Thread: Tire Tread Thickness
12-28-2002, 05:29 PM #1
- Join Date
- Oct 2002
- Greenwood In USA
Tire Tread Thickness
I have two engines that I think need new rear tires. The guy at the city shop stated that they measured the tread thickness and it averaged 6 to 7 32nds. He stated that DOT standards were 2/32. I told him these are fire trucks not dump trucks. There are bald stops and chunks missing form them. Does anyone have information on what standard NFPA follows do they have a standard or do they follow DOT when it comes to tire tread thickness. Any information would be helpful.
12-28-2002, 08:35 PM #2
It's been a little while since I last had to look this up, but you need 4/32 on the front tires and 2/32 on all others, per DOT.
The Maine CDL handbook states that in addition to the tread depth, you should also look for cuts, tread seperation, wear between dual tires, and other damage, any of which may warrent replacment.
I do not believe there is a specific NFPA standard addressing tires, just that the vehicle should be kept in a serviceable condition (NFPA is very vauge about apparatus).
I can understand your desire to get new tires, but I can also see his desire not to replace them, especially if you have a tight budget situation. Truck tires are not cheap, they cost hundreds of dollars, and they do not last a very long time compaired to car tires. Since firetrucks spend most of their life sitting around, its easy for a mechanic to dismiss the need for replacement.
The letter of the law says you need "at least 4/32 inch tread depth in every major groove on the front tires." and 2/32 on other tires, if you have bald patches which cause tread depth to be less than the reqired amount over a large area, or if you have damage which is causing the tread to seperate (old tires will also dry rot) than I'd push a little weight around get me some tires, but less than that you might be asking for a war with the town garage. Chunks missing from the edges of the tires are quite common, especially in tandom axle trucks, as long as the tread does not seperate its fine. A chunk missing from the middle of the tire is bad, usually the result of poor recapping or as Firestone found out, crappy workmanship.
If you're not sure, ask at one of the local truck inspection stations and get a little info from them (or maybe you're lucky enough to have a mechanic working the FD with you) like how big of a cut before they'd fail the tires, etc.
Meanwhile, if its winter where you live, get some chains and start pounding the crap out of your wheel wells, as well as annoying your residents as you drive by
01-10-2003, 12:38 AM #3
- Join Date
- Jun 2002
The tread must be measured at all grooves across the face of the tire and at a minimum of three clockings around the circumference. If you find the minimum depth at two locations on the tire, the tire needs replacement. The minimum "tread depth" is 4/32" for any steering axle and 2/32" for all other tires. Beyond these measurements, go the the national (NAFTA) standard for inspection of apparatus tires that travel on highways. The national standard is the "North American Out of Service Criteria". There you will find standards on visual inspections. Please note that any crack, split, cut, injury to the tire that exposes the steel or fabric belts is manditorily out of service as is any steer axle at 3/32" tread depth and all others at 1/32". Remeber, these last depths are "Out of Service" criteria. Not minimum standards as listed above. The "North American Out-or-Service Criteria is what your State Highway Patrol agency uses to deadline vehicles.
Here is a known tire guy engineering fact. When the tire tread depth is reduced to about 5/32', it no longer can cool itself as well, as it cannot pump air through the grooves that are nearly depleted. The result is a hotter tire and accelerated wear. In the fire service this is less of a problem unless your apparatus make long runs. Most of the fire service wear is "scrub" wear.
I hope this helps.
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