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Old 10-09-2012, 03:16 PM   #1
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Question Roebling & Brakes

I tried searching here and M.net but didn't really come up with much. I have an HPDE at Roebling in two weeks and this will be my first time there. Assume I am a road course novice but have a few events under my belt.

I am currently running Carbotech AX6 pads front and rear, OE-replacement rotors, stainless lines and the stock '94 calipers. I'm hoping to install the TSE brake duct kit and I will have a fresh batch of Motul RBF600 in before driving up there. The car is on 15x8 6ULs with fresh Kumho XS tires. Power is stock (or less).

At some "mini road courses" and faster autocrosses, I have never had issues with fade assuming I had fresh fluid.

My questions for those that have run the track before:
  1. Would you expect the AX6 pads to be sufficient?
  2. Would you buy and bring spare rotors and pads even if the current ones look to have plenty of life on them?
  3. Would you recommend driving to and from on the AX6 pads but swapping to something like the XP8s at the track?

I am planning to drive the car there and back (~5 hours / 300 miles).
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Old 10-09-2012, 03:18 PM   #2
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You can't swap XP8s for AX6s on the same rotor, IIRC. 1521s yes, AX6 no.
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Old 10-10-2012, 06:46 PM   #3
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You can't swap XP8s for AX6s on the same rotor, IIRC. 1521s yes, AX6 no.
Thanks, Sav. I know Carbotechs have a reputation for being pretty picky with bed-in and pad/rotor relationships.

I started writing this long post, including quotes and links for what I thought was the answer. Then I picked up the phone and called 949 and got a definite answer in a few seconds.

I normally try not to bother vendors with questions like this if I can find the answer myself, but I did buy my current brake setup from him so I didn't feel too guilty about a quick call. They (I assume it was Emilio I talked to) confirmed that you can swap from AX6 to XP8 pads on the same rotor, assuming they have been properly bedded.

I figured I'd post up the answer here in case anyone had the same question and came across this post in a search.


I think I am going to go for it on the AX6 pads and fresh RBF600. I've seen a few people say that Roebling is not particularly hard on brakes, my car is slow, I'm on street tires (205/50-15 XS) and I'm an intermediate driver at best.

I hate to buy stock-sized XP8s because I will likely look to move to a BBK setup once the current pads and/or rotors are toast which will probably be not too long after this track day.
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Old 10-10-2012, 09:31 PM   #4
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They (I assume it was Emilio I talked to) confirmed that you can swap from AX6 to XP8 pads on the same rotor, assuming they have been properly bedded.
I stand corrected, then. I remember the AX6 being an older pad than their 1521s and the XP series stuff which is why there was an issue, but I guess I was mistaken.
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Old 10-11-2012, 09:45 AM   #5
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Roebling is easy on brakes. There's not any high-to-low speed braking zones at that track. Front straight into T1-T2 is the highest speed and it's a series of two braking zones- brake friendly.
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Old 10-22-2012, 11:08 AM   #6
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Roebling is easy on brakes. There's not any high-to-low speed braking zones at that track. Front straight into T1-T2 is the highest speed and it's a series of two braking zones- brake friendly.
That pretty much sums it up, especially for a very slow driver/car combo. I think I topped out a bit north of 105 MPH on the front straight (which made passing there pretty entertaining). I will have to check the pads when I have time, but I think I barely used more than a couple of mm of AX6es.
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Old 10-22-2012, 12:38 PM   #7
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Yes- Roebling's front straight is incredibly painful even with a fast driver and a slow car. Not very obvious- but it is all up hill- just feels like the anchor is digging deeper as you proceed to the braking zone. It's still one of my favorite "no hills" track. Excellent track day site for learning IMO. Just don't turn your wheels if you go off into the sand.
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Old 10-22-2012, 04:10 PM   #8
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Originally Posted by m2cupcar View Post
Yes- Roebling's front straight is incredibly painful even with a fast driver and a slow car. Not very obvious- but it is all up hill- just feels like the anchor is digging deeper as you proceed to the braking zone. It's still one of my favorite "no hills" track. Excellent track day site for learning IMO. Just don't turn your wheels if you go off into the sand.
I really enjoyed Roebling and think the PCA HPDE events can be great introductions to track days. I know most guys on here are more advanced, but after my crash I decided to reset my driving experience and try to get some in-car instruction, buy a video camera, etc.

I would say I learned and progressed more as a driver in my one weekend at Roebling than I did in all my other solo track time (limited as that is).


As for the front straight, there were a couple of times where I am sure the other driver was thinking "Why are you riding beside me? Just pass already!"

Meanwhile, I was thinking, "I have 100 WHP on a good day, you have to lift for me to get by you when I am already in 5th gear."
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Old 10-23-2012, 10:02 AM   #9
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All too familiar with that static feeling on the front straight. I tracked my stock 91 Miata for 2 years before racing it as showroom stock for 3. The difference being, in showroom stock it was the last man standing at the brake zone. But when I was doing the track events I think made every PCA event- it was cheap even with the travel, food and lodging from ATL. And some of the regions did instructor discounts... Roebling is an awesome track to learn on.
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Old 02-14-2013, 03:22 PM   #10
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Heading back up to Roebling this weekend.

Worse case scenario: If I need to have the car towed somewhere for a repair I can't manage at the track, any one have suggestions for a shop in the area?
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Old 02-18-2013, 03:48 PM   #11
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I don't know of any shops near by that are open on the weekend. Your best bet is spares and others at the track. Do you tow a track trailer behind the Miata?
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Old 02-18-2013, 04:23 PM   #12
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This isnt related to brakes, but I have a priceless tip for anybody new to roebling road.

If you go off on the last corner before the straight (pretty easy to do), do not try to pull right back onto the track. Just let it go out into the grass a little bit and pull back on the track carefully.
Its very slippery right there and people will go straight into the pit wall in an attempt to get back on the track quickly. I've seen a handful of bad crashes at roebling, all of them being right there. The ready of the track is pretty opened without much to hit.
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Old 02-18-2013, 04:49 PM   #13
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Wheels turned and hitting soft sand off track is a big roebling fail also.
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Old 02-19-2013, 11:07 AM   #14
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Quote:
Originally Posted by m2cupcar View Post
I don't know of any shops near by that are open on the weekend. Your best bet is spares and others at the track. Do you tow a track trailer behind the Miata?
This is where I drive, all the time:




No spares (well, one donut tire), no tire trailer, no fear.


Just kidding: it was a white-knuckled thrill ride all the way up there and we (my wife came along) were filled with a constant fear for our lives.


Besides the premium AAA membership, our friends/neighbors have previously offered to let us use their enclosed trailer to tow the car home in a worse case scenario while I decide on whether to sink some money in to a tow vehicle and trailer.


Fortunately, no issues this time around either (despite some spins in the wet/cold). Assuming you don't count the fact that I powered on the GoPro but forgot to hit the "shutter" / record button. On all of my runs.
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Old 02-21-2013, 10:43 AM   #15
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Question

So what sort of laptimes are people running at Roebling?

I am trying to figure out if my car is horrifically slow or if it's actually in-line with reasonable expectations. With an experienced instructor and SM racer, the car ran in the 1:31s. I was a few seconds off that pace.

I've only found one post on M.net in the "post your best lap times" and that was a a 1:27.527. Car is listed as a '96 with a '99 engine with MS on 235/45/13 V700s.

More recently was this thread from a guy with a "Spec Miata+" build ('03 with 129 WHP and about 2400 pounds with driver). That guy turned a 1:23.9 and a top level SM racer ran a 1:21.8 in his car. Apparently the "real" SM lap record there is a 1:21.9. More info on his car:
Vehicle weight with driver: 2390 lbs (1 gallon of fuel)
Wheel horsepower: 129 RWHP, 121 RWT (Dynojet, SAE CF)
Tire size and model: P205/50ZR15 Hoosier SM6 (4 cycles)
What really caught my eye was that the last guy above said he was hitting 118 MPH at the end of the main straight. My car hits an observed ~105 - 107 MPH.

Relevant info for my car:
  • 1994 with original ~130k mile powertrain
  • About 2250 pounds without driver (I'm about 155 and the instructor was probably 175)
  • Tein Basic coilovers with RB front bar, no rear bar
  • 205/50-15 Kumho XS on 15x8" 6ULs
  • Zero power mods other than what appears to be an old Jackson Racing cat. That includes a panel air filter in the factory box.
  • No idea of power output
  • No useful data acquisition at the time of my last runs

Do the lap times and trap speed for my car, given the tires, weight and factory power levels seem reasonable or way off?

Last edited by Scrappy Jack; 02-21-2013 at 11:11 AM.
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Old 02-21-2013, 12:27 PM   #16
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Way back I ran 1:26.4 qualifying time in a 92 showroom stock C Miata. When I say showroom stock, I mean 99whp, full exhaust including cat, stock suspension (springs/shocks/bushings), full interior, no soft top, hard top, full cage, Toyo dot RA1 205-55-14 on stock daisies. We ran 0 toe front/back and max neg camber- which was -1.2 up front. I turned a 23.1 in a cheap ITA Miata that had probably 10 more hp, 2080 lbs (w/o driver), sway bars, coilovers with koni street adj shocks, more neg camber and same tires.

The SM car mentioned is top notch- and Tom is a very quick driver with 25+ years of driving/racing experience. Tom owns OPM in ATL and builds some of the quickest SMs around. Consider the starting turn key price of $30k as an indicator of the level of prep. It goes up from there.
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Old 02-21-2013, 03:31 PM   #17
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I'm planning on running with NASA-SE at Roebling for the first time in April so I'm paying attention.
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Old 02-21-2013, 03:45 PM   #18
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So far everything I am seeing indicates that my car is a ****-show, my instructor is not as good a driver as I thought, and/or my tires and "race weight" (~2600 lbs with two people in the car) are a limitation on the order of 5+ seconds.

I need to get better data to verify. I'll have video and a Pbox out there next time and will double check my corner-balance notes to make sure I am remembering weight correctly. It might have been 2,250 with driver but that seems lighter than I would have thought.
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Old 02-21-2013, 04:28 PM   #19
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some thoughts-

When I did track events I thought I was kickin *** because I was quicker than most of the people on track, including those that had been doing track events forever. Going racing was a real eye-opener, not because everyone was so much quicker, but because of how much quicker I got from being in a competitive environment- something track events just don't have. I just thought I was close to the limit before.

A Driver Ed instructor's first job is keep newbs from being a hazard. If they do that, mission accomplished. If you get an instructor that knows how to drive fast, bonus. Best you can do is listen to their advice and then decide for yourself what good it is.

Watch your instructor on track in their car - it will tell you a lot. If they look good on track, then ride with them. I did private instruction for 7 years and the two things that made the biggest gains in my students were riding with me so they could feel car where it "should be," and data acquisition to compare instructor/student. I actually pulled over second of my own best Rd. ATL lap by comparing data to my "student's."

Car set up is HUGE. IMO the two very best things you can do for your car is corner weight and alignment. The last race I corner weighted and aligned the owner's car and he was almost 2 seconds a lap quicker at Rd. ATL. Of course throwing a 200# instructor in the pax seat is less than ideal.

Also watch videos on youtube. There are a ton of spec miata videos on yt from Roebling and they'll help the track become secondary so you can concentrate on the car and driver.
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Old 02-21-2013, 04:42 PM   #20
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I hear ya. I have no illusions that I am quick and could tell you off the bat where I could find the 3-4 seconds to close the gap between the instructor and myself (actually getting myself to do all of those things correctly in one lap is something else). However, I was assuming my instructor would be "in the ballpark" of a reasonable lap time given his experience with the Miata platform which is why I used his time instead of mine.

Granted, he might have been taking it a little easy because he wasn't familiar with my car (and/or didn't want to hurt it) but it seems like a big gap from ~1:31 to even 1:27, let alone sub 1:25.

My car was corner-weighted and aligned prior to the event that I'm using times from. Unfortunately, the message board I had my "build thread" on got vaporized so I have to go back and check my hard copy notes to verify the actual alignment settings.

I've got video of his laps and mine, but no data overlay and there was no legitimate timing equipment in the car at the time.
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