Sierra subframe bolts - size?

[Chris Scott]

Evening all, does anyone know the dimensions of the big bolts that hold the rear subframe to the chassis?

I thought they were M12 but when they arrived the shouldered part seems too narrow.

I’ve measured the old bolts and it seems to be 12.4mm diameter so slightly bigger than M12, any ideas? 

[IanS]

If imperial was a possibity I would say 31/64th inch. (worked in aircraft industry where imperial bolts still used with increments of 1/64) 31/64 would be 3rd oversize repair bolt for 7/16 initial bolt.

On most builds the rear subframe rubber donut was removed and a new hole drilled to fit a 12mm bolt throught the floor and reinforcing plate as advocated by RS in the build videos.

[Foz]

My 2B has two M12 bolts through each side.  1 through the centre of the rubber bush (although I've now removed the bush and made it solid), and a second about 60mm further back, both going through the corner plate of the chassis.  I'm not sure how this relates to a 3A but I reckon M12 bolts should hold things together OK.

[Chris Scott]

20 hours ago, IanS said:

If imperial was a possibity I would say 31/64th inch. (worked in aircraft industry where imperial bolts still used with increments of 1/64) 31/64 would be 3rd oversize repair bolt for 7/16 initial bolt.

On most builds the rear subframe rubber donut was removed and a new hole drilled to fit a 12mm bolt throught the floor and reinforcing plate as advocated by RS in the build videos.

Now this interesting - because mine has an additional M12 bolt and the reinforcing plate - so maybe the other bolt is a little redundant. If that’s the case I’ll likely just go M12 for both 

[Chris Scott]

Thanks all…as always