Is there a reason motorcycle tanks are made out of metal?  Legal stuff?

I ask because i have a 4-wheeler plastic tank sitting on the shelf.... that looks like it would fit inside the gs tank.  (i think it is a 3.5 gallon tank).

Seems to me this would be a far superior setup..... much easier to remove, and i could cut the bottom of the tank out and use it just as a cover.

AND NO RUST.

hmmmmmm

A lot of the modern Ducatis have plastic tanks. They have had a lot of troubles with them warping though. A lot of the blame is being put on ethanol blended fuels. If they can find a plastic that can with stand the warping I can see a lot postives over the metal tanks. Weight and durability (no dents) to name a few.

If anything I would think they could at least make them out of aluminum. Still pretty durable and you wouldn't have any rust issues.

Some dirtbikes have plastic tanks as well. One thought is because they hold so much gas. It's easier to bolt down a 3 gallon gas tank than a 5 gallon tank, and you wouldn't want the mounts to crack and risk the tank falling off and breaking.

There are plenty of aftermarket enduro tanks for dirt bikes that hold upwards of 4 gallons. I can't think of a lot of major reasons sport bikes run metal tanks.

biggest reason is crash durability, getting a plastic tank to hold up as well as a steel tank is hard, one thing no one wants is to drop a bike and have gas rush across thousand degree headers, theres plenty of crashes already where the chicken/petcock breaks and woosh. I vote neigh on a plastic tank, carbon fiber... now thats a whole new ballgame 

GS500 tank doesn't touch the ground unless the bike hits a curb or flips. Metal isn't necessarily more rash resistant than plastic (voice of experience.)

yes but the GS500 tank is also only held on by 2 little metal tabs, if that was ABS plastic or whatever you want to make it out of, and you drop it hard, i have money on that breaking and the tank falling off lol. I give engineers credit where credit is due... Plastic is cheaper and easier to cast, if they didn't need metal they would of made it out of plastic, now... a inner liner on the other hand, now that could be cool, might be tough to install though...

How about this crazy idea for a gas-tank liner made out of plastic?...


Find a sealed bag that is gas-resistant...

Get your tank, clean it out, and fill it with resin or epoxy, swoosh around to cover as much as the inside as possible..

Put the bag into the tank, leaving the opening out of the gas cap area... find a way to seal it off with an air compressor, and inflate the bag, which will expand inside the gas tank, and press against the sides.. Leave it with pressure till the epoxy or resin cures. then, trim off edges or fix them or whatever, and you got a plastic coated tank...

Same idea of how they made fiberglass molds when the suction out the air to press the glass, but your using air pressure inside the tank..

Maybe?

-Justin

You're taking an extra step you don't even need. Just find something to coat the inside of your tank like the resin/epoxy. No need to glue something else inside. That's basically with POR15 does. You roll it around inside your tank, it dries, coats it, and it'll never rust again. People usually only do it after the tank rusts, but you could always do it ahead of time.

The easy part of an enduro/dirtbike tank is that it sits around the backbone of a frame and is then just bolted in place. Like crzydood said a sportbike tank is held on by nothing more than a few tabs. that would definitely snap easily. Another difference is that a sportbike can go 170mph, and if you're gonna crash and have a gas tank sliding across the ground at 170mph the metal will manage to last a few seconds longer than a plastic one. Crashing at 30mph on a dirt road is a lot less work on a tank.

Every street legal dirt bike I have owned has had a metal gas tank so I assume it is a legal thing.  I don't think aluminum would work that well in a crash.  Steel bends, aluminum cracks!

-Jessie

I feel like it might be a safety thing in the event of a crash. When I went down last season, I wasn't going very fast (maybe 40kph), but it was enough to bend my handlebars into my tank and leave a nice dent. If my tank were made of something like ABS plastic, I'm positive it would have cracked or shattered.

Aluminum bends just as well as steel when done properly. Check out the custom aluminum tanks at www.roccitycafe.com

Plastic bends as well. Heck, you can hit a plastic tank with a hammer and it won't hurt.

yeh but take say 100 grit sandpaper to a tank and see what one wears through faster... its not so much the smack as the slide...

I'll be very careful around the sandpaper factory.

Like Burning1 said- the GS500's tank shouldn't slide so it doesn't matter. And nobody here is planning on making a plastic tank, so again- it doesn't matter. As long as it doesn't melt from sitting atop the engine, a plastic tank on a sport bike shouldn't hurt.

If your tank touches the ground in the event of a crash you are begging for a fire. Doesn't matter if it's plastic, or metal. I say this based on my experience grinding metal parts along the ground at high speed - there is absolutely no way any tank is going to survive a lowside if it's in contact with the ground for more than a a fraction of a second, metal, plastic, unobtanium, anything. I've crashed my GS at high speed twice now, and I haven't seen major rash on the tank. The tank did rupture during the latest crash though, when it hit a curbing.

In the AFM, there are a large number of bikes that are required by the rule book to install aftermarket engine covers because the 2mm thick cast aluminum cover tends to wear through leaving a fat pool of oil on the track.

IIRC, a few models of the R6 had a tank that actually would slide along the ground in the event of a crash. Those bikes were known for catching fire. Again, very bad juju. Most of the owners ended up installing after-market tank sliders to combat the problem.

I cant comment about the issue with mounting points raised earlier. I strongly suspect that someone could engineer around the problem though. FWIW, the GS500 tank is mostly supported by the tab at the front, and the lateral grip provided by the rear mount point. The bolts aren't designed to take the full weight of the tank, instead they are locating and retainment points.

Well, what i was planning on doing was cutting the bottom of the GS tank completely out... so it would just be a cover, with the plastic tank underneath it.  (I wasn't really planning on doing it, but just wondering about it.)

The plastic tank would mount to the frame via modified attachment points... just as it mounts to a 4wheeler. 
(i beat that 4wheeler to death... it had been upside down, left, right, landed on front bumper, rolled.... rear bumper.... handlebars... yeah, i'd say if it never broke loose from all that, it isn't going to... unless the crash killed me anyway.  Plus all the jumps i did with it and rocky terrain it had been over and normal wear&tear).  I ended up sidelining that quad because i bent the axle to shazam, and twisted the frame where the swinger attaches (tank was still there, didn't figure out the swinger misaligned until after a new axle.... figures).

yeh but take say 100 grit sander to a tank and see what one catches fire faster... its not so much the smack as the slide...

It seems ironic to me that metal would be less likely to start a fire.  Every time i have dragged metal across something quickly, or something across metal quickly.... i got sparks.  Sparks + fuel == fire.  (not that the frame dragging ground wouldn't be making sparks.)  Never had i made sparks with plastic.

But turns out my idea was rubbish...  as i would have no way of filling the tank!  The fill holes are totally different spots.  It is always the details.  Plus it turns out my problem was the frame mounted petcock, not the tank (yet). 

I'm not going to re-engineer the GS if i don't have to.

I need to stop keeping old parts around... wouldn't have been the first time i spent a weekend working on something just because i had stuff laying around.  Like: that perfectly good raptor660 motor that use to sit under that gas tank.... would be a good fit for the GS.... hmmmmm..... naaaaah.  GS: BRRRRRRRRRRaaaaaaaaaaAAAAAAAAAAAAAAPP hmmmmm, big single GS.

For what it's worth... The gas tank is a major point of support and contact for the rider on a sport bike. A plastic tank is going to flex, posing huge problems to riders like me. I think, that, more than anything, has kept tanks metal on our motorcycles. Most of the ATV and dirt bikes are running plastic tanks these days, including the DRZ.

From 05 onwards most Ducati tanks are plastic even on their Super bikes. They did have a problem with tanks expanding at first but I am pretty sure they've fixed that issue.

Unlike most bikes Ducati tanks have a hinge on them so you can swing them up to work on anything underneath. When down there is a clasp to keep it in place.

Ducati, BMW and Triumph use tanks made from a nylon polymide, call it plastic if you want but its nothing like the stuff milk bottles, fuel cans and dirt bike tanks are made from.

Quote from: Twisted on June 13, 2011, 04:19:36 AM
From 05 onwards most Ducati tanks are plastic even on their Super bikes. They did have a problem with tanks expanding at first but I am pretty sure they've fixed that issue.

Unlike most bikes Ducati tanks have a hinge on them so you can swing them up to work on anything underneath. When down there is a clasp to keep it in place.

My 04 Suzuki GSX-R 600 had this feature. Also had a prop-stand located under the seat. I usually ended up pulling the tank, though the stand and the hinge made it much easier to disconnect the fuel and electrical lines.