Brake pedal pressure

[lundy]

This is directed to owners who may have updated an Alpine from 2000 to 2005 or 06. My question is on braking pedal pressure. It seems that I have to really stomp on the brake to stop my '06 compared to my 2000. My towed vehicle is the same.

Recently I drove a friends unit (45' and an '06). The first time I hit the brake, I just about went thru the windshield!! I have an appointment at the factory this month and want to discuss this with them.

[lundy]

This is directed to owners who may have updated an Alpine from 2000 to 2005 or 06. My question is on braking pedal pressure. It seems that I have to really stomp on the brake to stop my '06 compared to my 2000. My towed vehicle is the same.

Recently I drove a friends unit (45' and an '06). The first time I hit the brake, I just about went thru the windshield!! I have an appointment at the factory this month and want to discuss this with them.

[EngineerMike]

I have noticed on mine that on start-up, the first application of the brakes takes a lot of effort for the amount of stopping power, but then the subsequents stops feel normal. By normal, I figure a fair amount of pressure to stop 30,000 lbs is normal, but it isn't fatiguing. If the initial pressure on start-up was the norm, I'd call that fatiguing. Nowadays, I start up the coach & apply the brakes as soon as engine is idling, then a coupla times before moving and I don't have that initial panic-stomp req'mt.

[Ted III]

Mike & Lundy, I have found the our 2005 needs a good amount of pedal pressure to stop. In fact at a red light I find I have to lean on them pretty good to stay at a stop. Had it checked twice and was told everything was okay. I had one reasonable panic stop and it definitely did the job. Oddly enough the 1996, 40' Monaco we had which was definitely heavier than the Alpine needed very little pressure to stop and with a true panic stop it stopped.

[jerry davis]

I've noticed the same thing as E. Mike. If I use the brake a few times there is less pressure needed. In a panic situation the brakes were no problem.

[rmmpe]

Could some of the high initial pedal pressure requirement be attributable to the booster needing time to build up enough vacuum to operate the brakes normally?

[lundy]

My pedal pressure does not improve with usage. I am glad that I have the 2 stage engine brake because when using a downhill freeway off ramp, I must really stomp on it. Recently, I strained my right knee and I am telling you, it is not comfortable!! My calipers on my 2000 were recalled but the power was much more effective.

[rmmpe]

I am curious about the 2 stage engine brake.
The engine brake works but how is it selectable on a 1999 alpine 36SDS?

[lundy]

The two-stage engine brake is on the ISL 400 engine only. Your's is probably a Pac-Brake exhaust brake on the 275, 330 and 350 engines.

[rmmpe]

Mine is the 330HP engine.
Thanks for clearing that up for me (I was going nuts trying to figure out how to find the switch).

[Louie & Linda]

We have experianced the same HEAVY pedal effort required on our 05 as compared to our 2000. After several factory visits and bleeding of the brake system twice, we finally had the entire unit , master cylinder-booster pump, in the front of the firewall replaced. This inproved the effort required by at least 300%. The effort is still greater than that required on the 2000 but good enough now that I will let the copilot drive again.

[EngineerMike]

rmmpe- brake boost is hydraulic rather than vacuum. The same hydraulic pump that is flang-mounted on the RR side of the engine (visible from the rear cap opening) that drives the power steering and the hydraulic radiator fan also drives the brake booster. Hydraulic fluid courses thru the steering knuckle below the driver, then thru the brake boost unit, then back to the reservoir to the right of the engine, IIR the route correctly. Operating pressure is quite high, 1000psi or more at the Bosch brake unit (steering knuckle is rated to receive 2500 IIRC). There are variables here of pump output pressure, steering knuckle pressure loss, brake unit pressure loss, etc. Due apparently to manufacturing differences, some units were found to require a pressure reducing orifice in line and things like that. The one maintenance item in the system is a stack of 3 hydraulic fluid filters in the reservoir that require periodic changing. I've heard of one failed hydraulic pump on an Alpine that allowed the brake pedal to sort of auto-depress, causing brake drag and overheating (Cedar41 on this board) but actual brake troubles are apparently rare.

[rmmpe]

Hey Mike, that is good information. Being new to Alpines, I need all the coaching I can get.
Do not hesitate to offer any insight or advice, either on this forum or to my personal EM. All will be appreciated.

Thank you, thank you, thank you!

[Ted III]

Daddy Louie, was there ever any explanation from WRV when the master cylinder was replaced and the tremendous improvement in braking. I like you do not let me wife drive the coach because of the tremendous pressure I have to exert on the brake pedal.