Leaf Spring U Bolt Torque

[jpajax]

I know this has been beat to death. But was thinking about what someone had said earlier about the spring base that the shocks and u bolt is bolted to being on top. If the u bolts are torqued when there is no weight on the axle the plate is pulling the spring arch to the plate. But when the weight is put on axle that that changes the arch of the spring which I would think that would change the torque on u bolts. So if that is true you need to torque or re torque the bolts after the camper weight is on axle. Just a old country boy way of thinking. So it might need to be part of the PDI..

 

[hoefler]

The springs usually have a flat spot in them and the saddle/clamping area. On some springs the area is more noticeably bigger than others.

 

[Ray LeTourneau]

It makes sense to me to torque the u-bolts with the the tires on the ground and weight on the axles. Just as you described. Like you said, logical.

 

[jpajax]

Will get to see more of process at big rally. But it seems that after the weight has been applied and the trip to dealer they have had time to settle in. So that being said it should be part of the PDI. even the wheel manufacturers recommends and post that you should re torque after so many miles. Well it's time to get off my soap box. Every body have a safe and happy camping season and remember your childhood questions WHY AND ARE WE THERE YET?:angel:

 

[rebootsemi]

The springs set on the flat spring perch that is welded to the axle, you are clamping the center of the spring pack where there should not be any gap between the springs, should not make any difference if weight on or not you are clamping steel, providing that the torquing was done correctly in the first place. This would be the part of the process I would suspect. I check the U-bolts on our trailer and they were right on. One thing you could get is bolt stretch over time, might be a good question to ask them at the rally. Is there still some units where the axles are mounted over the springs? If there are all of the weight is held by the U-bolts.

 

[JohnDar]

I know early last year after reading about the torque on the spring bolts, I went and checked mine and found them all under-torqued. Since then, I check them before hauling and they've been holding 65 ft-lbs.

 

[caissiel]

After i did the spring change on my unit I retorqued them at 3 occasion and they were in need everytime. I did it at 1000 miles and 2000 miles and I felt good doing it. Now they are set in and have been good after 6000 Miles.

 

[2psnapod2]

Where is the torgue numbers coming from? I have not heard that these also need to be torqued. Just trying to get this maintenance stuff down pat.

 

[jpajax]

5.2K axle = 65 ft lbs
6 – 8K axle = 90 ft lbs 90ft if you have 9/16 u bolts Mine had 1/2'' but when they replaced springs they replaced with 9/16''. This has been a topic that has been discussed for some time. It all stems form Lippert axles and springs and their lack of QC. poor quality of parts. Heartland has since went to Dexter axles and springs. But still think it should be part of PDI just for safety sake.

 

[navyAZ1]

The tech with Lippert told me that for our 6000# axles the torque is 70 to 75 ft lbs with the weight on the axles.

 

[JohnDar]

Torque is dependent on the size of the fastener and the grade of steel it's made from. If you know size and grade, you can find torque tables on-line so you don't end up snapping bolts by gorilla-torquing them.

 

[traveler44]

I would think that you could stretch the ubolts if your not careful and that would be a bigger problem than being a little under torqued. When you torque a ubolt do you do one ubolt at a time--like the inside one and then the outside one or do you cross torque little at a time to try to keep even pressure on the plate? If the specs call for different torques for different size and grade what grade are ours? Looks like there should be a pin from the axle yoke through at least the first spring to help keep the axle from sliding back or forth like on our truck. These are reasons why I have just snugged ours down instead of trying to torque them. Tom M.

 

[traveler44]

I read the old posts about torquing the ubolts and it looks like I will try to go to the 65# and then mark the nut with the paint pen. I guess the spring does have a center pin through it or some of them do. So many things to watch for, like stretching the ubolts or bending the plates etc. but torquing is better than having an axle slip. Tom M.

 

[lwmcguir]

Definitely torque the bolts evenly by watching how much thread is exposed to start with. Then take them up on round at a time until you reach the recommended torque.

Most all spring sets have the hole in them to set the position on the plate.

You shouldn't have to tight them again after the second time. If you do something is wrong.