11 replies to this topic

[ppridday]

Hi all.  I've just picked up a 1990 Spec Miata and have finished my first DE at NOLA with it.  I had an absolute blast and am getting ready for the May DE.  Now on to my issue.  I have been getting a bad shake on heavy braking.  It seems mostly through the pedal but also some through the steering wheel.  Also I get the tell tale clicking when driving through the pits and especially on left hand turns.  The first thing I though was of course the hub bearing.  It however doesn't appear loose or "clicky" when shaking the tire/wheel from top to bottom.  I now have the wheel and brake calipers off and when spinning the hub by hand I don't feel any notchy feeling to it.  I'm not sure if that would be something you could feel or not though  Another thing I have found is the brake pads have a very uneven wear to them.  Inners to outers, top to bottom and front to back.  I don't run the springs or anti-rattle clips so am wondering if that may cause it.  I will be taking the rotors somewhere tomorrow to check for warpage, but I would expect if they were it would not just be under heavy braking.  I am also going to pull the hubs to check the bearings of course.  Just need to get a 29mm socket tonight or tomorrow. 

 

Attached are a few pics of the pads.

 

If anyone can suggest anything else to look for I would be grateful....

 

Cheers,

 

Paul

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[FTodaro]

My first guess is warped rotors, If you had a hub going you would hear it before you felt it. I would jack up the front and check the play in the front wheels by grabbing at the 12 - 6 position and see if you have play. then slowly rotate the tire looking for grinding feeling.

 

but my bet i is the rotors.

[Ron Alan]

As frank said...rotors likely cause of big vibration under braking. No need to pull hubs to "check" them...it will be obvious in checking the wheel if there is a problem. Your "clicking" noise in the paddock may be your diff. I've heard the Mazdacomp make noise as the car turns slow...clutches slip...at least that is what I've thought it was??

[ppridday]

Thanks guys.  I'm going to try to bust out of work today to get the rotors checked.   I'm not at home so my dial indicator/mag base are all 1500 miles away.  I am going to have to hit a shop somewhere. 

 

Paul

[Bench Racer]

The tell tale clicking in the pits could be the pads floping around because of lack of springs and anti-rattle clips . Try a light foot on brake pedal when driving thru the pits while making the tell tale clicking. 

[davew]

Based on your pix and descri[ption you need calipers pads and rotors.

 

Pads are just worn out

Rotors are warped causing the vibration

Caliper slides and/or pistons are sticking, causing the uneven pad wear.

 

You will never go fast if you don't trust your brakes.

 

Do it right, do it once.

 

Dave

[ChrisA]

What kind of pads are you using?

[ppridday]

They are Carbotechs

[Brandon]

DaveW hit the nail on the head - full brake "wear parts" rebuild (pads, rotors, springs/clips, pins/seals) is in order.

 

During my first year of racing I inadvertently put too much caliper grease in/on the pin/seal and what would happen under hard braking is you'd get a shimmy/pulsation through the pedal & steering wheel.

Had the track-side support give it spin for a few laps during the test day and that's immediately where they went to first - checked how much grease on the caliper pins/sliders, squeezed a (relatively) large amount out (I'd say about 50% of what I had put into the holes) and it was no longer a "braking monster" going into turn 1.

 

Nutshell:

1. Uneven pad wear indicates the pad is not contacting the rotor square.  Usually an indication of bent/loose caliper pin (if you're running the springs/clips), but if you're not running the clips then there's your problem.  This also will cause hot spots to form on the rotor which is why replacing those is a good measure as well; plus they're cheap as hell considering ($20/ea for fronts?)

2. Always use the springs/clips and make sure your seals (what are installed into/onto the caliper) are pliable and not seeping any grease.

3. Hubs will generally exhibit movement perpendicular to rotation (grab the left/right sides of the wheel & check for play) or growl/noise under constant rotation if they are bad.  If you don't hear or see either of these two then no need to break out the 29mm socket.

4. At no time have I heard of a hub "clicking" but I've never driven a car w/a Mazdacomp differential to know what that sounds like.

 

Order the front & rear axle brake rebuild package from MSP.  These are a "single axle" kit that contains parts for each side of either axle (1x front kit, 1x rear kit).  This kit will include the springs, clips, & seals you would need to restore your calipers.  If you don't have an account with Mazdaspeed Motorsports (the factory-support group in CA), definitely get in on that.  Seriously good pricing relative to retail.

 

Good luck!

Brandon

[ppridday]

All good advice and that is what I am going for.  Full rebuild all around.  Thanks for the heads up on the MSP as well. 

 

Cheers,

 

Paul

[ChrisA]

PM sent

[RazerX]

The clicking is your pads.  If the assumption of the warped rotors is true, what is happening is rotor is dragging the pad up to the top of area (given you have no clips or sprints) and then once the rotor turns a little more warped area moves on and the pads drop back to the bottom up and down of the pad hitting the top then dropping is the clicking sound.