Tightening u bolts

[tez]

I was installing new leaf springs into my Hilux over the weekend and the factory workshop manual says that the u bolts should be torqued up to about 90 ft-lb (123 Nm).

Im having trouble getting it to torque up to 90 ft-lb, feels as though Im going to either strip the thread, or the ubolt will break once I get to about 50 ft-lb.
Any ideas? The torque wrench Im using is fine. U bolts are new ones I got with my suspension kit.

Thanks

[Z()LTAN]

u wont strip ubolts, if they are new dont worry

Torque for ubolts - FT








(Fkkn Tight)

[Shadow]

I was installing new leaf springs into my Hilux over the weekend and the factory workshop manual says that the u bolts should be torqued up to about 90 ft-lb (123 Nm).

Im having trouble getting it to torque up to 90 ft-lb, feels as though Im going to either strip the thread, or the ubolt will break once I get to about 50 ft-lb.
Any ideas? The torque wrench Im using is fine. U bolts are new ones I got with my suspension kit.

Thanks

Just torque it to 90 and see what happens really.


if it fails I would go back and tell them thier ubolts are shit.

[hilux79]

Something would have to be seriously wrong for them to fail at 90.

It is not a excessive torque for a bolt that size.

How long is your torque wrench? If you are near the end of the scale at 90 that's why it feels like you are going to do damage. lack of mechanical advantage.

[tez]

Rightio, 90ft-lb it is, i'll either be ordering new u bolts or a new torque wrench

Torque wrench isnt all that long so I might just have to slip some pipe over it to get the advantage.

[alien]

just remember once you've cranked them up to 90, go for a drive with bumps, zig zags, figure 8's, hard accel and braking, and some more bumps - then go back to re-torque them =)

[Slunnie]

It may also feel like its going to strip as the spring moves and the U-bolts flex.

[ferrit]

i have stripped a u-bolt before tightening it- let go at about 60ft/lb

but that was a stock toyota U bolt, that had been torqued about 3 times already!

[Z()LTAN]

I might just have to slip some pipe over it to get the advantage.

Doing this will alter the setting on the torque wrench...

U put more leverage on it like that and you are making the output b4 it clicks less...

U hold it at the back only on the handle, not behind not infront

[RDM]

I asked the same question over on the 4wdAction Forum, here's the link:

http://www.4wdaction.com.au/forum/showt ... hp?t=67224

[LuxyBoy]

I might just have to slip some pipe over it to get the advantage.

Doing this will alter the setting on the torque wrench...

U put more leverage on it like that and you are making the output b4 it clicks less...

U hold it at the back only on the handle, not behind not infront

Fail to see how that can happen when they are designed to release upon reaching the desired torque setting. Maybe on a cheap crap wrench but if you have something decent it should not matter.

Having said that they are meant to be used slowly

[hilux79]

I might just have to slip some pipe over it to get the advantage.

Doing this will alter the setting on the torque wrench...

U put more leverage on it like that and you are making the output b4 it clicks less...

U hold it at the back only on the handle, not behind not infront

Fail to see how that can happen when they are designed to release upon reaching the desired torque setting. Maybe on a cheap crap wrench but if you have something decent it should not matter.

Having said that they are meant to be used slowly

It will make a difference because you are now trying to bend the torque wrench. Instead of weight being applied to one point it is now two points with a tube which will make the wrench flex and release at a lower than indicated point. It is probably only a marginal difference and in this case not a big deal.

[Shadow]

I might just have to slip some pipe over it to get the advantage.

Doing this will alter the setting on the torque wrench...

U put more leverage on it like that and you are making the output b4 it clicks less...

U hold it at the back only on the handle, not behind not infront

Fail to see how that can happen when they are designed to release upon reaching the desired torque setting. Maybe on a cheap crap wrench but if you have something decent it should not matter.

Having said that they are meant to be used slowly

It will make a difference because you are now trying to bend the torque wrench. Instead of weight being applied to one point it is now two points with a tube which will make the wrench flex and release at a lower than indicated point. It is probably only a marginal difference and in this case not a big deal.

at 100ft/lbs, thats a fair wack of force. Would change it significantly IMO.

Dont use a pipe, unless the wrench is too small for the job, (should be about 400mm?) then any pansy can put 100ft/lbs of force on a torque wrench.

[tez]

Well this arvo, I decided to set the torque wrench to 90ft-lb and go for it.
The passenger side got to the specified torque, although the drivers side as soon as it started getting tight, the bolts starts to split, same case as what RDM was having.

Pic here http://img23.imageshack.us/img23/515/r0012203large.jpg

[Slunnie]

Hmmmm, I'd cut them off and get new bolts/nuts/washers.

Is your torque wrench in good knick and calibrated reasonably?

[-Scott-]

Did you lubricate the thread?

[tez]

Felt like it has some lubrication on them.
So its not recommended I reuse these u bolts, even though they are new?

The u bolt on the driver side also has a flat top, so its strength could differ to the passenger side?

[Slunnie]

Felt like it has some lubrication on them.
So its not recommended I reuse these u bolts, even though they are new?

The u bolt on the driver side also has a flat top, so its strength could differ to the passenger side?

Personally I wouldn't. Bending them through the thread will crack them.

[-Scott-]

Felt like it has some lubrication on them.
So its not recommended I reuse these u bolts, even though they are new?

Googled page on bolt torque: http://www.zerofast.com/torque.htm

The amount of torque required to properly tension a bolt can vary dramatically depending on whether the threads are dry or lubricated - a lubricated thread may only need half the torque of an unlubricated thread.

The table in this article shows that by using this formula a 1/2-13 Grade 5 plain bolt should be tightened to 82 foot pounds, but the same bolt that is waxed only requires 41 foot pounds to tighten the same tension. A perfect 1/2-13 Grade 5 waxed bolt will break if it is tightened to 81 foot pounds because the K factor is drastically lower.

[bimbo]

my drivers side u bolt on my hilux did exactly the same thing. other 3 corners are fine. I just left mine like that and left a spare ubolt in the toobox just incase one let go. been like that for 50 odd thousand km and still going strong

[tez]

That makes a few of us with the same problem then.

Is your drivers u bolt the one with the flatter top?
I suspect mine is not as strong as the passenger's side because of the flat top.

[tez]

my drivers side u bolt on my hilux did exactly the same thing. other 3 corners are fine. I just left mine like that and left a spare ubolt in the toobox just incase one let go. been like that for 50 odd thousand km and still going strong

Also, what brand u bolt are you using?

[redv8lux]

That makes a few of us with the same problem then.

Is your drivers u bolt the one with the flatter top?
I suspect mine is not as strong as the passenger's side because of the flat top.

Flat topped U bolts are normally forged to provide them with more strength, while allowing room for the draglink to move

[bimbo]

mine where EFS, Personally i think it is just the design of the plate which sits under the diff and the larger diameter u bold putting pressure closer to the edge causing it to bend outwards

[Micky-Lux]

I had new EFS leaves, shackles and ubolts on the Lux not too long ago. The guys at Carrolls told me 70ft-lbs. They torqued them for me at 70, and I haven't had one come undone yet (after about 2000 kays - probably 50-50 on/off road).

The workshop manual says 120nm which is about 88.5 foot pounds.

Wouldn't it depend on the manufacturer of the u-bolt as to what the recommended design torque should be?

[Jacked]

fancy boys with there torque wrenchs. Its all in the feel.
u-bolts go halfway between tight and f'n tight, unlubed like a prison cell man party.

biggest thing with u-bolts is you must tighten them evenly across the bolt and across the spring plate.

if its turning turning out like the pics above it is because you are going to tight for the spring plate. would suggest stronger plates or not go as tight and check them after 1st drive then every so often till you know they not going to come undone.

me pesonally would be getten a flat bit of thick steel and buzzing them up with a rattle gun.