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View Full Version : Q: Tank tabs prone to cracking ?



gravitywerx
06-29-2014, 6:56 PM
are the tabs that come off most the tanks on the market these days prone to cracking when mounting rigid to a frame? i have never seen anyone say anything but my buddy has bet me $100 that my tank will crack at the tabs. my bike is a softail but i welded bungs into the backbone and mounted the tank. other than some rubber washers it it strait on the backbone?
http://i1024.photobucket.com/albums/y303/metricmotomike/20140610_130331_zpsrl4dkfbw.jpg (http://s1024.photobucket.com/user/metricmotomike/media/20140610_130331_zpsrl4dkfbw.jpg.html)

LinkBelt
06-29-2014, 7:03 PM
Keep a hundo ready.

TheDave
06-29-2014, 7:05 PM
My buddy and I have ran similar tanks on several bikes both rigid and swing arm and never had one crack. I'd take his bet

BadMonkeyMW
06-29-2014, 7:16 PM
I've built several rigids with tank mounts similar to this with no issues. It is important to run rubber or leather washers between the tank and the frame to prevent metal to metal contact, but you've got that covered. The thing that will cause issues is the mounting bolts loosening and allowing [I]excess[I] vibration. Put in a wrench on the bolts every so often to make sure they're tight, otherwise I wouldn't worry.

SamHain
06-29-2014, 11:27 PM
I've seen a lot more of those break than tanks with four mounts.

BMG
06-29-2014, 11:59 PM
leather washers on both sides of tabs.
ran it this way for years and several bikes..
not one problem..
do it like this and collect your $$$$$
49395

tmb99
06-30-2014, 2:34 AM
Guess it depends on the quality of the tank. I've got a split alien (looks same as yours) mounted on rubber washers and it cracked.

5mm plate shaped it up, filled tank with water - as it'd had petrol in it, good solid weld. All good now.

farmall
06-30-2014, 6:35 AM
5mm plate shaped it up

I like your thinking.

On any tab, ensure the fastener doesn't deflect it for some reason when tightening. If it does, shim so it does not. I don't use soft washers but do ensure even tab contact on any tank I do after dealing with cracked fatbob tabs.

Clockwork444
06-30-2014, 10:53 AM
i ran my xs650 like that had rubber on each side of the tab and a washer on top. bike vibrated like a bastard and so did the tank, but nothing cracked.

gravitywerx
06-30-2014, 7:05 PM
so far i don't seem to see anything that should make me worry. i am going to use leather bushings like suggested top and bottom. i have two tanks for the bike also so if one does crack it takes me 5 min to swap it out. i have a 3.1 gal sporty tank that uses the same mounts that i am going to keep for longer trips. 3.1 vs 2.2 gallon on a 80ci.

LinkBelt
06-30-2014, 8:37 PM
OK, I said keep a hundo ready and if mounted like is being said there is still a chance it may crack. I had a tech thread on here at one time telling the secret to mounting a two tab tank with no worries but I guess it got deleted. Here is the secret, drill oversized holes in the tabs, rubber mount using a gromlet that goes all the way through the hole, shouldered brass washer on top and bottom (found in the lamp repair isle at your local hardware store) the one on the bottom will bend to the backbone and the shoulder keeps the rubber from buldging out. Now the true secret, get some spray adheasive and find a piece of rubber and either stick it on the backbone or in the tunnel of the tank to take up the space there. No worries it's like a solid rubber mount tank. Do it this way take your friends hundo then charge him a xtra hundo for the secret.

farmall
07-16-2014, 3:54 PM
Neat trick! I'm gonna try that on next appropriate tank.

That backbone rubber acts like the rubber tank biscuits on many non-HD factory tanks. Thanks for posting.