DragStuff

Hi everone. I've been taking notes from this site for some time now. I have a 69 chevelle 427BB. th400 with a 8" A.T.I. (flashes @5000) 4:56 rear with 28" tall slick. Car runs 11.30's-11.60's. My problem is I cannot hold the car on the line if I footbrake it more than 1500 rpm's. The front end raises and it wants to push. I swapped out the front drums for disc about 10 years ago, but from what I remember it did the same thing with the drums and a little 307. I've notice that my rear brakes do not work so well and was wondering how to cure the problem. I was thinking of installing a adjustable proportioning valve. Is this what the other footbrakers do? Thank you for any info.

Ray Cook

Power or manual brakes?

I have wilwood brakes up front and drums in the back. I can footbrake mine to 3k before it starts pushing the car, its less than that on the street, the rubber on the track seems to hold it better. I leave at <1500 when racing unless I'm running a pro tree.

Manual brakes

Bob West wrote:I have wilwood brakes up front and drums in the back. I can footbrake mine to 3k before it starts pushing the car, its less than that on the street, the rubber on the track seems to hold it better. I leave at <1500 when racing unless I'm running a pro tree.

Not to break the thread her but congrats on the 2 page picture in chevy high perfromance, mr west very nice.

If it pushes the front tires when they are locked up the brakes are holding the front ,your tires are just skidding on the track.If the tires are actually rolling your brakes are not holding .Did you try to adjust the rear brakes out more? Which master cyl did you put on when you added the disc brakes? What kind of disc setup ?

I'm using a M/C from a 70-72 Trans Am with manual brakes.The brakes are stock rotors and calipers for a 69 chevelle. I always thought that the rear brakes should hold the car at the line. It feel likes the fronts are slipping but not sure. I do have skinny's on the front.

It sounds like you might need a m/c for a disc/drum car and change your pedal ratio, you probably have another hole in the pedal for disc brakes.

I'm pretty sure that the Trans Am M/C is for disc, drum. I'm replacing the rubber brake line for the rear, as that might be flexing. I'm also going to put new drums,and brakes on the back. I'll see if this helps.

Thanks for the responses. Ray Cook

Have you had anyone watch to see if you are actually "pushing" the front wheels?

No, but I can feel the brakes slip through the pedal. And I don't like how the frontend rises because I lose my weight transfer. I figure if I can get the back brakes to work better I wouldn't have this problem.

Ray Cook

You need to find out how much pressure is required for your calipers then get a gauge and check it. Stop guessing as to why it doesnt work. If you put a prop valve in it only reduces pressure up to 57% which will not help.

I know that it's been awhile but here is what I found out. First my rear drums where almost .100" out of spec. And also there was air in the brake system. After replacing the drums and a couple of hours of bleeding the brakes they seem to work better. I went to the track today and I was able to get about 300 more rpm. at the line, so almost 2000 rpm's. I needed this to lower my reaction times. Thanks for all your replies.