Thread: Front Tires

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    Default Front Tires

    OK, just to let everyone know, this is my first post. I have been reading these threads for awhile now and have gotten alot of useful information out of them. My question is to find out if there is an advantage/disadvantage to having the super single type tires on the front of your apparatus. I have only been in the Maintenance field of Fire Apparatus for about 1 1/2 years and have been on the Spec Committee for only a couple of years. We are in the process of putting together Specs for a New 3000 gallon tanker. This truck will/should not ever see any off road action, but will see alot of dirt roads that are not that well maintained. We cover alot of country side within our district and also have mutual aid with surrounding districts. We have not yet decided what brand of truck we are going with yet, so I don't know if that will make a difference or not. I just don't know if the wider tire will benefit us or hurt us. Any advice will be greatly appreciated.

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    Turning radius is not only determined by the length of the wheel base, but the width of the wheel base too that is, how far apart the front tires are. Larger tires and axles tend to have an effect on turning radius, and not in a good way.
    Last edited by firepiper1; 12-07-2007 at 11:01 AM.
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    You are correct the 385 tires can make turning a rig hard. It will also depend on what # axle you get. We have a truck with 385's at work and it takes about 2 acres to turn it around.
    Forrest Gregg
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    Holtville/Slapout
    Fire & Rescue Inc.
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    www.holtvilleslapoutfd.org

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    Steer tires are always single, a super single is used in the place of duals. A bigger front tire is just a bigger front tire. Or a float. Whatever you want to call them.

    Most steer tires are bigger to handle increased weight loads. Depending on the front axle weight on your tanker, you may have to go bigger than you have planned.

    Now, wider tires don't have to mean bigger turns. If the wheels are offest out from the frame far enough, the turning radius can be pretty tight. The right axle, hubs and wheels will do wonders. Get the wrong setup, and you'll turn like the Titanic with the same identical truck.

    We've got a Peterbilt w/ a 22k front end w/ 445 tires on it and it turns wonderfully tight. Tight for a truck, that is.

    Work with the salesman for the chassis manufacture. They can set you up right. If the chassis is supplied by the builder, set specs for the turning radius or cramp angle, and they will order the chassis setup you need.

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    Savage / Hyneman 08'

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    Almost forgot...

    If you are getting a commercial chassis, spec a setback front axle. Better turning radius.

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    Turning radius and weight issues aside...having the poorly maintained dirt roads makes the wider front tires desireable. The higher floatation will keep them from sinking in as easily on muddy roads or on the off chance this rig goes in the field, soft ground (and we both know its going to end up in a field!!!)
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    You were correct with the term "super single". Super single is the industry term for wide base tires like 385/65R x 22.5, 425's and 445's. A few years back Michelin came out with the X-One which is supposed to replace a set of duals. The X-One set-up saves weight but you wouldn't find them on a steer axle.
    Your axle capacity will determine the tire size unfortunately. You can get a 315/80R x 22.5 tire on an 18,000 lb front end but I'm sure you'll need at least a 20,000 lb. A super single won't reduce your cramp angle that much. Anything that's designed to carry 3000 gallons won't be the sharpest turning truck unless it's a cab-over or custom chassis. Like already mentioned, if it is a commercial chassis a set back axle is a good idea.

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    Front loading is based on both front axle AND frt tire."Floats"give you a higher rating but CAN affect both turning radius and the ability to turn on surfaces other than asphalt.I'm not in full agreement with efd having extensive time in the construction trade with conventional and float steer tires.While they DO offer a little support on mud/unmaintained roads they ALSO like to "skate"when turning.This condition is even more pronounced on ice and snow.In the case of a tanker you may have NO choice besides a "float"depending on your weight spread.Talk over your concerns with a REPUTABLE truck salesman that understands fire service chassis.They are best suited to point you in the right direction. T.C.

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    As stated by others, your front axle rating and tire size will be determined by the amount of weight on the axle. Remember, this is a tanker which means you're running empty 50% of the time. How much weight will be on the axle when it is empty? That is where you get into trouble with the big tires. Big tires are more prone to "pushing" through the corners when empty. 315's are big without being overkill. You can run 16,000 (some brands will spec at 18,000 but have a speed rating) on them safely, yet they aren't so big that they will "push" too easily.

    In other words IN MY OPINION, design the truck to have as close to 16,000 on the front axle as possible, and keep as much weight as possible on the front axle when empty. A set back axle is a good start (maybe even a cab-over). This usually means a shorter wheelbase which also works in your favor. It won't ride the best, but so what. It's a fire truck!
    Last edited by mongobob; 12-16-2007 at 08:01 AM.

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    The tires size depends on the estimated each axle weight and GVW both loaded and unloaded... the engineering dept. at whom ever your choosing should give the right sizes for your application. Per NFPA they have to do a weight analysis. that will define what axle's will be put under your apparatus and then the tires size will be defined by the weight. You can never just guess without engineering what tire size or axle is need.
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    Default Steer Tires

    If you need a high weight rated tire, you could look at Goodyears G287 HSS which will handle loads up to 10,500lbs. I will be putting this tire on a couple of our trucks next year.

    http://www.goodyear.com/cfmx/web/tru...ine=G287%20HSS

    or Goodyear 286A SS which is a super single

    http://www.goodyear.com/cfmx/web/tru...ine=G286A%20SS

    Goodyear (I'm sure others are similiar) have a government pricing and the above tires can be bought for around $400 - $500 per tire.
    Jim Shultz
    Oshtemo Fire Dept
    Fleet Maintenance Specialist

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