Brake Proportioning Valve

I am convince the front brakes on my car lock up much to early and the rear brakes are not doing as much as they could. This has been an issue on a couple of my cars that I addressed in two different ways. First, I installed a new master cylinder in my 1965 Corvair and took the opportunity to install a valve. It made a HUGE improvement. I made small additional adjustments based on hard braking in turns to ensure there would not be premature rear lock up. It is the best braking car I have ever owned.

Second, I observed similar shortcomings in my 1988 Lincoln MK VII. In that case I ordered higher friction rear pads to match similarly custom front pads. The combination was known as 'autocross' pads. The rotors are the best ventilated and drilled available and are cryo-dipped. This combination is very very good. The strangest issue on the Lincoln is it has anti-lock brakes, but the rears never seemed to get involved. I believe it could actually accommodate higher friction rear pads, but the current set up is good enough.

Now to the Ferrari. I suspect it HAS a brake proportioning valve, but not sure where it is, and when I have inquired about it in other forums was told not to mess with it. And thus I am hoping to find someone who has messed with it.

 

I will see if I can find my stop watch. But I have one nearly insurmountable problem. I live in the mountains which presents two problems. First, there are no level roads. And even if there were I would need a a spirit level to mark it off from optical illusions. Mountains do that. I have, however, one local bridge, concrete, and certainly level. I have practiced quick stops on the bridge and can stop before passing over it from one side to the other.

I can do two things. I can pace off the bridge to find its length, and also try to put a stop watch to it. It can only be done at rare intervals because there needs to be no traffic in either direction. Eventually this could be fun. There is also the problem of accurately measuring actual speed. The Mondial is off by about 10%. Someplace around here I have a gps which I have never used in the Mondial. I know when I am going 90 mph because that is what the gear data give for 7,700 rpms in third gear. Its how I interpolated my 90 mph 1/8 mile speed.

In that contest I took my MAXX, for which I have actual 1/8 mile track data at 10.1 seconds @ 71 mph. Then I ran that car up my interpolative hill. I have GPSed that car and it is exactly 10% fast. So. Runnning the MAXX (starting on that very same bridge) I run it up the gradual slope to the orange sign and checked the speedo. The the 220 hp vvt MAXX showed just over 70 mph indicated. Theoretically the MAXX might only have been doing about 65 mph on my clandestine run. But I awarded it 70 mph out of sympathy.

However, by extension, that would mean the Ferrari would`have exceeded the MAXX in an actual timed 1/8 run by as much as 25 mph. Not just the 20 I have previously posted. Ninety five mph in the 1/8 mile seems a bit much, even for my very very snappy Prugna Metalica.

I am beginning to give myself a headache. But I might be able to do some timing on that bridge. Perhaps it will not be a 'Bridge Too Far'. I am not certain it even is much over 100 ft wide. A car that can stop in 100 ft is doing pretty well.

I need another beer.

 

ABS has solved all our problems. And quite frankly, I do a lot of fast stopping with the 3.2 but it only gives me problems at the very final limit and then only if I overshoot my practice run, and only at lower speeds such as 30 mph when they become tricky at the limit. So it is nothing really bad. But I have tuned my other cars to be just right. Especially that Corvair!

 

Hi! Two things,

1) I am very leery of do doing maximum anything without both hands on the wheel. But thats just me.

2) I have three devices for timing; two watches and one stop watch. One watch and the stop watch have dead batteries. The one watch that is working I have not thus far figured out how to activate the stop watch function.

Anyway, I have easy access to that flat, short concrete bridge near my house. I am going to take stock of it today, and might even pace it off (there is a dirt parking lot next to the trout stream over which the bridge passes.)

And here is an interesting factoid. One G adds or subtracts 22 mph per second.

Standard Gravity to Miles Per Hour Per Second | Kyle's Converter

 

Depends on if you were actually doing 60 mph

But I've started perusing my local concrete bridge! Earlier this morning got the MAXX out for some errands and pulled into the fishing pull-over by the bridge. I paced it four times and got 140 ft each time. Its old but smooth concrete. So I did my first two tests.

Conditions: 33F foggy no wind. Car. 2007 MAXX with police interceptor rotors and ceramic pads, 225/50 ZR 17 tires Contintintal ExtremeContact Summer DW. First pass set cruise control on 66 mph to compensate for probable 10% fast. Results. HORRIBLE. One hundred fifty feet for each stop! Just a few feet beyond the bridge on each occasion. The car and the brakes felt perfect. Full anti-lock, no dive, completely straight and no swerving. Rock steady.

Returning from my errands, slightly warmer, less overcast I set cruise at 55 mph to compensated 10% fast. Stopped pretty much in the middle of the bridge. Certainly no more then 100 feet. But did not get out to pace it off. If nothing else at least I have a place to make comparisons over time and various conditions.

 

May not really be much of a problem. Took the Mondial over the bridge today. As you recall that bridge is about 140 ft concrete and the MAXX stopped at about 150 ft twice from indicate 66mph. The Mondial did it at least 10 ft shorter and was not an especially well done stop on my part. Both cars have the same tires but the Mondials are much more used tread.

I plan to use this bridge for routine training! Can't wait to get the Corvair on it!