LS1 front brakes on G body spindle

81cutlass said:

Glad to hear it worked out well for you! It's good the info is here you ran into and although it seems
Just curious, when you had stock G body calipers and master cylinder, was your pedal squishy?

My 2+2 had a soft pedal from the day I bought it. I put disks on the rear, still soft. Went to a caprice master cylinder, still soft. Went to LS1 brakes? Very firm.
Wondering if my experience in the pedal firming up is consistent with other LS brake setups.

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I've had this car for 25 years. Until this year, I ran nothing but tires and wheels on it that were stock sized or close.
For the entire time I drove it that way, I'd say the brakes were OK but not great. The pedal was soft feeling relative to other cars. But since they were factory you just think that's just the way they are and you live with it but I never liked them.

What really made it evident that the brakes were lacking was my wheel and tire change that I did earlier this year. I put a set of 16X8 GTA wheels and a set of pretty grippy tires on it. 235/55R-16 front and 255/50R-16 rear. After test driving with those new tires, it immediately became apparent I had to make a change. I could not lock the tires up at all in a panic type stop. Your instinct is to press harder on the pedal which then makes you notice you can push it nearly to the floor with a feeling that can only be described as mushy.

The first thing I did was buy a kit from Powerstop that gave me drilled and slotted rotors, new powder coated stock calipers and brake pads that they highly tout.
What garbage that was. The pads came apart on me during the brake-in procedure they gave me and I followed to the letter. I changed the pads back to a regular metallic but then I was back to no better than when I started.

So the next thing I did was buy a set of Wilwood cast metric calipers with oversized 2.75" pistons (versus the stock 2.5"). They were only slightly better than the stock ones but I still couldn't lock the brakes and still felt mushy when trying. It was at that point I put on the 11" booster and 1" bore master That didn't help at all. In fact it just made the brakes feel more mushy than before. Even tried a 1 1/8" master and that didn't help anything either.

At this point I tried this test. I used vice grips and clamped off the front brake hoses close to where they go into the calipers. I then started the car and hit the brakes. Got a very high and rock hard pedal. Couldn't be pushed down to the floor (or even close) no matter how hard I pressed with my leg. I gave it everything I had!
This told me the problem wasn't in the rear brakes or master. It was all in the calipers. What I believe is that metric calipers flex once the pedal pressure reaches a certain point. You just can't get much stopping power with them. More pedal pressure just makes them flex more.

So it was then I started doing this LS1 brake project. And yes, now I get a very high, super firm pedal that will lock up the brakes with ease. Feels just plain great!

I was wondering about the Caprice booster? Looks like it bolts right in. Does it? Is the caprice rod the correct length for G-body? They are bigger around, but don't seem to be as long as the 9". Have you heard they work better than the 9" booster?

BOXCARS said:

I was wondering about the Caprice booster? Looks like it bolts right in. Does it? Is the caprice rod the correct length for G-body? They are bigger around, but don't seem to be as long as the 9". Have you heard they work better than the 9" booster?

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Yes, it bolts right in with no mods and the rod it comes with is perfect. Pretty easy install unless you have trouble fitting your body under the dash to get to the back side.
The worst part with these is the only way to buy them is with a bare steel finish. So you have to paint it with something to keep it from rusting. I painted mine with SPI epoxy primer followed by Summit's flat black acyrlic urethane.

It has more boost so if that's what you are looking for, you will get it. However if you have metric calipers, I would not upgrade to it. It makes them feel even more mushy and the pedal return felt slow because the pedal travel was so much.. I decided to keep it installed and wait until after I got my LS1 brakes installed and then give it further judgment. I like it. I'm guessing a new replacement 9" would be just fine with the LS1 brakes as well but I like the feel of the low effort the pedal has now.
So better? I'd say not unless you want lower pedal effort and then you will get it.

I put my parts list together for the LS1 brake conversion I just completed.
I only included shipping and/or tax on the ebay purchases. I didn't include the extra expense for the machining I had done to the hubs either. I shouldn't have had to do that. If I had to do it again, I'd just have taken the stock hub/rotors I already had to a machine shop.

Optional items are the 1" master cylinder, 11" vacuum booster and the wheel spacers. I needed the spacers for my 16" GTA wheels. Other 16" wheels shouldn't need them.
I'd say the stock master and booster might be fine but I don't know. I can say that what I've got feels just perfect to me.