mark kibort

just talked to Bruce at performance shock at Sonoma.... he said he can rebuild the Koni shocks in time for the runoffs! wrenching to get them off tonight!

GregBBRD

Fooled me again, with your photoshop changes....you're great at that!

I thought that the temperature paint was actually right down into the tiny little radius where the rotor meets the hat.

I guess that is where some bird **** on it and not temperature paint?

If the rotor is 1400 degrees right where it touches the aluminum...the aluminum is very stinking close to that same temperature, where it touches that rotor. Since there's nothing there to dissipate the heat....it's a direct transfer from one part to the other part. "Locally" (where the rotor is bolted to the aluminum hat) both were within a few degrees of being the same temperature! Granted, the temperature is going to go down rapidly as it moves into the rest of the aluminum....but "locally" it's very close to 1400 degrees! And "locally" is where the rotor is bolted to the hat! (Again, a science thing...you are not going to understand it.)

You have transformed those hats into unsafe junk.

But that makes no difference to me....that's not the point of my question...just your distraction away from the question...which, looking at all your threads, you are good at....

And I'm making the question gradually simpler, for you!!!

Without any changes, how do you plan to reduce that rotor temperature?

mark kibort

what do you think is photo shopped?? Im confused here. nothing looks photoshopped and nothing is photoshopped. all raw pictures from before and after qualifying and the race . the race had the long line of paint from outer diameter to inner diameter and hub...... the qual just had the outerdiamter and the thin line at the meeting of the hat and rotor.

that's a good point. it looks like the rotor that is the dab of temp paint along the circumference, is very hot. even if its 1200degrees, that's hot. from the color, it looks to be near 1400. and yes, that rotor is mounted to the aluminum, but for some reason, it didn't turn the paint on the hat to over 5-600 degrees. But, you are right, its touching a very hot rotor.
now with a true 13" rotor and slowing distances pretty close. (look at that mustang im running with. only slightly slower top speed, but heavier and stopping near the same). he is running the 14" rotors and isn't seeing anywhere near the temps im seeing.

I put temp paint all over that cars rotors too just to see. I haven't seen his rotor yet, but I bet its not very hot at all. I did it before I really covered his rotor with paint. (he wanted all parts tested for temp) and the part on the rotor on the inside diameter, was no where near the temp I had. remember, this is a 14" rotor, not 13" rotor. that 7% thermal mass difference AND 7% more leverage might be the difference.

GregBBRD

You can see what the aluminum looks like, when you change the rotor. I'm betting it is galled from being hot and working on the steel at those really high temperatures.

At any rate, you don't actually have to answer the question....the answer is obvious to everyone. Unless you want to change rotors every event, you are going to need to reduce that 1400 degree temperature down below 1000 degrees (at least).

And the heat generated from the delta in Kinetic energy (by friction) isn't going to decrease, regardless of what brake pad you run...if everything stays the same.

You have very limited alternatives (I listed all five)....and as I was saying on your previous brake thread....the thing you eventually will need to do is to reduce the weight transfer to the front end and get the rear brakes to do some additional work....or be stuck at your current plateau forever.

ABS would be of a great benefit....once you get the car "reasonable". Right now (obvious from your brake temperatures) the car is a mess. Note that I'm not saying you can't make it turn fast laps....but I'd submit that you are doing this "in spite" of the car.

RKD in OKC

Good news on the damper refurb.

If you think your brakes are dragging you might try some high temp dry lube on the slider pins to make sure the calipers are floating and not sticking when they get hot.

How's that for an out of the box solution?

mark kibort

Thanks Greg, but I tend to think that im at the limit of the tires, which is taxing the front rotors. I haven't seen anyone at the track dissipating the KE I am. a few have challenged, but there is always a catch. earlier braking point or bigger rotors. you say, get more rear bias, but as I explained, I think im near their limits as well. I don't know if you know this, but any greater stopping force, even at the rear, transfers weight to the front. yes, even adding rear brake , makes the rear brakes less effective. weight transfer is a function of only 3 things. CG height/position, wheel base, and deceleration rate (negative g). at 1.5g decal, the weight on the rear tires is near what the engine braking provides....... slip percentage is a curve, with effects up to 25% slip. optimal is in the 5-10% range based on the tires compound.

the interesting point about your observation , is that we have a temp issue. agreed. BUT, the only thing that is potentially possible by adding rear brakes, as I will (or any decent racer) will use the front tires to their limits. BUT, the time will be slightly shortened if the rear brakes have more effect. how much.... that's left to be seen or calculated. I estimate.... not much. unless you have some idea of how I have less than max braking force on the rears as is, incorporating engine braking as well as whateverbias I have today.

The point to you is, that we did some changes. we have a larger rotor. its helped, along with the holes , and possibly the hat material BUT, as you say, we are still in the high temp range. when I pull the hat, ill post the pics
maybe that color is 1000 degrees and not 1400. if so, I might be ok. if not, its time for 14" rotors. keep this in mind. say we were able to optimixe the rear brakes..... say we added 20% more braking force in the rear. and lets say it allowed me to slow and save .25 seconds in the 4 second braking operation from 130 to 45mph. we can calculate that KE change. BUT, as soon as we go to a tack like road America or Fontana, ill be right back where I was. because, you want as much weight transfer to the front as you can, the rears increase this weight transfer and overall breaking force, but less and less as they become fully utilized.

thanks for the endorsement of the fast laps in spite of the car. yes, ill admit, due to budgets and time, ive been driving around a lot of issues in the past few years. however, the car has been a little bit backward over the past 2 years. we know its not power.... so its that shock, the used tires or me. I think im constantly improving a little bit every season, so I do think its the tires and maybe the blown out shock..... ill know more next week!

there are slider pins? you mean the "shelves" where the pads sit?
I have a hard time beleiveing the rubber seals are responsible for the piston pull back. in fact, don't most race cars have no rubber seals anyway? plus,the drag I feel on the tire,is inconsistent, due to a slightly warped rotor. we know they were beat to begin with . new ones with new pads might be different.
I also forgot that 10 ftlbs of torque at the rim, isn't 10hp, 20hp for both , its in 3rd gear, so that's 10 divided by 4.6 :1, so that's only about 2hp. not enough to effect lap times as I saw. im thinking its a handling issue due to the shocks and old tires.

RKD in OKC

Slider pins connect the outboard caliper half to the inboard caliper half.

mark kibort

are you talking about S4 calipers?? I don't remember seeing anything in the caliper that resembles this.

svp928

These calipers are fixed- no moving parts except the pistons, and yes, the seal is supposed to pull the piston back a very slight amount at release.

andy-gts

Mark ,

I admire your abilities, , and I understand you want everything to be the best they can be so you can do your best on the track....

that being said, seems like you would be best served by going to Greg at precision motorsports , and let him walk you through what he knows is critical and needed and help you do your best.

We are all on the same side here, wanting to help you do your best ....

so [B]PLEASE [B] just take your car to Greg and have him help you....sure it will cost something but it will be done right and you can move on with racing....and WINNING like we know you can do!!!!!

mark kibort

Here are some pics.

Sorry Greg, im glad you are not right about the rotor hats, but the temps seem to be much lower at the hat, as the temp paint leaked down and gave some readings. still pretty warm, but no where near 1000 degrees, though the rotor was near 1200-1400 degrees. the air gap and rapid dissipation probably helped here.
one rotor had HUGE cracks.. ...... pulled this apart just in time. holes in the rotor, and a 2 piece rotor design is very dangerous to have cracks. solid , not as bad. there is not much material at the attachment points.

I did a test with no front brakes at all. pulled the rotors and put spacers in the calipers so that the pistons wouldn't blow up. (simulated a rotor thickness). the rear brakes , into ABS, stop as fast as 2nd gear can from 5000rpm and slower. tested this sevreral times. proving that there is not much rear brake effect. also, with fronts working, there is more weight transferred, so even less is available from the rears than my test.

mark kibort

found the fuel pump short.... as Anderson had suggested... it was the wire shorting out at the chassis, but we thought it would be the gas tank straps not the swaybar to pinch the wire. mystery solved.

mark kibort

Those ST41s lasted 2 weekends. so much for "nascar " pads!

think that shock could be a problem??

GregBBRD

I'm happy for you that I'm wrong. Out of interest to everyone....

So that hat surface looks perfectly normal to you? The areas where the hard anodizing is missing is a perfectly normal thing? What the Rockwell hardness of that surface, compared to the rest of the hat? What does that hat look like when you think it is bad?

And I'm not sure what you are saying about the rear brakes....are you saying they have a bunch of stopping power, or not much power? It seems like you are saying they don't do much....which is exactly what everyone has been saying.

mark kibort

I know what you are talking about. that rough area is from the rotor moving and grinding on the hat. all of the holes were cracked and oversized. so much so , that the rotor rattled around when you shook it.
the other side was just as hot, but no movement and surface looks nothing like the picture. none of the friction wear . (not surface hardness compromising)
that rotor was moving all around. I don't know how close I was to complete rotor failure, but it was too close for me.

as far as the rear brakes, did you miss the part where I was enabling the rear brake ABS? that's the limit, as YOU say. at the limit, it doesn't do much, but that's what ive been saying the entire time. with the test, rear brakes at ABS limits equals what the 2nd gear engine braking produces. and by the way, that's with a very slight decal rate. remember you mentioned getting more weight transfer to the rear with more rear brakes? actually, the opposite happens. the more the rears can work, if they are not working already, the less they can do because any increase in decal rate, actually increases even more weight transfer to the front.

I still want to experiment on the track, so I will up the bias just to either validate or contradict my theory here.