I have a friend that purchased a Chevelle wagon. He is having some brake problems that I think I have a handle on but is in an area that I know little about.

Here is the scenario.

To start;

He would get in the car and the pedal would feel like there was no power assist (with out starting it). If you started the car the pedal now felt like normal power assist (with the car not moving).

My first thought was that the check valve on the power booster had failed and I suggested that be replaced. He did that.

Then the problem became that in a panic stop you could not lock up the tires.

He took the car to a shop they installed a new power booster and did some brake work. This did not fix the panic stop problem.

The car does have a cam in it. The shop stated that they could get no more then 10 pounds of Vacuum. I put a gauge on it and at idle there was a steady 15 pounds, and at 1000 RPM there was 20.

Now here is what I think. The car has larger rims and tires on it. I think the brake system is now working the best it can for the size of the tires and rims. I’m thinking that the brakes (rotors and calipers need to be upgraded to handle the rims and tires). What do you think?

How large of a rim and tire package can be handled by a stock disk/drum brake system.

My plan is to put a gauge on the brake system to see what pressure is actually being developed by the stock system. If there is 1,500 pounds of pressure at the caliper that would say the stock system is functioning and the brakes cannot handle the wheel and tire package????????????????

Your input is more then welcome. Thanks

Bolt on a set of normal-sized wheels and tires; see how it works?

Bolt on a set of normal-sized wheels and tires; see how it works?
Great idea, now why did I not think of that?