12 replies to this topic

[Michael Cola]

Hey Guys,

I've been using my 91 Miata for HPDE's for the last couple years (I'm in Group 3 or 4 depending on the track) with plans on going to SM eventually.

I have rebuilt the stock brake system on the car using reman'd front calipers and stock rear calipers with the carbotech XP10/XP8 pad combo. I also added front brake ducts to the car using trackspeed engineering backing plates before the last track weekend.

 

As I've gotten faster, I've noticed that the seals on the reman front calipers (el-cheapo Advance Auto Parts "Fenco" brand with a lifetime warranty) have tended to crack/deform from the heat of track use. This has led me to have to replace the calipers with replacement reman'd units after the last two track weekends. It doesn't sound like this is a normal thing for the SM community, but I could be wrong. I'm wondering if the seals in these reman's are just low quality...I'm considering exchanging for another pair of remans (so that they're cleaned up) and then rebuilding them with better seals.

 

I'm sure that I can improve my braking and compress my brake zones more, which can help with putting less heat into the system, but I don't think I'm really long on the pedal. All my instructors have been pleased with my braking technique (although none of them have been SM drivers....).

 

Also, I've heard of having to re-lube the caliper bolts after each track day to make sure that the caliper slides properly. I know mine need it after a weekend because the slide-bolts become pretty gummed up (I'm using Permatex Ultra Disc Brake Caliper Lube). This isn't a huge deal to do, but I'm wondering if there's anything better out there.

 

So my questions are:

1) How long do your caliper seals last you and what brand are you using?

(Do OEM Mazda seals or another brand of rebuild kit seals hold up better? I see that the guys at AdvancedAutosports sell the Raybestos ones...)

2) Is there a better higher-temp caliper lube that you guys use?

 

Thanks!

-Mike

[Keith Andrews]

Disclaimer: I'm not an engineer or pro, just a driver.  

 

I've only used Mazda OEM brake rubber kits and hardware.  I've been using a CRC lube that I'm sure is similar to what you are using.  I've used the same bake pads you are using for 4 seasons.

 

You say the seals crack and you get new calipers.  Are they leaking?  Do you mean the piston boot or the piston seal?  To see the seal you have to remove the piston from the caliper.  I'm not sure why you would replace a caliper and not just put new rubber on it.  Do your pads wear relatively even?  I'm just trying to understand what is going on.       

 

 

Q1- OEM, Fronts 8 race weekends usually more.  The rears annually 12+ race weekends. 

Q2- Like I said I use a CRC synthetic grease but I have never had issues with other lubes. 

[tom1977]

I use a permatex caliper lube that has ceramic in it. (comes in an expensive purple bottle)   I have had no problems on both the miata and my other racecar for the past several years. I re lube upon every pad change just out of habit.  As far as seals, I just rebuilt the miata front and rear at the beginning of this year with some rock auto rebuild kits.  I will keep an eye on them thanks to your findings.

[Michael Cola]

You say the seals crack and you get new calipers.  Are they leaking?  Do you mean the piston boot or the piston seal?  To see the seal you have to remove the piston from the caliper.  I'm not sure why you would replace a caliper and not just put new rubber on it.  Do your pads wear relatively even?  I'm just trying to understand what is going on.       

 

Sorry, Keith...I should have been more clear. The caliper seals seem fine...they've never leaked on me. It's the piston boot that has appeared melted/deformed, once to the point where the folds of the boot kind of fused together. I don't have any pictures, else I'd post them here. I'm going to take off the calipers in the next week or so, and I'll take some if it's happened again.

 

I've replaced the whole caliper because it was easier (free, under the lifetime warranty) for me to just return it for a rebuilt unit that was ready to bolt on. I also questioned the longevity of the seal if the boot got that hot, so that was one more reason to just replace the whole thing. I've not actually taken the boot off to inspect the seal itself though. I've never actually taken one of the miata front calipers apart....I'm not opposed to doing it. I just went by the philosophy that it's easier to replace the caliper than rebuilt them after reading some of the threads here.

 

Is it common to just replace the boot if/when they crack? Do they crack frequently?

 

My last set of pads were worn in a tapered fashion. I've had attributed that to the calipers not sliding properly, based on my reading. I forget exactly how they were tapered...i don't have any of the old pads laying around. I'll check when I take it apart again.  With this current set of pads I'm going to try flipping them from inside to outside to try to increase the life.

 

The other negative brake-related thing I've experienced is the long pedal on the first lap or two, exactly like what these guys (Jason/Yosh) described here: Long Brake Pedal, Lap 1, Then Fine

I'm about to replace my rear hubs/bearings/seals, and I'll inspect the fronts as well (one was recently replaced, the other is used, but both were rebuilt with Redline CV2 two track weekends ago). I'll be interested in seeing if this helps....

 

I use a permatex caliper lube that has ceramic in it. (comes in an expensive purple bottle)   I have had no problems on both the miata and my other racecar for the past several years.

 

This sounds interesting. I'll take a look at it. Thanks!

[Bench Racer]

I use the Permatex synthetic (green in color). Oil based pin lubes will play hell with the rubber pin bushings and rubber pin boots. From my perspective reading your info your brakes/pads are getting WAY to HOT. Espically when using brake ducts. I use Wagner reman calipers with Carbotech 10's and 8's and don't really burn boots or seals.

[Michael Cola]

Wow. I hadn't seen this Permatex Extreme Brake lube (Purple Bottle) before, but the specs are impressive compared to the stuff I've been using and even compared to the CRC lubricant.

Permatex Ultra Disc Brake Lube (Green Viscous Grease, Synthetic):
Operating Temperature: -45°F to +425°F
Technical Data Sheet

CRC Industries Brake Caliper Synthetic Grease (Dark Grey, Semi-solid Grease, Synthetic):
Operating Temperature: -40°F to +500°F
Technical Data Sheet

 

NAPA (AGS Company) Sil-Glyde Lubricant (White Gel Grease)

Operating Temperature: -20°F to +500°F (Although the techncial data sheet indicates that most testing was only performed to 400°F)

Technical Data Sheet

 

Permatex Ceramic Extreme Brake Lube (Purple Paste, Synthetic):
Operating Temperature: -50°F to +3000°F
Technical Data Sheet


All of these are listed as compatible with rubber/plastic brake hardware and boots. Not sure I completely believe the 3000°F capability of the ceramic extreme, but the point is that it's WAY higher temp rating than what I have. I'll be converting over on this next round of maintenance.

[left hander]

 

The other negative brake-related thing I've experienced is the long pedal on the first lap or two, exactly like what these guys (Jason/Yosh) described here: Long Brake Pedal, Lap 1, Then Fine

I'm about to replace my rear hubs/bearings/seals, and I'll inspect the fronts as well (one was recently replaced, the other is used, but both were rebuilt with Redline CV2 two track weekends ago). I'll be interested in seeing if this helps....

 

My first thought on the long pedal was vibration moving the pads out and after reading the long brake pedal thread I woudl say this rather than the master cylinder is the cause.  Odd it does not occur each lap.

 

I'll pass on someting I learned a couple of years ago - I was riding with a professional driver / driving school instructor who was giving demo rides of the new cayman R and prior to each corner he would left foot tap the brake.   I could see his foot moving but felt zero slowing of the car.  I asked why and he said it was long time habit from racing and explained they woudl always do this to ensure the pads were set next to the rotor right before the brake zone so any brake pad movement from vibration had been addressed and they would have a firm pedal when needed.  

[Keith Andrews]

I agree with Bench it seems like things are getting hotter than normal.  With the replacement warranty I understand why you just replaced the calipers.

 

Cracked boots is not a problem in general.  It does happen with time but not like you are describing. 

 

I'd try some of the higher temp lube and check them for freedom of movement each day.  By that I mean, the calipers slide easy on the pins and the wheel spins freely (fronts).  The other thing you could do is ensure they spin freely without the calipers in place.  I hope by making sure things are moving freely, like they should, your problems will go away.

 

Don't brake so much   

[tom1977]

Something additional to check... Wheel bearings...

[Alberto]

Some thoughts...

 

There were some older threads on this board about the quality of the parts used in remans with the pros swearing by OEM only for quality internal caliper parts.  I think Saul Speedwell and davew posted there.  May want to look for it if you wish to research that topic.  When I first built my car, I got new calipers from Mazda Motorsports.  I had an issue with one of the rears where it started leaking fluid so I replaced with one sourced locally and wasn't happy with it.  I have a thread somewehre on here if you want to look for it.  Overall, I haven't been entirely happy with the quality of the calipers that I have received from the generic parts stores.  Because of that, I'm probably going to get them from Mazda Motorsports or brake calipers from East Street Racing next time I need them.  

 

What you referred to as a seal - it's main purpose is as a dust seal to keep the brake dust out from between the piston and bore of the brake caliper so that the piston to caliper cylinder bore doesn't get gunked up.  I've also melted them but that was earlier in my racing 'career' when I used to use the brakes harder than I do now.  With new pads, the pistons are retracted deep into the caliper and the rubber dust shield is bunched up and close to the back of the brake pad so it is exposed to more heat.   As you get faster and more experienced, you will use the brakes less and not as hard and probably won't generate as much heat.  

 

When my brake pads and rotors are worn to about their half life, I also experience a long pedal but it is usually in the pits when I first start driving the car.  By the time I'm on track, I think the pedal feel might be back to normal and stays normal through the session.  This does not happen with new pads and rotors.  I do use the brake pad hardware since it spreads the pads away from the rotor and decreases drag.  There is a thread about that also somewhere on here that I posted on.

[Michael Cola]

My first thought on the long pedal was vibration moving the pads out and after reading the long brake pedal thread I woudl say this rather than the master cylinder is the cause.  Odd it does not occur each lap.

 

I'll pass on someting I learned a couple of years ago - I was riding with a professional driver / driving school instructor who was giving demo rides of the new cayman R and prior to each corner he would left foot tap the brake.   I could see his foot moving but felt zero slowing of the car.  I asked why and he said it was long time habit from racing and explained they woudl always do this to ensure the pads were set next to the rotor right before the brake zone so any brake pad movement from vibration had been addressed and they would have a firm pedal when needed.  

Good advice. I've actually been trying to get in the habit of doing this as well. My instructor recommended it to me when i told him what was going on. I've heard this from a lot of other racers as well.

 

What you referred to as a seal - it's main purpose is as a dust seal to keep the brake dust out from between the piston and bore of the brake caliper so that the piston to caliper cylinder bore doesn't get gunked up.  I've also melted them but that was earlier in my racing 'career' when I used to use the brakes harder than I do now.  With new pads, the pistons are retracted deep into the caliper and the rubber dust shield is bunched up and close to the back of the brake pad so it is exposed to more heat.   As you get faster and more experienced, you will use the brakes less and not as hard and probably won't generate as much heat.  

 

When my brake pads and rotors are worn to about their half life, I also experience a long pedal but it is usually in the pits when I first start driving the car.  By the time I'm on track, I think the pedal feel might be back to normal and stays normal through the session.  This does not happen with new pads and rotors.  I do use the brake pad hardware since it spreads the pads away from the rotor and decreases drag.  There is a thread about that also somewhere on here that I posted on.

 

Alberto, Thanks for your comments. The boot that melted on me was with newer pads and was still at the point where the piston was quite deeply retracted into the caliper, so that tends to agree with your thought process.

 

The long pedal does occur for me when the pads are worn past halfway. For me, it happens the most on the first lap, and the pedal travel gets shorter and shorter with each progressive stop as everything starts to warm up. Usually by lap two or three the pedal is back and everything remains fine for the rest of the session.

After reading that long pedal thread, I'm thinking that it has some to do with the pads being far away from the rotor (pad knockback), but I also think it might be something related to heating up the pads. Since my pads have the tendency to wear in a tapered fashion, I'm wondering if the pads become better aligned at temperature and allow for a shorter travel till full contact is achieved.

 

In any case, I'm going to replace all four wheel bearings before this next event, check all the calipers for damage, and make sure to use the high-temp ceramic extreme lube.

Then I'll be checking them at the track to make sure everything is still sliding like it should.

 

Beyond that, I think I need to follow Keith's advice and:

Don't brake so much   

 

[Ron Alan]

As you get faster and more experienced, you will use the brakes less and not as hard and probably won't generate as much heat.  
 .

This is a head scratcher....

[RazerX]

Ok, i have gone two years without any boot issues.  always used Mazda OEM rubber stuff.  I don't take chances with brakes.

 

good grease recommendations above.

 

Your taper wear is a huge red flag.  If the taper is from outer edge of the rotor to the inner you either have a bent caliper/slider pins or a bad wheel bearing.  If the taper from say front to back along the direction of rotation you have a bent caliper/slider pins or something wedged between your caliper and pad, like klag.