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Some bridge formula questions


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Im working for a guy that does bulk cement, and he was thinking of converting his truck from a regular tandem to a single axle with a lift tag. It is just like how a tri axle dump is set up. A lever to lift/lower the axle, and a know to adjust the air pressure. He already did this to his other truck and has seen good results in fuel mileage. I had a couple questions:

The truck has 34000 on the tandem now, 17 and 17. Is it legal to run 20 on the drive and 14 on the lift axle? He wants to run it at 23 on the drive and 11 on the tag because its a 23000 drive axle, but I know you cant go over 20 on any one axle.

Would it be ok to run just one tire on the lift axle insted of a dually setup. I see some tri axle dumps with this. I also heard that over a 10,000 axle you need a wide based super single above a 355 in with, but that was from someone out west. This setup will run pa and nj. Maybe md and va and ny. I found a goodyear 285 75 22.5 rated at over 7,000 per tire, that would hold 14k and should be legal in these states. It works out to about 620 lbs per inch of with.

thanks for any help

79 U

237 5 sp

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Im working for a guy that does bulk cement, and he was thinking of converting his truck from a regular tandem to a single axle with a lift tag. It is just like how a tri axle dump is set up. A lever to lift/lower the axle, and a know to adjust the air pressure. He already did this to his other truck and has seen good results in fuel mileage. I had a couple questions:

The truck has 34000 on the tandem now, 17 and 17. Is it legal to run 20 on the drive and 14 on the lift axle? He wants to run it at 23 on the drive and 11 on the tag because its a 23000 drive axle, but I know you cant go over 20 on any one axle.

Would it be ok to run just one tire on the lift axle insted of a dually setup. I see some tri axle dumps with this. I also heard that over a 10,000 axle you need a wide based super single above a 355 in with, but that was from someone out west. This setup will run pa and nj. Maybe md and va and ny. I found a goodyear 285 75 22.5 rated at over 7,000 per tire, that would hold 14k and should be legal in these states. It works out to about 620 lbs per inch of with.

thanks for any help

not much help,but having an equalizer valve will give you even ground pressure on both axles

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I have 31R22.5 on lift axle and front axle of my tri-axle dump that works in Penna. They are rated for over 9000 lbs. depending on which manufacturer you chooser. Legally you are supposed to use a 9" rim with these tires. If you have the correct weight rating for tires,wheels and tag or pusher axle mounted with correct spacing between axles you should be ,legal. Quite a few fleets used that combination for years with no problems. Best is to check with DOT Officer or get information from PennDot.On a regular tag or pusher dual wheels are the norm but on a steerable pusher I never saw dual wheels. This is not to say they will not work but seems like they will scrub a lot. Joe D.

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Make sure they put a new decal in the door frame showing a chassis modification weight per axle . Ive seen DMV not notice a tag axle with out the decal . Just recent i was pulled over in my tri axle . DMVask me if i knew wy i was being pulled over i said you like MACKS he said your lift axle was up . I told him to put his finger on the brake drum He wouldn't then he said freget about it

.

M

Ed

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I wouldnt have a problem running equalized,i could adjust the pressure with the knob for euual weight. I would probablly need to run duals on the tag or at least a wide tire. I wanted the 20k on the drive more for traction, especially in the rain. In the snow i could adjust it so just about all the weight is on the drive, i dont think the scales would evev be open then. The truck is going to have the same number of axles, so i didnt think about a new door tag. right now its 12000/19000/19000 on the door sticker.

79 U

237 5 sp

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Alot of states are looking for the weak point spring , tire rating ,brake lining,17000lbs to 23000lbs ratings front axle 9000 12000 14300.lbs also they making you install the controls on the out side of the cab

Ed

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I wouldnt have a problem running equalized,i could adjust the pressure with the knob for euual weight. I would probablly need to run duals on the tag or at least a wide tire. I wanted the 20k on the drive more for traction, especially in the rain. In the snow i could adjust it so just about all the weight is on the drive, i dont think the scales would evev be open then. The truck is going to have the same number of axles, so i didnt think about a new door tag. right now its 12000/19000/19000 on the door sticker.

5 lbs of air on that valve makes a big difference.Especially if your trying to equilize while still moving to scale.

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Horwith had two new F-Liners with sleepers, an they both had factory tag axels! The computer automatically adjust the weight, so if your drive starts to slip the computer automatically adj. your air to the drive plus or minus! I spoke to one of the drivers who has one that's about a year old an he likes it, I guess we'll see?

Bullhusk

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if you do a steerable axle install a hidden switch in the cab when you blow a tire and that axle goes from stop to stop it makes for a very wild ride! and you want that thing in the air NOW! ALSO TIE IT INTO THE BACK UP SWITCH. IT GETS EMBARRASING WHEN YOU SPACE IT OFF

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if you do a steerable axle install a hidden switch in the cab when you blow a tire and that axle goes from stop to stop it makes for a very wild ride! and you want that thing in the air NOW! ALSO TIE IT INTO THE BACK UP SWITCH. IT GETS EMBARRASING WHEN YOU SPACE IT OFF

Hell with the tire when the shocks start going bad and you get the death wobble it is a fun filled ride

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it wasnt going to be a steerable axle, more like a regular trailer axle. No computer stuff, the truck is a 92, so its all mecahnial. Maybe a hidden dump switch would be a good idea. Run the weight equal, and when its spins hit the dump switch. I already have one i use on the spread axle trailer to make it turn easier. On the 3 axle trailer it dumps the air and brakes on the front trailer axle.

79 U

237 5 sp

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Fed rules say 20,000# per axle max with certain axle spacing, if the tag is too close it doesnt qualify unless you are running a permit, the most you can legally run on any tandem is 34,000# at 17,000# per axle and this is the same for a tandem or a single axle and a tag unless they are spaced out and I cant remember the axle spacing needed to get to 20k, you also have to have the tire and wheel rating to handle it as said above if the axle rating is good bnut the tire is too light youll get popped for the lesser of the two.

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