Brake temps/ rotor cracks.

[Venom525RWHP]

On Mosport I have two VERY hard braking zones, into 5a braking in an uphill hitting ABS sometimes before the back straight and into 8 slowing down from 240km/h plus to around 150km/h. The rest of the track are pretty easy on the brakes.
After every event I have to resurface the rotors to keep an eye on the surface cracks. Twice I had the cracks right through after only 100laps.

Question: With all the brake ducts in place and running an entry level race pad (Gran Sport GS3, GS5&6 are full race pads), am I coolling down the rotors too much down the backstaight after a temps spike into 5a and then another temps spike into 8?

 

[JSpeed]

its possible but i doubt it unless it was cold out. Try a different rotor like Coleman.

 

[ac427cobra]

I was just at Mosport on June 1st with Dexter Days for the first time. Although I may have been a little hard on my brakes being the first time there, I don't see Mosport as being hard on brakes. As a matter of fact, Thomas Moran (Green '99 Cobra with Silver Maple leaves on it #99) told me Mosport was easy on brakes. I agree with him.

But, having said that, you do have a heavy car and if you're driving at the limit I could see how you may be having brake issues?

What kind of rotors are you running? IMHO you should never run a turned rotor at a track as fast as Mosport. I only use a turned rotor when I go to a slow safe track like Gingerman. MAM or even Auto-Bahn for that matter. FWIW

Are you putting your rotors through any type of seasoning process? That is very important.

Need more information from you for further diagnosis.
:thumbsup: :coolman: :beer:

 

[ac427cobra]

Oh, one other thing. It is my opinion that a source of a lot of rotor cracking is bringing them up to temp too fast on track. So, if you're going fast into turn 8 on the first lap you're throwing quite a bit of heat into the rotors when they are relatively cold.

This is what many people see going into turn 5 at Road America.

YMMV

:thumbsup: :coolman: :beer:

 

[sleepless]

Frankly, at roughly 3800lbs wet (I had mine weighed recently), these cars need 14" or 15" brakes! Those poor 13" really have a hard time shedding the heat.

So, the 13"ers really need a lot of TLC to make them last. I agree with Bruce:

- season, season, season new rotors
- heat them up slowly in the first two laps
- use pads that suit your driving style; for me, I want the most aggressive pads possible; I've been using Hawk HT10s, but am now about to try the DTC 70s.
- and, of course, cooling ducts

I'm pretty sure that unless it is freezing outside, it's pretty hard to cool off the rotors too much.

 

[Venom525RWHP]

I am sure I am close to the limit of the Brembos...
To get 1,35,18 on Mosport with 3800lb and with 420 - 440rwhp on 2 year old GAC Hoosiers and stock shocks I need to dive deep into the corners, set the car up for a straight exit and use the power to carry more speed.
laptimes from last year
car #333 class SGT2
http://www.mylaps.com/results/newResults.jsp?id=415889 On Hoosiers.

and
http://www.mylaps.com/results/newResults.jsp?id=353271 On RA1's

I am using stock Brembo rotors with 4 piston calipers in the front. Before every event I usually do 1 lap to bed the pads and let them cool down for at least 45min.

 

[Venom525RWHP]

Oh, one other thing. It is my opinion that a source of a lot of rotor cracking is bringing them up to temp too fast on track. So, if you're going fast into turn 8 on the first lap you're throwing quite a bit of heat into the rotors when they are relatively cold.

This is what many people see going into turn 5 at Road America.

YMMV

:thumbsup: :coolman: :beer:

Makes sence... 5a must be my problem. So 2 warm up laps may work for me?

 

[ac427cobra]

To get 1,35,18 on Mosport with 3800lb and with 420 - 440rwhp on 2 year old GAC Hoosiers and stock shocks I need to dive deep into the corners, set the car up for a straight exit and use the power to carry more speed.
laptimes from last year
car #333 class SGT2
http://www.mylaps.com/results/newResults.jsp?id=415889 On Hoosiers.

and
http://www.mylaps.com/results/newResults.jsp?id=353271 On RA1's

I am using stock Brembo rotors with 4 piston calipers in the front. Before every event I usually do 1 lap to bed the pads and let them cool down for at least 45min.

Well, my first time there I managed to finish up my last session running a 1:37 on Nittos with a passenger. Once I hit 1:40 I was shaving a second off every session. Your car is heavier and it has more power than mine. So it's close to equal equipment but your car is harder to stop.

That being said, I think you could benefit from some front suspension upgrades which will allow you to carry a little more corner speed so you don't have to slow the car so much. Same thing on the IRS. If you're still running on all of that shitty OEM rubber in the IRS you need to ditch it ASAP. See my sig! :-D

Last but not least, you're most likely at the maximum braking capacity of that 13" system. You probably should look into bigger front brakes! epper:

The 13" one piece Brembo rotor will give you decent service. If you don't drive your car on the street, see if there is anyone you know driving an SN-95 with 13" brakes. Replace their rotors for them and have them season your rotors for 500 miles or so putting them through numerous heat cycles. This will help the durability of the rotor tremendously.

YMMV

:thumbsup: :coolman: :beer:

 

[nightstalker865]

I cracked a set of blanks this year running at CMP. I threw them on the night before the event. I will never make that mistake again. Heat cycling makes good sense.

 

[Venom525RWHP]

Well, my first time there I managed to finish up my last session running a 1:37 on Nittos with a passenger. Once I hit 1:40 I was shaving a second off every session. Your car is heavier and it has more power than mine. So it's close to equal equipment but your car is harder to stop.

That being said, I think you could benefit from some front suspension upgrades which will allow you to carry a little more corner speed so you don't have to slow the car so much. Same thing on the IRS. If you're still running on all of that shitty OEM rubber in the IRS you need to ditch it ASAP. See my sig! :-D

Last but not least, you're most likely at the maximum braking capacity of that 13" system. You probably should look into bigger front brakes! epper:

The 13" one piece Brembo rotor will give you decent service. If you don't drive your car on the street, see if there is anyone you know driving an SN-95 with 13" brakes. Replace their rotors for them and have them season your rotors for 500 miles or so putting them through numerous heat cycles. This will help the durability of the rotor tremendously.

YMMV

:thumbsup: :coolman: :beer:

1:37 with a passenger!! Thats is pretty good. It took me atleast 2 events to break a 1:37 by myself in the beginning. :rockon:
As for suspension, I am running stock a-arms with Delrin bushings on all four corners, the IRS bushings are my next winter project. I think the iron block and heavy blower assembly is killing me on the sweepers.

So it is safe to assume that the cooling ducts is NOT the problem? Proper seasoning of the rotors must be my major concern!? For now I do not have money to upgrade, so I'll just have to take it easy...

On a side note: What did you think of Mosport?:banana: :burnout:

 

[Cobra-R]

I am a little confused.......are you actually cracking rotors or are you referring to stress cracks? If you are actually cracking rotors, (as in breaking them) you need to find the problem. If they are the stress cracks that show up after a couple sessions, that is normal.

Brian

 

[Venom525RWHP]

I am a little confused.......are you actually cracking rotors or are you referring to stress cracks? If you are actually cracking rotors, (as in breaking them) you need to find the problem. If they are the stress cracks that show up after a couple sessions, that is normal.

Brian

Well I broke 2 rotors already, one on Shannonville going into turn1 and one on Mosport as I was coming off in to the pits!

This one was Shannonville

It usually starts with stress cracks, that is why I resurface them after every event to see how deep they are... 3rd time I may not be so lucky

 

[ac427cobra]

Well I broke 2 rotors already, one on Shannonville going into turn1 and one on Mosport as I was coming off in to the pits!

It usually starts with stress cracks, that is why I resurface them after every event to see how deep they are... 3rd time I may not be so lucky

This type of symptom is very typical of a hub going bad. What happens is the hub has play and stress fractures the rotor ring where it meets the hat portion of the rotor.

Check your front hubs for play. Driving at the limit, they only last about 1,500-3,000 miles on the left front and about twice that on the RF.

That would be my guess.

Good Luck!

:thumbsup: :coolman: :beer:

 

[sleepless]

Check your front hubs for play. Driving at the limit, they only last about 1,500-3,000 miles on the left front and about twice that on the RF.

Is the short life of the hubs due to heat transfer from the rotor? Do floating rotors help considerably?

 

[ac427cobra]

Is the short life of the hubs due to heat transfer from the rotor? Do floating rotors help considerably?

Heat from the one pc rotor gets into the hub and accelerates wear due to the breakdown of the grease in the hub.

The two pc rotor keeps a LOT of the heat out of the hub and increases the life of the hub.

:thumbsup: :coolman: :beer:

 

[sleepless]

I'm going to try the DBA 5000 2-piece rotors. I've used them on another car and several Corvette buddies use them with great success.

 

[MFE]

This type of symptom is very typical of a hub going bad. What happens is the hub has play and stress fractures the rotor ring where it meets the hat portion of the rotor.

Check your front hubs for play. Driving at the limit, they only last about 1,500-3,000 miles on the left front and about twice that on the RF.

That would be my guess.

Good Luck!

:thumbsup: :coolman: :beer:

That's a downside to a fixed caliper in tandem with hubs like these

 

[Venom525RWHP]

I am putting on new Brembo blanks and installing new bearings on all four corners this week. hope this helps.
Thanks for the advice...

 

[ac427cobra]

I am putting on new Brembo blanks and installing new bearings on all four corners this week. hope this helps.
Thanks for the advice...

Well, to tell you the truth, the rear knuckle bearings are considerably more heavy duty than the front hub bearings. They are a tapered roller bearing and they should go a LOT longer than the front bearings do. :read: You just need to check the torque on the 36mm nut to the halfshaft before or after an event. They are considerably more effort to replace as well! :cryying:

Some guys just replace both of their front hubs every year. I prefer to keep a close eye on them and replace them when they get a little play in them.

FWIW,

:thumbsup: :coolman: :beer: