[Sabre7]

05 silvy 2wd Crew cab... is it possible to adjust the brake proportioning valve? I'm on my 3rd set of rotors in 2 years (70k) I think that I'm getting too much line presure at the fronts and rears aren't taking their share of the braking load..

 

[Sabre7]

Thanks.. yeah I was just gonna tweak it a little at a time.. mark starting point and adjust a little at a time untill the rear end starts locking up., mark that.. then adjust it back to somewhere in between.

I live on a very remote stretch of country road.. so I have plenty of safe space for testing.

 

[Sabre7]

Ok I think I found the valve... not what I am used to on other vehicles...

my brake lines run into this big 'ol pump looking thing on the drivers side frame just behing the tranny crossmember... is that the valve? How the heck do I adjust that thing?

 

[Sabre7]

That is perfectly normal. Under braking, a large portion of the vehicle weight is transfered to the front (inertia force). As a result, over time the front pads/rotors do wear much faster than the rear. Front/rear brake bias is induced in order to prevent the rear wheels from locking (easier to lock than the front because unloaded). Putting more pressure on the rear brakes will likely not improve your overall braking power. Most of the labor still has be performed by the front.

yes I am aware of the physics involved...Same reason you have dual discs on the front of a mortorcycle.. and why the discs are normally larger up front than on the rear of 4 wheel disc vehicles..
But it seems that the brake setup on my truck is set too strongly for the front. Brake rotors should last longer than 6 months.. after 3 sets, something is not right.(probably the fact that GM put itty bitty rotors on the front of a net 5000lb vehicle) It's like my rear brakes do not even engage...so I want to test the proportioning setup to see.. I'm not trying to improve my overall braking performance.. I'm just trying to get my rotors to last longer.

 

[Sabre7]

Sure, I understand and agree with your concern. I believe I read in some other posts that it may due to the material of the OEM rotors. A relatively soft steel that gets eaten up quickly.

Another aspect you may want to consider in your test is that if you have 4 wheel ABS, the ABS may overlap with the brake bias induced by the proportional valve (please note I am just thinking aloud - not talking by experience). This should somehow ease the concern of locking up the rear by modifying the bias.

Please keep us posted.

I was also thinking that the ABS might help prevent rear lockup... but my problem now is this Proportioning valve..

Jimminey this thing is huge.. it looks like a giant booster.. has a big electric motor and looks like electronic controls ...

Anyone Know how to adjust this thing? or do I need to get my tuner buddy to do it through the PCM?

 

[Sabre7]

I googled for your vehicle and found it came with an "Electronic brake distribution" Don't know what does this mean but from your description it looks it could be indeed like some sort of computer controlled system http://www.internetautoguide.com/ca...00-hd-short-bed-crew-cab-pickup/24/index.html listed in the Handling section

Hopefully, someone with more knowledge than us will chip in in this discussion...

yeah it's called the EBCM.. Electronic Brake Control Module.. and it looks like it will take a Tech 2 to play with the settings... It's "supposed" to electronically adjust braking force dependant on load.. vehicle speed..etc.

SO since I run unloaded and rarely tow... it is keeping most of the line pressure up front.. so now I think my choices are limited..

Either Pony up the dough for a bigger better brakes up front. Or just get used to changing out the rotors every 6 months... yay.. :no:

 

[Sabre7]

The EBCM system operates on inputs from the front brakes, rear brakes, and transmission, it's tied into the anti-skid system. Unlike the older systems that are mechanical. Inputs can be manipulated at the computer with the proper equipment, i.e. GM's diagnostic scan tool. Another way is to remove the EEBC and replace it with a manual porportioning valve then trick the brake system electronics so you dont have an ABS light.
Troll some of the drag race websites I know more than a few of them have deleted the EBCM and used manual BPV's and looped the system to stop ABS lights.

Hmmm.. so if I understand correctly.. I can adjust the settings through the PCM? If so I can get that done.. Got a tuner bud that owes me some tweaking anyway.

 

[Sabre7]

Thats my understanding, but how much the brake bias can be adjusted is a mystery. ABS can also be adjusted slightly and I'm only guessing here but I would think brake bias and ABS signals would be tied together.

well it should be an interesting and educational experiment...

 

[Sabre7]

Just a thought. But, I think by adjusting the front/rear braking ratio, you'll only be masking a possible problem. Generally on all of the vehicles I've owned, I change out the front brake pads about 2:1, sometimes 3:1. But if you're only getting 6 months out of the rotors, something seems seriously wrong.

True there is something wrong... I am just trying to see if the front rear adjustment is a contributor..
The pads look virtually new.. but I am replacing them anyway... going all OEM... I think honestly that the real issue is using a brake rotor too small for the weight of the vehicle... GM cheaped out on the crew cabs.

seems only the 1500 crew cabs are having issues with the brakes.... the 1500 HD and up are not...