. Once you have gotten to the point of boiling fluid it is time to upgrade :)

Keep an eye on your HP+ pads and rotors while tracking. It was probably the particular track, but the track was too much for my HP+es. I absolutely loved them, but they started to leave material on my rotors (check page 7 of this thread.) Also keep an eye on the thickness they went quick. Good luck and have fun!

Well...

Eagles Canyon was fun. It really was. And, it taught me quite a bit about brakes--or at least how various components respond to heat.

I upgraded my brakes to Hawk HP Plus pads and ATE Type 200 DOT 4 fluid (could not find Motul 600 locally in my time frame). When I installed the pads, I used the OEM shims and applied a light film of the included brake grease between the shims and pads and shims and pistons like I normally do when replacing brake pads. The heat generated at EC was so intense, it turned the grease to carbon and burned nearly all the paint off the pads and shims.

The friction material on the pads held up (to my surprise), as did the rotors, although I fear that if I push it any harder next time, I may need higher temperature pads.

So, here I am waiting for my Mazda dealer's parts department to receive shim/clip and caliper rebuild kits so I can rebuild my brakes again.

A few obvious questions (yes, I have done lots of searching):

1. Do those of you who track your cars use shims?
2. Do you bother to use brake grease at the track? Which grease? Is the Permatex 3,000 degree stuff any good?
3. Should I be thinking about a BBK to help deal with the heat? Is there a known good one?

I know after my grease burned up, my brakes when from a high pitched singing sound to sounding like a train whistle and a fog horn had an alien love child.

For now, the plan is to rebuild the brakes with OEM parts and drive it that way around town and at autoX. I will put whatever track pads on a few days before track day, potentially with aftermarket shims (Centric or similar) and potentially with higher temp grease until I find a good formula.

Cheers!

Hello, I think it'll be beneficial to upgrade your pads to a full track pad. I remove the shims when I put on the track pads, especially the front shims, since the two materials start to seperate and I've needed to repurchase them. Also they will howl with or without the shims anyway. I don't use the grease with my track pads.

I had problems with the HP pads the last time I used them. I over heated them. There are pictures and a description on the previous page. Now I am using Hawk DTC60 pads and they are working good for me.

^ That may well be where I end up too.

I have ordered all new OEM shims/hardware for my OEM pads. That setup will permenantly pair with my OEM wheels and street tires.

My track wheels and tires will pair with the Hawk Pads I have until I wear them out or experience problems with them. The next track day I attend (might be the 31st at Motorsport Ranch), I will try the Hawk pads with generic Centric shims and 3,000 degree racing grease. I don't want to go completely without shims if I don't have to, because shims do serve the purposes of heat transfer and torsion control in addition to helping to quiet things down. If that setup doesn't work, I will keep removing variables until I am down to no shims and no grease.

I was hoping it would be realistic to run a dual purpose setup and not have to change pads before and after every track day, but that seems to have been a pipe dream.

Anyone have any Stoptechs? I heard they are great, bite good and don't melt your calipers like HP+. Also heard they are quiet, but any experience with them on the 8??

Here is an excellent post on brake fluid, which includes a chart that shows the verified specs of a few dozen different brake fluids.

https://www.lelandwest.com/brake-flu...ow=1&SF=4&ST=2

Brake Question
 

Just bought to sell a 2004 RX8... Brakes went to the floor.. what is the big unit all the lines go into? ABS? Need to sell it.. But, need brakes.. E Brake is good Hear a woosh from the big unit... without the engine running... any ideas?

Sounds like the brake booster.
You could get lucky and have a bad check valve, might want to look at that.

Where is the check valve?

The "whoosh" sound is coming from the unit that all the lines go into,,, down line from the master cyl and booster.. I am old school and not sure what that thing is... has a electrtic motor on it too..

The whooshing is not coming from the booster?
I'm not sure if that's the proportional valve or ABS.
Only whooshing sound I've heard is from the check valve in the booster, or the booster itself.
Usually the pedal is hard if it's the valve, and goes to the floor if it's the booster.
I'll take a look at mine later to see what you're talking about.

One little thing I want to mention about the original post: it is actually possible to switch between a glycol-based and silicone-based fluid. You should never mix them, however, so flushing thoroughly (3-4 times) with an appropriate solvent is necessary before bleeding in the new fluid. I've used denatured alcohol in the past with good results, it won't affect the seals as long as they aren't rubber (modern brake systems use a nylon-based material).

Heavy vibration during braking at 50mph and below
 

Looking for a little insight on what to do. Brought my 2008 Rx-8 to the local dealership to get my tranny replaced as well as my brakes and rotors. They said nothing about my brakes or rotors, so i thought Id ask everyone else sincethey are of no help and you guys/gals are awesome. Thanks!





2008 Rx8 40th editio

What kind of insight?
They are not hard to do if you have any mechanical aptitude, and you can save a lot of $$.

Does anyone have the Mazda part numbers for the front rotors, caliper, master cylinder, and rear proportioning valve from the base AT model? I am considering the feasibility of converting to the smaller brakes due to the difficulty in finding gravel tires in 18" wheel sizes.

^ Not intending to be a jerk, but why would anyone have that?

All of your questions are answered here:

https://parts.com/

Jim Ellis Mazda Parts' website is your friend...
http://www.jimellismazdaparts.com/default.aspx

2005 Mazda RX-8 FRONT BRAKE MECHANISMS

2005 Mazda RX-8 REAR BRAKE MECHANISMS

2005 Mazda RX-8 BRAKE MASTER CYLINDER & POWER BRAKE

How about in 17"? Many 17" rims will fit over the sport brakes.

SCCARallycross

Gravel tires are mostly in 15" sizes and below, with a few vendors offering them in 16" sizes (though the selection drops off a cliff). I am also attempting to find out if there are any 15" wheels that can accommodate the base AT brakes; but, if no such wheels exist, then I will have to settle for 16" wheels and the meager choices of gravel tires that will go on them. I am getting my 2004 set up for it and will already be in the PR (prepared, rear wheel drive) class, as I had already switched to long stroke coil-overs from FlatoutSuspension, so I could stop grinding my car in the rear on the speed bumps in the condo where I live (crossing at extreme angles doesn't work as the worst ones are at narrow choke points in the driveway).

FYI, I do not think you were being a jerk. It was an entirely reasonable question.