Tundra brake question

[Squatch]

Just bought a 2006 Tundra double cab. I'm getting ready to add Firestone air bags to it.

Has anyone here adjusted the proportioning valve to compensate for leveling the truck with a load on it.

I've read this needs to be done with a lift not sure about leveling.

The brakes on this truck are decent but not great. I would like to use all the braking that's available.

 

[Old Crow]

Squatch-

You may have already found this in your research but I thought I'd attach it to this thread. The "LSP and BV Adjustment" section (about 2/3 of the way down the page) has an interesting overview and opinion on this topic and a link to the factory adjustment procedure.

It isn't clear which gen Tundras this applies to at first but I clicked on the 'Tundra Index' at the top of the page and the guy says he's documenting stuff on his 2004. Presumably it still applies to your 2006.

 

[Beach]

I never did it on my 06 access cab. Truck sat pretty level with the hawk on it. Even with the camper off and the rear up a couple inches past stock, still had plenty of stopping power.

 

[Squatch]

My concern is that the sagging rear end increases brake pressure to the rear brakes to stop the extra load. Raising it back to level with air bags I would think nulls this effect somewhat.

Thanks for the links. I'll read up and then take a look while I'm under there adding the air bags.

Before I do anything I intend to measure wheel well height at all 4 corners. Then I'll put the camper in the truck and do it again. That way I know where to set the height at with the bags. I have an Eagle shell with a few options. I'm curious to see how much it sags the truck. It should be a bit lighter than the fully dressed Hawks most are running in these trucks.

 

[Vic Harder]

i looked at that when I still had my Tundra. You are right in thinking that it needs to be tweaked. With the extra weight in the back, the truck won't send enough braking power to the rear brakes to take full advantage of it if you level it. HOW much to adjust it is the bigger question. If it was me, I'd find some abandoned roadway and do a few emergency braking tests. Of course, you do all this at your own risk!

With your truck/camper loaded up as you intend to use it:

- Test your stopping distance from 60 MPH
- Pull the ABS fuse
- Do a test from a slow speed if you need to get used to how the truck may feel without the ABS... it could fishtail rather nastily if setup wrong
- Once you have the feel for non-ABS braking, do a few test from about 30 MPH and see which tires lock up first, front or rear. Will likely be just one tire, likely in the back since it was setup for unloaded braking before
- Adjust the brake force prop valve
- Retest
- Repeat until the fronts lock up first
- Back off the adjustment and retest until in appears random which locks up first, back or front
- Plug the ABS fuse back in
- Re run the 60 mph test.

If our hunch is right, the stopping distance will have improved.

DANGER!!! If you take your camper off, the valve will need to be readjusted... with all that extra braking force going to the rear tires, without a load the overall effect will be vastly longer braking distances when unloaded!!!!!

 

[JHanson]

As I understand its operation, the load-sensing and proportioning valve only senses the height of the chassis above the axle. Thus when you put a load in the bed with stock suspension, it droops, the system senses this and increases pressure to the rear brakes. If you mount a camper and level the truck with springs or air bags, the system "thinks" you have an empty truck. Many people have adjusted the valves themselves, mainly by guesswork. In the days before ABS, you'd do it by trial and error, simply taking the truck out and stomping on the brakes, but with ABS limiting lockup it's more difficult to figure out the right front to rear proportion. While removing the fuse as per the previous post is one way to do so, I think you'd be smart to let a mechanic do it.

 

[SunMan]

I read some info about doing this but never bothered with it. Camper on full time (mostly) since 2007. I'm still alive and havent rear ended anybody. Could my braking be better? I don't know what I don't know. Report back if you do a before and after.

 

[Squatch]

Thanks for the info and the cautions. You've confirmed what I had read. I'm confident I can handle this. I've only owned a couple of vehicles with ABS. I'm used to old school trucks that break loose in the rear when empty and drive them appropriately.

I've done a lot of brake work and upgrades on vehicles over the years including aftermarket proportioning valve set up. Pretty much rebuilt 3 trucks from the frame up in recent years. One of which had an adjustable proportioning valve that could be adjusted from the drivers seat. Several close friends are certified mechanics including one who has a shop doing Honda's and Toyota's. Good resources if needed.

I'll be careful to mark and measure where I started so it can be returned when unloaded. I'll make small changes and then test it. Once it's where I want it I'll mark and measure that too. I live in the country but also have a couple of large commercial parking lots nearby. No problem finding a safe place to drive it.

 

[ntsqd]

Data point: On my '84 Xcab short bed 4x4 I eliminated the LSPV's arm and held it full up (max load condition) all of the time. This worked because I had 33" tires and a fiberglass shell on the truck. The combo of a little more weight on the rear and the greater wheel/tire inertia was enough to not allow the rears to lock first. Configured like that with no load in the bed it stopped fine. Removing the shell called for care to not lock up the rears.

I highly doubt that any reputable mechanic would deviate from the adjustment recommended by the repair manual. Their liability insurance wouldn't allow for anything else.

 

[cwdtmmrs]

On my '86 Xcab short bed 4x4 I have the LSPV almost in it's max position with a loaded Ranger II (Eagle) camper. I have std OME rear leafs and 31" tires. Wheel cylinders have been upgraded to larger Landcruiser type as well. Combo works well.

cwd

 

[Wallowa]

Interesting topic..

I have a '16 Hawk on an '05 Tundra AC 4X4 SR5...Firestone airbags and Heliwig sway bar...the truck w/Hawk and mods actually corners and handles better that when I had just a shell..corners like a dream and no swaying.

I have Toyo ATII "C" rated [had them when I bought the Hawk, will go "E" next time] and I set the airbag pressure to raise the rear wheel well height to 35" to match front height...not surprisingly the left air bag requires more pressure than right to level the vehicle...around 41 psi left and 29 psi right..assume 26 gallons of fuel on left is the game changer and most of the Hawk built-in appliances are on the left...only twin batteries on right.

My '05 Tundra has drum rear brakes, to bad, but that is what it is....only felt difference when carrying the Hawk is a longer stopping distance needs to be anticipated.

Phil

 

[Squatch]

I was under the Tundra yesterday looking at this set up. What a Rube Goldberg contraption! This whole thing suspended on a light steel tube in mid-air over the axle? Bizarre! I'm new to 'Yota's and they do some unusual stuff for sure.

 

[ntsqd]

I was under the Tundra yesterday looking at this set up. What a Rube Goldberg contraption! This whole thing suspended on a light steel tube in mid-air over the axle? Bizarre! I'm new to 'Yota's and they do some unusual stuff for sure.

To what are you referring?

 

[idahoron]

Interesting topic..

I have a '16 Hawk on an '05 Tundra AC 4X4 SR5...Firestone airbags and Heliwig sway bar...the truck w/Hawk and mods actually corners and handles better that when I had just a shell..corners like a dream and no swaying.

I have Toyo ATII "C" rated [had them when I bought the Hawk, will go "E" next time] and I set the airbag pressure to raise the rear wheel well height to 35" to match front height...not surprisingly the left air bag requires more pressure than right to level the vehicle...around 41 psi left and 29 psi right..assume 26 gallons of fuel on left is the game changer and most of the Hawk built-in appliances are on the left...only twin batteries on right.

My '05 Tundra has drum rear brakes, to bad, but that is what it is....only felt difference when carrying the Hawk is a longer stopping distance needs to be anticipated.

Phil

If you wanted disc breaks on the back you can do a Sequoia conversion.

 

[Squatch]

To what are you referring?

The entire brake lever doodad for the proportioning valve.

 

[ntsqd]

Ah! I'm not sure exactly what the circuitry looks like, but next time you're under there notice that there is a bleed nipple on it. That is actually part of the FRONT brake circuit & should be bled before bleeding the calipers and after the rear brakes.

 

[super doody]

Just bought a 2006 Tundra double cab. I'm getting ready to add Firestone air bags to it.

Has anyone here adjusted the proportioning valve to compensate for leveling the truck with a load on it.

I've read this needs to be done with a lift not sure about leveling.

The brakes on this truck are decent but not great. I would like to use all the braking that's availableI

Have the same truck and carry the camper full time. i will adjust the bpv and report findings. BTW, E load tires will make your truck handle even better and provides add protection while driving off road.

 

[Wallowa]

If you wanted disc breaks on the back you can do a Sequoia conversion.

Just saw this..thanks..but what is a "Sequoia Conversion"?

With my Hawk permanently on the '05 Tundra I drive a lot slower to compensate for the momentum created by the added weight...but Discs in rear would be nice!

Phil

 

[ntsqd]

I suspect it is using the rear discs off the Toyota Sequoia to convert the truck.

 

[Squatch]

I finally got around to looking at this closer. I measured the height of my truck at the rear wheel well while the truck was empty with 5psi in the airbags. That's my empty load setting. Firestone says to not run them empty. Anyway right at 27". I loaded the camper and the truck sank right at about 2". with 25psi in the airbags I was right back at about stock height. That seems to be about right for carrying the camper.

So at 2" difference I am probably a candidate for one of the aftermarket brackets they use for a 2" lift to raise the whole LSPV assembly at the axle. I may make or pick one up.

In the meantime I adjusted the doohicky on the axle all the way up which is about an inch. The difference was immediate. Not only is the braking with the camper noticeably better. But the pedal feels better as well.

I live on a big hill surrounded by 2 creeks that join around the corner. To leave home I have to basically go down and back up a 1/2 mile long 10% grade. Lot's of curves and hills here. Great for load and brake testing! If I have a Brake issue I'll know it before I hit the main county road!