Fiberglass Fastback fuel tank rubber support pads

I'm ready to mount my freshly painted '68 Commando (Fastback) fuel tank and I checked the parts manual to see if the thick pad goes to the front and thin to the rear. I was surprised to see that on all years the Fastback tank only had the thin pad at the front and no rear pad! The kit that Andover advertises for Roadster and Fastback tanks includes both pads.
For those of you with fiberglass Fastback tanks, what are you using? Maybe a thin pad front and rear? I can't understand the factory mounting the 'glass tank directly on the frame tube by the rubber strap with no cushion. Looking at the tunnel in the tank, the thick pad may seat the rear of the tank too high.

Don't bother to tell me to scrap the fiberglass tank and buy an Indian-made steel tank. It's not worth the crap shoot and this is the badge style tank. I have cleaned and Caswell novolac epoxy lined this tank and I only plan on using ethanol free fuel and drain the tank when stored.

Pads in my old S type tank were gone, so I just experimented with some rubber from flip flops from the dollar store. I didn't even bother sealing my tank, I just use ethanol free fuel. Avgas works great too. I've got a Citgo station that sells racing gas, but it's $60 for 5 gal of 110LL.

Bought a new FG tank in '08 from Burton Bike Bits. They said it was made with ethanol-resistant resin. I did the Caswell treatment anyway before putting it in service. I've had no issues at all using standard unleaded fuel from any gas station since '08.

Re the padding, I just made up the rubber pad by gluing strips of inner tube rubber, building up the thickness until everything lined up/fit correctly. Pad, tank, and frame have been close associates for 12 years!

my 1968 fastback fibreglass tank has 2 thin rubber pads.

Thanks, guys. I used a 1/4" closed cell foam pad front and rear and it looks pretty level without hitting the frame tube.

I used a couple of layers of 1/4" closed cell neoprene from an old wet suit.
The tank slips on in a snug, not too tight manner that leaves it fully supported by the spine. You can make really small adjustments forward, backward, or up and down and is stays wherever you set it.
The front and rear mounting fasteners keep it in whatever final position is chosen.

Lineslinger said:

I used a couple of layers of 1/4" closed cell neoprene from an old wet suit.
The tank slips on in a snug, not too tight manner that leaves it fully supported by the spine. You can make really small adjustments forward and backward this way and is stays wherever you set it.
The front and rear mounting fasteners keep it in whatever final position is chosen.

View attachment 17459

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I originally fitted this exact design oil tank breather, in the very same place. But with the roadster tank and seat fitted. The breather was just too visible for my liking

This breather/vent is recessed enough that is is completely covered when the seat is mounted. I retired the original seat and mounted a Corbin.
Its still as dry as the day I bought it.

I unfortunately have had to replace my original fibre glass fastback tank, but found the engine now runs much cooler... Did they act like a thermal jacket or at least impede airflow

oldmikew said:

I unfortunately have had to replace my original fibre glass fastback tank, but found the engine now runs much cooler... Did they act like a thermal jacket or at least impede airflow

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If I understand correctly you suspect cooler engine temps are related to the material the tank is made of and or its position on the frame?

Lineslinger said:

If I understand correctly you suspect cooler engine temps are related to the material the tank is made of and or its position on the frame?

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Possibly both,the Fastback tank shape does not permit much air flow.