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BBK Q and rotor cracking

Joined
30 August 2005
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5,406
Location
STL
Ok, I finally found a pad that works great. Hawk DTC60s. Yea, they dust but they don't squeal, stop good enough when not warmed up and no fading at all at the track.

So here is my problem. I am going through 2 piece RB rotors like crazy. When I came into the pits yesterday (after a cool down lap) the front temps were 480F. Rear running 300F. I am running 2" air ducting F & R. My rotors aren't cracking, but there are spider stress cracks everywhere and getting bigger and bigger. So I pulled the rotors - better safe than sorry. And how much spider cracking is too much? You can't feel them yet, but there are alot and a quite a few that are 1/2" or so. None towards the edges yet - all in the middle.

So I have little or no fade - happy there, but I have to get these temps down or my rotor budget is going to cost a fortune.

I want to keep my 16 OEMs for the street so the only BBK that will fit is the Dali 4 pot Alum. But it uses the same size 298mm rotor as the RB that I am running now. The 324mm RB rotor or other BBKs won't fit unless I go to 17s.

So I am assuming going to the Dali 4 pot and using the same rotor isn't going to help bring down temps. I am also wondering how much of an improvement I would see? Fade isn't much of an issue as I brake hard and short on the track and they seem to be holding up now with the new Hawk DTC60s.

Anyone tracking with the Dali 4 pots? Need new rotor rings ($400) so in essence it really only cost me $1k more to get the Dali 4 pot kit which comes with new 2 piece RBs.
 
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You need high temp paint to figure out what operating temps your rotor is seeing. 480*F is nothing and not accurate as you have already stated that you've done a cooldown lap before measuring the rotor temps. Common operating rotor temps are well over 800*F for track use
 
I really don't think spider web cracks on the surface matters, I had used them for 2 yrs track days.(around 10-13 events. I'm not too sure.) with no problem. I changed them out this season as I found the crack just starting to develop at the edge and I can see it cracks through, and that, is the time you really need to swap.

Then again, the track I usually run are not too hard for the brakes. Are you going to join the nsxpo 08 track day? If so, you will know what i mean.
 
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In general if your fingernail dose not get caught on the cracks and they don't extend into the edge you are fine.
 
this may be a silly question but since you are using 2-piece rotors, have you thought of bolting up a cast-iron disc instead of steel one?
 
You need high temp paint to figure out what operating temps your rotor is seeing. 480*F is nothing and not accurate as you have already stated that you've done a cooldown lap before measuring the rotor temps. Common operating rotor temps are well over 800*F for track use

I agree with Billy, you need data from on the track and what your peak temps are. Here is what I use:
http://www.hrpworld.com/index.cfm?form_prod_id=3811&action=product
Paint 2 or 3 of the vanes on the inside between the friction surfaces. Then you will know what is the next step. Perhaps more ducting???

Spider surface cracks are no big deal, you will find them on any rotor which has been run hard. I agree with docjohn, I run them till they crack and keep a spare set of fronts in my track kit. It only takes 20 minutes to swap them out at the track so run them till they die. When they go, usually it will be at the end of a session, when they are hot and the crack is open you might not even notice the crack. Once they cool down, the crack will be obvious and catch on the pad, causing a nasty noise and some judder. With a street set up, 90% of the time the crack will be on the outside surface and easy to see, because we duct to the inside of the rotor and heat is pulled away more efficiently from that surface, causing the outside to crack first. You may be seeing normal surface cracking and not have a problem...

Thermal shock can have some effect on the spider cracks, easy warm up and slowly bringing heat up in the pads and rotors will help everything last longer too. A higher coefficient of friction pad can help too, allow you to brake later and harder for a shorter period of time, thus allowing the rotors to cool for a longer time. Use 2 different pads, street and another set for track!

Another option is to get heavier rotors made which can adsorb more energy...
 
Using both sounds like a good idea.

Get the paint though...you need more data!
 
Rotors are wear items just like pads. My last set (STi not NSX) lasted about 10 track days. I've never bothered with 2 piece just because I'd need to get 20 days out of them to justify the price difference.

I replace the rotors when either a) the crazing flakes off the rotors and leaves rough patches or b) a crack is visible at the edge of the rotor. Maybe even c) something doesn't feel right.:smile:

Spare tires, pads and rotors are now standard equipment to bring to the track for me (no spare engine yet:biggrin:). It beats going home early.
 
Do you have a brand name in mind when you say "proper"? Cheaply made products occur in more places than just China.
Yes i'm aware that cheaply made products are made in more places than China, i'm also aware that the Chinese production processes and quality can rank right up there with the original depending on what the product is.

Most of AP, Brembo, or Performance Friction -an all of their racing line. But a 'Brembo' labeled product can be made elsewhere, and you even see this on some production cars as the manufacturer buy the rights of the Brembo name to use and label their own calipers and rotors rather than a Brembo developed component.
 
I use the dba4000 which are the primary source of my experience in needing to change rotors after about 1000 track miles. The last time I replaced them, I used a premium chinese 1-piece similar to Centris (mostly because the lead time on the dba was longer than I could wait). I've got about 500 miles on them with really no noticable difference in performance-- at least at my amateur skill level. The OEM Brembo rotors (again this is all relative to the STi) aren't really worth the price and have a marginal life.

I'd consider a 2-piece, but I keep hearing conflicting information as to whether they really have 2x or 3x the life/performance to match the price. Honestly, Billy was the first I'd heard on the positive side-- though his opinion is held in much higher regard than my other sources. :smile:
 
I use the dba4000 which are the primary source of my experience in needing to change rotors after about 1000 track miles. The last time I replaced them, I used a premium chinese 1-piece similar to Centris (mostly because the lead time on the dba was longer than I could wait). I've got about 500 miles on them with really no noticable difference in performance-- at least at my amateur skill level. The OEM Brembo rotors (again this is all relative to the STi) aren't really worth the price and have a marginal life.

I'd consider a 2-piece, but I keep hearing conflicting information as to whether they really have 2x or 3x the life/performance to match the price. Honestly, Billy was the first I'd heard on the positive side-- though his opinion is held in much higher regard than my other sources. :smile:
Thank you. Hmm, I always had the impression the DBA (not sure what model) was a good product, some teams in Grand Am Koni Challenge use them, but then again I havn't heard any follow-up information and teams change products if they dont work on a session-basis. Since i havn't heard a follow up, I shouldn't have had that impression in the first place. I havn't heard or seen too many people and have no personal experience with any DBA products so I cannot comment.

Not all products are created equal and just because a rotor is a 2-pc dosn't make it better, it has just as much potential (maybe even more) to warp, break, fall apart, crack as a 1-pc rotor -if they are both made by a company that uses cheap, poor quality material with a lack of engineering behind the product.

Did you say that you had bad experience with OEM-replacement Brembo "Blank" (solid 1-pc, no slots) rotor? or the OEM rotor for the STI that's 'made by brembo'? -FYI, (i'm not sure if the STI fits in this category) some manufacturers develop their own calipers or rotors and buy the rights from Brembo to use their name/call it a 'Brembo'. Sometimes these aren't up to the same quality as a Brembo-produced product. I've had good luck with "Brembo Blanks" from tirerack.com

What tires (compound, width, etc...), HP, suspension, brake pads, are you using? -This is all on your STI correct?
 
I understand your point about Brembo. It may be worth consideration to look at "direct from Brembo" products. Their name shows up in so many cars now, it seems they may have extended their brand beyond their control.

As for the car, I have Ohlins 2-way adjustable coilovers with F/R 8k/6.5k springs, 27mm front and 22mm rear adjustable sways, all urethane bushings, Toyo RA-1 235/40r17 (I've used 235r45 too). HT-10 front pads with no ducting. Basically stock power built for NASA TTB.

The NSX never sees the track as I don't fit with a helmet on-- hell, I barely fit with my head on.
 
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I understand your point about Brembo. It may be worth consideration to look at "direct from Brembo" products. Their name shows up in so many cars now, it seems they may have extended their brand beyond their control.

As for the car, I have Ohlins 2-way adjustable coilovers with F/R 8k/6.5k springs, 27mm front and 22mm rear adjustable sways, all urethane bushings, Toyo RA-1 235/40r17 (I've used 235r45 too). HT-10 front pads with no ducting. Basically stock power built for NASA TTB.

The NSX never sees the track as I don't fit with a helmet on-- hell, I barely fit with my head on.
I'm not sure about the STI, but their are many cars that run "Brembo"-labeled calipers: STi, EVO, GTR, Mustang GT500KR, IS-F, and many more. Some of which were not developed by Brembo. Through racing, Brembo has improved their brand image to be synonymous with great performance and quality. Maybe they are capitalizing off of this and selling their name to OEM manufacturers who produce their own calipers, rotors, hats, pads and label them "Brembo" after buying the rights.

From first hand talking to OEM engineers and project managers, some of the cars listed outright buy the rights to use the name for their own products that were designed and produced elsewhere while others work in conjunction with Brembo to co-develop products.

Sounds like you have all the right products on your car. They don't weigh all too much at around 3,300lbs...

So what exactly is happening to your OEM 1pc Brembo rotors as well as the DBA rotors? You have just explained that they last X amount of miles but not what causes them to need to be replaced.
 
The non-slotted rotors typically have the same failure pattern. Spider cracks appear and then the rotor surface seems to delaminate under further heavy use (same as in CL65's original post). The slotted dba4000 cracked through the end of one of the slots. A marginal size crack, but a crack nonetheless. They had survived the longest at about 1000-1200 miles. It's hard to say that any one thing may have caused these rotor failures. After each problem I changed at least something about the brakes/tires-- pad material type, cooling, or r-comps. I'm not especially hard on the brakes, in fact, for similar lap times to other drivers I have had surprisingly fewer problems at least with respect to fade. I had come to expect the replacement cost was just part of the game until you pointed out that longer life should be possible.
 
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