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Have you considered the possibility that this problem is all in your head, and that your brakes actually are functioning correctly in the real world, where gauges and tests are not employed?
Thinking back to your obsession with oil starvation few years ago, and your multi-layered solution that ultimately created a … oil starvation problem, it’s a fair question.
At Sebring it required huge pedal pressure to get the car to stop reasonably well. Huge as in “as hard as I possibly could.” I’m sure down the road I’ll look back at this somewhat hapless effort with a wry smile. But I learned a helova lot about how to test and fab brake hydraulics, so it’s a net gain. I can now swap out MC or swap/bypass bias valve, or ABS pump in minutes.
In a perfect world I’d have been able to do real tests on the car by getting up to speed and braking at threshold. Can’t do that tho. One has to play the hand that one is dealt.
The fact that the apparent F/R pressure disparity nicely accounted for the symptoms at Sebring may or may not have been a red herring. Figuring out that there was a problem with the test rig was a painful process, but tenacity won in the end.
Sometimes problems mysteriously go away. Maybe that will be the case this weekend.
There is always a silver lining. Just gotta be determined to find it.
The issue is kinda thrown into a chaos of “I don’t trust anything 100%”.
Rigorous tests can fool you. Sure, anyone with some experience has all sorts of stories re. tests that had them chasing after red herrings, but this was a brutal one. Dang how one can’t really trust a test result until they’ve found ways to confirm their suspicions in several different ways.
Non-rigorous tests can fool you. The brakes seemed to work ok at RA last weekend. Not terrific or bad, just pretty average. I was surprised that I couldn’t seem to engage abs going into 10a. No matter how hard I pressed, no abs. The “no abs no matter how hard I pressed” symptom is eerily similar to Sebring.
ABS was working tho. With colder tires and stabbing the brakes instead of squeezing them on, abs would engage.
I wonder if it’s possible for a track to occasionally have so much traction that in a braking zone the tires are more able to hang on to the cement then the little OEM pads are able to clamp on to the rotor. In that scenario you’d stop pretty fast, but no matter how hard you pressed, no ABS. One could easily be fooled into thinking that he wasn’t getting enough clamping force on the rotor because he was used to abs occasionally engaging.
So I dunno. I figure I’ll just let it go and see what happens. I will test the many spare ABS pumps tho. I hate having “maybe good” hardware laying around, and I want to see if my “works every time” test protocol finds the same problems with the ABS pumps as I was finding weeks ago. Then I’m done.
Was there every any resolution to this? I ran into a similar issue this past weekend at RA where I was having to brake at the 200 marker instead of the 100. The pedal seemed quite soft and the car just didn’t want to stop (not binding hard enough).
I bled the brakes at the track which didn’t seem to make a difference. Currently using PFC-08 pads.
The effort was ultimately interesting, but it was also frustrating and grueling. In a year I’ll look back at it and smile. I’ll compare the 100x I hooked up something differently, night after night, bled the system and then tested again and struggled to understand the bizarre gauge readings, to the 10? engines in 18 months back in '09 and '10. Not tonight will I smile about it tho. Next year.[/quote]
So… it’s been a year. Can you look back and smile now?
Som
I suppose. I learned a lot by putting the gauges on to the brake hydraulics at various points, and I still have the hardware necessary should I need to do more testing in the future.
Some people have funny ideas about how brakes work. Things like small vs. large MC’s, different size F/R pistons in the MC, brake bias, slave size, ABS pump failure modes, bleeding tips and techniques…but I’m one of the few guys that put gauges on at various points to really see what was happening. It was good to see some wivestales fall apart once tests got conducted.
As an engineer, I can’t abide “not understanding” how something works, so it’s all good.
It was a hard road getting the test rig to work. When I first put gauges on the brake lines, I didn’t realize that it was necessary to bleed each gauge, and that long hoses made that much harder. Also, the first high pressure hydraulic hose that went to a gauge was partially plugged and caused an awful lot of aggravated head-scratching until I finally figured that out.