Checking brake pressure

[91vette]

I have a 91 Corvette and have had it about 3 years and the brakes are just awful. I did the following.. up grade front brakes 12 inch to factory optional 13 inch uses same caliper and pads, new rotors all around NOS gm, had booster rebuilt, I rebuilt front calipers, 2 NAPA rebuilt rear calipers, Hawk HPS pads, stainless chassis to caliper lines, NAPA rebuilt master cylinder, after market bias spring to add a bit more rear brake pressure and reccomended by others when changing to 13 inch front brakes, flushed entire system with DOT 3 reccomended factory fluid, bleed brakes in the order listed in factory service manual. None of the hard lines looks damaged or crushed in any way and when bleeding brakes plenty of fluid seems to flow out at every corner.

The brakes stop the car though not very confidence building to be honest. The pedal is stiff though not as stiff as with engine off good vacuum no hissing fluid loss etc. Things that might help and not sure if important or not, brake dust left front the most right front a bit less rears close to none in 1000 miles. Rolling along and pulling e-brake that is properly adjusted does close to nothing though if you set the brake while stopped and pull away with it set it noticibly drags the engine down a lot. No squeels or noises. Impossible to set off ABS on a dry road though a wet one doing something really silly will get a chirp out of ABS, tires are Kuhmo all season high performace 275/40/17 at correct inflation of 34 lbs. nothing real special and street tires. The car stops dead straight with zero pull in any direction and suspension is stock and in good condition. If I go through the Hawk bedding in procedure for the pads they are better for a short while though these are sold as street pads and would think doing it once would be enough and does not explain the firm pedal or if I ever needed the e-brake it would be a pointless effort and a distraction to even bother to use it. What I really lack is any kind of feel and the fact it takes a noticable effort to really stop. My comparison is my 2002 Pontiac GP sedan, it has a smooth progressive brake that starts soft and gets stiffer with travel about 2 inches to full lockup though less than 1 inch for normal driving and a fairly light progressive feel. They easily set off ABS if I grab a lot of brake fast with 225/60/16 Goodyear high performance all season tire s as spected when the car was built though only a few years old.

My thoughts for possible problems the booster is still not right and brake line pressure is low, the calipers are some how draging and only using 1 pad if any, the ABS has issues or the master cylinder is bad or the pads are just wrong for street driving.. My thought on checking is to measure line pressure at the caliper with a pressure sensor and do have access to one that will go to 2000 psi and compare engine running and not to see what the change is. I assume engine running should make a big difference if the booster is good and master cylinder is good. If this checks out though have no data as to what is a good brake pressure then is there a way to measure the amount of force to see what the pads are seeing for pressure against the rotor?

I am up for any and all ideas of what to check and how to check it. My goal is a progessive pedal with enough force to set off the ABS if I go so hard to actually lock the wheels in less than snow or a very wet road acting like a moron grabbing too much brake in a corner. Sorry for the long post but most ask for more info so rather than making this 3 pages of need more info posted everything up first time out..

[jsgarage]

Some mfgrs advise temporarily adding 0-2000 psi gauges to the bleeder port(s) and check actual pressures at the rotor, then adjust via a manual bias valve to xxx line pressures front & rear. For a typical range, a GM 8" OD dual-diaphragm power brake will give about 1250 psi front & 1150 psi rear when properly adjusted and you stomp on the pedal. Non-boosted brakes will be maybe 250 psi lower but the % balance between frt & rear will be about the same. At least it will tell you if you have an obstruction in one or more lines or calipers.
A pair of 1-1/2" glycerine-damped gauges from MSC are cheap and weigh so little, I mounted them permanently to the brake master system. A very large effect comes from the type of pads: I happen to like Porterfields's R-4S 'racing' brake pads for the street.

[Calypso]

Wouldn't hurt checking the front wheel bearings as well. If the disc can move, it can cause issues... Happened to someone i know and took awhile to figure it out.

[raceman14]

Most folks purchase brakes and pads for racing applications and they are not even close to what a street car runs. Unless you have got some temp build up in them they won't stop for crap...

I would recommend green gator pads by Wilwood, I have used them on just about everything from Race trucks, Late Models, Titanium rotors, tool steel rotors and street cars, they are the softest stuff you can get that still has good heat resistance and awesome stopping without a lot of fade. They are pretty cheap and don't require a lot of extra babying to make them work.

Here is a link to amazon for a Monte Carlo but you should be able to get some D52 compound in sizes you need.

http://www.amazon.com/Wilwood-150-2475K ... B002G35KNG