Snox801

Ok so series 1 car I bought. Replaced all the brakes with ebc rotors and pads. All pins lined and free. Drove great on the road no issues. Let a friends wife drive it for an open track day in beginner class. She started getting a bad vibration under breaking.
I took it out today and nothing going to work. Coming home nothing till I ran it up to high speeds and when slowing down hard it started then got worse. Then even did it at 15mph when applying brakes.
Drove easy for 10 min and next stop fine. Did seem to have a slight vibration down the highway at 90ish
nothing on the brakes seems froze bound or in bad shape. Was about to order all new brakes thinking she just cooked them but when cold they are fine even normal drive and stoping on off ramps is normal but when you really stand on them it starts then stays for a bit. It’s got 98k original miles. So I was just gonna throw some bearing and keep going till it goes away.
But figured it ask the experts first.
Thanks

Loki

iTrader: (1)

Did you bed in the pads before track time? It sounds like inconsistent transfer layer to me. Or what some mechanics might decide is a warped rotor. You might try rebedding them.

Was the track day in wet weather? Is it a brake-heavy track? Did the user warm up the brakes on the warm up lap before stomping?

Do pad traces on the rotor face or wear of the pad itself tell you anything?

Snox801

So I did the break in by daily driving for a few days. Although now you mention it I didn’t do any heavy breaking until that day. Thinking she wouldn’t be to bad on them for the first few sessions. Dry weather and it lasted all day Saturday for her and 3/4 the day Sunday. Then started. I’m not seeing anything on the rotors that would tell me anything. I may pull them apart to see if the pads give me any feedback.
How would one start over. I was gonna order all new but doing pads and rotors front and back gets pricey if that’s not the issues.
I have the same rotors with cobalt friction pads and I brake hard and zero warp yet on mine.
It is indeed a brake heavy track and she had traction and dcs on the whole time probably working the brakes a bit more than normal.

Loki

iTrader: (1)

It's totally fixable, just do a proper bedin procedure and see how it is after that. If they're the high end compound (red stuff I think?), daily driving doesn't help them any. Think of it like trying to butter a pan. It doesn't go well if the butter is frozen and you end up with dabs of butter some places and mostly none anywhere else.

Snox801

Awsome nice to know. Thanks.
I have the blue stuff raceway pads. They are supposed to be the toughest streetable pads that can double for track duty. I’ll try a proper bed I. Today.
I’ll let you know. Trying to keep this car as a fun summer driver for her and an occasional track toy for her and freinds to try and learn in. This winter it’s going to get all new suspension, motor done by chips, and tuned to raise rev limit.
I’ll let you know how it goes.
Thanks again.
Never had this happen before and I’ve always bed them but ebc said no hard stops for the first so many miles so I was just driving. I knew I should have done what I know to do.

Snox801

Ok so I went out and did the proper break in. Started with no shake and felt great. Then started to get bad again. lol nice it started it seemed like a possible caliper stuck slightly but not enough to tell which one.
I’m gonna try and see if I can see any temp difference on rotor after trying it again.
Boy I hate these situations of just take a stab at an issue. Eventually I’ll find it but may require new calipers and what not. Also wouldn’t be bad I bet to do bearings as it’s got 98k and I’m sure they won’t like the new driving at high speeds and the heat. But hopefully I can find the caliper or other issues and just replace that instead of all of them to find the one.

Loki

iTrader: (1)

A stuck caliper would pull to one side though, not vibrate (usually). Hmm. The fact that it comes on after time tells me it's heat related... and there isn't much heat-sensitive in there other than the pad/rotor surface. Maybe have the rotors turned and start over? That'll clear any old uneven transfer layer. A bit of sandpaper might even do it.
​​
I'd also leave the bearings alone if they're ok. There have been stories here of new replacement bearings failing after one track day. Whatever Mazda used at the factory seems to last longest.

Snox801

That is exactly what I was thinking. I’ve never had this. Very strange.
But I agree I will only use Mazda hubs after some of those stories.
After it starts I notice it seems to have some kind of drag as it’s noticeable as you cost like something is dragging on the car. Hence maybe a caliper but nothing like a normal caliper failure.
Im thinking when it happens hit each rotor with a temp gauge and see if I can notice a difference from one side to the other. That would at least narrow it down to which one is doing it.

Snox801

DBAUSA | BRAKE SHUDDER WHEN HOT - SCALE

ran across this and thought maybe? But I cleaned them well with wire wheel and cleaner. Didn’t notice anything odd. Plus I’m still getting the slight drag feeling like it’s sticking but maybe because part of the slight warp.
Also noticed that ebc says to brake in rotors for the first 1k miles gently but that is opposite of the pad bedding. Yellow stuff has a needing compound that helps but the blues don’t. Maybe that’s what going on.
Still at a loss. Brought it to a very well known local shop to see what they said. No real answer either. They just want to start replacing parts which might not be the worst thing. Just stinks cause that was a short lived set of rotors and pads. Had about 1.5 tanks of daily and then 2 days of hpde track days in beginner with first time female driver. I’m not shocked if they are warped just shocked they drive fine till aggressive braking then get really bad and even vibrates while driving with brakes not being used. Goes away when it’s cooled down.

Loki

iTrader: (1)

Maybe... since it's only been driven a bit, if there is debris at the rotor mounting surface, maybe it can be cleaned and the rotors saved? Do you have a straight edge and feeler gauges to check if the rotor is true?

Does the effect just vibrate the car, or do you feel the braking force oscillate as well? What if you creep forward while the brakes are hot, do you feel periodic drag on the brakes?

I guess it could be warped but I'm still skeptical and still think its a transfer layer problem. When the pad and transfer layer are hot, you should see higher friction than when they're cold, so my theory/perception is that these are high temp enough pads that the pad glides over the transfer layer when cold, so no vibration, but when hot areas with more/any transfer layer will grip more giving you the effect you have. I can't really think of a test that you haven't already tried that would differentiate this from a truly warped rotor... except measuring the flatness of the rotor or just machining it flat and starting over.

TeamRX8

iTrader: (25)

it's just surface buildup of material transferring from the EBC pads; which I tried plenty in the past and frankly will never use again.

as with any kind of poo, flush that hot-mess down the loo ...
.
.

TeamRX8

iTrader: (25)

for the money these semi-metallic Centric pads are pretty decent, no experience with the other set and I stopped using dual-purpose pads a long time ago

Snox801

Good to know I’ll grab a new pair of pads and try those before I go spending a bunch of money

kevink0000

FWIW

I had the same issue on a BMW with EBC pads, never got rid of vibration. I used EBC on bikes with no problem for years, so was comfortable buying them.

Eventually started using Powerstops about 14-15 years ago, now use them on everything. Not sure about race use pads, but for the street they are great. Best pads I have ever used. Zero dust, and very easy on the rotors.

Snox801

ive had great luck with ebc so far but I’m taking. Advise and trying something else. I’ve also had great luck with powerstop. But been running cobalt friction on my track cars. Thought I’d try these duel purpose for my wife’s track as she’s not that hard in it so I’m gonna order some new pads and hope it cleans the surface.
Just still can’t figure out why it is perfectly fine till you get in them hard then they shake.

Loki

iTrader: (1)

Because friction for high performance pads increases with temperature. You're hitting areas of high and low friction because the transfer layer is uneven and when they're up to temp, high friction is much higher.

If you're going to mess around with pads, make sure they're compatible between each other. Some pads (Cobalt is one I think?) don't play nice with transfer layers from other pads, you need to resurface the disk to bed them in properly.