U-bolt and lug nut torque

[IC2]

I've done my search on the Dexter site as well as here --- and just because, a general 'net search.

We will be departing in a couple weeks for an extended trip so it's time to do the wheel bearings and brake check. The bearing project will cause no problems but since the wheels will be off, it's easy to do a U-bolt torque check. As I noted above, I've looked but no joy on the value for those 1/2" bar stock U-bolt figures, having found everything from a too low 45 lb ft to 100 which seems too high for a mid grade steel. My recollection is that 65-90 is the right number with the wheels (aluminum) at 100-120 lb ft.

Any good thoughts? Am I close with 70 lb ft for the u-bolts? 100 for the lug nuts (what they are at present)?

[99-Am.Star]

the u bolts are generally a lower grade material, grade 5 at best. If it wer me I would give them about 65 FP and put a second nut on it to make sure there is way it can work loose.

[lynnmor]

Here you go:

http://www.dexteraxle.com/i/u/614960...uspensions.pdf

http://www.etrailer.com/question-75604.html

[IC2]

Originally Posted by lynnmor

Here you go:

http://www.dexteraxle.com/i/u/614960...uspensions.pdf

Lug Nut Torque Chart for Trailer Wheels | etrailer.com

That's part of the confusion factor. Page 3 of the Dexter info has two different sets of values on three separate lines for a 1/2" U-bolt. eTrailer on the chart you posted where they say 90-100 lb ft (too high for Gr 5) and another etrailer thread that I saw prior to starting this thread has the 45-70 lb ft which is too low. American Bolt and Imperial Bolt call for 75 lb ft for a Gr5 bolt. Dexter used to have the complete maintenance manual with torque figures on their website and I had a copy but it may have been left with the last 5er as it seems to be gone from my trailer binder.

I think I'll use 70-75 for the u-bolts and 100-110 for the lug nuts

Thanks for the links.

[lynnmor]

I used the middle of the 1/2" hex nut torque (58 lb.) and can tell you that was more than enough. It seems as though the bolts will never stop stretching.

For my aluminum wheels the manufacturer quoted 100 lb. and that seems just right.

I know that I used the word "seems" twice, but with much experience with this kind of work one can get a pretty good feel of what is right.

[IC2]

Originally Posted by lynnmor

I used the middle of the 1/2" hex nut torque (58 lb.) and can tell you that was more than enough. It seems as though the bolts will never stop stretching.

For my aluminum wheels the manufacturer quoted 100 lb. and that seems just right.

I know that I used the word "seems" twice, but with much experience with this kind of work one can get a pretty good feel of what is right.

U-bolts are strange fasteners. You are correct that they always seem to have too much elasticity. I've 'played' with automobiles and trucks for way too many years including quite a few as a part of my income in the last century. Springs/u-bolts never seemed to be tight enough regardless of how much I wound them with a torque wrench.

[Franka548]

IC2,
From years of experience and also looking at the Dexter torque chart, I would believe that your 70 to 75 ft-lb would be correct. For your wheels, it depends on the stud diameter, if memory serves me correctly 90 to 100ft-lbs for 1/2" stud, 110 to 120 ft-lbs for 9/16" stud and 130 to 140 ft-lbs for 5/8" studs. With a retorque after the first 200 miles, and a check every 1000 miles or so thereafter. On the u-bolts you are supposed to retorque after 200 miles then thats it, if they lossen after that , you are supposed to install new ones.
Frank

[BrianGlenn]

On my previous trailers, the plate on top of the spring leaf would bend before I reached the correct torque spec for the size of u-bolt. I torqued them down until the plate just started to flex. Any more would not increase the clamping load, and only possibly fail the plate.

My thoughts,
Brian

[IC2]

Originally Posted by BrianGlenn

On my previous trailers, the plate on top of the spring leaf would bend before I reached the correct torque spec for the size of u-bolt. I torqued them down until the plate just started to flex. Any more would not increase the clamping load, and only possibly fail the plate.

My thoughts,
Brian

So true that these RVs have spring plates that really aren't 'automotive' quality. It sounds as though you also had an underslung axle as ours is as OEM

[IC2]

Originally Posted by Franka548

IC2,
From years of experience and also looking at the Dexter torque chart, I would believe that your 70 to 75 ft-lb would be correct. For your wheels, it depends on the stud diameter, if memory serves me correctly 90 to 100ft-lbs for 1/2" stud, 110 to 120 ft-lbs for 9/16" stud and 130 to 140 ft-lbs for 5/8" studs. With a retorque after the first 200 miles, and a check every 1000 miles or so thereafter. On the u-bolts you are supposed to retorque after 200 miles then thats it, if they lossen after that , you are supposed to install new ones.
Frank

Unless I'm doing a torque check on my truck, 1/2" is all I have to consider - and that truck went from 150 lb ft for my '06 to 165 on my '11 with an M14 diameter Gr 10.9.

[1bigmess]

Originally Posted by IC2

That's part of the confusion factor. Page 3 of the Dexter info has two different sets of values on three separate lines for a 1/2" U-bolt. eTrailer on the chart you posted where they say 90-100 lb ft (too high for Gr 5) and another etrailer thread that I saw prior to starting this thread has the 45-70 lb ft which is too low.

Sounds to me like you have your answer, ot at least one that you'll accept.

[QUOTE\I think I'll use 70-75 for the u-bolts and 100-110 for the lug nuts.[/QUOTE]

I was gonna say 80 for the u bolts, as that falls right in the middle of your two unacceptable ranges if you look at the highest low numbers and the lowest high numbers.