Strange bolt on fuel tank

[IIA]

At the back of the fuel tank on my Series IIA there's a heavy shoulder bolt with 2 thick rubber washers. This bolt is one of a set that holds the tank to the outriggers. I've got 2 questions about it:

1. What is it for? The other 5 bolts on the tank are normal ones (I don't have the measurements handy)
2. How tight should I make it? Because the rubber washers are so thick, I could crank the bolt tight and squish them or not.

Andy

[stomper]

It is there to absorb vibration, and prevent the tank flange from cracking. Put a nyloc nut on the bolt, and snug it up to about 1/4 compression of the rubber washer.

[lumpydog]

What Stomper said. I'd add - that should be the ONLY bolt securing the rear of the tank.

[IIA]

What Stomper said. I'd add - that should be the ONLY bolt securing the rear of the tank.

Really? That makes me a little nervous. After all, there are 2 other bolt holes on the flange in addition to the shoulder bolt hole in the middle. Wouldn't it be at risk of wobbling with only one bolt back there? And why wouldn't the front flange have the same risk of cracking? (...On the other hand, that would explain why the diagram in the Green Bible doesn't show any bolts for the back flange other than the shoulder bolt)

[lumpydog]

(...On the other hand, that would explain why the diagram in the Green Bible doesn't show any bolts for the back flange other than the shoulder bolt)

Yup - all it needs is the single flex point. As you saw - that's the way Rover designed it and it works. Those that second guessed it and added bolts or removed the rubber grommets learn the hard way ;-)