Brake Response

[CARVAL Motorsports]

This a very general question. We have an older National RV Dolphin. 36 ft. w/ tag axle, P-30, 454 vortec. When applying the brake, there is a gradual or vague input of braking power, necesitating a pretty firm application of more peddle, which still doesn't give me the stopping power I would like to see. I am just up to Class A from 27ft. Class C, so I do understand that I won't get the same functionality or stoppping power as on the smaller unit. However, is this a pretty common "explanation" of braking ability on these units? Also, a consideration. While parked, engine just started, the brake peddle is pretty spongy, long travel. It gets better with vehicle motion, but has left me a couple of times, pumping on the brakes just backing out of my driveway. Is this just the vacuum booster building up? First thing I did when I bought this unit was have front brake pads, rotors and calipers replaced, have recently had rear brakes adjusted and the system bled, so that has all been done. Maybe I just need to understand that this is common amongst P-30 chassis.... or not?

[CARVAL Motorsports]

This a very general question. We have an older National RV Dolphin. 36 ft. w/ tag axle, P-30, 454 vortec. When applying the brake, there is a gradual or vague input of braking power, necesitating a pretty firm application of more peddle, which still doesn't give me the stopping power I would like to see. I am just up to Class A from 27ft. Class C, so I do understand that I won't get the same functionality or stoppping power as on the smaller unit. However, is this a pretty common "explanation" of braking ability on these units? Also, a consideration. While parked, engine just started, the brake peddle is pretty spongy, long travel. It gets better with vehicle motion, but has left me a couple of times, pumping on the brakes just backing out of my driveway. Is this just the vacuum booster building up? First thing I did when I bought this unit was have front brake pads, rotors and calipers replaced, have recently had rear brakes adjusted and the system bled, so that has all been done. Maybe I just need to understand that this is common amongst P-30 chassis.... or not?

[Gary RVRoamer]

I never owned a P30 chassis, but it doesn't sound normal to me. Spongy brakes are never "normal".

[RV Wizard]

Have the master cylinder and vacuum booster checked. You should not have to pump the brakes. What year is the chassis?

[Tom N]

Older gas chassis' with a tag axle utilize a non-standard braking setup for the tag axle.

Follow the lines forward from the tag axle and look for some sort of auxiliary master cylinder or equalizer valve. You may have a leak here or a problem with the tag axle braking system.

-Tom

[J Walker]

I had an older P-30 and had the master cylinder replaced to help the brakes. After I went through a red light trying to stop and hoping that people saw me and stopped I had an epiphany. My fix for the problem was to buy a diesel pusher with air brakes and an exhaust brake. I have never looked back.