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Mini Cooper Wheel Fitment (Stud Bolt Issue)

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Came across an annoying issue recently thought I'd ask if anyone knows more about it.

Basically I got some wheels 4x100 to fit onto my Mini Cooper.

Later I found out that the bolt holes on the mags itself are only M12 and the mini uses M14x1.25 bolts so the bolt doesnt even fit through the hole.

option 1: get a machine shop to drill out 16 holes bigger to fit the m14 bolts (will it be perfectly centered if done so? worrying..)

option 2: bolt to bullet stud and nut conversion? Do they even have bullets that go from m14 down to m12??

What a pain in the a**.. why do they make wheels/cars with different sized bolts? as if having different PCD is not annoying enough as it is...

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Any half decent machine shop should be able to drill the holes out perfectly, you would need to be happy that it won't compromise tbe strength of the wheels doing so.

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have seen this already thanks dave.. but for its over $200.. for a problem that shouldnt exist in the first place..

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2 hours ago, M3AN said:

#2 is the only viable option for the reasons you mention about #1.

Nope, Wrong #1 is the best option because it is meeting the manufacturers specs, that is BMW / Mini determined that 14mm was the required stud size, 

Any decent wheel shop like Arrow  wheels does this on a daily basis  sometimes they install steel inserts only time it wont work is with a large centre bore and small PCD 

Even if ( and they won't be) slightly out it is the HUB centre that is what defines wheel centering not the studs, thats assuming you have matiching hub and centrebore diameters 

Reducing stud size increases load and any failure is outside manufacturers spec and could be considered an unsafe mod 

Its not a common problem  it is a common error - people not doing their homework and buying un suitable wheels. 

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Okay Bill.

 

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I have looked at so many wheels and not once had a problem with bolt hole sizes before..

Since I encountered this problem I have looked high and low but no spec sheet specifies a wheels' bolt hole size anywhere..

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3 minutes ago, qube said:

I have looked at so many wheels and not once had a problem with bolt hole sizes before..

Since I encountered this problem I have looked high and low but no spec sheet specifies a wheels' bolt hole size anywhere..

I also assumed they were all the same and most seem to be 12mm which is obviously enough for most applications. Why BMW/MINI went for 14mm is beyond me. Any normal person could make this grievous error I'm sure. 

I'd still rather spend the $ on the studs than a machine shop.

 

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11 hours ago, M3AN said:

I'd still rather spend the $ on the studs than a machine shop.

 

Dave, there are reasons why wheels are not square and new cars don't come with studs and it's not an anti American conspiracy - put the spade down and stop digging .

Modern well engineered cars have wheel bolts for good reasons  and if you are concerned about saving nanoseconds in wheel changes you simply install a locating dowel. 

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4 hours ago, 3pedals said:

Modern well engineered cars have wheel bolts for good reasons  and if you are concerned about saving nanoseconds in wheel changes you simply install a locating dowel. 

Curious as to what those reason are?

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7 hours ago, 3pedals said:

Modern well engineered cars have wheel bolts

Still yet to come across any Japanese cars with bolts, so not all "Modern well engineered cars" have them. Or are you just showing your ignorant bias and meaning European cars?

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it doesnt matter if its a bolt or a stud does it?.All i know is if i google "mitsubishi pajero wheel specs it tells me it has m12 x 1.5 

If i google toyota landcruiser 200 series it tells me it has M14 x1.5 so the information is readily available but wether that information always goes with the wheel is another matter.

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3 hours ago, KwS said:

Still yet to come across any Japanese cars with bolts, so not all "Modern well engineered cars" have them. 

Kelvin , all we can conclude from that is the Japanese don't engineer their wheel / hub connections as well as the Europeans. Do the mechanical engineering analysis 101 and you should be able to work out why it is a superior system. 

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Please explain it to us.

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No, come on guys, do the mechanical engineering analysis 101, duh!

Anybody making even a casual scientific observation (or having a rational state of mind) would realise that in real-world applications it DOESN'T MAKE A F'ING DIFFERENCE.

Sigh.

 

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What year mini do you have? Likey reason is that the early ones, R56 etc, were a Rover design so probably used different wheel bolt sizes. I suspect the newer Fxx Minis have the same as BMW. 

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2008 R56. 

You may find it interesting to know that some BMW's also use the "odd" m14x1.25 bolts. Such as the new 2 series.

 

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On 2/8/2018 at 10:39 AM, 3pedals said:

Modern well engineered cars have wheel bolts for good reasons  and if you are concerned about saving nanoseconds in wheel changes you simply install a locating dowel. 

 

On 2/8/2018 at 9:50 PM, 3pedals said:

Kelvin , all we can conclude from that is the Japanese don't engineer their wheel / hub connections as well as the Europeans. Do the mechanical engineering analysis 101 and you should be able to work out why it is a superior system. 

Hmmmm I don’t have an engineering degree but I am good enough with physics to know this can’t be true.

Nano second wheel change arguments aside, and ignoring wear and tear of stud or bolt, with appropriate material properties and thread pitch you can yield the same clamping force, sheer force and yield strength in both stud and bolt fastening methodology but you have the following mechanical advantages with a stud and lug\nut set up.

- consistency of tightening torque as the amount of thread engaged on a stud and lug nut is the same and not dependent on how many threads are picked up in the hub (more torque the more threads/friction or more bolt stretch you introduce - if any)

- safer and easier to inspect stud and lug\nut wear over bolt and hub wear.

- single vertical force acting on a stud and nut during the tightening phase vs two forces being acted upon on a bolt through stretch and twist in the tightening phase leading to a more accurate and even clamping between the two mating surfaces (think cylinder heads).

but apart from that I agree that the M14 to M12 stud kits are a bad idea vs enlarging holes in the wheel.

But give me centre lock anytime over everything else because “race car” lol!!   : )

Edited by M3_Power
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Centre locks FTW!

You just need the roof racks as well to carry the 10 foot long torque wrench required to tighten the bloody things up correctly, and be either strong or fat enough to exert enough grunt on the end of it!!

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14mm vs 12mm is a decision taken at BMW.

It started with the E53 X5. The MINI change came about during the move from the R50/3 to the R56, although some R50/3 cars also got 14mm bolts. The taper in the rim and on the bolt is the same regardless of 12mm or 14mm, so re-drilling is a practical solution.

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Certainly there were a few mixed opinions and I have seen plenty of those on overseas forums running m14 to m12 bullet studs but if I were to do it I would have gone with drilling bigger holes. Anyway I have decided against it and have since sold the said wheels.

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 consistency of tightening torque as the amount of thread engaged on a stud and lug nut is the same and not dependent on how many threads are picked up in the hub (more torque the more threads/friction or more bolt stretch you introduce - if any)

- safer and easier to inspect stud and lug\nut wear over bolt and hub wear.

- single vertical force acting on a stud and nut during the tightening phase vs two forces being acted upon on a bolt through stretch and twist in the tightening phase leading to a more accurate and even clamping between the two mating surfaces (think cylinder heads).

Analysis, logic  and science all suspect - try this: 

  • The stud  is usually inserted from the back of the flange,
  • The wheel bolt threads into the flange. 

The purpose of the wheel connection is to provide clamping force of the wheel onto to the flange.

  • The stud is longer and the force is generated at the head of the stud onto the back of the flange and the nut onto the front of the wheel (so the flange and the wheel are being squeezed by the longer stud) - some force will be lost stretching the stud in the flange,  total length of stud that  can be stretched in centimetres,  
  • The wheel bolt is shorter and the force is generated at the interface between the flange and the wheel and the wheel and and head of the wheel bolt ( so only the wheel is being squeezed  between the flange and the bolt head)  - total length of bolt that can be stretched is millimetres. 

The shorter more direct clamping mechanism of the wheel bolt, like the racing centre lock, provides a more effective connection. 

Inspection is required for studs because they are more likely to get damaged  and checking the wheel bolt is just as easy as checking the stud ( they are the two "male" components) - checking the stud insertion and the head integrity is difficult but more important as this is the more likely point of failure - common failures are head detachment resulting in a  stud pulling out and stud shear failure due to lack of clamping force allowing wheel rotation. 

The head analogy is also wrong - most modern cars use head bolts threaded directly into the block  meaning  there is a single item (the head)  being clamped between the bolt head and the block - this is exactly the same mechanism as a wheel bolt , not a stud. 

Edited by 3pedals

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Yep who needs wheels on a road car anyway !!! 

And now that Brexit is in full steam maybe the poms will reinvent their car industry and we can have Austins and Morris's losing wheels and dropping oil at every corner - unless they fall over first. Engineering is over rated - bah humbag 

I'd edit / delete that bit of rocket science jono before too many people read it :wub:

 

Edited by 3pedals

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To expand on this then if Nissan sees fit to use studs rather than bolts on its GTR (Just one example of a performance car using studs) then I would say there is probably very little if any reason to worry. What is more important is the design of the hub the diameter of the bolts/studs etc..  Of the pointless arguments on this forum over the years bolts vs studs could be the winner. 

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