Brake chambers..

What does the door sticker say? There was a guy posting other day why his door said GVWR was only 48,000. 12,000 plus 36,000. The three suspension Kenworth offers on is AG380 (38,000),AG400 and AG400L which are both 40,000. I didn't make the regulations, just spreading the facts.

 

@AModelCat is right. Its about the holding power of the park brakes. Maxi’s on only one axle drops the weight rating down that can be held. I think they also rate it by a certain percent of grade that it has to be able to hold on to without slipping too. But not sure what that is.
Guys commonly added the extra 2 maxi’s on the drives If they ran heavy through the mountain grades all the time. Back in the days of no spring brakes on trailers maxis on one axle would not hold a hill. Always had a block of wood handy for a chock.
The rating is relatively a new thing within the last 20 years. I think it is to get everyone to spec maxi’s on all axles instead of just the 2 standard.

 

True mayby, with only setting the tractor. But common sense would dictate setting the trailer brakes as well . Mayby leave the truck in a lower gear also if leaving it set with engine off.

 

Just looked at my door sticker. GVWR is 50,000 lbs. 12k on steer, 19k and 19. Total 50k. To me its not of concern how many spring brakes 2 or 4. A few pounds either way is not, or ever been a problem when parking.

 

A lot of lowbeds and pole trailers still in service only have service pots, even into the late 90's. I would not trust 1 axle worth of spring brakes to hold 100k lbs on a grade.

 

I had a old trailer like that. If the air tanks were empty and I backed up to get under I sometimes had to chase it as it kept moving back. Hook up air and charge tanks, then pull the hand valve, or trolley brake to make it hold still. Oh and once in awhile I get a rail box mounted on a chassis with no, or very poor brakes, chasing it brings back memories. Good times.

 

What's not proper about it?

 

My 01 with 40k rears only has maxi brakes on the front drive. I don't think there is any standard, just whatever was specced by the original purchaser

 

That might be a Canadian thing. Down here spring brakes have been required for a lot longer than the late 90s. I don't know what year but id guess late 70s maybe early 80s. Ive got an old 73? drop deck that doesn't have them, but the 2 van trailers I got do and they are early 80s I think.

 

Could be due to the operating conditions too. I swear I read on here not long ago that lowbed manufacturers had spring brakes as an option. Someone was specing one out I think?

I was always under the impression that it was law since Schedule 121 went into effect in the 70's I think.