V70 Wheels/Tyres: Not the usual Axle Bolt query

[ASt85]

I fitted the new exhaust this morning.

However, the new found peace and quiet showed up axle bolt ping, lowering the windows seemed to indicate the source was the near side front.

On checking the N/S 13mm bolt's torque - it took well over 270° to achieve the 35Nm + 90° which was not unexpected - it appeared to be an almost new uncorroded bolt - I checked by re-setting the torque wrench to 50Nm, and it clicked correctly without further turning force applied.

I then checked the O/S bolt and was surprised to find that although it was at the correct torque it was a 14mm bolt and appeared to be a much older partially corroded bolt - maybe the original fitment - the N/S drive shaft doesn't appear to have been replaced as the physical appearance of the N/S and O/S shaft is identical - neither has the part number sticker still attached.

I've checked in Vida and can find no reason for the different bolt head sizes - I'm loathe to completely remove either bolt at this stage as the beast goes for it's MOT in 3 day's time at which point any other identified fault(s) will be found and subsequently corrected.

Having fitted new drive shafts in my older (2001) V70 a few months ago and checked their bolt heads as 13mm, I've no idea why there should be different bolt head sizes, but not necessarily thread sizes unless a replacement drive shaft has been fitted at some point and either the wrong one or and alternative/upgrade/downgrade has been fitted in error or a bolt went missing and was replaced.

From Vida it appears that there are a couple of part number changes for the bolts, but I've not been able to work out exactly what the difference are in those bolts.

Can anyone throw any light on why there should or might be different bolt head sizes for the spec'd M10x65mm bolts?