I am preparing to change the struts on my wife's R53 Mini Cooper S and I need to purchase the strut nut socket. I find two different sizes, 21mm and 22mm, at different websites. Which is the correct size? The BMW part number for the socket is 31.2.210.

 

21mm

here;s a basic/older write up.
https://www.northamericanmotoring.co...ll-how-to.html

 

Thank you!

 

You don't need that tool. A spark plug socket with a six sided outer area works perfectly. I can't remember what size translates to the 21mm, but it is a good match.

 

13/16th's is standard spark plug size, which translates to .8125". 21mm = .8268", so it might be snug, but would probably work.

 

Normally a air gun can just take it off but I have that 21m hazet socket if you want to borrow just send me an PM

 

I made my own by using the correct size socket and cutting a window in it using a high speed dremel with a cut off wheel. The spark plug socket will work in a pinch but you will not be able to use a torque wrench on it to get the proper torque.
Steve

 

DO NOT use an air gun on struts. The rapid spinning action will damage the seals/valves in your strut. Thus causing a ruined strut.
The tq. rating for the top nut is very low. its primarily a retaining nut. Thats why the special too is made. (its not just a depp 21mm socket)
Using an 18v type drill/impact gun is more than suffice & when carefully used wull not rapidly spin the piston/causing damage.

I've had customers ruin brand new suspension sets my using/having had shops use air tools. Most manufacturers(Koni/Bilstein/KW, etc) include install instructions stating DO NOT USE AIR TOOLS.

The BMW tool, or something similar, allows you to rotate the socket/nut while holding/keeping the piston from rotating.

 

My impression was that many of the suspension and steering nuts would all spin unless you put the 5mm or 6mm long allen wrench through a Sears Dog-Bone wrench to hold the stud or ball-joint still while loosening the nut with the Dog-Bone. Once you can let the suspension expand, you can use the 2x4 and jack method to remove the strut assembly. Then install spring compressors. Then use the 6mm long allen through the 13/16 spark plug socket on the strut top to remove the spring.

DOG BONE™ 8-in-1 Metric wrench. METRIC: 12, 13, 14, 15, 16, 17, 18, 19mm. Go-Thru swivel head allows easy access and fits any angle. 14.99 sold at Sears.

I have what looks like factory struts on my '03 R53 MCS. The bottom of the struts are round and go in an out of the lower control arm fairly easily.

 

You won't be able to use a socket on the torque wrench but an appropriately sized crowfoot will do the trick.

 

PinkLinc
Yes that will work but don't forget to do the math for the increased length of the leverage arm.
Steve