Locking Wheel Nuts
Right, first thing's first. They don't lock and they aren't nuts. Surely people of a driving age should know the difference between nuts and bolts. So for accuracy, let's call them security wheel bolts.
Security Wheel Bolts
If you own a fortwo or Roadster and just want to add a bit of security to your standard alloys then that's easy. You can buy them directly from many online and offline automotive shops such as SmartMods.
If you have aftermarket alloys then the standard wheel bolts and security bolts may not be suitable.
The smart bolts may be too short or too long and chances are the seat shape will be wrong.
Working Out The Correct Length
With one of your standard alloys off the car, push a standard wheel bolt into the wheel and measure the length of thread that protrudes out. Now push the same standard wheel bolt into your new alloy and again measure the protruding thread. If the bolt sticks out 15mm on the original wheels and 10mm on the new wheels then you will need security bolts that are 5mm longer than standard,
You can go a fraction longer but be careful going too long on the rear as the excess
bolt thread will protrude into the brake drum and could do all manner of damage.
Remember that you will need longer wheel bolts all round, not just the security bolts.
Hopefully your new alloys will come with the correct length bolts required to safely
fix them to your car, worth double checking though.
The seat shape is also known as the saddle or shoulder shape. It is the shape of the base of
the hole that the bolts sit in when it's in the alloy. As standard, the smart uses the slightly
more unusual radius seat. Most aftermarket alloys have a taper seat. It's very important to
get the correct shape as it distributes the pressure of the bolt head to the alloy. If you get
this wrong it can damage the alloy, snap the wheel bolt or loosen itself as you drive.
Thread Size And Pitch
The smart standard wheel bolts are M12 with a thread pitch of 1.5mm.
This must be matched to any replacement wheel bolts that you get.
Can I Fit More Than 1 Security Bolt Per Wheel?
Of course but I wouldn't recommend it. Security bolts tend to be a bit weaker than
standard wheel bolts so I wouldn't like to rely of them holding your wheels on but
they are fine to have 1 just ensuring they don't get stolen.
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