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offthewall · 03-09-2008, 04:51 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Latitude:
Hey Offthe wall!! Are you sure the '08 Wrangler has power assist brakes???

The BB says 60psi which I have been using 'BUT' with power assist only20psi!!!

Rick </div></BLOCKQUOTE>

I'm not sure what you're asking. What's a BB?

The Wrangler certainly has power brakes. It has a vacuum line from the engine to the master cylinder. The SMI brake system taps into that vacuum line (with a T and a check valve) to pull a vacuum on the brake system while the engine is not running so that reduced pedal effort is required to apply the brakes (power assisted brakes).

Happycarz · 03-09-2008, 05:52 PM

VACMAN,
One, the Jeep has vacuum assisted power brakes like the majority of all cars today. Two, Jeep Brake Assist activates when it senses quick brake pedal depression and gives the brake more force than you are actually applying. Three, you have Antilock Brake System (ABS) which pumps the brake rapidly when you push the pedal really hard. One is stepping on the brake pedal quickly and the other is stepping on the brake pedal hard. This works when the key is on and controlled by the computer. So, while driving, you have these three parts of the brake system working.
When towing the Jeep, the key is off, the engine is not making vacuum, and the computer is not monitoring anything. If you were to use a toad brake system, like EvenBrake, you place a box on the floorbaord in front of the driver's seat, attach a rod to the brake pedal, and plug in the electrical cord into the cigarette lighter. As you stop the motorhome, the box senses the decelleration and applies pressure on the brake pedal. Since there is no vacuum assist with engine not running, it takes tremendous pressure to push the brake pedal hard enough to apply the brakes to stop the toad. If you have ever experienced stopping a power brake eqquiped car with no vacuum assist, you know what I mean.
Now enter SMI. They apply vacuum to the booster without the engine running, thereby giving you power brakes when towing. Now it takes a lot less pedal effort (8-10 lbs.)to stop the toad. This allows a more compact design of their system. Air Force One uses a small cylinder that is permanently attached to the brake pedal, under the dash, out of sight.
So, in reviewing, you have vacuum assist power brakes when towing. And, when driving, you have vacuum assisted power brakes, hydraulic brake assist, and antlock brakes.
I hope this helps.

VACMAN · 03-09-2008, 06:09 PM

Thanks Happycarz.. I plan on using the unified brakes system and it uses vacuum to make brakes think the engine is running. One question though: My Jeep manual states that to tow the jeep I must tuen the key on acc to keep the steering wheel unlocked. By having the key to acc. will this allow the ABS brakes to work?

Happycarz · 03-10-2008, 04:33 PM

VACMAN,
My 06 Grand Cherokee did not have a steering lock and I could tow with the key out. My 08 Liberty manual states that I have to have the key on ACC. Not true! Only the manual transmission model have a steering lock. To verify, I parked on a gravel surface, took the key out, got out and locked the Jeep. Then I got back in and turned the steering wheel lock to lock with key still in my pocket. No steering wheel lock! Is your Jeep equipped with an automatic or manual transmission? If a you have an automatic try what I did.
With the key in the ACC position, you will not have ABS.

offthewall · 03-10-2008, 06:07 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Happycarz:
VACMAN,
My 06 Grand Cherokee did not have a steering lock and I could tow with the key out. My 08 Liberty manual states that I have to have the key on ACC. Not true! Only the manual transmission model have a steering lock. To verify, I parked on a gravel surface, took the key out, got out and locked the Jeep. Then I got back in and turned the steering wheel lock to lock with key still in my pocket. No steering wheel lock! Is your Jeep equipped with an automatic or manual transmission? If a you have an automatic try what I did.
With the key in the ACC position, you will not have ABS. </div></BLOCKQUOTE>

The 08 Wrangler automatic does in fact have a steering wheel lock. I've tried exactly what you've suggested when I first got it after reading on the web that it may not have a lock. You need to put the key in the 1st position to unlock the wheel. I had a key made at the local locksmith for a couple of bucks. This key will start the engine then it stops after a second or two since it has no chip in it. That way the toad can not be stolen with the key in it.