Unleaded fuel & fibreglass tanks

[Carrot Cycles]

I've heard one or two people mention unleaded fuel attacking fibreglass petrol tanks, does anyone have any experience of this ??

[33d6]

I think unleaded fuel has been blamed for anything you can think of from the Great Fire of London to climate change.
Given time the outer gel coat on all fibreglass tanks will start to crack and craze. When this gets bad enough it will allow any fuel to penetrate the substrate and eventually the tank will start to leak here and there.
As unleaded fuel is relatively new and many fibreglass tanks were around long before it was introduced I think you would find the leaking tank was in desperate need of recoating long before the unleaded was put in it.
It isn't the unleaded fuel, it's lack of maintenance.
Cheers,

[L.A.B.]

I've heard one or two people mention unleaded fuel attacking fibreglass petrol tanks, does anyone have any experience of this ??

It's not been too much of a problem in the UK - so far!.

As a member of a Norton Commando forum (accessnorton.com) I've noticed there have been several reports of fibreglass Commando tanks leaking (as early Commandos had fibreglass tanks) and this problem seems to be caused by a lot of the US fuel available now having a large amount of ethanol added to it.  

[33d6]

I think the remarks about early fibreglass Commando tanks leaking confirms the need to check the outer gel coat  and renew it. That also includes the outer gel coat on the inside of the tank. Remember those tanks are hitting the 40 year old mark now so will need refurbishing as a matter of course.
I went through all this with a Montesa King Scorpion tank (also fibreglass, also from the 70's). Being a two-stroke unleaded is the fuel of choice with possible additional ethanol plus it has the usual two-stroke oil in the fuel also.
The tank leaked when I got the bike. I had it professionally refurbished by a firm that knew what it was doing. The finished result looked beautiful, didn't leak and still wasn't leaking when I sold the bike some years later.
I'll stick to my guns and repeat the major issue with fibreglass tanks is lack of maintenance, not the fuel put through it.
Cheers,  

[Carrot Cycles]

The re-coating tank scenario seems perfectly plausable, given the nature of the material. So thanks to you all for your replies.
Theres been a few occasions where i've had a metallic tank repaired due to the ravages of time taking there toll.
So I guess that for most, that fibreglass tank leaking has occured at the same time as unleaded appearing purely by coincidence.
I know of a local fibreglassing company that make a fair few motorbike parts, next time i'm passing i'll ask the same question, as post my findings !!!
Phil