SLC impressions

[Jac Mac]

Most cracked brake rotor problems can be traced back to drivers or pit crew who dont take the simple precaution of rolling the car back and forth over one complete wheel rotation for several minutes when it arrives back at race end, this helps prevent caliper/pad localised heat soak from warping or cracking the rotor. Having a driver who sits in the pits with his foot planted on the brake pedal for the entire pitstop duration is another sure way to ruin an otherwise good brake setup. Running the slow down lap without using the brakes at all helps as well.

[Mesa]

Funny Ben.....I was thinking the same thing while reading JacMac's post....damn these cars have alot of rules to follow! More nuts, more bolts, more brakes,more wheels = more rules I guess!

For a bike - it's slap on a set of Galfer Wave rotors and "forgetaboutit". Actually stock discs work pretty good, the limitation for even a modern bike seems to be more from the calipers when pushed to the limit on track.

[J. Salmon]

I will forward some high res pics as requested.

Not sure why the rotors cracked myself. I can tell you that I try not to use the brakes at all from the checkered flat at the end of the run all through the cool down lap, and then some around in the pits. And I roll it to a stop and shut 'er down in first so no brakes.

Most of my track experience prior to my Lola FF is with really heavy cars. My RS4 is 3900 pounds, and 60% on the front axle, so it really only has two functional rotors. It does have cooling ducts (one of the best improvements over the S4, but rarely mentioned). I have pounded the car on the same track (VIR full) without issues. It has "drilled" rotors. I tend to use pads that are heat tolerant but not necessarily too grabby. Fran suspects the really aggressive pads on the SLC may be the culprit.

The best thing about all this is shaking out the little issues.

Fran, you cannot use my 355 as a planter.

Besides, how ironic is it going to be to have a GT40 parked next to a Ferrari? I even have the plate picked out: 84REN66. No one will get it

[Brian Hamilton]

Originally Posted by salmjo1

Besides, how ironic is it going to be to have a GT40 parked next to a Ferrari? I even have the plate picked out: 84REN66. No one will get it

Ate Ferrari In 66? LOL Great plate. I have one in my mind 026TN3...

[Molleur]

Good one Brian Zero to sixty in three...

[Howard Jones]

Setup data would really, REALLY be useful. Shock settings, suspension geometery, spring rates, tires pressures, anti roll bar info, wing attack angle. All of anything you develop would really be of help to me and the rest of us.

Thanks in advance. Howard

[Molleur]

+1 Howard!

[Fran Hall RCR]

Guys..

I have all the Data from the Run and Gun....

But as with any race car...your results may vary..

I will gladly send it along to you all in an email...

[Paul Osborn]

Originally Posted by jac mac

Most cracked brake rotor problems can be traced back to drivers or pit crew who dont take the simple precaution of rolling the car back and forth over one complete wheel rotation for several minutes when it arrives back at race end, this helps prevent caliper/pad localised heat soak from warping or cracking the rotor. Having a driver who sits in the pits with his foot planted on the brake pedal for the entire pitstop duration is another sure way to ruin an otherwise good brake setup. Running the slow down lap without using the brakes at all helps as well.

JM:

During the cool down lap - which makes a lot of sense BTW - would you recommend periodically tapping the brakes to avoid potential shock cooling [cold air / hot parts], or is that not really a possibility?

Also, I wonder how NASCAR cars avoid cracked calipers after coming in under the yellow, braking hard in a heavy car, and then sitting in the pits. Is it because they are only in the pits for less than a minute, and then they have an extended run (airflow) back up to speed?

Thanks for your (or any other knowledgeable person) thoughts on the subject...

[Fran Hall RCR]

Interestingly ,on the NASCAR note...I am not aware of any other RCR model having rotor issues...the RCR40 and the like, use a NASCAR type vented rotor with no slotting or drilling and many guys have used them in heavy track conditions without issue....

We will be testing some slotted only rotors next week....

[Randy V]

Originally Posted by Darteaus

JM:

During the cool down lap - which makes a lot of sense BTW - would you recommend periodically tapping the brakes to avoid potential shock cooling [cold air / hot parts], or is that not really a possibility?

Also, I wonder how NASCAR cars avoid cracked calipers after coming in under the yellow, braking hard in a heavy car, and then sitting in the pits. Is it because they are only in the pits for less than a minute, and then they have an extended run (airflow) back up to speed?

Thanks for your (or any other knowledgeable person) thoughts on the subject...

The level of brake preparedness for NASCAR (particularly short tracks like Martinsville) is a world unto it's own.

They will use a brace of up to 8 12v electric blowers inline to individual cooling ducts.

Rotor material - you won't find these rotors available for $49. These are the good Curved vane ones made from Powdered metal steel castings, then given the full machine treatment before they are heat treated and then Cryogenically treated.

Brake fluid recirculators - each pump of the brakes gives the caliper an injection of "cooler" brake fluid from the reservoirs.

Pads - The best carbon metallic pads out there from the likes of Performance Friction and Alcon - et al...

[J. Salmon]

Pictures are too big to send by email uncompressed. If you PM me an address, I think I can copy and send some on a CD.

[Jac Mac]

Originally Posted by Darteaus

JM:

During the cool down lap - which makes a lot of sense BTW - would you recommend periodically tapping the brakes to avoid potential shock cooling [cold air / hot parts], or is that not really a possibility?

Also, I wonder how NASCAR cars avoid cracked calipers after coming in under the yellow, braking hard in a heavy car, and then sitting in the pits. Is it because they are only in the pits for less than a minute, and then they have an extended run (airflow) back up to speed?

Thanks for your (or any other knowledgeable person) thoughts on the subject...

Dont think you need to be concerned about tapping the brakes, the rotor will be cooling the pad surface anyway which will help bring the pad temp down below a critical level.
The first couple of minutes dont seem to be a major factor in a pit stop situation and its likely that in a wheel/tyre change scenario that there is some wheel /rotor rotation. Probably the biggest offender is when a car ends up in the 'kitty litter' and cannot be moved for several minutes.
When you hear the ' click ' of a rotor cracking back in the pits its usually a few minutes after race end. (( Have a mate who worked with Tulloch's "Cat" race truck, he mentioned when one of the front rotors on that cracked in the pits it was more like both barrels of a shotgun going off---- everyone hit the deck!! ))

[CRASH33]

Just as an idea of the cooling needed, on the Trans Am Mustang we ran, it had FIVE inch brake ducts to the front rotors. Coleman rotors last about half as long as the Brembos due to metalurgy, but are half the price. Don't use the drilled rotors unless the temps are too high during actual track conditions. This can be checked with brake paint. They also reduce the surface area and reduce braking capability. If you are going to track the thing a lot and have issues with heat even after putting big ducts on, instead of using the drilled rotors, go to the new carbon/ceramic brake packages and you will have NO further issues.

BTW- The heavy duty NASCAR packages for short tracks are just that, extremely heavy, thick undrilled rotors. Using this setup makes the wheel bearing grease you need to use and service kind of a PITA.

[Brian Hamilton]

Originally Posted by crash33

Just as an idea of the cooling needed, on the Trans Am Mustang we ran, it had FIVE inch brake ducts to the front rotors. Coleman rotors last about half as long as the Brembos due to metalurgy, but are half the price. Don't use the drilled rotors unless the temps are too high during actual track conditions. This can be checked with brake paint. They also reduce the surface area and reduce braking capability. If you are going to track the thing a lot and have issues with heat even after putting big ducts on, instead of using the drilled rotors, go to the new carbon/ceramic brake packages and you will have NO further issues.

BTW- The heavy duty NASCAR packages for short tracks are just that, extremely heavy, thick undrilled rotors. Using this setup makes the wheel bearing grease you need to use and service kind of a PITA.

I had heard the same thing about reduction of surface area due to cross drilling. Generally, as I said, I'd recomment slotted rotors to our track guys and crossdrilled to our street guys so they could have that "Bling" factor. LOL

[Randy V]

Rotors were drilled many years ago not as a measure to lighten or cool the rotor, but as a method to allow the outgassing from the brake pads to dissipate. This was back in the days of Asbestos and Organic material pads.

It was normal for pads to outgas at such a rapid rate that there was actually a substantial boundary layer built up between the pad and the rotor. This would actually prevent the clamping action on the rotor to be realized.
It's happened to me back in the very early 70s while racing my B/P Corvette. The brake pedal was high and as hard as a rock but the braking action was nil. Darned scary when entering a corner with an extra 80 MPH...

Today's brake pads contain no asbestos and very little organic material at all. The composition is more Carbon Metallic and Ceramic. Outgassing is almost nil.

Yes I'm aware that Ferrari drills their rotors - but why I'm not so sure.

But from my perspective - drilled rotors are just bling factor.. It's substantially less surface area to work, stress risers at every hole, simply not needed...

----

Cast steel vs, Cast Iron rotors.. The Iron ones feel like they're made of aluminum in comparison to the steel ones..

[Chad]

Here's a study (written by 4 Ph.Ds) I found a while ago comparing peforated and notched disks. They concluded using FEA that the perforated disks had a better temperature distribution and heat flux compared to the notched disks.

Here is the powerpoint presentation, sorry I don't have the actual study with all of the results.

Thermoelastic Instability in Disk Brakes: Simulation of the Heat Generation Problem

However, I did not see any mention of calculated stress levels. Anytime there's a hole, you're going to introduce stress concentrations.

[Ben Whittle]

Interestingly as you say, Ferrari (and Porsche) drill their carbon ceramic discs where as someone like SystemST DON'T and they apparently supply to Ascari and Koenigsegegesgssegseg.

Fran, you seem to have a few links here and there don't you? SL-C....SystemST carbon ceramic discs....

[J. Salmon]

Complete new digidash just arrived. We hope to run the car again Thursday if we get the rotors.

As to the carbon brakes... even with no budget limits, I would not look beyond the brakes that are on this car. It's all physics. This car is not going to be as hard on brakes as any big modern fast car. Again, look at my RS4, with repeat stops from 140 at 3900 pounds, and the rotors are fine at 25000 miles on the clock. They make a CCB kit for the RS4, on option in Europe, and available as an add on here... 15k for the fronts. Tell me how that is supposed to make sense? Once we get the rotor and pad combo right, you will see that the steel brakes are the way to go, unless you just want the bragging rights.

I will say the rotors on my 40 are really impressive. They are smaller diameter (about 12 inches) but they are really wide with a huge airspace. I don't think Dean is even running cooling ducts. I am not planning on it unless I have to.

[Ben Whittle]

A lot of people when you start bringing up the whole CCB discussion immediately jump to the argument that they aren't necessarily more powerful and thus aren't needed.

It's not the power of CCB's I'm interested in, there probably isn't any gain at all (although they'll remain consistently powerful the hotter they get vs conventional brake discs), but more the huge (and I do mean huge) reduction in unsprung weight with CCB's.

I've picked up a MASSIVE front CCB Mercedes SLR front disc, then I picked up a normal REAR Mercedes SL disc (it's quite a bit smaller) and the front (larger) SLR CCB disc was *SIGNIFICANTLY* lighter than the conventional rear SL disc.... and thats just one corner.....unsprung weight reduction remember.

I couldn't think of a more perfect combo than SystemST CCB's and Dymag carbon/magnesium wheels, that'll make an already featherweight SL-C stupidly agile on it's feet.