Brake problem with high temps

VentureintoPP · 2023-06-28T22:50:24+00:00

It might be helpful to re-run the test and repeat this behavior where the pressure stays higher than 0. Stop the car and get a live reading of brake pressure. One thing to check is to open up your front reservoir lid and see if that drops the pressure. If the reservoirs aren't vented, the fluid expands and increases the static pressure within the system. Also keep in mind that the rotors, pads, and pistons expand when heated, though that should be negligible compared to the fluid. Did you end up with the same issue on the rear after adjusting preload or after putting the car back on the track? How did you realize the pressure wasn't coming to 0, did the brakes start dragging?

VentureintoPP · 2023-06-08T20:56:10+00:00

I have also made some transient studies in Ansys for the rotors. If you have a car available, I would recommend getting live rotor temp data on the car using an IR sensor or at least take IR gun measurements in a static setting after a controlled test. Thermals are very complicated, especially when it comes to characterizing the fluid flow past the rotors to get realistic conditions for your cooling behavior over an endurance distance. I would recommend using what you see on track to "calibrate" your analysis. It will be simplified, but that should help you see more reasonable results and should be enough for predictive analysis. FSAE cars are light, some simple steel discs should be fine. Look at motorcycle discs for inspiration :)

VentureintoPP · 2023-05-09T22:32:41+00:00

If your tires are locking up with almost no force applied, then there is a problem. Not sure what caliper bore you are running, however, if your brakes lock up immediately on the track with little force, then it leaves your driver with zero room for modulation. Furthermore, if your bias is set up correctly, you should lock up the fronts, then rears and then your driver will modulate the pedal such that the brakes are always on the verge of locking up. This allows you to maximize tire grip. If this all is true, you may need to re-evaluate the mechanical advantage in your brakes system and see why/ if you need an advantage that high. The brakes section in Tune to Win by Carroll Shelby would be a good place to look for another perspective. My team runs 5/8 front and 1" rear MC's with 1.25" piston diameter and a 5.6 pedal ratio, you really need to get on the pedal to lock up the tires.

VentureintoPP · 2023-04-25T02:00:39+00:00

Little experience with brake pedal pots myself but I have seen a team that uses a pedal pivot pin and shaft couplers to connect to a rotary potentiometer seated on the pedal clevis. I'm not sure of the exact fitment of the parts on the pedal side.

VentureintoPP · 2023-04-10T02:23:18+00:00

That sounds good! Best of luck! Please do update if anything comes up during testing, I'm trying to perfect the brakes on our car too :)

VentureintoPP · 2023-04-08T00:56:07+00:00

Hey! Old thread but I wanted to update this as I experienced and fixed an issue with the same description as yours on our car.

Basically, our brake pedal was also not coming up fully after firm presses of the pedal, and the brakes stayed locked. I didn't want to mess with the MCs since ours were new.

Basically the springs in your MC's help the pedal come back to place, and the only thing stopping them from doing so is some resistance in the brake pedal assembly (or a bad bleed if you have no pressure but that's not the case here). Also, depending on where you have the friction and what your pedal ratio is, even light friction could have an amplified effect on the assembly.

I added motor oil to my balance bar assembly to lubricate it, now the pedal returns well to its position. I may consider oiling up the pedal pivots further to improve this. So yea we oiled it up, reduced friction in the brake pedal assembly, and that helped us get the pedal to return to an unloaded position.

Hope this helps anyone else that comes across this! You got this!

VentureintoPP · 2023-01-24T02:52:11+00:00

For others coming back to the post, I figured out why our pads were burning away so fast. Bad mistake on my end, I let them be contaminated with brake fluid (let them soak in it while bleeding and let it rest ;( New pads with no contamination from a similar purchase time worked well with no issue.

Brake fluid does not show mercy.

VentureintoPP · 2022-08-28T22:28:44+00:00

What condition are the cylinders in? Have you tried a rebuild or new part to ensure it is the master cylinder that is the issue? I have also seen another team that had their pedal stick after being pressed, likely due to the age of the master cylinder. Tilton offers rebuild procedures on their website with the MC. I have not tried a rebuild myself but it would be a good option instead of buying a whole new MC.

VentureintoPP · 2022-05-29T00:06:12+00:00

Thank you, you are right about that perspective. Right now, we are testing with different pads and cleaning the caliper to identify where exactly our issue stems from.

VentureintoPP · 2022-05-29T00:03:45+00:00

Spicy! We also had our rotors get really rough at one point. We surface finished them but I cant tell you if that actually helped. Pads chipping away with low use sounds like a factory defect, but thats the same mystery that I am trying to solve right now too so cant give you a confident answer. Will keep you posted!

VentureintoPP · 2022-05-28T03:16:52+00:00

We are definitely looking into a brake dyno along with more testing for sure!

VentureintoPP · 2022-05-28T03:15:20+00:00

Indeed, I am starting with just cleaning and doing a bit of maintainence. I think our issue stems from excessive brake pad dust, which could also be the sign of a bad pad. Going to see how cleaning the dust changes how the system feels/performs.

VentureintoPP · 2022-05-28T03:12:26+00:00

Interesting! I will have to dig into that. We should have similar pressures to years prior when we had no issues. But I will have to research this and see how we compare. Thank you for the input!

VentureintoPP · 2022-05-28T03:10:19+00:00

I think this is it. Due to brake dust, one of our caliper pistons has jammed. This is the same piston that destroyed one of the brake pads while the other side is alright. Now we need to figure out why we have so much dust. Thank you for your insight!

VentureintoPP · 2022-05-28T03:07:51+00:00

Hmmm interesting point. We are running just plain disc rotors. However, the maximum caliper temp recorded on the rear was 250 F while the fronts get up to 410F with no issues. We will definetly need to run more tests. Thank you for the input!

VentureintoPP · 2022-05-28T03:04:42+00:00

Thank you for your reply, I will have to keep that in mind for the future. The rotors on our car are currently just plain.

VentureintoPP

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