trailer brake adjustment

[divedigger]

I have a 2 axle 50K tag a long and need help adjusting the brakes. If you adjust them for loaded conditions you have good braking but if empty it is real easy to flat spot tires. The front axle has type 30 single can and the back has dual can 30/30s. Thai is a older eager beaver trailer and the factory calls for a relay valve with 4.5 cracking psi. Any ideas or tips on adjustment would be greatly appreacited since I just bought new 17.5 tires and wheels and at that cost I want to avoid flat spotting tires. THANKS Divedigger

 

[stumpjumper83]

does your run the newer maxi's that hold when air is taken away from the trailer, or does yours have the older type that freewheel when air is taken away?

 

[divedigger]

brakes

does your run the newer maxi's that hold when air is taken away from the trailer, or does yours have the older type that freewheel when air is taken away?

They are 30/30 double can type spring brakes that lock down when you pull the trailer valve and or unhook from the truck. The trailer weighs about 10K empty. Thanks

 

[Birken Vogt]

Adjustment is not the concern here. Adjustment does not have too much effect on braking effort until the maximum stroke of the chamber is exceeded. (There is a little bit of effect but not very much.) A type 30 chamber with 30 lbs of air applied gives 900 lbs force to the push rod whether it is half an inch stroke or two inches stroke.

One question is, are you sure it has the right size chambers? You would need to contact Eager Beaver for this. If it was designed for a type 24 chamber then the same 30 psi would only give 720 lbs force on the push rod.

Another question is, are the brakes on the towing truck in good condition? If it requires extra pedal pressure to get the towing truck to slow down, then that same extra pressure might be enough to make the trailer lock up.

Finally, if none of this works then you might want to upgrade the trailer to ABS brakes. This is my own idea and I hope somebody else will chime in whether it is a good idea or stupid. To do this you would need to replace the relay valve on the trailer with a combination ABS controller/relay valve and apply tone rings to 2 of the hubs at least, and mount the 2 sensors. They make retrofit and new trailer kits that could probably be made to work except I'm not sure how difficult it would be to mount the tone rings and sensors on the smaller hubs and axles. Other than that all it would need is 12v electrical power through the trailer connector that is probably already there, and then it just works. I think that a 2 sensor/1 modulator (2S/1M) would be fine for this trailer.

Anybody care to tell me if this is a good idea?

 

[divedigger]

brakes

Adjustment is not the concern here. Adjustment does not have too much effect on braking effort until the maximum stroke of the chamber is exceeded. (There is a little bit of effect but not very much.) A type 30 chamber with 30 lbs of air applied gives 900 lbs force to the push rod whether it is half an inch stroke or two inches stroke.

One question is, are you sure it has the right size chambers? You would need to contact Eager Beaver for this. If it was designed for a type 24 chamber then the same 30 psi would only give 720 lbs force on the push rod.

Another question is, are the brakes on the towing truck in good condition? If it requires extra pedal pressure to get the towing truck to slow down, then that same extra pressure might be enough to make the trailer lock up.

Finally, if none of this works then you might want to upgrade the trailer to ABS brakes. This is my own idea and I hope somebody else will chime in whether it is a good idea or stupid. To do this you would need to replace the relay valve on the trailer with a combination ABS controller/relay valve and apply tone rings to 2 of the hubs at least, and mount the 2 sensors. They make retrofit and new trailer kits that could probably be made to work except I'm not sure how difficult it would be to mount the tone rings and sensors on the smaller hubs and axles. Other than that all it would need is 12v electrical power through the trailer connector that is probably already there, and then it just works. I think that a 2 sensor/1 modulator (2S/1M) would be fine for this trailer.

Anybody care to tell me if this is a good idea?

Good thought, I will check with eager beaver on chamber size but the truck has auto slackers , so do you set them ip or do they adjust theirselves? Thanks

 

[Birken Vogt]

They should maintain adjustment between 1 and 2 inches without any interference from you so long as they stay lubricated, on type 30 chambers. Check to see that one or more aren't out of adjustment or some other problem with the brakes.

 

[stumpjumper83]

I was working in the parts dept. of an eager beaver dealer when they first came out with the abs for the 20 ton tags and such, most owners were thrilled when they learned the price of new brake drums with the abs sensors, and not in a positive manor either. Not saying abs wouldnt possibly correct your issue, just I remember the brake hubs being rather salty.

 

[Birken Vogt]

The way I was thinking of doing it puts the tone rings on the insides of the hubs near where the spindles connect to the axle ends. I assume the brake drums you reference have the tone rings machined on the outside edge near the backing plates, correct? Was the sensor installed in the backing plate, then? My way would not require a brake drum change but would be more difficult to install (taking off the hubs and welding the bracket on, and also the tone rings supplied have to be made to fit the hub which I have no idea if it would work). The trick here is going to be making stuff fit on these smaller hubs/drums/wheels. My guess is it would work fine but I don't know that. The kits referenced are intended to work with standard 16.5" drums of course.

Do you recall if the trailers had sensors on all 4 wheel ends or just 2 of them?

 

[OCR]

trailer brake adjustment and thrilled in a positive manor??

most owners were thrilled when they learned the price of new brake drums with the abs sensors, and not in a positive manor either.

Well Stump, I looked and looked, but I just can't find her, that's probably why...

I'll bet it was old 7828 they got thrilled in, and here's a really good picture.

http://upload.wikimedia.org/wikiped...s.jpg/800px-Minehead_7828_Jubilee_Express.jpg

And... the story about her.

http://en.wikipedia.org/wiki/GWR_7800_Class_7828_Odney_Manor

And... the ones that are preserved.

http://en.wikipedia.org/wiki/GWR_7800_Class#Locomotives


Ok, back on track...



OCR...

 

[Dualie]

Most of the tag trailers i have drug around did the same the dang thing. You had to be super careful when coming to stop or you would drag flat spots in 8 tires in no time flat.

 

[Tiny]

One other thought , Are the brakes on truck your pulling it with adjusted up to snuff . Have seen that help .

 

[mitch504]

Gee, I hate to agree w/ Tiny in public, but...

I put manual slack adjusters on my trucks, because automatics just don't last w/ the amount of time they have to spend submerged in mud. I back the truck adjusters off 1/2 turn, and back off 3/4 turn on the trailers. It makes the trailer brakes come on a fraction of a second later, and really seems to help.

 

[stumpjumper83]

See I probably shouldn't admit this, but if I'm hauling an empty trailer behind the dump, I turn the air off to it. My brakes are the older type that dont hold with air removed, they just coast. Its probably not dot compliant, but i don't flat spot tire...

 

[CRAFT]

As mentioned before ... make absolute sure that your trucks brakes are up to the proper adjustment, "auto slacks or not", it is still the drivers responsibility to be sure that all of the brakes have the correct travel ...... having said that no one here has mentioned that possibly if the treadle valve is working proper in the truck ... have you got application gauges showing your truck and trailer air application pressure ??? ..... maybe the relay valve on the trailer is dirty/sticky ??? There are lots of little things that you could check, if you are unsure of the type of air-brake system you have in your truck maybe you should take it to some one that can check it out with you there and explain the different functions to you ........
My Trail-King 20ton tilt deck has auto slacks and my tractor does not ..... personally I hate the auto slacks, I feel that I don't have control of what is happening where as the manual ones you are under the truck checking and have a grip on things ...... the next brake job I do on the trailer the Autos are gone ! ......jmho ..... cheers

 

[DirtHauler]

The best way to avoid flat spotting your trailer tires when empty is to make sure the truck brakes are adjusted up properly. As for what Mitch said about taking the automatics off and putting manual slack adjusters on... Commercial motor vehicles manufactured after October 20, 1994 and equipped with air brakes are required to have automatic brake (slack) adjusters. The DOT is big on writing tickets around here to guys for putting manual slack adjusters on newer trucks.

 

[mitch504]

Yep, I should have included that warning, and I wasn't really recommending that, just telling what I do. We haul and spread fertilizer on farms, and also build and repair logging roads. I get 3-6 months out of a $150 automatic, and 5 years out of a $15 manual. When your truck is stopped by SCDOT, you get a $100 or $200 ticket no matter what, and they've never gone to the effort to write them up.

 

[Dualie]

I have heard rumor of that fact that a quarter will fit in the service side of the gladhand. and nurse a bad QR valve back to a better repair spot.

 

[Komatsu 150]

We used to have this problem pretty severely especially as we would often put a load on the truck in the morning and then pull an empty trailer with very strong brakes to the job. I solved it on our trucks by installing a brake limiting valve. This proportionally reduces service air pressure to the trailer by about half (45%, I measured). This is controlled by a flip valve or air toggle on the dash which is labeled loaded and empty trailer. These systems were designed to reduce front brakes on semi tractors and were very common but have been illegal for years. The last truck I did was 12 years ago and the valves were not available new, probably had been illegal for ten or twenty years by that time, but I found rebuilt ones. This works very well, the trailer brakes are proportional to pedal pressure. The truck driver has to remember to flip the switch when a machine is on the trailer and I'm sure it's all completely forbidden.

 

[Hendrik]

We used to have this problem pretty severely especially as we would often put a load on the truck in the morning and then pull an empty trailer with very strong brakes to the job. I solved it on our trucks by installing a brake limiting valve. This proportionally reduces service air pressure to the trailer by about half (45%, I measured). This is controlled by a flip valve or air toggle on the dash which is labeled loaded and empty trailer. These systems were designed to reduce front brakes on semi tractors and were very common but have been illegal for years. The last truck I did was 12 years ago and the valves were not available new, probably had been illegal for ten or twenty years by that time, but I found rebuilt ones. This works very well, the trailer brakes are proportional to pedal pressure. The truck driver has to remember to flip the switch when a machine is on the trailer and I'm sure it's all completely forbidden.

Yeah pretty illegal to mess with a brake system, also leaves yourself open for being sued by a driver, other motorists etc.
This is one of those don't even think about it ideas.
Sure older trucks had this sort of set up with a valve in the cab but nowadays it's all done automatically.
I reckon if the trailer brakes are locking up there could be a fault with the system, however road train dollies run without brakes when not coupled.

 

[Birken Vogt]

however road train dollies run without brakes when not coupled.

Here in the States they also close off the service side to the dolly when unloaded. However, the emergency side is supposed to be connected so that if the dolly gets loose, the brakes will come on. I don't know how many drivers do this in practice....