I was reading one of the challenge-related threads and there was much discussion about replacing lug bolts with studs for safety reasons. Why?
Lots of cars (most Euro cars) have lug bolts. Why would you replace them with lug studs? If they aren't as safe, why does Porsche (to name one) use them?
Personally I hate them but only because it makes putting a tire back on a PITA.
DANGIT! Can someone fix the thread title for me? I'm still waking up.
Lug bolts are plenty safe - from an engineering standpoint, safer than studs. Think of it this way - with a bolt there is only one thread interface to fail. With a stud and a nut you have two interfaces. Honestly though, if quality materials are used and they are properly tightened... the difference is irrelevant.
The only reason I favor a stud over a bolt for racing is that during a fast tire swap in the pits there is something to guide the weight of the wheel on while you start the thread.
Studs make tire changes faster. The wheel hangs on the studs, so 2 hands and a foot are not needed to start a bolt. If rules permit, longer studs with threads removed from the ends will allow gluing the nuts into the wheels ala NASCAR.
OK, that's what I thought. What is the discussion about then? Did I misunderstand something then?
All true points. If it's a vehicle which sees frequent wheel changes, studs are very convenient, particularly bullet nose studs which don't require starting each nut - nice if you're swapping off hot wheels and nuts.
Another thing to consider is that that the active threaded interface is replaceable. I replace the nuts every year or 2, studs every 2-3 on my M3 track rat. The threads in the hubs only see use when the studs come out, and the studs and nuts are coated for prevention of corrosion, and are designed to withstand the cycles. The typical German bolt-into-hub is robust, but doing a cars lifetime of assembly/disassembly cycles every season wasn't what Fritz had in mind when it was designed.
As I've said often in design review meetings "There are no bad materials - only bad applications"
I don't have time this minute to go look up what Carroll Smith has said about this topic, but I seem to recall him opining that a stud is the way to go when frequent disassembly is likely.
I have had studs almost pull though the hub on a chevy truck, I know there was an error somewhere in replacing them, but still kinda scary because I only drove it a little bit and it felt fine, but if I had taken it on the freeway it likely would have lost the wheel with the studs still bolted into it.
wat.
Bolts are safer than studs?
I disagree.
Sure, with a stud, you have twice as many threads to fail. But how often do threads fail? The only threads I've ever seen fail were due to human error.
ignore this because I can't find a source to back this up said: Studs provide more elastic clamping forces. A bolt will shear more often than a stud. This is why heads are usually held on with studs. The elasticity allows the head a little movement without any losening of the fasteners.
For me it will always be studs. (If I have a choice)
That said, if your car uses bolts, then you can put on giant wheel spacers without buying and pressing in new studs.
I really don't see how you have less threads with a bolt. The bolts have to thread into something. In my simple mind, bolts work just the opposite of studs. You either have a bolt clamping down or a nut clamping down. Same result. But with studs the extra threads stick out.
FWIW, next year bolts/studs will be 'free' in the budget.
wlkelley3 wrote: I really don't see how you have less threads with a bolt. The bolts have to thread into something. In my simple mind, bolts work just the opposite of studs. You either have a bolt clamping down or a nut clamping down. Same result. But with studs the extra threads stick out.
Well, with a bolt, you only have the threads in the hub. With a stud, you have the thread in the hub, and the threads in the nut.
Also, with a bolt, the fastener is effectively twisting when it's tightened down. In my personal, non professional opinion, this is why over tightening lug bolts/nuts is so bad.
A stud mitigates these twisting forces better than a bolt.
studs handle frequent removal better, but what are you all talking about with having twice as many threads? i have never seen a car with a thread in wheel stud.
wheel bolts annoy me cause of how difficult they are to put a wheel on than with studs.
i like the idea of studs/bolts/nuts being free next year. 2 wheels lost this year is two too many.
PhilStubbs wrote: studs handle frequent removal better, but what are you all talking about with having twice as many threads? i have never seen a car with a thread in wheel stud. wheel bolts annoy me cause of how difficult they are to put a wheel on than with studs. i like the idea of studs/bolts/nuts being free next year. 2 wheels lost this year is two too many.
Yeah, you're right. Not sure what I was thinking. But yeah, usually they are splined bolts that are pressed in. So that would mean they are easier to service than a hub with stripped threads for a lug bolt. Another point for studs imho.
But I'm not sure how that effects the twisting forces. I'll let you know in 3 years haha.
PhilStubbs wrote: studs handle frequent removal better, but what are you all talking about with having twice as many threads? i have never seen a car with a thread in wheel stud. wheel bolts annoy me cause of how difficult they are to put a wheel on than with studs. i like the idea of studs/bolts/nuts being free next year. 2 wheels lost this year is two too many.
When you convert a german car to studs - they screw in unlike the press-in splined ones. I prefer it actually since when the gun strips one at the race track I don't have to disassemble the whole thing - just zip it out, screw another one in.
Per Schroeder wrote: FWIW, next year bolts/studs will be 'free' in the budget.
All bolts and studs or just wheel bolts and studs?? [if the former, "hello ARP?"] ;-)
Giant Purple Snorklewacker wrote:PhilStubbs wrote: studs handle frequent removal better, but what are you all talking about with having twice as many threads? i have never seen a car with a thread in wheel stud. wheel bolts annoy me cause of how difficult they are to put a wheel on than with studs. i like the idea of studs/bolts/nuts being free next year. 2 wheels lost this year is two too many.When you convert a german car to studs - they screw in unlike the press-in splined ones. I prefer it actually since when the gun strips one at the race track I don't have to disassemble the whole thing - just zip it out, screw another one in.
I was not aware, I ASSumed when converting you went to some sort of press in stud. I have had my share of German cars and currently own a 95 m3, but never needed to convert to studs
Taiden wrote:ignore this because I can't find a source to back this up said: Studs provide more elastic clamping forces. A bolt will shear more often than a stud. This is why heads are usually held on with studs. The elasticity allows the head a little movement without any losening of the fasteners.
Ignoring the effect of thread fit and wear, the material properties will determine the strength of the fastener.
Clamping force is determined by the stretch of the fastener and the modulus of the material. Theoretically a stud and a bolt of the same material should be able to achieve the same clamping force, yield strength and shear strength.
The problem is that the length of threads engaged with a lug bolt is not consistent throughout the tightening process. The more you tighten it the more threads are engaged. This produces variations in torque required to achieve the desired clamping force, more threads have more friction requiring higher tightening torque to achieve the same stretch.
When using studs, once the lug nut threads are fully engaged with the stud the length of thread engagement is the same throughout the tightening of the lug nut. This should theoretically produce more consistent results.
About the only advantage I can think of to lug bolts over studs is that if you change to wheels with a different thickness (or use spacers) then it's easier to install longer bolts than it is to install longer studs (assuming press-in studs).
I have no idea why German cars use them.
not only german cars.. most european cars. My BMW, FIat, and Saab all use them.
In reply to Taiden: Personally I prefer studs myself but only because it makes putting the wheel on easier. As you have noticed, majority of studs are pressed in, which gives an advantage to bolts as pressed in studs could loosen and spin. I have seen this happen. I really don't see any mechanical advantage to either as they both have advantages and disadvantages over each other. Bolts will give a cleaner appearance over stud threads sticking out past the nut. Hence acorn style nuts. But I guess its what you're used to and prefer.
Manufacturers use bolts and a threaded hub because it removes one part (the nut) from inventory, thereby increasing profit. Same reason Ford quit painting the inside of the ashtray.
Bolts are a huge pain in the ass. They suck in every way possible.
I must be the only person here who does not mind bolts. With a proper hubcentric fit, you put the rim into place and balance it on the hub to line up the first bolt.. get that started and it all just falls into place
I dont mind the bolts with a hubcentric wheel, but light aftermarket wheels dont have the proper dia. I tried the plastic hubcentric inserts but melted them on a track day. Thinking of getting studs.
And don't forget there is a difference between conical and ball seat lug bolts/nuts.
not sure studs would help you there. Those rims need the rings to be centric on the hubs.
Wheels using tapered or conical seat fasteners do not need to be hub centric.
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