Aluminum trailer bogie bolt torque

[Backyard-Mechanic]

I have an aluminum car hauler. The main frame rails are 2 - 2x5 aluminum square tubes with 1/8 wall welded together. It had 2-5x3 steel angle iron pieces to mount the springs and axles on to the trailer. It has 2-5200 lb axles. In effect a separate bolt on bogie. They used 3 - 1/2 8.8 bolts to hold the bogie to the trailer.

It was bouncing quite a bit so I took off the 5x3 steel angle bogie, welded on some extended spring hangers and put a MORryde cre3000 center point hanger on. The original spring hangers were too short for the MORryde system.

Now I need to bolt this bogie back on the trailer. It has 3-1/2 8.8 bolts on each side. What torque should I put on the bolts?

​

 

[Firebrick43]

So your mixing up terms

SAE bolts are grade 2, 5, and 8

Metric bolts are 4.6, 8.8, 10.9, and 12.8

So 1/2" can't be grade 8.8

You also need to know coarse thread or fine thread.

If they are grade 8, 1/2-13 bolts torque is 100-110 fts dry or 80 lbs well lubricated. If they are 1/2-20 fine thread add 10 lbs to those numbers.

Make sure there is a stainless washer under the head of the bolt and its on the aluminum and would be best if a hardened steel washer is under the nut on the angle iron side.

 

[rooster59]

M12 bolts? 19mm head? Are you bolting through square / rect aluminum tube? Did the original use Loctite?

 

[Backyard-Mechanic]

M12 bolts? 19mm head? Are you bolting through square / rect aluminum tube? Did the original use Loctite?

• Rect aluminum tube 2x5, 1/8 or 3mm wall, 2 tubes welded together of total 4 inch width
• bolts are 1/2 inch (equals m12) , 8,8. fine thread 3/4 head.
• Nuts were lock nuts but not nylock and I don't see any loctite
• Washers on both sides.
• I can put loctite on them.
• I can also put a backer plate

 

[rooster59]

Your question is what torque. If you go by a torque table for those bolts you’re probably going to distort the aluminum tubes. Tubes will bend before a steel bolt stretches. My guess is the original bolts were pretty tight but not enough to start bending the tubes. Thus the locknuts. 19mm same size head as ¾. Flat washers, backer plates, even lock washers, then locknuts if the locknuts still lock. Check after some miles.

 

[Wrench97]

You can't get a good torque reading with lock nuts, especially used lock nuts.
I suspect they used lock nuts because the tubes flex and regular nuts will loosen up.
M12 8.8 About 95 nm or 70lbft

 

[PCustoms]

• bolts are 1/2 inch (equals m12) , 8,8. fine thread 3/4 head.

No

I can't imagine being so concerned about torques but not understanding basic bolt specs.

 

[Jacko264]

If the bolts go though the aluminium box they should have round tubes though the aluminium box so not to crush the box

 

[gte718p]

If the bolts go though the aluminium box they should have round tubes though the aluminium box so not to crush the box

Should, but I bet they don't. That is extra time and money that trailer manufactures rarely spend.

 

[Jacko264]

This is the type of thing you should ask before buying If it has tubes welded in the box there should be no problems torquing the bolts

 

[Wrench97]

This is the type of thing you should ask before buying If it has tubes welded in the box there should be no problems torquing the bolts

Like the salesman will have any idea what you're asking...................

 

[PCustoms]

Anyone seen the op?

 

[Wrench97]

Anyone seen the op?

His profile shows him last here last Wednesday

 

[Jacko264]

Well if they don’t know they should go and ask

Like the salesman will have any idea what you're asking...................