SOhappy

Had an interesting experience I thought I'd better share. We have annual state safety inspections to deal with. I take my vehicles to Jiffy Lube because there's nothing in it for them if it fails (they don't do brakes, tires, steering, etc.).

However, Jiffy Lube does a brake balance test instead of checking the pads like most places (unless you ask for a visual). Basically it's 4 scales they drive your truck up on and hit the brakes. The scales compare the braking force of each wheel*. Sounds like a weird way to do it, but I discovered my daughter's leaky wheel cylinder this way on her 4Runner. Anyway, back to my story...

My truck failed. The rears where producing way more force compared to the fronts. They ran the test 3 times and got the same result within a percent each time. I went home and pulled the front wheels. Plenty of pad, rotors looked good. Scratching my head I wondered if they were glazed. For the past week or so I braked aggressively (checking my rear-view mirror first of course) and towed my trailer on a 400 mile trip over several mt. passes, relying more on the truck brakes more than I normally would (vs. the trailer brakes) in an attempt to give them a good work-out.

Hoping that would remove any glaze, this morning I took it back for a re-test and nope- exact same results from 3 tries.

I've been running 10psi in my airbags driving empty, kind of like the extra firmness for handling. A light bulb went off and I dropped the airbags to 5 psi and asked them to try it again. Low and behold, it passed!

I guess the take-away is, if you're running your airbags above 5psi empty you may not be getting the best brake performance.

Would be interesting to try some braking tests from speed to distance to see if the difference in airbag pressure shows up there....


*Attached pdf shows the good test (page 1) vs. a failed test (page 2). Big arrows have to fall in the range shown by the tick marks.

gorms

I've never heard of that before....neat tool for tracking brake problems. I have to wait till it snows to do that...and watch for which wheels lock up first or not at all.

How would more pressure in the airbags result in more braking though?

6cylinders

Why? What is going on there,,more PSI = less weight transfer or what ?

SOhappy

I' m not exactly sure how to explain the physics.

I'm guessing that more PSI in the airbags transfers more weight to the front. With the front already carrying the weight of the Mighty Cummins, I was overpowering the front brakes compared to the rear.

Hvytrkmech

No fan of Jiffy Lube simply cause they do nothing like that here cept change oils and blow up engines. With that said, I am glad to see they have some interesting tech that actually makes a difference. Really cool how sensitive their equipment was to differentiate the slightest amount of weight transfer by adjusting your air bags.


Thanks for posting this up!