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Discussion Starter #1
Is it possible that I'm just over driving this car? If it is, cool, I'll buy a bbk. But I just don't think I'm over driving the car. I'm VERY aggressive on my track days, but I just don't think I should be feeling like these brakes should be on a kids Barbie car!!

Amazon rotor kit (kt elite I think)
Centric ss lines

Cmax ceramic pads, (I already went through the set that came with the rotors and another set). Pads usually last me two track days.

Motul rbf 660 fluid

The problem I'm having is I can only get one hard brake in (100mph down to 40mph) before they go mushy and just will not stop my car. I've been supplementing with the e shift, it helps to slow me down so I don't have to use the brakes.

If I purchase $400 brake pads, I'm really concerned that my stopping power won't really change. Anyone with lots of track time have something to share? I need the pads to make a 300 percent difference, my brakes feel that weak!

I've bled probably 4 liters through, so I don't feel like there is any air in there.

I have not been able to bleed the abs yet. But honestly I don't think I've ever felt the abs kick in!

For comparison, I have another is300 with unknown brand rotors and pads, it feels like it's sufficient.

So, after all that I guess I'm asking which component on mine could be weak? And will expensive pads really make an incredible difference? And if they will, will they last any longer than two sessions?

Thanks for reading and any for any helpful responses.
 

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Wow, I can't believe you didn't go off in a ditch with those pads. Bear minimum I'll generally recommend to people is a Hawk HPS. And that I'll even limit based on track and recommend being mindful.

There are different failures to braking. mm71522 eludes to one, tire limitation. But you mentioned ABS hasn't kicked in. So you're not locking the tires up and therefore that isn't your limitation.

2. The pedal goes to the floor after repeated stops. This is commonly caused by fluid boiling. Most common, poorly bleed brakes. I've dealt with some systems that unless you pressure or vacuum bleed, it just isn't going to be great. Poor brake fluid is the next. You're using high quality fluid, but is it a left over can that was sitting open on your buddy's shelf? Remember, brake fluid is hydroscopic.

3. Pedal doesn't go to floor, but goes stiff and you're not slowing down. This is pads are hotter than they can handle. See first paragraph about pads. Personally I find the Hawk HPS as more heat tolerant than Stoptech Sport pads. But the dust is far better with the Stoptech, plus they're cheaper. They would be my recommendation for you. Do front AND rear. Bed the pads in correctly too.
 

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Make sure your under-tray/ducting going to the brakes is in tact and functional.

I really hate cheap pads for any kind of driving. I've felt like going from a crappy generic auto store pad to actual OEM pad or track pad can be several hundred percent % better just because of how bad some pads are. They might have an ok material, but who actually knows what the friction vs. temp curve is or what the max temp rating is.

Cheap rotors can also be a problem on a track car as well.. The vanes inside the rotors can have a pretty big impact on cooling. If the replacement rotor is straight vane and OEM wasn't it could offer worse cooling than stock. There are also various patented designs that do even better
 

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Discussion Starter #5
I forgot to mention tires are sport comp 2. I'll be switching to proxes r888. But anyway the tires are pretty sticky. Not just regular passenger tires.

As for the date on the fluid, I didn't check. Just purchased it and flushed it in.

No problem purchasing hawk pads, I'll just be ENRAGED if my brakes still suck with hawk pads.

I'm trying to determine #1 if my current setup has a problem and if corrected will my brakes be sufficient?

And #2 if the stock setup is functioning properly with premium pads etc is it enough to stop me 140 mph down to 40mph for turns?

Where do I decide if bbk is necessary? After I get the brakes dialed in I'm boosting the motor to 450 @wheels. So it's imperative I can stop.

If I'll absolutely need a bbk for that speed and my heavy car i don't want to mess with any more stock options.
 

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I was thinking that you were NA, but you really have to pick the final purpose and goal of your car.

If you need to do a single stop from 140mph on an NA car, then a decent set of pads and rotors on the stock calipers should work fine.

If you are going to do multiple back to back stops from 140mph, often tracking some beastly turbo car - the best way to ensure braking is spend the money on 4 piston calipers, a pad that can handle higher temperatures than Hawk (do the research for whatever pads fit the calipers that you buy. Aftermarket caliper brands tend to have better friction/temp curves than OEM caliper replacement pad options), and get a quality set of rotors (my preference is not drilled if possible with better internal fin design).

If budget is primary concern, you may be able to cheap out stock calipers, on some unknown shitty rotor, with a completely track oriented pad (if they make one for IS300) that can maintain some amount of friction at super high temperatures (not Hawk or anything similar). The trade-off is that kind of pad will be noisy as hell, dusty, and have almost no friction when cold and be dangerous on the street because of it.

You make the really aggressive pads safer on the street by going with 4 piston calipers. The extra hydraulic force helps when it's cold because 4 times almost no friction is better and hopefully enough to stop the car (or at least moreso than 2 times almost no friction when cold).

The problem is that the amount of friction a pad generates changes with temperature. There is no magical binder for the pad compound that performs at every single temperature. Pick your goal, pick the suitable compromise and buy the right set up.

If multiple 140mph stops isn't a concern, then for $100-$400 for a set of performance pads, I'm not quite sure how you would be enraged if the solution didn't work given the alternative will be much more?

I forgot to mention tires are sport comp 2. I'll be switching to proxes r888. But anyway the tires are pretty sticky. Not just regular passenger tires.

As for the date on the fluid, I didn't check. Just purchased it and flushed it in.

No problem purchasing hawk pads, I'll just be ENRAGED if my brakes still suck with hawk pads.

I'm trying to determine #1 if my current setup has a problem and if corrected will my brakes be sufficient?

And #2 if the stock setup is functioning properly with premium pads etc is it enough to stop me 140 mph down to 40mph for turns?

Where do I decide if bbk is necessary? After I get the brakes dialed in I'm boosting the motor to 450 @wheels. So it's imperative I can stop.

If I'll absolutely need a bbk for that speed and my heavy car i don't want to mess with any more stock options.
 

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Being that ABS isn't engaging and assuming there are no ABS faults, it sounds like your tires are adequate.

I would try a different set of pads and rotors to start. Not sure of the timeline but you may also consider changing the fluid more frequently.

Not all BBK's are track rated either. Buyer beware if you're on a racing budget.
 

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Discussion Starter #10
All good info, I appreciate it.

To address a couple things -

About the "enraged comment," I just mean that if I bought specialty pads that did NOT give me a noticeable improvement, it would be money wasted. That's all. I almost bought some hawk hps pads but after seeing some performance graphs, I think only hp plus pads will work. Those aren't made for my car, I would only have access to that particular pad if i ran supra calipers and rotors.

And for the braided lines guy... Because the manufacture date on my "better" stock lines 08/01. That's dangerous imo.

Basically I've come to the conclusion that for the way I'm using this car, I need race only calipers and race only pads. I'll just have to keep a regular set around if I decide to street my car.

So now I'm wondering if I should get larger rotors or just keep stock size? Also, if larger calipers are warranted?
 

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I'm still unclear if this is a track car or a daily driver that goes to the track.
 

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Discussion Starter #12
I've been looking at carbotech xp12 pads or project Mu pads. Rated for up to 800 deg Celsius.

Rotors I need some capable of handling the heat, best ones I found are good to 600c --Project mu club racer.

Anyone heard anything about these? Or have a recommendation?
 

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You're new and NA, trust me and throw some Hawk HPS on there. It'll be 300% better than what you went with the first time. I've been doing this 10 years, race and instruct.

And the reality of it, pads will last you possibly two track weekends. So if you don't like them, well you're replacing them soon anyway.

More pistons does not necessarily mean more friction. And saying Hawk is not a track pad...hawk is a brand. They make other compounds. Not 100% positive, but in amateur racing, they are probably the most utilized pad on every given weekend. Want race oriented, get something from their DTC lineup, blues or blacks. But they won't work when cold, are aggressive in rotors, etc.

Brake pads are like tires. A Hoosier R7 is awesome when hot. But when it's cold, you'll tear it up and an all season compound will beat it out. But take that all season out in the hot and it'll get greasy and tear up. Different pad compounds like different operating temperatures.

Another company that makes a lot of pad options is G-Loc. We've been using them on our race team car for endurance. Their R10 compound has been great for us and works when cold surprisingly well.
 

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Forgot to mention. Hold off on a big brake kit unless you've got money to burn. Keep in mind that you'll need bigger rims to clear the brakes and you need to think about front and rear bias matching, as well as master cylinder bore. I've seen too often people slap a BBK assuming better performance to actually get worse.
 

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I've been looking at carbotech xp12 pads or project Mu pads. Rated for up to 800 deg Celsius.

Rotors I need some capable of handling the heat, best ones I found are good to 600c --Project mu club racer.

Anyone heard anything about these? Or have a recommendation?
You need pads to handle the heat, and rotors to shed the heat in between stops. The DBA design is slightly higher temp AFAIK then Project Mu Club racer and likely has cooling similar to the Project Mu SCR Pro type rotors based on internal fin design. There should be other equivalents on the market....

The best bias set up that I've had on my car was the Figs adapters, Supra TT rotors (DBA), and Hawk pads (keep forgetting that I have this in my garage should anyone want a good deal for a xmas present). From highway speeds it was slam me in my seat belt good and felt good in rain, or other poor conditions. For lower speed track days, I would have ran with this for as long as I could have.

I switched to 4 pistons because I wanted a more aggressive/higher temp capable pad with some street manners for over 600whp+. The Hawk pads are under 1000° before serious fade issues occur vs. <1500-1600° on what I have now. I'm confident I could stop down from 150+mph if needed, but the trade-off is brake bias. I can lock up the fronts before the rears which won't translate into shorter stopping distance in most situations. Situations where pads end up over 1000° it sure will stop better, but otherwise.... I doubt it.

On a pure numbers side... at one point, I built myself some calculators and looked at friction factor of all the pads I could find, and various brake options/diameters/etc. for the IS. The brake bias is borderline horrendous with 4 pistons up front on a large diameter rotor and an aggressive pad... while keeping stock diameter and calipers in the rear. Most internet wisdom will say 'stopping power comes from the front, my 4 pistons are awesome, and don't even touch the rear brakes'. But, I'm glad to see guys like Hardvin chiming in stating some actual truth that BBKs can ruin the bias and make things worse.

Personally, I think guys should be looking into rear brake upgrade options when doing 4 pistons on the IS. The options coming out for larger diameter rotors and 6 piston calipers front with larger diameter rotors and 4 piston rears merit more research... just as would some kind of rear brake upgrade to match 4 pistons now.

Some other reading/real world thoughts for you...

Brake Myth #1

Was watching a vid on tuned that made me think of this thread. 4 minutes in you can hear the fantastic race pad squeal. Even listen to the pro drivers comments after the lap test about too much brake up front, etc.
 

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No fan of any ceramic pads- every set I have ever tried was returned and switched out.
Years ago I ran repco pads, cant find them anymore but found what I think is better.
Im running Porterfield's R4-s brake pads on the street and they are the best I have ever found.

If you are a scca racer they give a discount when you contact them direct.
They also sell many other makes and can help with brake pad advice.

Anyone compare the Parterfields to other brands?
 

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I use Carbotech XP12 Front and XP10 rear, Motul RBF600, and oem type plain rotors on my trackcar with Hoosier A6's. No issues as of yet with 15-20 minute sessions and not using air ducts at the moment. The backing plates are removed though.
 

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Discussion Starter #19
I use Carbotech XP12 Front and XP10 rear, Motul RBF600, and oem type plain rotors on my trackcar with Hoosier A6's. No issues as of yet with 15-20 minute sessions and not using air ducts at the moment. The backing plates are removed though.
Good to know! This is almost exactly the setup I'm planning on running. For your rotors, are you using cheap ones like brembo blanks, or bosch blanks? Or are you using specialty rotors like DBA, Project Mu club racer, etc...? $150-$500 per piece.

ALSO, what is the function of the backing plates? My XP 12s didn't come with any, I was thinking to just peel the plates off the old pads and apply them, not a good idea?
 

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Sorry just saw your reply. I should have been more specific. I removed the backing plates from the hubs themselves. The metal ones that look kinda like an air duct sticking out. I also do not use the shims for the brake pads. The rotors are just plain Centric type.
 
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