mark kibort

Thanks Mike. Ill investigate, as there are two things going on here.... fade, which i have just learned to work around over the years. (not a solution) and then with the more agressive pad, the grooving. (and no fade was solved , but more initial bite with the ST41s) . I still have a suspicion that the forces are just too great for the calipers/pads and rotor size. i think they are plenty cool as i approach turn 2, but he increased speed due to the extra hp over the last 5 years , is too much. remember, kenetic energy is 1/2MV^2. its highly speed dependant not so much the mass. this is why the extra 10mph due to the extra 50hp is causing a huge issue, and at sears,/thunderhill there are no issues at all. i just think the huge stopping power required to get into turn 2 is a beyond the pads. certainly, if there was a pad that could handle the heat at the end , that would be a solution, but i dont think air flow in that area, can dissapate the extra 100s of HP for that 1-2 seconds where the problem is. maybe it can.... certainly there is concesus here, saying that it will, so ill give it a try. my cooling setup today, is not that bad, but it isnt as good as others ive seen at the track. so, ill design something that will work. i have duct areas available in the headlight fixtures, so ill use them, or duct the integral air inlets in the lower splitter /airdam area. ill post a picture to show what i might do.

thanks again. Ill try and do a POC or NASA race with you, maybe during the SCCA break before sept. see you then.

mark kibort

I dont know how you roasted the brakes on such a light car. usually , with cars with that kind of power (see spec miata) you dont even use brakes!
actually, the stink is the resin. when i bed the pads on the hyway. (the 100 to 60mph repeat process) ..... i know they are bedded when the stink is reduced and it will fill the cabin , its bad. thoose pads have all the paint on the backing, sides and pads themselves. Only a little white trim on the contact of the pad is seen. so, the paint is still there. but at the track, after the first day, the paint is gone , the backing plates are white from heat and so are teh pads. but the stink is nothing near what i find during the initial bed in.

I do have some decent cooling but its more deflective than ducted and i think certainly it can be improved on. Will it help the infamous entrance to turn 2 at laguna issues???? Well, i will see! thanks!

as an example. Here is the video from the laguna test/ race with the ST41s. at 6min in the video, i go purposely about 20 to 50 feet deeper in the zone and push as hard as i can when they are not slowing as they should (or i would expect). i have to give up, trail brake and use the downshift and turn in to make the turn.
Mk

KaiB

I can honestly say I have NEVER seen anyone steer a race car with one hand and then his thumb until now.

What has been seen cannot be unseen...

flatsics

Need some more **** on that keychain

flink

Additional cooling will help because it will decrease the average rotor temperatures - if you enter T2 with rotors 100F cooler then they will be ~100F cooler at the end of the braking zone, and that's 100F further away from the point of pad fade.

I have a suspicion that the rotor grooving is related to the pad fade - if the pads are cooking and puking out dust and gases, that effect might not be happening uniformly across the pad surface, dunno.

When prepping a new set of pads I remove all that stupid paint from the back with paint stripper - it just makes a mess and interferes with taking thickness measurements. I also skim the faces with an orbital sander to remove the mold release compound.

I have measured the effectiveness of the 3" ducting on my car and the effect was surprisingly small. Remove the ducting and backing plate from one side, come in hot after a few laps and measure the rotor temperatures with an IR thermometer. At Sonoma it was 600F vs 660F and at Thunderhill it was 700F vs 770F, so say 10% cooler on the ducted side.

Mahler9th

I only have experience with old school brake pads. I learned recently that my trusted pad has been changed by the manufacturer during my ~20 month hiatus. But it should be easy to find a replacement. My current car is not all that sensitive in terms of braking performance.

I have never worried about rotor wear, but I don't drive enduros. And my current rotors are really cheap.

I encourage you to get and read the Puhn brake handbook. But I think you know all of the basics. You want a good clear path for the air. Appropriate sized hose. Backing plates that cover the entire back side of the rotor. Even blocking off any openings in the hubs can help. This is described in Puhn.

I remember when SRP was developing their 911 hub block off plates... I visited with CW when he was working on this as he wanted to see if a product made sense for 944 family cars (it did not).

I think you are barking up the wrong tree when it comes to braking and thermal particulars at Laguna. That is don' t think turn 2 is anything special. In my experience, turn 11 is where pedals typically get long.

If things get and stay too hot to perform correctly, that is where the focus should probably be applied.

I think you should address basics first, then start assessing any additional needs. The last thing I would want is to spend unnecessary $$ and install heavier parts.

I don't think excessive heat cares about any particular turns/corners. I think the goal is to have proper ducting to keep the temps in an optimal range, and if necessary increase the mass for further help. And to have fluid that maintains its performance across the operating conditions.

All of the stuff about pad feel and fade and yada, yada, yada is just overkill in many cases. I cannot recall a situation with a properly set up Porsche track or racing car (including proper components like rotors, calipers and pads) where these things were an issue. But I have been many instances where improperly set up and/or maintained cars had issues. And that's about 3 decades worth of observation and experience.

Mahler9th

962s used the ducting for brakes and wheel bearings. Some 917's had an interesting design.

I went a little crazy with my ducting design a few years ago.

Veloce Raptor

+ Juan

mark kibort

you must have not heard about my 2nd gear. I wore off the edges of the 2nd gear synchro, so I have to hold it (really hold it down) in gear, or it will pop out. only 2nd though.

mark kibort

928 list guys gave me a good luck charm. and of course, the rear hatch key..

mark kibort

I get your point about temp starting point but, if the temp rise happens by brake fade and then increased pressure, max pressure, in other words, the power factor goes up in short order, regardless of temp starting point. I could start with frozen rotors, and the temps could be much cooler to the point of , brake fade, and then by pushing to the limit, temps could get very high , quick. I didn't and never had any grooving until the ST41 s as I said, the only diff was a lot more initial bit and stopping power for less pressure initially, and then at the end, when all the pads fade in turn 2, the
fade was the same. stopping distance was in the end , near the same.
10% during your tests, sounds encouraging, so worth a try with the 3" ducts.


why turn 2 is so special, is because its using the most amount of total braking power vs time (KW-seconds). turn 11 has NO where near any issues due to the lower staring speed, and very very short brake duration. but it is demanding, at turn 11, no doubt. However, if you are dragging brakes out of the corkscrew, and dragging through 10, you can effect temps at the starting point of the braking zone of 11, and might get fade. over all, I don't have any issues and never had any issues with fade. don't have a soft pedal at all. doesn't change during a demanding all out race, but now with the greater hp, turn2 is a challenge. the only other turn that is a challenge for the brakes now, is turn 13 at thunderhll. again, do to the higher approach speeds and slower entrance speed target. I think with the ducting, that might not be an issue at thunderhill due to the high speed of the track, and greater effect of the duct work.

again, you have to realize a 1:36 at laguna, is a lot of work on the brakes with only 12.6" rotors and 370rwhp 3000lbs. 10-15% more leverage for the guys with the larger diameter rotors, which is HUGE on reducing heat.
a BMW or 911 with 320 hp, 2700lbs can have 10% less kinetic energy to deal witih at the same entrance speed, so with the same rotors, it might not have an issue. give it a 14" rotor, and suddenly, there is a nother 10-15% benefit. it all adds up . there is a reason why the 14+ plus " rotors are so popular in race cars. even the low end stoptech ST40s use 13" rotors, for lighter touring cars.

certainly the first move will be brake ducting, and ill due to some temp tests too before I change anything. then, I think the larger diameter rotors will be next. remember, single piece rotors have a LOT more mass than the 2 piece a lot of folks use. I put a lot of heat in the hubs, but there is a lot of heat getting dissipated. 2 piece and you need more cooling just to start, to get the same heat out of the rotors . something else to think about.

2BWise

You have all the right answers in this thread but your thought process to get there is all wonky. Its a relatively simple energy balance problem. Energy in equals energy out. Where's all that energy going when you hit the brakes?

Simple ducts that point into the wheel well are nearly useless. The air flow in that area is much more complex than a little tube dumping air in the general vicinity will ever overcome. That's why these ducts that encompass the rotor and hub area are being pushed. It is the only efficient way to get airflow to the brake assembly.

Jim Devine

Get some of these and use them as directed. Until you do , you won't know your max temps.
Proper brake ducts are a must no matter what, but you have to know your temps before a pad can be properly matched.

https://www.pegasusautoracing.com/pr...p?Product=3161

333pg333

Ducting aside, not sure that this qualifies as lateral thinking but can't you lighten the car some? That's not too difficult or expensive. Venting the entire wheel-house area not only helps brake cooling but also reduces front end lift. Also, what's wrong with going with larger rotors also? Coleman rotors are so cheap and they last well enough. We got some custom rotors and hats made up by them when upgrading from the 320mm to 375mm and they were dirt cheap considering they have such a large bearing on that rather necessary concept as retardation. Shipping costs made it a little harder to deal with but you won't suffer that.

ir_fuel

Maybe you should get that fixed then?