I think if the front's were to lag on, you would tend toward increased rotation, due to sustained weight transfer to the front, it your style didn't change.. But OTOH the rears being free to turn would tend to keep them gripping I think the transition in pressure is very fast.. My car is still tossable, before I had to heal and toe downshift to get reasonable braking performance. All of these problems won't show up until I am running 10/10ths, which I avoid on the street. I maintain the performance on the track will be much improved, as is, and I have no plans to try to get a little more. The problems associated with the rears locking first are just too great. I would still like to know how long it takes to fade porterfields with sport brakes on track days.
Regards CB ----- Original Message ----- From: "Eric Schieb" <[email protected]> To: "CB" <[email protected]> Cc: "Miatapower" <[email protected]> Sent: Monday, March 23, 2009 9:33 AM Subject: Re: Big brake upgrade, installed front porporing valves > By modulation I was thinking a bit more like . . . > > Blazing around your favorite race course . . . > Upcoming turn . . . maximum decel. > Corner entry . . . wind in the the steering and trail out on the brakes > (like a string connecting the steering wheel and the brake pedal in > Bondurant etc. type speak). > > As this is done the car will transition from appropriate brake bias to > very front (as the rears drop and the fronts do not) and the car may have > a hard time rotating. > > This and other scenarios are easy to dream up and are fine as long as > realize that this is what is going on. > > Eric Schieb > Electron Speed > > CB wrote: >> Eric said: >> disadvantages: >> (the front brake pressure will not reduce until master cylinder (and >> rear) pressure is lower than front pressure) >> >> This is an interesting point, and with a regulator type device is likely >> accurate. Fortunately, I have SS lines all around, and the pressure drop >> is near instant. Any lag will no doubt caused by the calipers' clamps >> stretching, and the time and pedal travel it takes for them to relax. I >> haven't noticed any loss in the ability to modulate the fronts once >> locked. (I still have it set to significant front bias) I can lock the >> fronts from initial brake application, or mid brake event, and even after >> all the weight is transferred, and just as easily back off enough to >> unlock. So far no ill effects, except a fear that the person behind me >> has no chance of matching my braking performance. >> >> Regards >> CB >> ----- Original Message ----- From: "Eric Schieb" <[email protected]> >> To: "Miatapower" <[email protected]> >> Sent: Monday, March 16, 2009 8:13 PM >> Subject: Re: Big brake upgrade, installed front porporing valves >> >> >>> CB:>OK....... should have said >>> DON'T TRY THIS AT HOME >>> ONLY FOR TRACK USE >>> >>> I'll buy this. One of the potential advantages of a front proportioning >>> valve set up is that the inside front will drag during trail braking >>> instead of the inside rear (kind of like a formula car ;-) ). >>> Unfortunately you really need to keep after the adjustment as track >>> conditions change. >>> >>> Eric Schieb >>> Electron Speed >>> >>> Charles Brown wrote: >>>> While I am aware that it is an imperfect solution, the only other >>>> solution I am aware of is "carbotech panther + (6 years old compound) >>>> on rear. >>>> Stock 2001 pads front "= *excellent braking* >>>> >>>> Problem is, not well balanced when cold, and the front pad will fade >>>> before the carbotecs, if you can push them that hard. You are >>>> essentially >>>> in the same boat, of unknown grip balance during warm-up, and failure >>>> mode would be extreme rear bias with little warning.. >>>> >>>> The best solution is smaller front caliper pistons, the rear calipers >>>> are already the largest available. >>>> >>>> OK....... should have said >>>> DON'T TRY THIS AT HOME >>>> ONLY FOR TRACK USE >>>> >>>> Regards >>>> CB&Stoker >>>> >>>> ----- Original Message ----- From: "Eric Schieb" <[email protected]> >>>> Cc: "Miata Power List (Miata Power List)" <[email protected]> >>>> Sent: Monday, March 16, 2009 2:57 PM >>>> Subject: Re: Big brake upgrade, installed front porporing valves >>>> >>>> >>>>> While front proportioning valves have been done before (including by >>>>> Lotus once) and can have some advantages if you know what you are >>>>> looking for, the disadvantages are significant enough that I would try >>>>> to come up with a brake package that does not need the brake pressure >>>>> reduction in the front. >>>>> >>>>> disadvantages: >>>>> >>>>> -significant modulation challenges (the front brake pressure will not >>>>> reduce until master cylinder (and rear) pressure is lower than front >>>>> pressure) >>>>> >>>>> -theoretically incorrect slopes of pressure rise (if you have correct >>>>> bias on one surface and then find a grippier one, you will become rear >>>>> biased at a rate faster than normal)(if have correct bias on one >>>>> surface >>>>> and then it rains, you will become front biased at a rate faster than >>>>> normal). >>>>> >>>>> Sorry to play a bit of a downer, but brakes are a potentially serious >>>>> safety matter and the positives of a front proportioning valve should >>>>> be >>>>> balanced with some of the negatives before anyone tries it at home. >>>>> >>>>> Eric Schieb >>>>> Electron Speed >>>>> >>>>> CB wrote: >>>>>> Well I finally did it. >>>>>> I have been living with a 2001 big brake upgrade on my 90 with way >>>>>> too much front bias. >>>>>> So I put in two adjustable brake purporting valves in the front! >>>>>> lines, with no rear valve of any kind. >>>>>> It took 7.5 turns out to get great brake bias. The fronts can still >>>>>> be locked at will, it just takes a lot more will. >>>>>> >>>>>> The braking is stellar, and the rears so far have never locked using >>>>>> porterfield R4-S all around. >>>>>> I hope that the stock 2001 12" vented fronts don't fade before the >>>>>> ~12.5 solid rear rotor setup, and all will be good. >>>>>> Does anybody have the fade mode on sport rotor setup? Thinking about >>>>>> direct ducting from the front spoiler to prevent it. >>>>>> >>>>>> I sure is nice to have great brakes again, hopefully the front bias >>>>>> remains greater in all circumstances. >>>>>> >>>>>> Odd that the 02 sport brakes are so out of balance on a 1990 with a >>>>>> very tight suspension setup. !???! >>>>>> >>>>>> >>>>>> CB&Stoker >>>>>> >>>>>> ------------------------------------------------------------------------ >>>>>> >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> Miatapower mailing list >>>>>> [email protected] >>>>>> http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower >>>>>> >>>>> >>>>> _______________________________________________ >>>>> Miatapower mailing list >>>>> [email protected] >>>>> http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower >>>> >>>> >>> >>> _______________________________________________ >>> Miatapower mailing list >>> [email protected] >>> http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower >> >> > _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower
