Air bags and the LSPV (1 Viewer)

[KliersLC]

Hi Folks,

I was wondering the other day about the effects of running air bags (which I have) and the LSPV. I have my LSPV adjusted for normal driving and it works fine. However, when I load up the rear and air up the bags, it seems like I am losing some braking power at the rear axle.

Normally the LSPV would direct more pressure to the rear brakes when under load, lessening the strain on the front brakes and providing a more even brake force distribution. In my case, the LSPV returns back to the empty position via the Air bags and my rig thinks it is empty--this makes the braking worse.

Is there any way to get around this short of adjusting the LSPV every time I load the rig up? Quick release maybe?

I am open to ideas and possible solutions. My goal is to maintain unloaded braking, have a level ride, and still take full advantage of the rear axle brakes when loaded.

Thanks!

Dan


Forgot to add. I have the TJM heavies on my rig. Lift is about 3 inches.

 

[KliersLC]

Anybody?

 

[cody c]

what kind of weight do you carry in it? I would think it would be easier to adjust the brakes somewhere in between loaded and unloaded, you might need a proportioning valve though.

If you really want it to be done automatically, theoretically you could have an air actuator rotate the LSPV which you would have to mount on a hinge of sorts, and feed it off the same lines that control the bags, but thats a little bit of work.

 

[KliersLC]

Normally I have the third row and a tool box in the back, but at times have a bike rack, camp trailer, Wife and five kids+gear for a week on the roof rack....

I like that idea, but am not sure how to make it work with the solid arm that comes off the frame.

 

[KliersLC]

Anybody else?

Surely one of you cruiser geniuses has an idea....

 

[cody c]

why not just a proportioning valve in the cab then? You could also run a line lock for extra parking brake ability.

 

[semlin]

dan,

first off, this always makes my head hurt but are you sure you have it the right way around?

-you are lifted
-you adjusted the lspv for the lift
-your air shocks now prevent as much sag as should occur with a given weight.

i thought that the suspension being higher than it should at a given weight meant more rear brake and less front.

anyway, my suggestion is that you add a steel plate extension at the lspv axle mount using two slotted overlapping flat steel plates so the extension is adjustable. use carriage bolts, lock washers and wing nuts to set the plate overlap. mark the correct adjustment points on the plate for running low and heavy. then adjust the lspv bracket at the frame to allow for the lift you just added at the axle length (i think the ratio is 4-1). this will allow you to adjust the lspv at the axle very quickly with your bare hands or pliers if you don't mind climbing under there.

 

[psfpilot]

i thought that the suspension being higher than it should at a given weight meant more rear brake and less front.

Vice versa because more weight bearing on the tyres means better traction. Therefore the LSPV sends more to the rear to take advantage of this greater braking action capability when the rear sags with added weight.

A manual proportioning valve such as those used in racing applications might be a suitable replacement. The trick would be calibrating it for known rear axle weights and/or plumbing it into the cab for dynamic adjustment.

 

[alia176]

I have air bags in the rear of both of my 80's and don't have any issues with regards to the braking performance. What I've done is this - my LSPV is set for normal height (unloaded rear cargo area, no trailer). When towing or carrying a heavy load, I just make sure that the rear height is back to the normal height by inflating the bags; yes, I use a measuring tape. I try not to inflate the bags to the point where the rear is higher than normal.

 

[KliersLC]

why not just a proportioning valve in the cab then? You could also run a line lock for extra parking brake ability.

I like this idea. I'll have to look into what is out there and where to mount it so I don't accidentally send all of my pressure to the rears:whoops:

I have air bags in the rear of both of my 80's and don't have any issues with regards to the braking performance. What I've done is this - my LSPV is set for normal height (unloaded rear cargo area, no trailer). When towing or carrying a heavy load, I just make sure that the rear height is back to the normal height by inflating the bags; yes, I use a measuring tape. I try not to inflate the bags to the point where the rear is higher than normal.

My 80 stops fine as well and I currently do the exact same thing as you, but looking at it logically, we are not taking advantage of the extra weight on the rear axle. This will cause premature wear up front and less efficient braking.

 

[KliersLC]

Vice versa because more weight bearing on the tyres means better traction. Therefore the LSPV sends more to the rear to take advantage of this greater braking action capability when the rear sags with added weight.

A manual proportioning valve such as those used in racing applications might be a suitable replacement. The trick would be calibrating it for known rear axle weights and/or plumbing it into the cab for dynamic adjustment.

Do they make an electric one that I could tie in to my trailer brake controller?

 

[alia176]

I
My 80 stops fine as well and I currently do the exact same thing as you, but looking at it logically, we are not taking advantage of the extra weight on the rear axle. This will cause premature wear up front and less efficient braking.

Considering the percentage of time the rear of my vehicles is loaded enough to pump up the air bags, I'd have to say that brake performance has not been an issue for me. Break pads are wearing evenly on all four corners. Of course, YMMV.

In theory, mucking around with external devices to control braking power seems like a good idea, practically speaking, it sounds like opening up a can of worms. Sort of takes the Plug and Play out of the equation and you're entering the world of "constant tweaking". Just my .02 cents.

 

[boydmick]

It would be interesting to see how Mr. T addresses this issue on trucks that are self leveling, i.e GX470, LX470. . .

I would think it is addressed somehow!?!

 

[Jack G. Nichols]

I have air bags in the rear of both of my 80's and don't have any issues with regards to the braking performance. What I've done is this - my LSPV is set for normal height (unloaded rear cargo area, no trailer). When towing or carrying a heavy load, I just make sure that the rear height is back to the normal height by inflating the bags; yes, I use a measuring tape. I try not to inflate the bags to the point where the rear is higher than normal.

x2 - I just raise it back to level, and have trailer brakes. No issues that I can determine.

 

[KliersLC]

It would be interesting to see how Mr. T addresses this issue on trucks that are self leveling, i.e GX470, LX470. . .

I would think it is addressed somehow!?!

Good point. I will have to do some digging on that as well.

Considering the percentage of time the rear of my vehicles is loaded enough to pump up the air bags, I'd have to say that brake performance has not been an issue for me. Break pads are wearing evenly on all four corners. Of course, YMMV.

In theory, mucking around with external devices to control braking power seems like a good idea, practically speaking, it sounds like opening up a can of worms. Sort of takes the Plug and Play out of the equation and you're entering the world of "constant tweaking". Just my .02 cents.

I probably air them up once a month, more in the summer though. I really don't have any complaints about the braking, I just know that I am not getting the work out of the rear brakes that I could be.

As far as your second point, I was thinking about that too as I typed my last posts. What will I gain by re-plumbing the brakes? 10% better braking loaded? maybe... Perhaps not worth it. I need to spend some time under there fiddling with things. Maybe Semlin's idea is the best course of action at this point.

x2 - I just raise it back to level, and have trailer brakes. No issues that I can determine.

I don't have any issues either, I just want more out of my rear brakes. Also, when not towing a trailer, but loaded with a hitch rack, roof rack and bike rack, I don't have the option of trailer brakes.

 

[alia176]

I probably air them up once a month, more in the summer though. I really don't have any complaints about the braking, I just know that I am not getting the work out of the rear brakes that I could be.

Interesting, it seems to me that you're using the air bags AS constant springs and not as supplemental load bearing springs (for occasional heavy loads). If this is indeed the case, you may need uprated rear springs or perhaps even progressive rate springs. Just a thought.

 

[KliersLC]

Interesting, it seems to me that you're using the air bags AS constant springs and not as supplemental load bearing springs (for occasional heavy loads). If this is indeed the case, you may need uprated rear springs or perhaps even progressive rate springs. Just a thought.

This is my DD on the 95 corridor into DC every day. I like the ride of the TJM heavies for daily use, and they can take a good amount of weight by themselves without sagging. Progressive springs would be great, but they cost too much and still don't allow the rear axle to reach its full potential.

I sold the camry and the T100 so the 80 gets used a bit more.....

Were this not a DD, heavier springs might be an option....

 

[alia176]

This is my DD on the 95 corridor into DC every day. I like the ride of the TJM heavies for daily use, and they can take a good amount of weight by themselves without sagging. Progressive springs would be great, but they cost too much and still don't allow the rear axle to reach its full potential.

I sold the camry and the T100 so the 80 gets used a bit more.....

Were this not a DD, heavier springs might be an option....

Understood. But, if you have heavies already, why is there a need to inflate your air bags for a heavy load carrying capacity on a DD basis? What are you carrying back there that requires 1000lb of extra carrying capacity afforded by the air bags? Each air bag at 25psi is able to carry up to 500lb of load - per air lift.

Not being argumentative, just trying to understand your particular application.

 

[KliersLC]

Understood. But, if you have heavies already, why is there a need to inflate your air bags for a heavy load carrying capacity on a DD basis? What are you carrying back there that requires 1000lb of extra carrying capacity afforded by the air bags? Each air bag at 25psi is able to carry up to 500lb of load - per air lift.

Not being argumentative, just trying to understand your particular application.

The TJM heavy spring has a 20lb/in lighter spring rate than OME. This makes it ride a little nicer, but also doesn't carry the weight quite as well.

On a daily basis I have the third row, a tool box and two adult passengers. No need for the bags. On a weekly basis I have the third row, the tool box, one adult passenger, 5 kids complete with carseats and misc kiddo gear--no need for the bags. Monthly, I will have the 7 of us, overnight bags for all, a hitch rack with cooler and camping gear, a roof rack with camping gear, and a bike rack with 2 adult bikes, 2 kiddo bikes and a kiddo trailer. (I have a hitch splitter so I can use the bike rack and the hitch carrier...) That is when I use the bags... Also when towing the camp trailer.