Weak brakes?

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J

JDUBinCO

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Sep 25, 2010
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Denver, CO
I recently bought my LX450 and have a receipt for a brake job about 10K miles ago with new front rotors.

The brakes are strong initially but on a panic stop don't work that well. It's kinda scary actually how poorly it stops when STANDING on the pedal. I know these things are not known for their strong brakes but I would never be able to lock up the tires (or engage ABS) on dry pavement. It have a new brake MC so the fluid is brand new.

Thoughts?

Bulging rubber line?

Also i've got a little anti-stinkbug with some worn out old springs. Would this make the brake proportioning valve send too much fluid rearward and leave the fronts weaker than they should be?

Thanks

John
 
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Using aftermarket pads seems to really detrimentally affect the brakes on the 80s for some reason. I don't know why...maybe because the 80s are so heavy and use up a higher percentage of maximum brake force during normal operation that lower quality parts are more noticable than they would be on a lighter car or truck.

If you rig has aftermarket pads, I'd recommend installing OEM pads, even if the rotors are aftermarket. It's not been my experience that changing rotors to OEM makes as much of a difference as OEM pads and OEM pad material.

Second, make sure your brakes bled really, really well. If you have what seems like longer than normal brake pedal travel, they probably need to be bled some more.

Lastly, your rear proportioning valve will affect overall brake performance, depending on where it's set. On a lifted rig, the valve will most likely not have been adjusted or modified by the PO to compensate and will give far too much braking force to the front.

If height is stock, but the rear is sagging due to worn springs, and not because of excess weight in the back, then braking force will be decreased up front and transferred to the back, reducing overall brake performance somewhat.

However, I can't really say how much of an effect either one of these would have on braking performance. When I played around with the adjustment, the differences between different adjustments was definately noticable. When it was set up for rear bias braking, overall braking performance was horrible.

Since you should have ABS, the brakes should not lock up, but when you get to point of lock up, you should feel the pedal pulsating. If you are standing on the pedal with all your might, especially from a higher speed stop and the pedal doesn't pulsate and nothing locks up, then your braking forces are reduced to the point that the vehicle can't reach the outer limits of lock up.

One more thing. There is adjustment on the master cylinder between the pedal and master cylinder that has be adjusted with the master cylinder off the vehicle. This usually affects pedal travel, but it's possible that yours is not adjusted properly and therefore you have maybe 80-90% of your brake power, but not 100%. But that's just a guess. I bring that up, because most of my other suggestions are indicative of a poor brake performance overall. Your situation seems to be that you have adequate brake performance, except all full brake application.
 
I don't know for sure but I assume they are NAPA brake pads, which I would typically use and consider good quality.

In this case would you suggest I just skip to step 2: get my rotors turned and install 100 series brake pads?

I would say that brake performance feels like there is a tiny amount of air in the lines or something acting like a buffer to keep full pressure from getting to the pads.
 
I just installed OEM rotors and 100-series pads up front with house brand rotors and pads for the rear and the truck stops very nicely. My house brand front rotors were warped after 5,000 miles. NAPA premium rotors and pads are fine to run out back in my opinion.
 
I'm not impressed with OEM pads, prefer aftermarket. 100 series pads do nothing for performance, they increase life. When properly setup, the FZJ80 has strong brakes for it's weight/age/year.
 
Tools R Us said:
I'm not impressed with OEM pads, prefer aftermarket. 100 series pads do nothing for performance, they increase life. When properly setup, the FZJ80 has strong brakes for it's weight/age/year.
Click to expand...

Ditto 100%. I have aftermarket PBR pads and Brembo rotors on both 80s and they stop on a dime. I have driven a 6" lifted 80 with NAPA pads and rotors and it stopped great as well.

You probably should check out the braking system thoroughly to see if something else is going on. Things like sticky caliper pistons, LSPV out of adjustment, etc. Rebuilding the calipers is a very inexpensive affair and worth your time. Lots of gunk comes out of those calipers.
 
make sure your wheel bearing are tight. I had this issue prior to installing new oem rotors and 100 series pads, new bearings and races. The way it was explained to me, if your wheel bearings are loose, when you apply the brakes in a hard/panic stop, your not getting 100% pad to rotor contact, and most of the force is used trying to "stand the tire/wheel up" perpendicular to the pavement. made sense to me.
 
Bleed the system!
Sometimes a little air in the system will only be noticed when standing on the breaks. But you can usually tell by a soft pedal...
Just a guess.
 
I'm starting to think that it more along the lines of air in the lines. The brakes are very sufficient initially and for braking in all but panic situations. In a panic I just cant push hard enough to get abs to kick in or to stop really fast.
 
Make sure your back brakes are in working order. They are only about 25% of braking but that still makes a big difference on a heavy truck. Start with your parking brake and get it in working order first.
 
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