2nd Gen R56 Cooper S Most liked posts in thread: Lug nut torque on R56 S?

My wheels rotate every time I drive it!:lol:

Dave

 

Bentley Service Manual lists tightening torque for ROAD WHEELS (not Space Saver) at 103+-7 foot pounds.

 

103.3 ft lbs.... page 146

The forum library is your friend....

http://www.motoringalliance.com/pdf/manuals/2011_MINI_Hardtop.pdf

 

103 ft lb. That spec is in your owners manual. :wink:

We got a liberry?

Welcome to M/A Micheal...

 

Yeah, and no card necessary, no return policy, no fines....

 

Old thread, but that torque spec in the manual is specifically for the steel spacesaver tire.. Not the standard alloys. Alloy wheels are much softer and generally need less torque than steel wheels to avoid galling the seats. I'd tighten to 85lb-ft and recheck after 100 miles.

 

I'm assuming the high torque spec is mostly for the thick 14mm bolts, no?

 

Good question, I'll check the Bentley book after work to see it it listed bolt size.

Did all R56's come with 14mm lug bolts? or did that change early after the intro?

 

All Gen 2 MINI's are on 14mm lug bolts. Also all 1st Gen built after 07/06 are on the 14mm too.

 

So thicker bolts = more torque? The R53 12mm bolts were 89 ft/lbs, were they not?

 

Not primarily the thickness of the bolts. It's how coarse or fine the thread is along with thread pitch that determines the needed torque to apply adequate pressure against the available surface area of the threads.

Read this white paper on torque spec's if you want the math behind it.

Analysis of Bolt Torquing

 

My E36 BMW with five 12mm bolts has a 100 N-m torque spec. My R53 with four 12mm bolts has a 120 N-m torque spec. The R56 with four 14mm bolts has a 140 N-m torque spec. (14mm bolts have 36% more cross-sectional area.) The R56 also has a finer thread pitch, I believe.

Bolts Size Torque
5 12 100
4 12 120
4 14 140


My engineer brain sees a pattern here...

 

Okay, guys. Thanks for "clearing" that up. :crazy:

The steel bolts can handle the torque, yes.. Never doubted that. But I thought there was usually a different torque spec for the softer alloy wheels being sandwiched between them. If there were washers / free-spinning seats or a steel ring that we were bolting to, I could see the bolts being torqued to the max with an aluminum wheel between them... but otherwise, no.

I'm not trying to start trouble, I've just seen different specs quoted in manuals before for steel and alloy wheels... just not on MINIs (one example is my old BMW 320i).

 

You aren't alone. I've seen different spec's for aluminum and steel wheels. My Ford Expedition has different spec's for the different materials.

Just reporting what's listed in the manuals.

 

FWIW I used the factory spec's for torque on my aluminium wheels for 97,000 miles now. My wheels have not fallen off & my wheels are just fine. Maybe I got lucky, but I think those engineer's who figured the torque spec may be onto something.