16 replies to this topic

[jrhenson]

Hey all,

 

I have a 1.6 I built into an ITA car. I need some help diagnosing an issue with the front brakes.

 

New calipers, rotors, pads (Hawk DTC-60/30) and stainless lines all around. I have only done one track day at Nelson and a wet weekend at MId-Ohio. I didn't notice anything at Nelson but during the practice day at MO, another driver (Frank Todaro) noticed a lot of sparking coming off the fronts. Everything looked ok when I pulled it apart and Frank said that the sparking seemed to have gone away after a few more sessions. I will say that the brakes felt inconsistent over the course of the weekend, but I couldn't pinpoint any issue.

 

My plan was to replace everything at each corner before going out again. When I pulled the rears, the calipers were as clean as the day I put them on and the pads and rotors showed very little wear if any. The fronts however show severe wear on both the pads and rotors. The pads are almost gone and both rotors have worn a mm deep or more on both sides. I was thinking a stuck caliper before I pulled them off, but both sides?

 

I need to try and diagnose the actual problem before putting all of this back together again, but I am not sure what to dig into. I have verified that the pads are the correct part number and I got the rotors direct from Mazda. I have attached pics of the caliper, pads and rotors from the left front. What do I need to look at before installing all the new stuff? 

 

Thanks for the help.

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[LarryKing]

Did you grease the edges of the pads where they ride on the brackets? Pads should not wear that fast - they appear to be binding. 

 

Personal choice - I never liked Hawk pads - prefer G-Lock.

[Bench Racer]

"When I pulled the rears, the calipers were as clean as the day I put them on and the pads and rotors showed very little wear if any."

 

Your comment of "very little wear if any" could be an indicator there is minimal brake fluid pressure to the rear brakes?

 

The master cylinder has a separate piston/fluid for the front and rear calipers.

 

Was the brake system correctly bleed?

 

Is the OEM proportioning valve in place or did someone install an adjustable proportioning valve?

[jrhenson]

Thanks for the responses so far guys.

 

Did you grease the edges of the pads where they ride on the brackets? Pads should not wear that fast - they appear to be binding. 

 

Personal choice - I never liked Hawk pads - prefer G-Lock.

I did. Another racer suggested a pad problem. I have always used Hawk and never had an issue like this. However, I am installing Carbotech pads this time around.

 

"When I pulled the rears, the calipers were as clean as the day I put them on and the pads and rotors showed very little wear if any."

 

Your comment of "very little wear if any" could be an indicator there is minimal brake fluid pressure to the rear brakes?

 

The master cylinder has a separate piston/fluid for the front and rear calipers.

 

Was the brake system correctly bleed?

 

Is the OEM proportioning valve in place or did someone install an adjustable proportioning valve?

Minimal rear pressure is certainly what it looks like due to the rears not wearing compared to the front. The separate systems in the master cylinder would help explain the rears, I am not sure how that would cause the front issue though. I have been bleeding brakes the same way since I was in autoshop in high school. I am fairly certain these were done right (you never know though...). The OEM unit is still in place. I am thinking about just replacing the master and proportioning valve and seeing if that rectifies the issue. Still, I am looking for some confirmation that I am on the right track doing that.

 

Thanks

[Alberto]

I ran the Hawk DTC60s for years on my 1.6.

Twice over those years I experienced a similar issue where new Hawk pads were... crap?  defective?

The smell was horrid as well with those defective pads.

Replacing the defective pads solved the issue.

 

Did you have any issues with your braking system before this event?  If not, then there is probably nothing wrong with your braking system other than a bad set of pads.  

[Bench Racer]

 However, I am installing Carbotech pads this time around. Running different brand pads on rotors that were used for different brand pad can cause brake issues.

 

Minimal rear pressure is certainly what it looks like due to the rears not wearing compared to the front.  Check the fluid pressure to the rears. Install a pressure gauge # 1 in the rear line between the master cylinder and the proportioning valve. Install a second pressure gauge # 2 in the rear line between the proportioning valve and the rear caliper. When you read up to 427 psi in gauge # 1 you should read 427 psi in gauge # 2. When you read 995 psi in gauge # 1 you should read 597 psi in gauge # 2. If you do not view these numbers or close to these numbers take the proportioning valve apart/inspect/clean and repeat test or replace the proportioning valve. 

 

The separate systems in the master cylinder would help explain the rears, Open this link to view separate rear piston (called primary) and front piston (called secondary) master cylinder. Scroll to page 9:7 for illustration.  

https://books.google...ylinder&f=false

 

I am not sure how that would cause the front issue though. You could be pressing harder on the brake pedal to get slowed down because the fronts are doing all the work.

 

I have been bleeding brakes the same way since I was in auto shop in high school. I am fairly certain these were done right (you never know though...). The OEM unit is still in place. From my experiences bleeding Miata brakes (Spec Miata). The right front brake line travels upward/attached to firewall from the master cylinder to the caliper. Air gets caught in that upward section and is hard to bleed out. When bleeding brakes the rear is done first and because of the dual separate pistons the brake pedal will get hard but with a low pedal. The low hard pedal from bleed rear brakes keeps from getting a full stroke when bleeding the front brakes, hard to move air bubbles and bleed air out. Get some help bleeding the front brakes. A pedal pusher, a front bleeder and someone to bleed the rear simo with the front bleeder to get a full brake pedal stroke. I understand bleeding may not be an issue, but this info is tried and works.  

 

Still, I am looking for some confirmation that I am on the right track doing that. How about some support  site LURKERS.

[jrhenson]

 

 However, I am installing Carbotech pads this time around. Running different brand pads on rotors that were used for different brand pad can cause brake issues.

 

Minimal rear pressure is certainly what it looks like due to the rears not wearing compared to the front.  Check the fluid pressure to the rears. Install a pressure gauge # 1 in the rear line between the master cylinder and the proportioning valve. Install a second pressure gauge # 2 in the rear line between the proportioning valve and the rear caliper. When you read up to 427 psi in gauge # 1 you should read 427 psi in gauge # 2. When you read 995 psi in gauge # 1 you should read 597 psi in gauge # 2. If you do not view these numbers or close to these numbers take the proportioning valve apart/inspect/clean and repeat test or replace the proportioning valve. 

 

The separate systems in the master cylinder would help explain the rears, Open this link to view separate rear piston (called primary) and front piston (called secondary) master cylinder. Scroll to page 9:7 for illustration.  

https://books.google...ylinder&f=false

 

I am not sure how that would cause the front issue though. You could be pressing harder on the brake pedal to get slowed down because the fronts are doing all the work.

 

I have been bleeding brakes the same way since I was in auto shop in high school. I am fairly certain these were done right (you never know though...). The OEM unit is still in place. From my experiences bleeding Miata brakes (Spec Miata). The right front brake line travels upward/attached to firewall from the master cylinder to the caliper. Air gets caught in that upward section and is hard to bleed out. When bleeding brakes the rear is done first and because of the dual separate pistons the brake pedal will get hard but with a low pedal. The low hard pedal from bleed rear brakes keeps from getting a full stroke when bleeding the front brakes, hard to move air bubbles and bleed air out. Get some help bleeding the front brakes. A pedal pusher, a front bleeder and someone to bleed the rear simo with the front bleeder to get a full brake pedal stroke. I understand bleeding may not be an issue, but this info is tried and works.  

 

Still, I am looking for some confirmation that I am on the right track doing that. How about some support  site LURKERS.

 

Thanks Bench. I'll work on that. It does help explain why I have had difficulty bleeding the fronts well in the past. I bought a vacuum bleeder so that may help as well. I'd better buy some more fluid..

[LarryKing]

Guthrie loan me his power bleeder once. It's the tits! If you have the means I highly recommend one. I never have much luck with a MityVac, it seems to suck in air around the bleeder threads.

 

Nice touch with the blueish text Bench, you're artistic endeavors do not go unnoticed. (Little on the purple side for my taste.)

[Steve Scheifler]

Bleeding: Start on the LR and go counterclockwise around the car, but FINSH with the LR again. I’ve always assumed it’s related to the stock proportioning valve but finishing on a front often leaves a softer pedal. I’ve bled brakes on NAs more times than I care to count and NBs enough, but never had a problem with trapped air in lines.

On the pad wear I’m assuming you know the car and track and what to expect, but at some tracks I could destroy a set of Carbotechs or Hawk Blues during a single track day, not sure about the DTCs. 1/2-1/3 of the wear in back is not surprising but yours sounds less, so yes, consider the proportioning valve and the possibility of defective pads. I take it that the rear pads are softer than the fronts. I’ve never found that to work well in the 1.6 (with the correct prop valve) or in our limited time in NBs, in fact I hated it. Get more bite in back, make them do some work. If you aren’t locking the rears first under sustained threshold braking then you don’t have too much rear pad. Get closer to that then back off if needed, and possibly at just certain tracks. We ran same compound all around almost everywhere and when super quick guys drove our cars they liked the brakes better than theirs. I’m constantly perplexed by the range of compounds used by others; there’s always a limit to “what you like” being best.

As noted, don’t change pad brands without turning or at least sanding the rotors clean, unless you are switching to Hawk Blues in which case just drag the brakes a bit cold and they’ll make like pinwheel fireworks as they grind off a layer of iron with the old pad material. (Are you sure you didn’t have Blues up front? The sparks, until hot, is their trademark.)

And what about bedding/heat-cycling? Did you play nice and faithfully follow the recommended procedure? If it sounds like a BS PIA, particularly at times when track time is hard to get and expensive, you are right. Switch to Cobalt Friction and never worry about that nonsense again.

OK, that’s my rant on brakes, do with it what you will.

[Bench Racer]

 

Nice touch with the blueish text Bench, you're artistic endeavors do not go unnoticed. (Little on the purple side for my taste.)

Red just looks all wrong.

 

jrhenson, please keep us informed with your progress.

[jrhenson]

Bleeding: Start on the LR and go counterclockwise around the car, but FINSH with the LR again. I’ve always assumed it’s related to the stock proportioning valve but finishing on a front often leaves a softer pedal. I’ve bled brakes on NAs more times than I care to count and NBs enough, but never had a problem with trapped air in lines.

On the pad wear I’m assuming you know the car and track and what to expect, but at some tracks I could destroy a set of Carbotechs or Hawk Blues during a single track day, not sure about the DTCs. 1/2-1/3 of the wear in back is not surprising but yours sounds less, so yes, consider the proportioning valve and the possibility of defective pads. I take it that the rear pads are softer than the fronts. I’ve never found that to work well in the 1.6 (with the correct prop valve) or in our limited time in NBs, in fact I hated it. Get more bite in back, make them do some work. If you aren’t locking the rears first under sustained threshold braking then you don’t have too much rear pad. Get closer to that then back off if needed, and possibly at just certain tracks. We ran same compound all around almost everywhere and when super quick guys drove our cars they liked the brakes better than theirs. I’m constantly perplexed by the range of compounds used by others; there’s always a limit to “what you like” being best.

As noted, don’t change pad brands without turning or at least sanding the rotors clean, unless you are switching to Hawk Blues in which case just drag the brakes a bit cold and they’ll make like pinwheel fireworks as they grind off a layer of iron with the old pad material. (Are you sure you didn’t have Blues up front? The sparks, until hot, is their trademark.)

And what about bedding/heat-cycling? Did you play nice and faithfully follow the recommended procedure? If it sounds like a BS PIA, particularly at times when track time is hard to get and expensive, you are right. Switch to Cobalt Friction and never worry about that nonsense again.

OK, that’s my rant on brakes, do with it what you will.

 

Nice thought on the second bleed LR, never did that. Otherwise, I follow the pattern.

 

I have always used the Hawks one grade down in the rear, i feel more stable than the same pads all around. At least when I first started racing. Maybe I'll try that next set.

 

One of the things I double checked during the teardown was the pad part number on the back of the pads; DTC60 and correct fitment part number.

 

I'm going with Carbotech XP10 front and XP8 rear and I had them pre-bedded before they shipped them. New rotors of course. These rotors are so inexpensive that I typically just replace them with the pads, especially if changing compounds. In this case, I did bed them in per the procedure prior to heading to the track.

 

I agree, I am leaning towards the master cylinder and/or prop valve.

 

I'll try to remember to come back and give a final result. I know that is frustrating when these "HELP" posts never get concluded...

 

Thanks for the advice guys. Anything else someone may have to add is certainly still helpful as well!

[Steve Scheifler]

Nice thought on the second bleed LR, never did that. Otherwise, I follow the pattern.

I have always used the Hawks one grade down in the rear, i feel more stable than the same pads all around. At least when I first started racing. Maybe I'll try that next set.

One of the things I double checked during the teardown was the pad part number on the back of the pads; DTC60 and correct fitment part number.

I'm going with Carbotech XP10 front and XP8 rear and I had them pre-bedded before they shipped them. New rotors of course. These rotors are so inexpensive that I typically just replace them with the pads, especially if changing compounds. In this case, I did bed them in per the procedure prior to heading to the track.

I agree, I am leaning towards the master cylinder and/or prop valve.

I'll try to remember to come back and give a final result. I know that is frustrating when these "HELP" posts never get concluded...

Thanks for the advice guys. Anything else someone may have to add is certainly still helpful as well!

Well, they may be pre-heat cycled but they can’t be pre-bedded unless they are sending you rotors as well. There are at least three things going on during the traditional process and two of them require the pads against the rotors that will be run. Hopefully their fresh-baked oven process really does relieve you of one responsibility but you still need to mate pad to rotor surface and transfer some material to it.

[Alberto]

I have always used the Hawks one grade down in the rear, i feel more stable than the same pads all around. At least when I first started racing. Maybe I'll try that next set.

 

I'm going with Carbotech XP10 front and XP8 rear and I had them pre-bedded before they shipped them. 

 

I started out using the 60s f and r.  Braking was great but there were a couple of corners that I couldn't trail brake well.  Going to 30s in the rear helped a little.  Going to Carbotechs made it a lot easier to trail brake at those turns.  

 

FYI The Carbotech 10/8 have less bite than the DTC60/30.  I needed to use more pressure.  Eventually I got used to it.  Bedding was also difficult.  Pre-bedding just means that they were de-gassed iirc.  You still need to bed them to the rotors.  I called them to clarify what that meant when I first switched over.  Call them if you want to dig deeper into that topic.  They were really helpful.

 

Next time around I'm going a level higher to 12/10.  

 

Hope that helps.

[jrhenson]

Well, they may be pre-heat cycled but they can’t be pre-bedded unless they are sending you rotors as well. There are at least three things going on during the traditional process and two of them require the pads against the rotors that will be run. Hopefully their fresh-baked oven process really does relieve you of one responsibility but you still need to mate pad to rotor surface and transfer some material to it.

 

I spent some time with them on the phone and he explained that their process is more about the pads and that the bedding to the rotor is a quick transfer process once the car is on the ground. I for sure do my due diligence when it comes to bedding.

 

I started out using the 60s f and r.  Braking was great but there were a couple of corners that I couldn't trail brake well.  Going to 30s in the rear helped a little.  Going to Carbotechs made it a lot easier to trail brake at those turns.  

 

FYI The Carbotech 10/8 have less bite than the DTC60/30.  I needed to use more pressure.  Eventually I got used to it.  Bedding was also difficult.  Pre-bedding just means that they were de-gassed iirc.  You still need to bed them to the rotors.  I called them to clarify what that meant when I first switched over.  Call them if you want to dig deeper into that topic.  They were really helpful.

 

Next time around I'm going a level higher to 12/10.  

 

Hope that helps.

I am pretty heavy on the brakes already and I trail brake a lot (probably a little too much...). I am hoping that the change puts the braking capability right where I need it. I will make the level change to 12/10 if I need more.

 

Thanks guys!

[Nathan Pring]

My first and last set of Hawk DTCs started crumbling and cracking after 2 rounds in my 1.6 SM.  I moved over to G-LOCs and never looked back.

[jrhenson]

Best Answer

Well, all is well.

 

I replaced all four calipers, the master cylinder and the prop valve. New carbotech pads and ctek rotors all around. Performed a good bleed session after ensuring all old fluid was removed.

 

The braking felt great! No pulling at all, very smooth and confidence inspiring. The Carbotechs are not as grabby as the Hawk's were, but they were there when I needed them to be all weekend.

 

I wish I knew exactly what the issue was, but it is no longer there so...

 

I'll tear into the master cylinder and prop valve and see what I can figure out and then the calipers if nothing is evident there.

 

Thanks for all the help guys!!

[JNJ]

The NB like DTC 60 front and DTC 30 rears.  the rear pads do overheat a bit.  The NA DTC 60 fronts and DTC 30 rear, the rear pads over heat leaving the front to do all the work.  I put heat paint on hte rear pads and they wear way past the heat range, the factory paint was white ash.  Using DTC 60 front and rear made the car stop much better and the front pad life much increased.