The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 55.2-59 Gas Tank to road dimension?

dsraven · 02-15-2024, 10:45 AM

when I was certified to do propane conversions waaay back in the day, we were taught to draw an imaginary line from the contact patch under the rear tires to the lowest point on the rear bumper and to keep the lowest part of the tank higher than that line. also it needs to be higher than the lowest part of the wheel, so if you were to take the ties off the wheels and had just the wheels on the truck, no tires, the tanks would be higher than that. this is to compensate for a blown tire, the lowest hard point is what should be used. if you were to look into the highway traffic act in your local area you ight see mention of this where it says something like no part of the vehicle suspension or body is allowed to hang lower than the lowest part of the metal wheel. this is o that should a tire blow out your vehicle will ride on the rim and not a body or suspension part-or a fuel tank, engine oil pan, etc. allow for suspension travel worst case scenario, like when the axle bottoms out on the suspension snubbers and keep the tank higher than that imaginary line from the tire contact to the bumper .
in other words, imagine your truck with just the bare wheels on, with the suspsension bottomed out, and then draw a line from the wheel contact on the ground to the lowest point on the rear bumper. I say bumper but if you dont have a bumper then use the hard points on the rear of the frame. if you use the body sheet metal you will be disappointed because it will crush easily up to the point where the frame hits the road or curb or whatever. placing the tank closer to the axle will help, having a tank that is tapered at the rear will also help. if your tank is large and does hang down then placing some guards under it at the rear may help. on some really low cars, like corvette, they used sacrificial wear bars on the "frame" so that the wear bars would bottom and make a terrible racket before major body parts were damaged. a lot of the body that is low to the ground uses "soft" plastic parts that clip on or are screwed on with light duty retainers so that the air dam, or whatever that part is, will tear away rather than damage a larger, more expensive, body part.

02-15-2024, 10:45 AM	#3
dsraven Registered User Join Date: Nov 2010 Location: calgary alberta Posts: 7,864	Re: Gas Tank to road dimension? when I was certified to do propane conversions waaay back in the day, we were taught to draw an imaginary line from the contact patch under the rear tires to the lowest point on the rear bumper and to keep the lowest part of the tank higher than that line. also it needs to be higher than the lowest part of the wheel, so if you were to take the ties off the wheels and had just the wheels on the truck, no tires, the tanks would be higher than that. this is to compensate for a blown tire, the lowest hard point is what should be used. if you were to look into the highway traffic act in your local area you ight see mention of this where it says something like no part of the vehicle suspension or body is allowed to hang lower than the lowest part of the metal wheel. this is o that should a tire blow out your vehicle will ride on the rim and not a body or suspension part-or a fuel tank, engine oil pan, etc. allow for suspension travel worst case scenario, like when the axle bottoms out on the suspension snubbers and keep the tank higher than that imaginary line from the tire contact to the bumper . in other words, imagine your truck with just the bare wheels on, with the suspsension bottomed out, and then draw a line from the wheel contact on the ground to the lowest point on the rear bumper. I say bumper but if you dont have a bumper then use the hard points on the rear of the frame. if you use the body sheet metal you will be disappointed because it will crush easily up to the point where the frame hits the road or curb or whatever. placing the tank closer to the axle will help, having a tank that is tapered at the rear will also help. if your tank is large and does hang down then placing some guards under it at the rear may help. on some really low cars, like corvette, they used sacrificial wear bars on the "frame" so that the wear bars would bottom and make a terrible racket before major body parts were damaged. a lot of the body that is low to the ground uses "soft" plastic parts that clip on or are screwed on with light duty retainers so that the air dam, or whatever that part is, will tear away rather than damage a larger, more expensive, body part.