[flashollie]

I'm still in bed and got thinking. Im going to fit my 10mm and 12mm spacers today and they are still in the garage..... Is there torque setting supplied for the bolts? Or do just used the same value when not using spacers. If so what torque do people use?

[Craig-SM]

140nm on dry bolts

[flashollie]

Originally Posted by Craig-SM

140nm on dry bolts

Thanks.
assume by dry bolts your suggesting they shouldn't be greased?

[Craig-SM]

Copper grease on the wheel mating surfaces but the bolts should be grease free.

[flashollie]

Originally Posted by Craig-SM

Copper grease on the wheel mating surfaces but the bolts should be grease free.

thank you

[DonDP]

Originally Posted by Craig-SM

140nm on dry bolts

Glad I read that, I just assumed it would be the same as older BMWs at 120NM.

Turns out BMW recomened 140NM on all all Fxx cars wonder what prompted the increase...

[Edinburra]

Originally Posted by Lobb

No, no, no, no!

Never, no.

A little around the spigot but never on the surface that transmits the torque.

Could you expand on that please, as I'm unsure what you mean.
I've always used copper grease on the wheel mating surface to ensure that the alloy does not stick to the hub, having once experienced that situation.

[Craig-SM]

I’d like an explanation too. I’ve got three decades of doing this and more miles than I’d like to count , both on and off road, with not a single issue. Am I about to die in some horrible accounts accident when the wheels coming flying off my car?

[Lorcan]

Originally Posted by DonDP

Glad I read that, I just assumed it would be the same as older BMWs at 120NM.

Turns out BMW recomened 140NM on all all Fxx cars wonder what prompted the increase...

The change from 12mm to 14mm bolts.

[flashollie]

my car has done 5k miles just taken wheel off to fit spacers and copper grease is only on the spigot sticking out. Not on the flat section where wheel meets hub.

[Edinburra]

Originally Posted by Lobb

Only round the spigot ring. NEVER on the face.

Thank you. I will ensure that my ring is well greased.

What would the consequences be of copper greasing the face then?

[HighlandPete]

Originally Posted by Edinburra

Thank you. I will ensure that my ring is well greased.

What would the consequences be of copper greasing the face then?

Reduces the coefficient of friction on the face, the part that transmits the torque.

[Drek]

Glad I saw this, I was just about to swap my wheels over without any grease at all.

[Edinburra]

Originally Posted by HighlandPete

Reduces the coefficient of friction on the face, the part that transmits the torque.

Thank you, understand now, will take heed.

[Edinburra]

Originally Posted by Lobb

The torque from your engine is transmitted via the face of the wheel. The bolts on the wheel merely hold the two facing plates together. If you put grease on the facing plate, you reduce its ability to transmit torque. This will increase the shearing load on the wheel bolts.

I will now defer to the Oracle, whom some say is HighlandPete for a more full explanation.

Thanks, will now adjust accordingly. (Every day's a school day)

[HighlandPete]

Originally Posted by Craig-SM

I’d like an explanation too. I’ve got three decades of doing this and more miles than I’d like to count , both on and off road, with not a single issue. Am I about to die in some horrible accounts accident when the wheels coming flying off my car?

We may get away with less than best practise, but doesn't mean its always going to serve us well.

Although a wheel fixing appears the simplest of fastener systems, it has quite a complex function to perform, as fasteners go.

We have to accommodate radial position and load, axial loads, vibration and the transmission of torque, all with a simple bolt, with no secondary 'backup' locking feature.

The spigot supports the radial position and load, (hence the importance of correctly matched spigot and hub dimensions. The bolt deals with the axial loads and supplies the clamping force to the friction face, which subsequently transmits the torque without slip.

No way should a wheel bolt support the radial load, (loose spigot), or be transmitting the driving torque, neither functions are intended in a wheel's fastener system. Lubricants change the fastener's dynamics, both in the bolt's applied torque and the coefficient of friction between the wheel and hub.

Lubricants can contribute to relaxation of the torqued assembly. Hence why we only apply anti-seize compounds where there is no compromise to the clamping force or bolt torque value, just the spigot area.

Lubricant on the bolts... we have to recalculate the torque value, based on the new coefficient values, as a result of the lubricant we are using (lubricant type) and where we put it.

For example a 'wet' bolt, where threads and under head face are lubricated, a torque value of 140 Nm for the M14 bolt will mean it is grossly over torqued.

[flashollie]

Originally Posted by HighlandPete

Reduces the coefficient of friction on the face, the part that transmits the torque.

This make a lot of sense.

Thanks

[dazwhite]

Originally Posted by Craig-SM

I’d like an explanation too. I’ve got three decades of doing this and more miles than I’d like to count , both on and off road, with not a single issue. Am I about to die in some horrible accounts accident when the wheels coming flying off my car?

This seems like another urban myth to me!

Nope, there's no problem using copper slip on the hub faces. It prevents the wheel seizing on the hub. The clamping force provided by the bolts provides enough friction between the mating faces to negate this once the wheel is torqued up.

[HighlandPete]

Originally Posted by dazwhite

This seems like another urban myth to me!

Nope, there's no problem using copper slip on the hub faces. It prevents the wheel seizing on the hub. The clamping force provided by the bolts provides enough friction between the mating faces to negate this once the wheel is torqued up.

What's the reasoning/calculation for "enough friction"? I'd like to see it.

[dazwhite]

Originally Posted by HighlandPete

What's the reasoning/calculation for "enough friction"? I'd like to see it.

Each wheel is held on by a clamping force of around 5 tonnes-force or 50KN, so even if the coefficent of friction is lower due to anti-seize compound its still enough force. Don't forget the bolts and spigot also hold on the wheel via a shear force and the shear strength of each bolt is approx 5 tonnes-force. So its not going anywhere!

[Craig-SM]

HighlandPete I would love to accept the theory that the bolts hold the wheel on and the torque is transmitted between two smooth surfaces. Why is the rear of the wheel cast to reduce the mating surface and if the surfaces were designed to transmit the torque why are they not keyed to each other to prevent slippage?
Still doesn’t explain why my wheels haven’t fallen off. I’ve searched the internet but can’t find anything on the consequences of using copper slip on the mating surfaces.
Also baffled why F1 and exotic cars use Center Lock (one big nut) and locating lugs which reduces the mating surfaces but allows lighter wheel designs and bigger brakes.

[MickyD'bo]

Originally Posted by Lobb

MickyD'bo is your man then

Lol. My ring has been fingered that much that I don't need grease.