Help on bridge law formula for semi dump

My fleet runs in Indiana, Ohio, Ky and our latest spec is 34' frameless East Genesis with lift axle. We were running 39' Mac Macsimizers. IN lets us go 48,000 on rear being triaxle so we can load more to the rear. We have some 39' East Genesis hybrids, but most prefer the triaxle so they can cross scales without worries.

 

It was just around 1500lb. The East has a 9' liner vs 5' in the Mac. Seen many a Mac wore to pop can thin or thru right above the liner. The Mac also is way more prone to cracking @ welds all over. East Genesis Hybrid over 36' due have a recall for draft arms cracking. We said seven 39' repaired with four getting new draft arms.

 

The East is more expensive, but is built better in my opinion. We have way less issues with the East Genesis Hybrid. Both are 34' and 39' are the hybrid. 39' seems Mac is about 700lbs lighter than East. We use to able to haul 27 ton easily with our daycab Petes and macsimizers. Genesis actually have lower center of gravity vs the macsimizer. Our guys that pull them say they seem more stable dumping, especially the 34'. Seemed like we would lay one Mac over every 18 months on average.

 

Mac will have a lot of cracked welds. They crack a lot!!!! Nose around hoist, up around top of hoist cylinder, tub to sub frame, rear of trailer inside by tailgate is most common. Sub frame were air bag mounts tends to corrode up pretty bad also. Check for sure how thick tub is just above liner just in front of tandems. Changing an air bag is a pain on them due to corrosion. The East recall was 2013 up I believe. They changed the rubber pads to quiet the draft arms. If it has round ones, I doesn't fall under the recall. Only place an East has cracked so far is a 2012 we have around the bulkhead. The updates to the draft arms is an 18 hour process. We had ours done at the East factory. They paid mileage if we brought them up.

 

One of the 39' East.