wheel studs/bolts how much is enough?

toopy

toopy

Club Member
What's the safe amount to have of the stud protruding past the bolt hole surface, and therefore actually secured inside the wheel nut?

Also if you have to fit a spacer, you no longer have the hub centric assistance with centralising the wheel, does it really matter?

Reason being i have bought some new 16" 8J wheels, but they weren't available in zero offset, and are +10 offset instead, and the rear of the rim just contacts the lower spring perch as the nuts begin to tighten!
So i need a 5mm spacer as a minimum, but probably safer with a 10mm one, however I suspect i will then need longer studs :confused: this is on the front, haven't tried the rear yet.
Standard suspension, other than it being lowered a couple of inches
 
johnymd

johnymd

Club Member
The fronts are not hub centric. The section that sticks out is just rough cast. With regard to how much thread should be used then I've heard 6 threads mentioned but don't take this as gospel.
 
toopy

toopy

Club Member
Rob Gaskin said:
I used to want 10 turns to feel safe.
Click to expand...

10 full turns seems like a lot, but then I've never actually counted before!

Will try that on the Wolfie nuts tomorrow, from a physically turning the wheel brace sort of feeling, i suspect it will be more like 7 or 8
 
Rob Gaskin

Rob Gaskin

Treasurer
Staff member
Site Administrator
toopy said:
10 full turns seems like a lot, but then I've never actually counted before!

Will try that on the Wolfie nuts tomorrow, from a physically turning the wheel brace sort of feeling, i suspect it will be more like 7 or 8
Click to expand...

Ok, I had 'open ended nuts' and it was with long studs on my trackday car - but it seemed about right tbh.

Try your road car.
 
M

Moriarty

Well-Known Forum User
Pick from Motorsport or general engineering practice
Failures tend to be the stud rather than pulled theads

Automotive "lugs" tend to be longer than general engineering nuts n bolts so
MSA blue book regs state 1.5 times the stud diameter

So 12mm stud should have at least 18mm of thead engaged so it is permissble not to have any thread protruding

General Engineering good practice is 1-2 full threads
 
toopy

toopy

Club Member
Moriarty said:
Pick from Motorsport or general engineering practice
Failures tend to be the stud rather than pulled theads

Automotive "lugs" tend to be longer than general engineering nuts n bolts so
MSA blue book regs state 1.5 times the stud diameter

So 12mm stud should have at least 18mm of thead engaged so it is permissble not to have any thread protruding

General Engineering good practice is 1-2 full threads
Click to expand...

:thumbs: after a little Googling last night, that's the consensus i came too as well, 1.5 times stud diameter or an absolute minimum of 5.5 full turns, although most would advocate 6.5 - 7 as acceptable.

From what I read most would also agree that it depends on the intended use of the vehicle as well, so road car pootling about, 5.5 would likely be absolutely fine, fast road use/track, where clumping the wheel on something is more likely, then the upper range as above.

And visually check the wheel nuts and re-torque on a reasonably regular basis if running at the lower end of the full turns scale, it seems to be more of an issue with things coming loose rather than the threads stripping under stress ;)
 
toopy

toopy

Club Member
johnymd said:
I use ali nuts and have replaced all the studs for much longer ones.
Click to expand...

Can you confirm the correct spec please, I believe it to be M12 x 1.25 with a 14.3mm spline, and any pointers on where to buy at reasonable prices?
 
toopy

toopy

Club Member
Having a measure up today to see what the standard length studs are, i realised that definitely one if not two of the wheel nuts on the left front have a shank/sleeve that are too long :eek:

nutz1.JPG

correct, approx 1mm below the wheel centre

nutz2.JPG

Debatable, couldn't quite tell if it was flush or proud

nutz3.JPG

Definitely proud by 1mm atleast!!!

That would explain the vibration and steering wheel wobble above 55mph then! :unsure: I'd always assumed it was balancing or tracking!

The existing wheel studs do seem pretty short, only 20 - 21mm of thread available, 38mm approx total length, head to end of thread,
I'm assuming this is because the cars were designed to be used with lug nuts that have the extra shank that sits inside the wheel and brings most of the thread into play, unlike more modern nuts that fit purely on the outside of the wheel.
 
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toopy

toopy

Club Member
Rob Gaskin said:
Ok, I had 'open ended nuts' and it was with long studs on my trackday car - but it seemed about right tbh.

Try your road car.
Click to expand...

11.5 turns for lug nuts and wolfies, and therefore engaging approx 20mm of thread, and that doesn't include the first half turn or so required to engage the thread properly
 
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