Wheel Bolts

[DavidM]

I've got a couple of questions for car engineering mechanical experts about wheel bolts and minimum thread length safety - bearing in mind manufacturer's specific requirements.

1. I am running 7 mm spacers with extended wheel bolts on my rear alloys - is it possible to run these 7 mm spacers with OEM 26 mm BWW Z3 wheel bolts on the hub and satisfy safety standards?

2. What is the minimum bolt thread length that can be used in a general sense whilst still maintaining UK and EU safety requirements?

Z3 OEM 26 mm Bolt dimensions:

 

[t-tony]

What are EU and UK requirements David, I have no idea. Every car I remove wheel bolts on at work are always difficult to remove if they've been in for ages as the thread which protrudes through the drive flange or hub rusts up and is usually around 7-8mm at least. I'm not sure why they need to be this long as, as far as I can see, after the full depth of the female thread is reached any more is wasted. Stud and nut type fixings never have this much stud through the nuts when they are tightened.

Tony.

 

[Stevo7682]

Personally i wouldn't
Work with wheel and tyres all the time we get it hammered into us about hub and bolt cleaning and correct fixings.
This is my thinking your thread length 26mm
Minus 7mm for spacer
Minus the width of the wheel my 18 wheel is 11mm. (Just measured it)
So that's 18mm that would leave you approximately 8mm screwed into the hub .
This is probably enough to hold the wheel on but i wouldn't be happy with that personally. Stephen.

 

[DavidM]

I read on one or two company websites that sell wheel bolts the minimum number or full turns of a bolt should be no less than 6.5 referring to EU/UK standards - in other forums they refer to to 7-8 full turns - in others they refer to 1.5 times the diameter of the bolt as minimum thread depth in the hub - no reference to standards though - thought I would get the views of forum experts.

 

[Stevo7682]

How long are the extended bolts

 

[DavidM]

They are 32mm thread

 

[Stevo7682]

Right if they are 32mm thread and your spacers are 7mm then your extended bolts already 1mm shorter into the hub than the standard one. i would leave well alone

 

[t-tony]

Personally i wouldn't
Work with wheel and tyres all the time we get it hammered into us about hub and bolt cleaning and correct fixings.
This is my thinking your thread length 26mm
Minus 7mm for spacer
Minus the width of the wheel my 18 wheel is 11mm. (Just measured it)
So that's 18mm that would leave you approximately 8mm screwed into the hub .
This is probably enough to hold the wheel on but i wouldn't be happy with that personally. Stephen.

I would agree with you that 8mm screwed into the hub probably would not be enough, the point I make is that any amount of bolt which protrudes though the drive/hub flange is wasted, it does not do anything.

They are 32mm thread

This in effect then gives you 8mm (as per Steve's thoughts) plus an extra 6mm giving a total of 14mm which I think is more than sufficient to secure a wheel to the hub, It's unlikely the flange is thicker than 14mm. I will check on mine as I'm having the wheels off soon.

Tony.

 

[oldcarman]

The only advantage I can see with going beyond the hub 8mm is that should your lug start to loosen you will likely feel that in the handling and gives you time to tighten them before the wheel comes completely off the car! JIM