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Old 06-14-2017, 02:39 PM   #1
Zefy
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Default Pad choices for my time attack RS

I am getting crazing on my front rotors. Sounds like it's not much of a genuine problem but I wanted to get opinions on pad choices. It sounds like this this could be a sign of poor heat transfer through the pad.



I am using the subaru 4/2 brakes on my RS with centric premiums and hawk HT-10 front pads. My calipers are handling it fine with intact piston boots. I did have them fade a bit at the last time attack but I think it was a brake fluid problem that can be fixed with a flush.

the rears I'm using HP+ with subaru groupN rotors (using r180) and I don't swap them between street and track. No problems with heat on those.

The track I frequent is hard on brakes as there are 3 heavy braking zones and 1 really heavy braking zone. All within 1.2 miles... Not a lot of time to cool the brakes.

The HT-10 pads are probably not going to last the remainder of the season so I'm debating whether to get the same, different, or different brakes. I don't think I'm needing bigger brakes but interested to hear opinions. I'm also building a new motor currently that will be in the 300whp range.

Current car specs are: 01 RS with avo turbo kit, 175whp, ver5/6 type R trans and cusco front diff, kw v3, 255/40 re71r. About 3150lbs with driver.

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Old 06-14-2017, 03:07 PM   #2
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I'd suggest moving up to a more track oriented pad. If you want to stick with Hawk, use DTC-70 front and DTC-60 rear.
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Old 06-14-2017, 03:31 PM   #3
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I'd suggest moving up to a more track oriented pad. If you want to stick with Hawk, use DTC-70 front and DTC-60 rear.
While it's a bit old-school, an HT-10 is as track-oriented as it gets.

I think the reality is that he's going to go through rotors almost as quickly as pads, something not at all uncommon for a car of this weight/tire.

His solution is to buy $20 autozone rotors by the pallet.
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Old 06-14-2017, 03:33 PM   #4
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You're going to get that until you increase the rotor size or increase the cooling to the rotor. There's only so much heat they can take before looking like that. See what the C5Z does to it's rotors for reference.

For pad choices, if you're looking at Hawk, the DTC line is good, although HT-10's aren't bad. I like Carbotech too (XP10 or XP12 would be my recommendation for you). If you're not really fading the HT-10 then I don't see a reason to go higher in compound as it will just eat the rotors faster.
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Old 06-14-2017, 03:40 PM   #5
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You're going to get that until you increase the rotor size or increase the cooling to the rotor. There's only so much heat they can take before looking like that. See what the C5Z does to it's rotors for reference.

For pad choices, if you're looking at Hawk, the DTC line is good, although HT-10's aren't bad. I like Carbotech too (XP10 or XP12 would be my recommendation for you). If you're not really fading the HT-10 then I don't see a reason to go higher in compound as it will just eat the rotors faster.
Yup, those little brakes need some airflow to alleviate heat. Maybe a nicer 2-piece rotor up front for the time being without going to a larger BBK.

How many laps do you usually do in a session? Or better yet, how is your local Time Attack structured? Is it lap based, or timed sessions?
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Old 06-14-2017, 04:45 PM   #6
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Lol ya the HT-10 is a bit old school. The shop I got them from had them sitting on the shelf for a while because the original buyer never picked them up. So I got them for a good deal! Overall I've been very pleased with them and I don't think a more aggressive pad would benefit me much. The car does dive a fair bit with the imbalance from the difference in pad front to back. The main reason for me not swapping rear brakes is just due to the price of the rotors. I swap pads and rotors together so the bedding matches. KNS has the cheapest rear groupN rotor at $120cnd while fronts are $45cnd centric premiums.

DTC pads were probably going to be my next choice. Reasonable price and readily available. Getting carbotech here is a bit of a pain but not unreasonable. Does anyone run XP10-12 daily? I would probably leave the rears on and just swap the fronts. I autoX with this car at least once a month.

I was actually thinking of upgrading the rears to sti 2 pots because the rotors are way cheaper, make it more balanced (or would it be overpowering...?) if I keep a similar pad, and they'll still fit under my 16" winters haha

Moving the front rotors to something like the DBA 5k rotors is over $1kcnd. I can get a lot of centric premiums for that, or move up to a larger brake package that use a more generic rotor. Like sti brembos or some caddy brakes. Swap for summertime so the winters still fit. The DBA 4k rotors are reasonable enough but still 5-6 sets of centric premiums in price. Will they last 5-6 times longer? probably not... but I fear cracked exploding rotors! haha

I do have RCE brake duct brackets that have yet to be installed. I just didn't have a ton of space or time to figure out the routing to the front bumper. Currently the OEM brake ducts in the bumper (ver 4 bumper) are there and then I have an extra hole in the fender liner to hopefully get more air behind the wheels. No dust shields either.

And for the time attack sessions... 3 sessions throughout the day (2 practice, 1 timed), ~15 minutes each. No lap limit and I usually get around 8-11 laps. I'm not at the point yet of trying to plan for a fast lap.

Here is a video from a time attack so you can get an idea for the track. Since this video, I've upped my pace a little bit and gotten down to a 1:19.8.

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Old 06-14-2017, 05:20 PM   #7
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By using such a weak pad on the rear, you're asking the fronts to do most of the work. In my experience, Hawks are also very hard on rotors.

I have recently been using Ferodo DSUNOs and they are amazing so far. Good pad and rotor life and no fade. This is on a 600+ whp car that weighs almost 3000 lbs. You might even be able to go down to a DS 1.11, which will work better before they come up to temp but have a slightly lower peak heat capacity.
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Old 06-14-2017, 06:42 PM   #8
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Shifting to less laps per session will definitely help, as running that many laps in a session is just getting everything extra hot and probably out of your optimal temps, etc.

Sidenote: Are you taking temps on those 71s? Granted I'm pushing ~350hp more on roughly the same weight, but my window is only 2-3 laps. I'd be curious to see how much heat you're getting in to those tires at that power/weight ratio.
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Old 06-14-2017, 08:14 PM   #9
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Quote:
Originally Posted by kos View Post
Shifting to less laps per session will definitely help, as running that many laps in a session is just getting everything extra hot and probably out of your optimal temps, etc.

Sidenote: Are you taking temps on those 71s? Granted I'm pushing ~350hp more on roughly the same weight, but my window is only 2-3 laps. I'd be curious to see how much heat you're getting in to those tires at that power/weight ratio.
I was thinking of shifting to fewer laps, although I am still not at the point where I can get my fastest times in the first 2-3 laps. My fastest is usually between laps 5-8. It takes me a while to get in the rhythm and sort out a nice spot in traffic. I've only done 3 time attack events so far. I treat it more like a track day. The level of competition isn't high either. Time attack isn't a respected form of racing here.

Temps on the 71's... I was taking temps however I have to wait until I'm back in the pits and unstrapped myself. I'm normally there alone so nobody to jump into the pit lane to grab my temps. I am usually seeing around 60-70 degrees celsius with a 5-10 degree delta across the surface if I recall correctly after 3-4 minutes of parking. Next event I will try and get some more accurate measurements. I am really not beating them up too much though. I see a ton of people destroying them after 2-3 events. Mine are still at probably 30% after 3 time attacks mix wet/dry, a hill climb, and probably 50 autoX runs in mix wet/dry. This is far better than what I see most people getting.

Looked up the ferodo. I originally was not considering them because of the premium cost. Looks like for that pad, they only offer the DSUNO for the front and the DS1.11 is special order. For rears they only have the DS2500 and DS3000. A little surprising given that these are the standard groupN rally brakes. The DSUNO also looks like it's going to be well over $600cnd!
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Old 06-15-2017, 02:01 PM   #10
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I agree that it would be worth putting more pad on the rear. The 4/2 pots have the most rear bias of any subaru brake setup so using the hp+ with a much lower mu means your fronts are doing much more work than they need to. I would get the front cooling ducts in there and go to more rear pad and try that.

Hawk appears to only do dct-60 for the front, dtc-30 rear. There is an HT-10 rear, which I guess you could use with the dtc-60 up front.

DS3000 might be your best bet, but I'm curious now and am going to check on the newer pads.

Last edited by jamal; 06-15-2017 at 02:08 PM.
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Old 06-15-2017, 02:09 PM   #11
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Originally Posted by jamal View Post
I agree that it would be worth putting more pad on the rear. The 4/2 pots have the most rear bias of any subaru brake setup so using the hp+ with a much lower mu means your fronts are doing much more work than they need to. I would get the front cooling ducts in there and go to more rear pad and try that.

Hawk appears to only do dct-60 for the front, dtc-30 rear. There is an HT-10 rear, which I guess you could use with the dtc-60 up front.

Ferodo does have the ds3000 front and rear, and possibly some of the newer compounds, I'm curious now and am going to check.
front:

http://ecat.ferodoracing.com/car-rac...ke-pads/FCP986

rear:

http://ecat.ferodoracing.com/car-rac...e-pads/FCP1372

What are these newer compounds you're talking about?
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Old 06-15-2017, 06:05 PM   #12
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IMO you need larger brakes, I have been through all this myself with the 4/2 pots, tried different pads, rotors, ducting and even water spray. At the end of the day those front rotors are just too small for a car that heavy.
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Old 06-15-2017, 09:49 PM   #13
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IMO you need larger brakes, I have been through all this myself with the 4/2 pots, tried different pads, rotors, ducting and even water spray. At the end of the day those front rotors are just too small for a car that heavy.
what brakes did you end up moving to?
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Old 06-15-2017, 10:10 PM   #14
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what brakes did you end up moving to?
I kept my wrx for gravel only and am building a BRZ for time attack now, see the "home made aero" thread.
For the BRZ I have rear brembos off an 08 STi and will most likely purchase an AP racing front brake setup budget permitting, otherwise matching front brembos as the least expensive option.

For the guys I was running with who suffered the same issues as me with the 4/2 pots they just went to OEM brembo package off an STi. They were able to get multiple years from the rotors and up to 10 track days from the pads. With the 4/2 pots I was getting about 2 - 3 events on the rotors and 2 events from a set of DTC60 pads so the Brembo upgrade pays for itself with time.
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Old 06-16-2017, 01:25 AM   #15
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By newer pads I mean the 1.11 and dsuno, but no, those aren't made in the rear shape.


The AP Essex kit or some stoptech st40s, or str40, would be good options. I think the essex rotor rings and pads are really inexpensive to replace as well. But still, that does leave you with limited rear pad choices. The DS3000 would probably be good though.
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Old 06-16-2017, 07:18 PM   #16
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The AP racing setup is cool but it's a little out of my price range at the moment. I am thinking I'll move to stock brembos.

Looking at other cheap alternatives though and the cadillac atsv brakes look promising. Also the KNS z32 kit. The KNS kit is definitely the cheapest and I can use the same pads I am currently using. Anybody have experience with these options? Both of these would leave me a fair chunk of money to get higher quality pads.
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Old 06-17-2017, 08:10 PM   #17
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I would actually not recommend the stock sti brembos. They have more piston area and a much more forward bias than the 4/2 pots. The ATS fronts or Z32 kit would put you closer to the current bias. Also, do you know if you have a 1 1/16 or 1" master cylinder?
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Old 06-19-2017, 01:39 PM   #18
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I would actually not recommend the stock sti brembos. They have more piston area and a much more forward bias than the 4/2 pots. The ATS fronts or Z32 kit would put you closer to the current bias. Also, do you know if you have a 1 1/16 or 1" master cylinder?
I am not sure. I haven't changed it. According to google, it is a 1". I'm apprehensive about changing it to a larger size if that's what you're recommending. I don't run ABS (i find it engages far before the limit of grip, especially in loose conditions) and I also have the booster disabled. I love the feel and modulation of manual brakes.
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Old 06-19-2017, 01:49 PM   #19
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Unless you'd like to be murdered by your neighbors, pedestrians, etc. DO NOT daily XP10s or 12s.
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Old 06-19-2017, 03:37 PM   #20
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The 1" MC is what comes on the 06-07 wrx with the 4/2 pots, I'm not sure what they did with the older JDM cars but 1" would sound right to me. Cars with the sliding front 2-pots, which use larger pistons than the 4-pots, get the 1 1/16 MC, and so does the sti with brembos.

If you're happy with the bias, then you really want to be careful about what you put on there. Bigger front brakes and more aggressive rear pads might balance out right, depending on what you use.

I started my own brake math spreadsheet to have some newer and aftermarket stuff in it. Not as fancy as Josh's but maybe later it will get some better features. I have the essex kits in there but not stoptechs yet

https://docs.google.com/spreadsheets...it?usp=sharing
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Old 06-19-2017, 07:02 PM   #21
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If you have already removed ABS and the booster then a dual master cylinder with balance bar is the next step. In my wrx which runs the 4/2pots I modified the factory pedal box to save money over buying a pedal box which would have been a lot easier.





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Old 06-19-2017, 09:57 PM   #22
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I am not sure. I haven't changed it. According to google, it is a 1". I'm apprehensive about changing it to a larger size if that's what you're recommending. I don't run ABS (i find it engages far before the limit of grip, especially in loose conditions) and I also have the booster disabled. I love the feel and modulation of manual brakes.
Little hijack however, how hard did you find it to adapt to the lack of ABS. Ive had a hunch the factory abs has been prolonging brake events in my track car but have been reluctant to remove it as it does come in handy in the rain.

Also, if for some reason you do go with a oem brembo set (I did see it was previously recommended against) I went with an AP setup on my car and the factory brembo's are on a shelf with new DTC70's, ss lines etc. ill cut a deal to move them knowing they will be on a track car. I upgraded as im looking to endurance events and the oem brembo's on a 3000lb car wont last 9 hours
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Old 06-19-2017, 10:55 PM   #23
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Little hijack however, how hard did you find it to adapt to the lack of ABS. Ive had a hunch the factory abs has been prolonging brake events in my track car but have been reluctant to remove it as it does come in handy in the rain.

Also, if for some reason you do go with a oem brembo set (I did see it was previously recommended against) I went with an AP setup on my car and the factory brembo's are on a shelf with new DTC70's, ss lines etc. ill cut a deal to move them knowing they will be on a track car. I upgraded as im looking to endurance events and the oem brembo's on a 3000lb car wont last 9 hours
I didn't really have to adapt to the lack of ABS. My previous subaru was a 99 TS that didn't have abs. I did lots of autox and rally stuff in that car and got very used to manual brakes and not having abs. In the RS, I found it very intrusive and it was always engaging on the street in the wet or dry, even when there was good grip levels. I know a few people that have mostly stock RS's that didn't have the same troubles as me so it's probably a personal preference more than anything. I tried disabling the vacuum booster and it didn't help, so I disabled the abs as well. Both systems are still there though... Future weight saving mods when I have more time.

I codrive an 06 sti sometimes at autox and I can tell you, the abs system in the newer cars are WAY better. It is way smoother to engage and still allows for threshold braking. It does let me take a far more hamfisted approach to rain driving in autox though. You can just stab on the brakes and it works! You will probably learn more by disabling them, but it's nice to have, even just for avoiding flat spotting tires.

This is not the same for ice racing though! The sti abs system totally craps out on the ice...

But hey, shoot me a PM about those brembos. I'm thinking of going a different direction but it's good to keep my options open.
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Old 06-20-2017, 10:22 AM   #24
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Wall of text PM sent.
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Old 06-22-2017, 12:44 PM   #25
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Unless you'd like to be murdered by your neighbors, pedestrians, etc. DO NOT daily XP10s or 12s.
ha ha, can confirm, I've been running XP10/12s for the last month between trackdays and the car sounds like a garbage truck. The girlfriend loves them too

AutoX'd with them last weekend and they are not ideal waaaaaay more bite than I'd prefer and somewhat difficult to modulate at those low temps.

real nice on the track though
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