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drfife · 04-22-2012, 11:04 AM

I have a 2012 GMC Sierra 3500 HD SRW Duramax with a GM integrated brake controller. I tow a 9,000 lb travel trailer. I've logged 1,500 miles towing since January 2012. I use a Hensley Arrow trailer hitch.

I set gain on the brake controller at 8.0 after following the set-up instructions in the owners manual.

Last weekend I had to perform a panic stop at 40 mph to avoid collision after a car turned left across my path. The force of the stop resulted in the shearing of two of the Hensley shear bolts on the left strut. I repaired the Hensley at the campground and our return trip was uneventful.

I adjusted the trailer brakes today. Very little adjustment was required. To verify they were functional I had my wife apply the brake pedal. There was a 2 to 3 second delay from application of the brakes in the truck to braking on the trailer wheels. If the manual lever was activated on the brake controller, the brakes applied instantly.

Is it normal to have a delay from truck braking to energizing the trailer brakes?

I have noticed that the trailer bumps the tow vehicle much more than my previous vehicle and brake controller.

I have towed the same trailer with an '02 K2500 Suburban with a BrakeSmart brake controller for many years and many miles. The BrakeSmart provided multiple adjustments to provide optimal, smooth braking. The truck and trailer truly braked in harmony.

The GM controller only has a gain setting.

Do I have a problem that needs to be checked by GM? Should I install a more sophisticated brake controller for my safety?

Thanks in advance for your advise and suggestions.

ntrsandman · 05-03-2012, 04:40 PM

Most, if not all, integrated trailer brake controllers are similar to the Tekonsha Prodigy in operation. When the brake pedal is applied, a motion sensor in the controller (or elsewhere in the vehicle) calculates speed and deceleration and applies power to the trailer brakes accordingly. If the brakes are applied while stopped, the controller sees no motion. Which likely causes the delay. When the manual lever is applied, it overrides the motion sensor and will send power to the trailer. Lever movement controls the power to the trailer.

drfife · 05-04-2012, 12:12 PM

Quote:

Originally Posted by ntrsandman

Most, if not all, integrated trailer brake controllers are similar to the Tekonsha Prodigy in operation. When the brake pedal is applied, a motion sensor in the controller (or elsewhere in the vehicle) calculates speed and deceleration and applies power to the trailer brakes accordingly. If the brakes are applied while stopped, the controller sees no motion. Which likely causes the delay. When the manual lever is applied, it overrides the motion sensor and will send power to the trailer. Lever movement controls the power to the trailer.

Not exactly.

Ford and Chevy both use a hydraulic pressure sensor in the brake line as part of the Integrated brake control system. I'm not sure about Dodge.

IWillRVToo · 05-04-2012, 12:17 PM

I would take it to the dealer. It makes no sense at all that the TT brakes would be delayed on purpose. Maybe the sensor is bad.

drfife · 05-05-2012, 09:51 PM

I took my truck with trailer to my local GMC service center. A service tech, that is an experienced RVer, took a test drive with my truck and trailer. After multiple gain adjustments, we agreed that 8.0 felt best and most secure.

We then hitched my trailer to a new 2012 GMC Sierra 2500HD CC SB Duramax which is similar to my truck, except mine is a 3500 and has the Z71 package. We took it out on the same route and performed the same tests. It too had the best braking with my trailer with the gain set at 8.0.

I do not know why, but the brake pedal felt "mushier" and had more travel than my 3500.

The braking response with both GM trucks with the ITBC were similar, but not as smooth as my previous BrakeSmart controller. The GM ITBC only has gain adjustment. The BrakeSmart provided additional adjustments like initial brake constant and power factor, in addition to gain.

The tech felt that I had become accustom to a more customizable controller. The GM controller is acceptable to most people. He could not explain delay I observed with the brake pedal vs manual lever when stationary. The system is hydraulic brake fluid pressure based. He felt that additional motion sensors do not activate immediate signal to brakes if stationary. He has not had to repair an ITBC before.

They offered to disable the ITBC and install the brake controller of my choice at no charge. I will play with the current system and decide if I think I'd be better off with a different controller. Too bad BrakeSmart is no longer being produced. That would be my first choice.

A friend performed the same test with his GM truck with ITBC and had the same result. When the trailer wheels are off the ground and spinning, the manual controller works instantly and a 2-3 second delay when the brake pedal is depressed.

The service manager and techs at Classic GMC of Carrollton treated me with respect and Were very friendly and helpful.

My conclusion: The ITBC in my truck functions as designed. It is good enough to make most people happy. GM could take a lesson from BrakeSmart and increase the available adjustments and improve their ITBC. They also should provide better information to the consumer of how their current product functions. Even the techs are in the dark.

ntrsandman · 05-06-2012, 09:25 AM

It is true that there is a sensor on the brake master cylinder to sense pedal movement. However, it is possible that a number of other sensor inputs may be required to activate the controllers output to the trailer brakes. A main power control module MAY need to see brake pedal movement, vehicle speed, and possibly some engine outputs, etc. BEFORE sending information to the ITBM to apply the trailer brakes instantly. It is possible that just applying the brakes while stationary is sending different information to a main control module and sending different information to the ITBM to perform differently. These modules/controllers have software (including the ITBM) to react the way they were programmed. The delay may be programmed. IF the delay happens with other similar vehicles, then it is likely normal. Obviously, the ITBM uses information inputs from other vehicle sources and is not an all-in-one brake controller. IF an "aftermarket" controller is wished to be installed in place of the ITBM, there may be some changes made other than wiring to complete the change.

drfife · 05-06-2012, 01:17 PM

I, for one, would prefer some additional adjustments in addition to gain.

ALSAN · 05-06-2012, 06:21 PM

Try the MAXBRAKE it is very much like the brakesmart so I am told , If you want more thoughts about MAXBRAKE check it on on the Turbo Register web site or goggle it

drfife · 05-06-2012, 07:10 PM

Quote:

Originally Posted by ALSAN

Try the MAXBRAKE it is very much like the brakesmart so I am told , If you want more thoughts about MAXBRAKE check it on on the Turbo Register web site or goggle it

I'm familiar with Maxbrake. I know others that have one and they are pleased.

Maxbrake is similar to BrakeSmart. They both tap the brake line and use a brake fluid pressure sensor to regulate the amount ov voltage sent to the trailer brakes. Both have gain adjustments. BrakeSmart also allows adjustment to initial brake constant and power setting.

The initial brake constant is especially nice for those of us that use a Hensley, ProPride or pintle hitch. It sends an initial higher (or lower) signal to the brakes. This helps keep the trailer from "catching up" with the tow vehicle.

But if the ITBC does not meet my needs, the Maxbrake is high on my list of aftermarket brake controllers.