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AlexRS2782

Wheel Bolts - min / max thread length for fitting

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AlexRS2782

Currently in the process of getting the last few bits together to fit my EXIP (7x15 ET18) alloys fitted which includes sourcing new bolts (including locking ones) as the ones i have are a combination of different thread lengths rather than all matching.  They're all the correct 60deg tapered, M12 x 1.25, but i'm currently trying to sort out the preferred size to use.

 

Bolt sizes as follows:

A - 65mm total length with a 40mm thread / shaft length.

B - 55mm total length with a 28mm thread / shaft length.

C - 70mm total length with a 45mm thread / shaft length

D - 58mm total length with a 31mm thread / shaft length.

 

Most of the bolts are split between type A & B so must be one of those and having looked at the old threadlock / marks on the bolt (and placed each of them through the wheel) the 28mm thread looks like it could be the bare minimum for fixing, whereas the 40mm thread seems longer & possibly used in conjunction with a minor spacer setup?

 

I'm fitting the wheels without spacers & want to ensure there's enough thread to ensure a secure fixing.

 

Cheers

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MrAndy

Hi Alex,

 

You can check and measure that quite easily. Take the brake pads and disc away and measure the thickness of the wheel + brake disc. Then add the measure of the wheel hub thread to that.

 

There is your minimum bolt length. The maximum should be not much more to prevent the bolt and from rubbing anything from the bottom.

 

I have all the parts separate at the garage, but I'm planning tho visit the garage earliest next week, so can not give the measures right now.

 

-A-

  

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AlexRS2782

Same as you - not with the car at the moment but thankfully a bit of Google has given the basis to work from and a couple of conversion tables state M12 x 1.25's seem to need at least 8 full turns for minimum thread engagement so managed to work out the relevant mm from there.

 

Based on the split of bolts i've got it looks like, when used with these wheels, the 28mm threads allow for about 12mm of engagement so just over minimum required, whereas the 40mm would be a bit long unless used with a mild spacer.

 

Either way, going to have a bit of a ponder this weekend as it looks like there are a couple of options to either try the 28's and see what the engagement is like when fitting, use a slightly longer thread length circa 32-35 to ensure a few more mm of engagement or change my mind about spacers and possibly use a set of the HR or Eibach 5mm's with the 40's to bring the offset out slightly to sit nicely in the arch.

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