small cracks in front metal rotors
09-19-2006, 03:15 PM
#31
Originally Posted by AeroGT3RedWing
...Anyways, heat doesn't crack rotors, extreme temperature cycles do. You can let the rotor sit in an oven all day, but if you toss cold water on it, or bring it down from 1200 F to 400 F instantly due to excessive brake cooling, yes, any rotor will crack, blanks included.
...you will crack anything going from 1200F to 400F, which is why there is such a thing as too much cooling. ....
...you will crack anything going from 1200F to 400F, which is why there is such a thing as too much cooling. ....
09-19-2006, 05:18 PM
#32
Originally Posted by wlittleman
I've always wondered why we do cool down laps after each 20-30 minute DE session. I've been told that the practice prevents the rotors from cracking. Now, I also have an engineering background, albeit not in thermodynamics, but the practice of cooling down never really made literal sense to me since we want hot things to cool down slowly instead of quickly. Does a cool down lap actually slow the cooling down instead of quickening it?
09-20-2006, 05:29 PM
#35
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Originally Posted by Blacksport350
One important purpose of the cool down lap is to run fluids through the hot engine and gradually cool it. If you just shut an engine off blazing hot, you could boil coolant, cook the oil in the oil gallies and create some other interesting thermal conditions. Also, you are lowering the temperature in the exhaust system to help prevent excessive heat buildup in the bumper cavity when you come in to the paddock. As to the brakes, the cool down lap helps to evenly disspate the heat from the brake pads into the rotors and then out of the rotors. This prevents a very hot pad from coming to rest on the rotor causing uneven cooling and boiling of the fluid if too much heat is in the brake assembly when it comes to rest. Basically, when you remove the airflow from the car, it turns into a giant blast furnace so as much of the heat you can shed slowly during a cool down lap, the better. I do not see any possible way of shedding too much heat too quickly on any track unless someone hoses you down.
Everything said about cool down laps in there is correct. In race conditions, excessively quick cooling can crack rotors however. If you throw a really high mass flow rate (of air) through a rotor's vents while the rotor is 1200F, you are going to cool the rotor VERY quickly, possible too quickly. This is race car stuff though. No track car should see this, only extremely competitive race cars.
09-21-2006, 03:40 PM
#37
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I have gone through 5 sets of front rotors with cracks showing after 2 or 3 track days. I had my last set frozen by Diversified Cryogenics and I have 8 track days on them with virtually no cracking. Needless to say, I sent them another set which is now standing by for use. They will acquire cup car rotors directly from Porsche for you, treat them and send them to you. The front set cost me $849 in May. They are an exact fit for the GT3. It looks like they are going to last about twice as long as the untreated rotors.
09-21-2006, 04:11 PM
#38
Former Vendor
Thought I'd pass this on:
My customers have mentioned that, in addition to cool down lap(S!), once the GT3 is in the paddock it is beneficial to roll the car forward or backward after sitting for a minute or so. Essentially removes & redistributes the heat via preventing the caliper from shrouding the disc. Longer pads & rotor life can be the result.
Ponder this concept for a moment.....
Craig
Rennstore
My customers have mentioned that, in addition to cool down lap(S!), once the GT3 is in the paddock it is beneficial to roll the car forward or backward after sitting for a minute or so. Essentially removes & redistributes the heat via preventing the caliper from shrouding the disc. Longer pads & rotor life can be the result.
Ponder this concept for a moment.....
Craig
Rennstore
09-21-2006, 06:04 PM
#39
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Craig I like that idea and I'll give it a try this weekend.
I installed cyro'd rotors in my cup at Cal Speedway back in late March after my rotors cracked in 4 weekends. To date I have 5 weekends on them going into my 6th tomorrow (a weekend being at least 2 days of practice with a qualifying and race each day). To date not even hairline cracks!....
I installed cyro'd rotors in my cup at Cal Speedway back in late March after my rotors cracked in 4 weekends. To date I have 5 weekends on them going into my 6th tomorrow (a weekend being at least 2 days of practice with a qualifying and race each day). To date not even hairline cracks!....
09-21-2006, 06:30 PM
#40
Former Vendor
Heat in one spot can develop a truly warped rotor - forgot to add that to my above post.
Skootching the car: People look at ya like you are a loon.....but WTH ;-)
Skootching the car: People look at ya like you are a loon.....but WTH ;-)
09-21-2006, 11:28 PM
#42
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Originally Posted by jrgordonsenior
Craig I like that idea and I'll give it a try this weekend.
I installed cyro'd rotors in my cup at Cal Speedway back in late March after my rotors cracked in 4 weekends. To date I have 5 weekends on them going into my 6th tomorrow (a weekend being at least 2 days of practice with a qualifying and race each day). To date not even hairline cracks!....
I installed cyro'd rotors in my cup at Cal Speedway back in late March after my rotors cracked in 4 weekends. To date I have 5 weekends on them going into my 6th tomorrow (a weekend being at least 2 days of practice with a qualifying and race each day). To date not even hairline cracks!....
Or, did you use something like this:
Frozen rotors
Cheers
09-22-2006, 01:01 AM
#43
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Originally Posted by RJFabCab
JR, did you have your Cup rotors cryo treated? If so, which company?
Or, did you use something like this:
Frozen rotors
Cheers
Or, did you use something like this:
Frozen rotors
Cheers
We sent several sets to a company somewhere in the South. I'll have to look it up Monday when I get back to my office. Off to the races for the weekend....
09-22-2006, 08:46 AM
#44
It is really interesting to me that some people here are reporting increased life from cryoed rotors. Our direct experience with them on open wheel cars and some touring cars is decreased life or no change at all. I wonder if I can find an engineer to explain why this might be the case but at the moment, I am scratching my head.
09-22-2006, 09:29 AM
#45
Three Wheelin'
Originally Posted by Blacksport350
It is really interesting to me that some people here are reporting increased life from cryoed rotors. Our direct experience with them on open wheel cars and some touring cars is decreased life or no change at all. I wonder if I can find an engineer to explain why this might be the case but at the moment, I am scratching my head.