Air Force 1 and "Hydro Boost" brakes

[Liam]

Just bought an AF1 and paid for the install of the car side on my 2005 Chevy Suburban. My local installer noticed I don't have vacuum boost brakes but have hydro boost - it apparently works off of the power steering pump. He called SMI and they thought it would still work, but I did a test and turned off the engine going down a hill and tried braking myself. 3 pumps and my brakes were dead no matter how hard I stomp the pedal - would not stop the car. You would never know unless you tried this test.

I spoke with M&G and they said their unit works diferently and would absolutely work.

Looking for anyone who has some real-life answers to this problem. I am out $250 for the install and now have to de-install - don't want to make the same mistake twice.

[Mark3101]

Call SMI yourself and find out for sure. It is clearly stated in their installation manual to call them if you have hydro-boost brakes.

I don't know what your test would tell you anyway. Most vehicles with vacuum assist act that way too. The SMI unit generates it's own vacuum when hooked to the coach's air brakes.

[Liam]

Thanks. My installer did and SMI said we were fine and told him how to change one part. I spoke with them as well.

I ran several tests out on local hills with the engine shut off and it took tremendous force (and I am a big guy) to slow the vehicle. It is a VERY dead pedal so zero advantage over a portable unit.

The Bosch booster (they invented hydro boost) has a small electric motor as a backup but apparently Chevy doesn't use one.

M&G said their design will solve this. Just love to hear from someone who has played with this.

[Mark3101]

But it wasn't hooked up to the bus so what good does that do? You need to have the airline hooked up to the bus and toad to make sure everything is going to work. You can test it while sitting still. You do not have to be moving, but do have to be hooked up. Have someone push the brake pedal in the bus while you watch the pedal in the toad. You need to try that to see what happens. Nothing will work unhooked from the bus!!!!!!!!!!!!!!!

[Liam]

Thanks for responding and appreciate the help but that isnt how it works with the hydro boost. They have you remove the part that would create vacuum for a normal booster. So there is zero connection to the car brake system. All the bus does is tell the AF1 to activate the little piston on the car brake pedal. So by using my foot with the car turned off, I am doing the same thing the AF1 would if the bus were at max breaking.

On yours, the bus air is used by the AF1 to generate vacuum for your booster as well as proportional control of the little piston. Totally agree on a normal setup, you have to be connected to the bus to test.

The AF1 guy said the little piston was strong enough to pull a "dead" pedal but I, a 270 pound guy was barely able to apply enough pressure. That is why Bosch has an emergency electric pump under the master cylinder. Not sure why Chevy does not.

[Pete]

You will not be disappointed with the M&G system. Simple to install, simple to connect each time you use it, and can be traded in to M&G if you change to another tow car.
Sorry to hear of your problem with the AF1.

[jack14r]

the M&G will work as long as it will fit,it does take about 3 extra inches of space at the master cylinder.

[Mark3101]

Thanks for responding and appreciate the help but that isnt how it works with the hydro boost. They have you remove the part that would create vacuum for a normal booster. So there is zero connection to the car brake system. All the bus does is tell the AF1 to activate the little piston on the car brake pedal. So by using my foot with the car turned off, I am doing the same thing the AF1 would if the bus were at max breaking.

On yours, the bus air is used by the AF1 to generate vacuum for your booster as well as proportional control of the little piston. Totally agree on a normal setup, you have to be connected to the bus to test.

The AF1 guy said the little piston was strong enough to pull a "dead" pedal but I, a 270 pound guy was barely able to apply enough pressure. That is why Bosch has an emergency electric pump under the master cylinder. Not sure why Chevy does not.

If you have talked with SMI and can't get it going, I think you should ask for a refund and try the M&G. Sounds like that may be the ticket if you have the room to mount it.